Description

AIR CONDITIONING SYSTEM AND THE CONTROLLING METHOD THEREOF

Technical Field

[1] The present invention relates to an air conditioning system, and more particularly, to an air conditioning system and a control method thereof which are capable of recovering energy wasted through exhaustion, thereby achieving an enhancement in energy efficiency. Background Art

[2] Generally, an air handling unit (AHU) is well known as an apparatus for conditioning air present in a room by supplying outdoor air to the room while exhausting or circulating the room air. The air handling unit heats or cools air, using a heating source or a cooling source, and blows the heated or cooled air to a space to be air- conditioned, through a duct.

[3] For the cooling and heating sources, a system comprising a combined coil for cold water and hot water may be used. In this system, cold water from a chiller is supplied to the coil in a cooling mode, and steam or hot water from a boiler is supplied to the coil in a heating mode. Recently, the use of a heat exchanger constituting a cooling cjcle has been increased.

[4] The air handling unit also has a function to clean air using a filtering operation, and a humidifying/dehumidifying function to humidify or dehutnidify room air in accordance with the condition of the associated room, in order to make the room agreeable. That is, the air handling unit is configured to purify, cool, dehumidify, heat, and humidify air supplied to a room. The air conditioned to meet a desired condition of the room is blown to the room by a fan.

[5] The air used to condition the room is returned to the air handling unit such that it is partially mixed with outdoor air, for ventilation. The mixed air is then cooled/heated for the reuse thereof.

[6] Referring to FIGs. 1 and 2, an air handling unit 1 is illustrated. The air handling unit

1 includes a circulation fan 12 to circulate room air R.A., a filter 14 to purify air supplied to a room, namely, supply air S. A., a heat exchanger 16 to heat or cool the supply air S. A., a humidity controller 18 to humidify or dehumidify the supply air S.A., and a blowing fan 20 to supply the supply air S.A. to the room.

[7] An outdoor air inlet 32 is provided at one side of the air handling unit 1, to allow

outdoor air O. A. to be introduced into the interior of the air handling unit 1. The air handling unit 1 is also provided with a room air inlet 34 to receive the room air R.A., for the circulation of the room air R. A., an outlet 36, through which the circulating air is partially discharged to the outdoors, and a blowing port 38, through which air is supplied to the room.

[8] The outdoor air inlet 32, room air inlet 34, outlet 36, and blowing port 38 are connected to a duct (not shown) defining a flow path, along which air flows. The duct communicates with the room or the outdoors. Accordingly, air is introduced from the outdoors or room into the duct, and is then discharged from the duct into the room or outdoors.

[9] The heat exchanger 16 is connected to an outdoor unit 40, to constitute a cooling cjcle. In detail, a compressor (not shown) and an outdoor heat exchanger (not shown) are arranged in the outdoor unit 40, and an expansion valve (not shown) is arranged near the heat exchanger 16, in order to constitute the cooling cjcle, together with the heat exchanger 16. As the circulation direction of a refrigerant passing through the compressor, outdoor heat exchanger, expansion valve, and heat exchanger 16 is changed, the heat exchanger 16 can function as a cooling source or a heating source.

[10] Hereinafter, the operation of the air handling unit 1 having the above-mentioned configuration will be described.

[11] When the air handling unit 1 operates, the circulation fan 12 and blowing fan 20 rotate to generate a flow of air. In detail, when the blowing fan 20 operates, a sucking force is generated, thereby causing outdoor air O.A. to be introduced into the air handling unit 1 through the outdoor air inlet 32.

[12] On the other hand, when the circulation fan 12 operates, room air R.A. from the room is introduced into the air handling unit 1 through the room air inlet 34. A part of the room air R.A. introduced into the air handling unit 1 is outwardly discharged through the outlet 36, as exhaust air E.A. The remaining room air R.A. is mixed with the outdoor air O.A. introduced into the air handling unit 1. The mixed air is supplied to the room through the blowing port 38 by the blowing fan 20 after passing through the filter 14, heat exchanger 16, and humidity controller 18. Thus, the room air R.A. is circulated. During the circulation of the room air R.A., a part of the room air R.A. is outwardly discharged, and fresh outdoor air O.A. is newly supplied, so that a ventilation function is carried out.

[13] The supply air S. A. supplied to the room is purified by the filter 14, and is then heated or cooled while passing the heat exchanger 16. The supply air S.A. is then

supplied to the room after being controlled to have a desired humidity by the humidity controller 18. Thus, the air handling unit 1 conditions the supply air S. A. to be supplied to the room such that the supply air S. A. has a condition desired by the user, and then supplies the conditioned supply air S.A., to achieve air conditioning of the room.

Disclosure of Invention

Technical Problem

[14] In the above-mentioned conventional air handling unit 1, however, waste of energy through exhaustion occurs because exhaust air E.A. is generated as a certain amount of outdoor air O.A. is introduced for ventilation. That is, as a certain amount of outdoor air O.A. is introduced, a corresponding amount of room air R. A. is outwardly discharged as exhaust air E.A. However, the exhaust air E.A. causes loss of energy because it is colder than outdoor air O.A. in summer, and is warmer than outdoor air O.A. in winter.

[15] In order to recover the wasted energy, the use of a total heat exchanger has also been proposed. In this case, however, total heat exchanging elements (not shown) installed in the total heat exchanger, for heat exchange, are expensive. Furthermore, air passing the total heat exchanger is subjected to pressure loss. In order to compensate for such pressure loss, an increase in fan power is required. For this reason, the above- mentioned proposal cannot efficiently recover energy. Technical Solution

[16] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an air conditioning system and a control method thereof which are capable of recovering energy wasted through exhaustion, thereby achieving an enhancement in energy efficiency.

[17] The object of the present invention can be achieved by providing an air conditioning system comprising: an outdoor unit; at least one air handling unit for supplying outdoor air to a room while exhausting or circulating air present in the room, thereby air-conditioning the room; and at least one auxiliary unit arranged at an exhaustion side of the at least one air handling unit, to recovery energy from air exhausted from the at least one air handling unit, the auxiliary unit being connected to the outdoor unit, to constitute a cooling cy_Je.

[18] The air conditioning system may further comprise at least one first heat exchanger installed in the air handling unit, and connected to the outdoor unit, to constitute the

cooling cycle, the first heat exchanger performing heat exchange with air, which will be supplied to the room, and discharging the heat-exchanged air to the room.

[19] The auxiliary unit may comprise a second heat exchanger and an expansion valve, which are connected to the outdoor unit, to constitute the cooling cycle.

[20] The air conditioning system may further comprise at least one indoor unit connected to the outdoor unit.

[21] The air conditioning system may further comprise a refrigerant distribution unit for controlling a flow direction of a refrigerant to simultaneously enable a part of the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit to operate in a cooling mode, and the remaining part of the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit to operate in a heating mode, the refrigerant distribution unit being connected to the outdoor unit at one side of the refrigerant distribution unit, while being connected to the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit at the other side of the refrigerant distribution unit.

[22] The air conditioning system may further comprise a line configuration including: a first refrigerant line for gliding the refrigerant, which is discharged from a compressor of the outdoor unit, to a part of the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit, which operate in the heating mode; a second refrigerant line connected to the outdoor unit, to glide the refrigerant discharged from the part of the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit, which operate in the heating mode, to a part of the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit, which operate in the cooling mode; and a third refrigerant line for guiding the refrigerant discharged from the part of the at least one indoor unit, the at least one air handling unit, and the at least one auxiliary unit, which operate in the cooling mode, to the outdoor unit.

[23] The refrigerant distribution unit may comprise a first refrigerant control valve for controlling opening and closing of the first refrigerant line, and a second refrigerant control valve for controlling opening and closing of the third refrigerant line.

[24] The auxiliary unit arranged at the exhaustion side of the air handling unit may operate in the cooling mode when the air handling unit operates in the heating mode, and may operate in the heating mode when the air handling unit operates in the cooling mode.

[25] In another aspect of the present invention, provided herein is an air conditioning

system comprising: an air handling unit comprising a first heat exchanger, to perform one of a cooling operation and a heating operation; and an auxiliary unit arranged at an exhaustion side of the air handling unit, the auxiliary unit comprising a second heat exchanger, to perform the other of the cooling and heating operations.

[26] In a further aspect of the present invention, provided herein is a method for controlling an air conditioning system, comprising: operating a compressor included in an outdoor unit, to begin an operation of the air conditioning system; and controlling, by a refrigerant distribution unit, a flow direction of a refrigerant to simultaneously enable a part of an indoor unit, an air handling unit, and an auxiliary unit, which are connected to the outdoor unit, to operate in a cooling mode, and the remaining part of the indoor unit, the air handling unit, and the auxiliary unit to operate in a heating mode.

[27] The refrigerant distribution unit may control the flow direction of the refrigerant, which is supplied to the auxiliary unit, to enable the auxiliary unit to perform an operation for recovering energy from air exhausted from the air handling unit.

[28] In detail, the refrigerant distribution unit may control the flow direction of the refrigerant supplied to the auxiliary unit, to enable the auxiliary unit to operate in the cooling mode when the air handling unit operates in the heating mode, and to enable the auxiliary unit to operate in the heating mode when the air handling unit operates in the cooling mode. Advantageous Effects

[29] In accordance with the air conditioning system of the present invention, there is an advantage in that energy wasted through exhaust air discharged from the air handling unit.

[30] Also, it is possible to conveniently save energy without using equipment such as a total heat exchanger requiring high costs and an increase in fan power causing increased energy consumption.

[31] In addition, there is an advantage in that it is possible to enhance the overall efficiency of the air conditioning system by appropriately using the energy recovered from the exhaust air to heat rooms selected to be heated and to cool rooms selected to be cooled, in accordance with the load conditions of the rooms. Brief Description of the Drawings

[32] The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the de-

scription serve to explain the principle of the invention.

[33] In the drawings:

[34] FIG. 1 is a schematic view illustrating the configuration of a conventional air handling unit;

[35] FIG. 2 is a schematic view illustrating air flows in the conventional air handling unit;

[36] FIG. 3 is a schematic view illustrating the configuration of an air conditioning system according to the present invention;

[37] FIG. 4 is a άrαit diagram illustrating a refrigerant path established when the air conditioning system aooording to the present invention operates in a heating- predominant mode;

[38] FTG.5 is a circuit diagram illustrating a refrigerant path established when the air conditioning system according to the present invention operates in a cooling- predominant mode;

[39] FIG. 6 is a circuit diagram illustrating a refrigerant path established in the air conditioning system aooording to the present invention when the air conditioning system has an expanded configuration including a plurality of outdoor units, and operates in a heating-predominant mode; and

[40] FIG. 7 is a circuit diagram illustrating a refrigerant path established in the air conditioning system aooording to the present invention when the air conditioning system has an expanded configuration including a plurality of outdoor units, and operates in a cooling-predominant mode. Mode for the Invention

[41] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. For the convenience of description, the constituent elements identical to those of the conventional case will be designated by the same terms and the same reference numerals, and no description thereof will be given.

[42] Referring to FIGs. 3 to 5, an air conditioning system according to the present invention is illustrated. The air conditioning system mainly includes an outdoor unit 140, at least one air handling unit 101, which conditions air present in a room, namely, room air R.A., by supplying outdoor air O.A. to the room while exhausting or circulating the room air R.A., and at least one auxiliary unit 150 arranged at the exhaustion side of the air handling unit 101, to recovery waste energy from air exhausted from the air handling unit 101, namely, exhaust air E.A., while being

connected to the outdoor unit 140, to constitute a cooling cjcle.

[43] The outdoor unit 140 includes a plurality of compressors 141 to compress a refrigerant, a plurality of outdoor heat exchangers 142, at which the refrigerant performs heat exchange, a four-way valve 143 arranged at the outlet side of the compressors 141, to change a flow path for the refrigerant, and an accumulator 144 connected to the inlet side of the compressors 141, to supply the refrigerant in a gaseous phase to the compressors 141.

[44] The four-way valve 143 performs a switching operation to change the flow direction of the refrigerant in accordance with whether the outdoor unit 140 operates in a heating-predominant mode or in a cooling-predominant mode. When the outdoor unit 140 operates in the heating-predominant mode, the four-way valve 143 guides the refrigerant discharged from the compressors 141 to flow outwardly from the outdoor unit 140. On the other hand, when the outdoor unit 140 operates in the cooling- predominant mode, the four-way valve 143 guides the refrigerant discharged from the compressors 141 to flow toward the outdoor heat exchangers 142.

[45] That is, the outdoor heat exchangers 142 function as evaporators when the outdoor unit 140 operates in the heating-predominant mode. In this case, a refrigerant flow path is established such that the refrigerant, which is evaporated in the outdoor heat exchangers 142, is introduced into the compressors 141, so as to be compressed. On the other hand, when the outdoor unit 140 operates in the cooling-predominant mode, the outdoor heat exchangers 142 function as condensers. In this case, the refrigerant discharged from the compressors 141 is condensed in the outdoor heat exchangers 142. Thus, the flow path of the refrigerant is determined in axordance with the switching operation of the four- way valve 143. In axordance with the determined refrigerant flow path, the operation condition of the outdoor unit 140, and thus, the air conditioning system, is determined.

[46] Details of the heating-predominant-mode and cooling-predominant-mode operations and the reference for the determination of a desired mode will be described later.

[47] An evaporation fan 145 is arranged near the outdoor heat exchanger 142, to assist the outdoor heat exchanger 142 in evaporating the refrigerant when the outdoor heat exchanger 142 functions as an evaporator.

[48] An outdoor expansion valve 146 is arranged at a line of the outdoor heat exchanger

142 opposite to the compressors 141. An electronic expansion valve (EEV) may be used for the outdoor expansion valve 146. The EEV is a valve for controlling the

amount of a refrigerant flowing through an evaporator, using an electronic controller. Recently, the use of such an EEV has been increased because the EEV can save the consumption of energy when it is applied to the case involving a long operating time and a large load variation.

[49] Meanwhile, the air handing unit 101 includes a circulation fan 112 to circulate room air R.A., a filter 114 to purify air supplied to a room, namely, supply air S.A., a first heat exchanger 116 to heat or cool the supply air S. A., a humidity controller 118 to humidify or dehumidify the supply air S.A., and a blowing fan 120 to supply the supply air S. A. to the room.

[50] An outdoor air inlet 132 is provided at one side of the air handling unit 101, to allow outdoor air O.A. to be introduced into the interior of the air handling unit 101. The air handling unit 101 is also provided with a room air inlet 134 to receive the room air R.A., for the circulation of the room air R.A., an outlet 136, through which the circulating air is partially discharged to the outdoors, and a blowing port 138, through which air is supplied to the room.

[51] The outdoor air inlet 132, room air inlet 134, outlet 136, and blowing port 138 are connected to a duct (not shown) defining a flow path, along which air flows. The duct communicates with the room or the outdoors. Accordingly, air is introduced from the outdoors or room into the duct, and is then discharged from the duct into the room or outdoors.

[52] The first heat exchanger 116 is connected to the outdoor unit 140, to constitute a cooling qcle. That is, the first heat exchanger 116 discharges the supply air S. A. into the room after performing heat exchange with the supply air S. A.

[53] In detail, the first heat exchanger 116 constitutes the cooling cjcle, together with the compressors 141, the outdoor heat exchangers 142, and an expansion valve 117 arranged at one side of the first heat exchanger 116. The first expansion valve 117 may comprise an EEV as described above. As the first heat exchanger 116 constitutes the cooling cyde, together with the compressors 141 and outdoor heat exchangers 142 included in the outdoor unit 140, it functions as a cooling source or heating source of the air handling unit 101, to heat or cool air passing the first heat exchanger 116.

[54] Although the first heat exchanger 116 is illustrated as comprising a single heat exchanger, it may comprise a heat exchanger assembly including a plurality of thin heat exchangers coupled together.

[55] As described above, the auxiliary unit 150 is arranged at the exhaustion side of the air handling unit 101. The auxiliary unit 150 is connected to the outdoor unit 140, to

constitute a ∞oling QcIe. In detail, the auxiliary unit 150 includes a second heat exchanger 152 and a second expansion valve 154, which are connected to the outdoor unit 140, to constitute a cooling cjcle. In this case, the second expansion valve 154 preferably comprises an EEV.

[56] The auxiliary unit 150 is adapted to conveniently recover waste energy from air exhausted from the air handling unit 101, namely, exhaust air E. A. In order to achieve the energy recovery, it is preferred that the auxiliary unit 150 be arranged at one side of an exhaust duct (not shown) near the outlet 136 of the air handling unit 101.

[57] When the air handling unit 101 operates in a heating mode, the exhaust air E.A. exhibits a temperature higher than that of the outdoor air O. A. When the second heat exchanger 152 of the auxiliary unit 150 operates in a cooling mode in this case, it is possible to absorb energy from the exhaust gas E.A. The absorbed energy can be used to heat another room to be air-conditioned.

[58] In detail, the refrigerant, which passes through the second heat exchanger 152, can be evaporated at a relatively high temperature. As a result, the compression work of the compressors 141 included in the outdoor unit 140 can be reduced. The correspondingly-saved energy can be used to heat another room to be air-conditioned. Thus, an enhancement in energy efficiency is achieved.

[59] When the air handling unit 101 operates in a cooling mode, the exhaust air E.A. exhibits a temperature lower than that of the outdoor air O.A. When the second heat exchanger 152 operates in a heating mode in this case, it is possible to effectively remove heat to be released by the outdoor unit 140. The removal of heat means the recovery of energy wasted through the exhaust air E.A. and the use of the recovered energy, in terms of the overall qcle of the air conditioning system.

[60] As the auxiliary unit 150, which includes a heat exchanger, is arranged at the exhaustion side of the air handling unit 101, as described above, the compression work of the compressors 141 decreases, whereas the energy supplied to the room increases. Aooordingly, the coefficient of performance (COP) representing the ratio of the compression work of the compressors 140 to the energy supplied to the room increases. Thus, the energy efficiency of the overall portion of the system is enhanced.

[61] Meanwhile, the air conditioning system further includes at least one indoor unit connected to the outdoor unit 140. In the illustrated case, two indoor units 160a and 160b are provided. The indoor units 160a and 160b include respective indoor heat exchangers 162a and 162b, and respective indoor expansion valves 164a and 164b connected to respective indoor heat exchangers 162a and 162b by respective re-

frigerant lines. Preferably, each of the indoor expansion valves 164a and 164b comprises an EEV.

[62] In order to enable the auxiliary unit 150 to operate in a cooling mode when the air handling unit 101 operates in a heating mode, and to operate in a heating mode when the air handling unit 101 operates in a cooling mode, it is preferred that the air conditioning system be configured to simultaneously perform a heating operation and a cooling operation for rooms to be air-conditioned.

[63] To this end, the air conditioning system further includes a refrigerant distribution unit 170 which controls the flow direction of the refrigerant to simultaneously enable a part of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150 to operate in a cooling mode, and the remaining part to operate in a heating mode. The refrigerant distribution unit 170 is connected, at one side thereof, to the outdoor unit 140, and is connected, at the other side thereof, to the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150.

[64] The refrigerant distribution unit 170 functions to control opening and closing of refrigerant lines inter-connecting the outdoor unit 140, indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150.

[65] The refrigerant lines of the air conditioning system according to the present invention will be described hereinafter, before the description of the refrigerant distribution unit 170.

[66] The air conditioning system includes a first refrigerant line 182 to guide the refrigerant discharged from the compressors 141 of the outdoor unit 140 to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the heating mode.

[67] The first refrigerant line 182 is connected to outlets of the compressors 141. The first refrigerant line 182 emerges from the outdoor unit 140, and extends through the refrigerant distribution unit 170. The first refrigerant line 182 is branched in the refrigerant distribution unit 170. The branched portions of the first refrigerant line 182 are connected to respective heat exchangers 162a, 162b, 116, and 152 of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150.

[68] The first refrigerant line 182 having the above-described configuration guides the refrigerant discharged in a high-temperature and high-pressure gaseous phase from the compressors 141 to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in a heating mode.

[69] The air conditioning system further includes a second refrigerant line 184

connected to the outdoor unit 140, to guide the refrigerant discharged from those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the heating mode, to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode.

[70] The second refrigerant line 184 is connected to the outdoor expansion valve 146 of the outdoor unit 140. The second refrigerant line 184 emerges from the outdoor unit 140, and extends through the refrigerant distribution unit 170. The second refrigerant line 184 is branched in the refrigerant distribution unit 170. The branched portions of the second refrigerant line 184 are connected to respective expansion valves 164a, 164b, 117, and 154 of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150.

[71] When the air conditioning system operates in a heating-predominant mode, the second refrigerant line 184 having the above-described configuration glides a part of the refrigerant discharged from those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the heating mode, to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode. The second refrigerant line 184 also guides the remaining refrigerant to the outdoor expansion valve 146 of the outdoor unit 140.

[72] Here, the heating-predominant operation mode represents an operation mode in which the refrigerant discharged from the compressors 141 flows toward those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the heating mode, without passing through the outdoor heat exchanger 142 of the outdoor unit 140, in axordance with a switching operation of the four-way valve 143. On the contrary, the cooling-predominant operation mode represents an operation mode in which the refrigerant discharged from the compressors 141 flows toward those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode, after passing through the outdoor heat exchanger 142 of the outdoor unit 140, in accordance with a switching operation of the four- way valve 143. Thus, whether the air conditioning system operates in the heating- predominant operation mode or in the cooling-predominant operation mode is determined in accordance with the operation mode of the outdoor unit 140.

[73] Also, whether the outdoor unit 140 operates in the heating-predominant operation mode or in the cooling-predominant operation mode is determined in accordance with whether a higher capacity is required for those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the heating mode, or those

of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the oooling mode. That is, whether the outdoor unit 140 operates in the heating-predominant operation mode or in the cooling-predominant operation mode is determined in accordance with which load is larger between a heating load and a cooling load.

[74] When the air conditioning system operates in the cooling-predominant mode, the second refrigerant line 184 guides the refrigerant, which has been condensed while passing through the outdoor heat exchanger 142 after being discharged from the compressors 141, toward those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in a cooling operation. Of course, the second refrigerant line 184 also functions to guide the refrigerant discharged from those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in a heating operation, to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode.

[75] Meanwhile, the air conditioning system further includes a third refrigerant line 186 which guides the refrigerant discharged from those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode, to the outdoor unit 140.

[76] The third refrigerant line 186 is connected to inlets of the compressors 141 of the outdoor unit 140. The third refrigerant line 186 is branched in the refrigerant distribution unit 170. The branched portions of the third refrigerant line 186 are connected to respective heat exchangers 162a, 162b, 116, and 152 of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150. In details, the branched portions of the third refrigerant line 186 are connected to respective heat exchangers 162a, 162b, 116, and 152 after being pined to respective branched portions of the first refrigerant line 182.

[77] The third refrigerant line 186 having the above-described configuration guides the refrigerant discharged from those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode, to the outdoor unit 140. In detail, a gaseous refrigerant is guided to the outdoor unit 140 via the third refrigerant line 186. The refrigerant is then introduced into the compressors 141 via the accumulator 144, so that it is compressed.

[78] As described above, each of the first, second, and third refrigerant lines 182, 184, and 186 extends through the refrigerant distribution unit 170, and is connected to the heat exchangers 162a, 162b, 116, and 152 or expansion valves 164a, 164b, 117, and

154 of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150 after being branched.

[79] The refrigerant distribution unit 170 includes first refrigerant control valves 172a,

172b, 172c, and 172d to control opening and closing of the first refrigerant line 182, and second refrigerant control valves 174a, 174b, 174ς and 174d to control opening and closing of the third refrigerant line 186.

[80] Preferably, ea=h of the first refrigerant control valves 172a, 172b, 172ς and 172d and each of the second refrigerant control valves 174a, 174b, 174ς and 174d comprise on/off valves to open and close the first refrigerant line 182 and third refrigerant line 186, respectively. The first refrigerant control valves 172a, 172b, 172c, and 172d are arranged in respective branched portions of the first refrigerant line 182, and the second refrigerant control valves 174a, 174b, 174c, and 174d are arranged in respective branched portions of the third refrigerant line 186.

[81] As described above, the first and third refrigerant lines 182 and 186 are connected to the heat exchangers 162a, 162b, 116, and 152 of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, after being pined to each other in the refrigerant distribution unit 170. In accordance with the opening or closing of the first refrigerant control valves 172a, 172b, 172c, and 172d and the opening or closing of the third refrigerant control valves 174a, 174b, 174c, and 174d, the directions of the refrigerant flows passing through the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150 are changed.

[82] For example, when the first refrigerant control valve 172b in the first refrigerant line 182 connected to the air handling unit 101 is opened, and the second refrigerant control valve 174b in the third refrigerant line 186 is closed, the refrigerant discharged in a high-pressure gaseous phase from the compressors 141 through the first refrigerant line 182 is condensed while passing through the first heat exchanger 116. Thus, the air handling unit 101 performs a heating operation.

[83] On the contrary, when the first refrigerant control valve 172b is closed, and the second refrigerant control valve 174b is opened, the refrigerant discharged from those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in a heating mode, is introduced into the first heat exchanger 116 via the second refrigerant line 184, so that the refrigerant is evaporated in the first heat exchanger 116. Thus, the air handling unit 101 performs a cooling operation. Of course, when the air conditioning system operates in a cooling-predominant mode, the refrigerant emerging from the outdoor heat exchanger 142 of the outdoor unit 140 is

also introduced into the first heat exchanger 116 via the second refrigerant line 184, so that the refrigerant is evaporated.

[84] Meanwhile, the air conditioning system further includes a controller (not shown) to control the opening and closing of the first refrigerant control valves 172a, 172b, 172c, and 172ς and second refrigerant control valves 174a, 174b, 174c, and 174d, and the overall function of the air conditioning system. When the user selects rooms to be heated or cooled, the controller controls the refrigerant distribution unit 170 to appropriately open or close the first refrigerant control valves 172a, 172b, 172c, and 172c, and second refrigerant control valves 174a, 174b, 174c, and 174d, in accordance with the user's selection.

[85] Hereinafter, the operation of the air conditioning system having the above- described configuration axording to the present invention will be described in detail.

[86] When the user determines rooms to be heated or cooled, and inputs the results of the determination to the air conditioning system, the controller determines a heating load and a cooling load, which are required in the air conditioning system, and compares the heating load and cooling load with each other. That is, the controller compares the capacity of those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which will operate in a heating mode, and the capacity of those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in a cooling mode, to determine which load is larger between the heating load and the cooling load. When it is determined that the heating load is larger, the controller determines the air conditioning system to operate in a heating- predominant mode. On the other hand, when it is determined that the cooling load is larger, the controller determines the air conditioning system to operate in a cooling- predominant mode.

[87] As the compressors 141 of the outdoor unit 140 operate, the air conditioning system begins to operate.

[88] First, the case, in which the air conditioning system operates in the hea ting- predominant mode, will be described.

[89] When the air conditioning system operates in the heating-predominant mode, the controller controls the switching operation of the four-way valve 143 to establish a flow path allowing the refrigerant introduced into the outdoor unit 140 via the second refrigerant line 184 to enter the compressors 141 after passing through the outdoor expansion valve 146 and outdoor heat exchanger 142.

[90] In this case, the outdoor expansion valve 146, which comprises an EEV, is

controlled to expand the refrigerant. The refrigerant, which has been expanded while passing through the outdoor expansion valve 146, is evaporated in the outdoor heat exchanger 142 in accordance with heat exchange. The evaporated refrigerant is introduced into the accumulator 144 connected to the inlets of the compressors 141, and is then temporarily stored in the accumulator 144. The accumulator 144 not only functions to control the amount of the refrigerant introduced into the compressors 141, but also functions to separate gaseous and liquid components of the refrigerant from each other.

[91] Thereafter, the refrigerant is introduced into the compressors 141 which, in turn, compress the refrigerant, and discharge the compressed refrigerant. The refrigerant discharged from the compressors 141 is guided to the refrigerant distribution unit 170 via the first refrigerant line 182.

[92] Meanwhile, the controller opens those of the first refrigerant control valves 172a,

172b, 172c, and 172d of the refrigerant distribution unit 170, which correspond to the rooms selected to be heated by the user. For example, where it is determined to operate the air handling unit 101 and one indoor unit, namely, the indoor unit 160a, in a heating mode, as shown in FIG. 4, the first refrigerant control valves 172b and 172c respectively corresponding to the air handling unit 101 and indoor unit 160a are opened. In this case, the refrigerant passes through the first heat exchanger 116 of the air handling unit 101 and the indoor heat exchanger 162a of the indoor unit 160a, so that the refrigerant is condensed. Thus, the air handing unit 101 and indoor unit 160a operate in the heating mode. Of course, the second refrigerant control valves 174b and 174c respectively connected to the air handling unit 101 and indoor unit 160a should be closed, in order to prevent the refrigerant from flowing backwardly through the third refrigerant line 186.

[93] In this case, it is preferred that the first expansion valve 117 and indoor expansion valve 164a, which are connected to the first heat exchanger 116 and indoor heat exchanger 162a, and comprise EEVs, respectively, be fully opened. This is because, when the refrigerant emerging from the first heat exchanger 116 and indoor heat exchanger 162a are immediately expanded, the pressure of the refrigerant is reduced, so that it is difficult for the refrigerant to flow to the outdoor unit 140 or to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode, namely, the indoor unit 160b and auxiliary unit 150.

[94] Thus, the refrigerant emerging from the air handling unit 101 and indoor unit 160a flows through the second refrigerant line 184. In this case, a part of the refrigerant is

introduced into the indoor unit 160b and auxiliary unit 150, which are determined to operate in the cooling mode. The remaining refrigerant is returned to the outdoor unit 140 via the second refrigerant line 184.

[95] As described above, the auxiliary unit 150 operates in a reverse manner to the air handling unit 101, in order to recover energy wasted through exhaust air discharged from the air handling unit 101. In this case, the refrigerant distribution unit 170 controls the flow direction of the refrigerant supplied to the auxiliary unit 150, in order to enable the auxiliary unit 150 to recover energy from exhaust air discharged from the air handing unit 101.

[96] In detail, when the air handling unit 101 operates in the heating mode, the refrigerant distribution unit 170 controls the flow direction of the refrigerant supplied to the auxiliary unit 150, to enable the auxiliary unit 150 to operate in the cooling mode. On the other hand, when the air handling unit 101 operates in the cooling mode, the refrigerant distribution unit 170 controls the flow direction of the refrigerant supplied to the auxiliary unit 150, to enable the auxiliary unit 150 to operate in the heating mode.

[97] When the air handling unit 101 operates in the heating mode, as shown in FIG. 4, it is preferred that the auxiliary unit 150 operate in the cooling mode. Accordingly, the controller determines the operation mode of the auxiliary unit 150 in accordance with the operation mode of the air handling unit 101. In accordance with the determination of the controller, the refrigerant distribution unit 170 controls the opening and closing of the first and second refrigerant control valves 172a and 174a.

[98] As shown in FIG.4, the second refrigerant control valves 174a and 174d in the third refrigerant line 186, which are respectively connected to the indoor unit 160b and auxiliary unit 150 operating in the cooling mode, are opened, whereas the first refrigerant control valves 172a and 172d in the first refrigerant line 182 are closed. As a result, the refrigerant emerging from the indoor unit 160a and air handling unit 101 operating in the heating mode flows to the indoor unit 160b and auxiliary unit 150 operating in the cooling mode, via the second refrigerant line 184. The refrigerant introduced into the auxiliary unit 150 is expanded while passing through the second expansion valve 154, and is then evaporated in the second heat exchanger 152. On the other hand, the refrigerant introduced into the indoor unit 160b is expanded while passing through the indoor expansion valve 164b, and is then evaporated in the indoor heat exchanger 162b. Thus, the auxiliary unit 150 and indoor unit 160b perform a cooling operation.

[99] The refrigerant emerging from the auxiliary unit 150 and indoor unit 160b is guided

to the outdoor unit 140 via the third refrigerant line 186 because the second refrigerant control valves 174a and 174d are in an opened state. In detail, the refrigerant is introduced into the compressors 141 via the accumulator 144.

[100] Now, the case, in which the air conditioning system operates in the cooling- predominant mode, will be described.

[101] When the air conditioning system operates in the cooling-predominant mode, the controller controls the switching operation of the four-way valve 143 to establish a flow path allowing the refrigerant discharged from the compressors 141 to flow through the first and second refrigerant lines 182 and 184. That is, the refrigerant discharged from the compressors 141 is branched at the outlets of the compressors 141 such that a part of the refrigerant flows to the second refrigerant line 184 via the outdoor heat exchanger 142, and the remaining refrigerant flows to the first refrigerant line 182.

[102] The refrigerant, which is introduced into the outdoor heat exchanger 142, is condensed while passing through the outdoor heat exchanger 142. The condensed refrigerant is glided to the refrigerant distribution unit 170 via the second refrigerant line 184 after passing through the outdoor expansion valve 146. In this case, the outdoor expansion valve 146 is in a fully-opened state.

[103] The controller controls the refrigerant distribution unit 170 to open those of the second refrigerant control valves 174a, 174b, 174c, and 174d connected to those of the indoor units 160a and 160b, air handling unit 101, and auxiliary unit 150, which operate in the cooling mode, and to close the first refrigerant control valves 172a, 172b, 172c, and 172d. For example, where it is determined to operate the air handling unit 101 and one indoor unit, namely, the indoor unit 160a, in a cooling mode, as shown in FIG. 5, the first refrigerant control valves 172b and 172c arranged in the first refrigerant line 182, and respectively connected to the air handling unit 101 and indoor unit 160a are closed. On the other hand, the second refrigerant control valves 174b and 174c arranged in the third refrigerant line 186, and respectively connected to the air handling unit 101 and indoor unit 160a are opened.

[104] In this case, the refrigerant flowing through the second refrigerant line 184 flows toward the air handling unit 101 and indoor unit 160a operating in the cooling mode.

[105] The refrigerant flowing toward the air handling unit 101 is guided to the first expansion valve 117 of the air handling unit 101 via the second refrigerant line 184. In this case, the first expansion valve 117 is controlled to expand the refrigerant. The expanded refrigerant enters the first heat exchanger 116, and absorbs heat around the

first heat exchanger 116 while passing through the first heat exchanger 116. Thus, the first heat exchanger 116 functions as a cooling source. The evaporated refrigerant flows toward the third refrigerant line 186 because the first refrigerant control valve 172b is in a closed state, and the second refrigerant control valve 174b arranged in the third refrigerant line 186 is in an opened state. Thus, the refrigerant is guided to the outdoor unit 140 via the third refrigerant line 186.

[106] Similarly, the refrigerant flowing toward the indoor unit 160a is guided to the indoor expansion valve 164a of the indoor unit 160a via the second refrigerant line 184. In this case, the indoor expansion valve 164a is controlled to expand the refrigerant. The expanded refrigerant enters the indoor heat exchanger 162a, and absorbs heat around the indoor heat exchanger 162a while passing through the indoor heat exchanger 162a. Thus, the indoor heat exchanger 162a functions as a cooling source. The evaporated refrigerant flows toward the third refrigerant line 186 because the second refrigerant control valve 174b arranged in the third refrigerant line 186 is in an opened state. Thus, the refrigerant is guided to the outdoor unit 140 via the third refrigerant line 186.

[107] The refrigerant glided to the outdoor unit 140 is introduced into the compressors

141 after passing through the accumulator 144, so that the refrigerant is again compressed.

[108] On the other hand, the refrigerant flowing through the first refrigerant line 182 is guided to the refrigerant distribution unit 170. In this case, the controller controls the refrigerant distribution unit 170 to open those of the first refrigerant control valves 172a, 172b, 172ς and 172d, which correspond to those of the rooms selected to be heated by the user, in order to enable the refrigerant to flow to the selected rooms.

[109] As described above, the auxiliary unit 150 operates in a reverse manner to the air handling unit 101, in order to recover energy wasted through exhaust air discharged from the air handling unit 101. When the air handling unit 101 operates in the cooling mode, as shown in FIG. 5, accordingly, the auxiliary unit 150 should operate in the heating mode. In this case, accordingly, the controller controls the opening and closing of the first refrigerant control valve 172a and second refrigerant control valve 174a of the refrigerant distribution unit 170, in order to enable the auxiliary unit 150 to perform a heating operation.

[110] When the auxiliary unit 150 and one indoor unit, namely, the indoor unit 160b, operate in the heating mode, as shown in FIG. 5, the associated first refrigerant control valves 172a and 172d are opened. As a result, the refrigerant passes through the second

heat exchanger 152 of the auxiliary unit 150 and the indoor heat exchanger 162b of the indoor unit 160b via the first refrigerant line 182, so that the refrigerant is condensed. Thus, esch. of the auxiliary unit 150 and indoor unit 160b performs a heating operation. Of course, in this case, the second refrigerant control valves 174a and 174d should be closed in order to prevent the refrigerant from flowing backwardly through the third refrigerant line 186.

[Ill] In this case, it is preferred that the second expansion valve 154 and indoor expansion valves 164b, which are connected to the second heat exchanger 152 and indoor heat exchanger 162b, and comprise EEVs, respectively, be fully opened, as described above.

[112] Thus, the refrigerant emerging from the auxiliary unit 150 and indoor unit 160b operating in the heating mode flows through the second refrigerant line 184. In this case, the refrigerant is introduced into the indoor unit 160a and air handling unit 101 operating in the cooling mode, and is evaporated. Thus, each of the indoor unit 160a and air handling unit 101 performs a cooling operation. The refrigerant is subsequently returned to the outdoor unit 140 via the third refrigerant line 186.

[113] Hereinafter, an embodiment, in which the air conditioning system according to the present invention has an expanded configuration, will be described.

[114] Referring to FIGs. 6 and 7, the air conditioning system according to the present invention includes a plurality of outdoor units 240a, 240b, and 240ς a plurality of air handling units 201a, 201b, and 201c, and a plurality of indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of. Similarly to the previous embodiment, each outdoor unit 240a, 240b, or 240c includes a plurality of compressors 241a, 241b, or 241c to compress a refrigerant, a plurality of outdoor heat exchangers 242a, 242b, or 242c, at which the refrigerant performs heat exchange, a four-way valve 243a, 243b, or 243c arranged at the outlet side of the compressors 241a, 241b, or 241ς to change a flow path for the refrigerant, and an axumulator 244a, 244b, or 244c connected to the inlet side of the compressors 241a, 241b, or 241 ς to supply the refrigerant in a gaseous phase to the compressors 241a, 241b, or 241c.

[115] Although this embodiment is illustrated as including three outdoor units 240a,

240b, and 24Oq it will be appreciated that the number of outdoor units 240a, 240b, and 240c may be increased in accordance with the required cooling or heating load.

[116] Also, the number of air handling units 201a, 201b, and 201c and the number of indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of may be increased in accordance with the number of rooms to be air-conditioned. For example, where the air con-

ditioning system is installed in a high-rise building, the air conditioning units 201a, 201b, and 201c, and indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of may be installed in the form of assemblies on respective stories such that the assembly installed on each story includes one air conditioning unit and a pair of indoor units. Thus, the number of such assemblies may be increased, if necessary.

[117] Each air handling unit 201a, 201b, or 201c includes a first heat exchanger 216a,

216b, or 216c, and a first expansion valve 217a, 217b, or 217c. Each indoor unit 260a, 260b, 260c, 26Od, 26Oe, or 26Of includes an indoor heat exchanger 262a, 262b, 262c, 262d, 262e, or 262f, and an indoor expansion valve 264a, 264b, 264c, 264d, 264e, or 264f.

[118] Auxiliary units 250a, 250b, and 250c are arranged at respective exhaustion sides of the air handling units 201a, 201b, and 201c. Each of the auxiliary units 250a, 250b, and 250c is connected to an associated one of the outdoor units 240a, 240b, and 240c, to constitute a cooling cycle. In detail, each auxiliary unit 250a, 250b, or 250c includes a second heat exchanger 252a, 252b, or 252c and a second expansion valve 254a, 254b, or 254c, which are connected to the associated outdoor unit 240a, 240b, or 240c, to constitute a cooling cjcle.

[119] As described above, in order to enable the auxiliary units 250a, 250b, and 250c to operate in a cooling mode when the associated air handling units 201a, 201b, and 201c operate in a heating mode, and to operate in a heating mode when the associated air handling units 201a, 201b, and 201c operate in a cooling mode, it is preferred that the air conditioning system be configured to simultaneously perform a heating operation and a cooling operation for rooms to be air-conditioned.

[120] To this end, the air conditioning system further includes a plurality of refrigerant distribution units 270a, 270b, and 270c, each of which controls the flow direction of the refrigerant to enable a part of the associated indoor units 260a and 260b, 260c and 26Od, or 26Oe and 26Of, associated air handling unit 201a, 201b, or 201ς and associated auxiliary unit 250a, 250b, or 250c to perform a cooling operation, and the remaining part to perform a heating operation. Each refrigerant distribution unit 270a, 270b, or 270c is connected, at one side thereof, to the associated outdoor unit 240a, 240b, or 240c, and is connected, at the other side thereof, to the associated indoor units 260a and 260b, 260c and 26Od, or 26Oe and 26Of, associated air handling unit 201a, 201b, or 201c, and associated auxiliary unit 250a, 250b, or 250c.

[121] Each refrigerant distribution unit 270a, 270b, or 270c functions to control opening and closing of refrigerant lines inter-connecting the associated outdoor unit 240a,

240b, or 240c, associated indoor units 260a and 260b, 260c and 26Od, or 26Oe and 26Of, associated air handling unit 201a, 201b, or 201ς and associated auxiliary unit 250a, 250b, or 250c.

[122] The air conditioning system includes a first refrigerant line 282 to glide the refrigerant discharged from the compressors 241a, 241b, and 241c of the outdoor units 240a, 240b, and 240c to those of the indoor units260a, 260b, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201ς and auxiliary units 250a, 250b, and 250ς which operate in the heating mode.

[123] The first refrigerant line 282 is connected to outlets of the compressors 241a, 241b, and 241c of the outdoor units 240a, 240b, and 240c. The first refrigerant line 282 emerges from the outdoor units 240a, 240b, and 240c in a branched state, and then ex tends in a pined state. The first refrigerant line 282 is again branched to extend through the refrigerant distribution units 270a, 270b, and 270c. In each of the refrigerant distribution units 270a, 270b, and 270c, the first refrigerant line 282 is again branched. In association with each refrigerant distribution unit 270a, 270b, or 270ς the branched portions of the first refrigerant line 282 are connected to respective heat exchangers of the associated indoor units 260a and 260b, 260c and 26Od, or 26Oe and 26Of, associated air handling unit 201a, 201b, or 201c, and associated auxiliary unit 250a, 250b, or 250c.

[124] The first refrigerant line 282 having the above-described configuration guides the refrigerant discharged in a high-temperature and high-pressure gaseous phase from the compressors 241a, 241b, and 241c to those of the indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, and 20 lς and auxiliary units 250a, 250b, and 250c, which operate in a heating mode.

[125] The air conditioning system further includes a second refrigerant line 284 connected to the outdoor units 240a, 240b, and 240c, to glide the refrigerant discharged from those of the indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250ς which operate in the heating mode, to those of the indoor units the indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250ς which operate in the cooling mode.

[126] The second refrigerant line 284 is connected to the outdoor expansion valves 246a,

246b, and 246c of the outdoor units 240a, 240b, and 240c. The second refrigerant line 284 emerges from the outdoor units 240a, 240b, and 240c in a branched state, and then extends in a pined state. The second refrigerant line 284 is again branched to extend

through the refrigerant distribution units 270a, 270b, and 270c. In each of the refrigerant distribution units 270a, 270b, and 270ς the second refrigerant line 284 is again branched. In association with each refrigerant distribution unit 270a, 270b, or 270ς the branched portions of the second refrigerant line 282 are connected to respective expansion valves of the associated indoor units 260a and 260b, 260c and 26Od, or 26Oe and 26Of, associated air handling unit 201a, 201b, or 201c, and associated auxiliary unit 250a, 250b, or 250c.

[127] When the air conditioning system operates in a heating-predominant mode, the second refrigerant line 284 having the above-described configuration guides a part of the refrigerant discharged from those of the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250ς which operate in the heating mode, to those of the indoor units the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201ς and auxiliary units 250a, 250b, and 250c, which operate in the cooling mode. The second refrigerant line 284 also guides the remaining refrigerant to the outdoor expansion valves 246a, 246b, and 246c of the outdoor units 240a, 240b, and 240c.

[128] When the air conditioning system operates in the cooling-predominant mode, the second refrigerant line 284 guides the refrigerant, which has been condensed while passing through the outdoor heat exchangers 242a, 242b, and 242c after being discharged from the compressors 241a, 241b, and 241c, toward those of the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250ς which operate in the cooling mode. Of course, the second refrigerant line 284 also functions to glide the refrigerant discharged from those of the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250c, which operate in the heating mode, to those of the indoor units the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250c, which operate in the cooling mode.

[129] Meanwhile, the air conditioning system further includes a third refrigerant line 286 which guides the refrigerant discharged from those of the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201ς and auxiliary units 250a, 250b, and 250c, which operate in the cooling mode, to the outdoor units 240a, 240b, and 240c.

[130] The third refrigerant line 286 is connected to inlets of the compressors 241a, 241b, and 241c of the outdoor units 240a, 240b, and 240c. The third refrigerant line 286

emerges from the outdoor units 240a, 240b, and 240c in a branched state, and then extends in a pined state. The third refrigerant line 286 is again branched to extend through the refrigerant distribution units 270a, 270b, and 270c. In each of the refrigerant distribution units 270a, 270b, and 270ς the third refrigerant line 286 is again branched. In association with each refrigerant distribution unit 270a, 270b, or 270c, the branched portions of the third refrigerant line 286 are connected to respective heat exchangers of the associated indoor units 260a and 260b, 260c and 26Od, or 26Oe and 26Of, associated air handling unit 201a, 201b, or 201ς and associated auxiliary unit 250a, 250b, or 250c. In details, the branched portions of the third refrigerant line 286 are connected to respective heat exchangers after being pined to respective branched portions of the first refrigerant line 282 in the refrigerant distribution units 270a, 270b, and 270c.

[131] The third refrigerant line 286 having the above-described configuration glides the refrigerant discharged from those of the indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250c, which operate in the cooling mode, to the outdoor units 240a, 240b, and 240c. In detail, a gaseous refrigerant is guided to the outdoor units 240a, 240b, and 240c via the third refrigerant line 286. The refrigerant is then introduced into the compressors 241a, 241b, and 241c via the accumulators 244a, 244b, and 244c, respectively, so that it is compressed.

[132] As described above, each of the first, second, and third refrigerant lines 282, 284, and 286 extends through the refrigerant distribution units 270a, 270b, and 270ς and is connected to the heat exchangers or expansion valves of the indoor units 260a, 260b, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, 201c, and auxiliary units 250a, 250b, and 250c after being again branched in the refrigerant distribution units 270a, 270b, and 270c.

[133] The refrigerant distribution units 270a, 270b, and 270c include respective first refrigerant control valves 272a, 272b, and 272c to control opening and closing of the first refrigerant line 282, and respective second refrigerant control valves 274a, 274b, and 274c to control opening and closing of the third refrigerant line 286.

[134] Preferably, each of the first refrigerant control valves 272a, 272b, and 272c and each of the second refrigerant control valves 274a, 274b, and 274c comprise on/off valves to open and close the first refrigerant line 282 and third refrigerant line 286, respectively. The first refrigerant control valves 272a, 272b, and 272c are arranged in respective branched portions of the first refrigerant line 282, and the second refrigerant

control valves 274a, 274b, and 274c are arranged in respective branched portions of the third refrigerant line 286.

[135] Meanwhile, the air conditioning system further includes a controller (not shown) to control the opening and closing of the first refrigerant control valves 272a, 272b, and 272c, and second refrigerant control valves 274a, 274b, and 274ς and the overall function of the air conditioning system. When the user selects rooms to be heated or cooled, the controller controls the refrigerant distribution units 270a, 270b, and 270c to appropriately open or close the first refrigerant control valves 272a, 272b, and 272c, and second refrigerant control valves 274a, 274b, and 274c, in accordance with the user's selection.

[136] Hereinafter, the operation of the air conditioning system having the above- described configuration axording to the present invention will be described in detail.

[137] First, the case, in which the air conditioning system operates in the heating- predominant mode, will be described.

[138] When the air conditioning system operates in the heating-predominant mode, the controller controls the switching operations of the four-way valves 243a, 243b, and 243c of the outdoor units 240a, 240b, and 240c, to establish a flow path allowing the refrigerant introduced into the outdoor units 240a, 240b, and 240c via the second refrigerant line 284 to enter the compressors 241a, 241b, and 241c after passing through the outdoor expansion valves 246a, 246b, and 246c and outdoor heat exchangers 242a, 242b, and 242c.

[139] In this case, the outdoor expansion valves 246a, 246b, and 246c, which comprise

EEVs, respectively, are controlled to expand the refrigerant. The refrigerant, which has been expanded while passing through the outdoor expansion valves 246a, 246b, and 246c, is evaporated in the outdoor heat exchangers 242a, 242b, and 242c in accordance with heat exchange. The evaporated refrigerant is introduced into the accumulators 244a, 244b, and 244c connected to the inlets of the associated compressors 241a, 241b, and 241c, and is then temporarily stored in the axumulators 244a, 244b, and 244c.

[140] Thereafter, the refrigerant is introduced into the compressors 241a, 241b, and 241c which, in turn, compress the refrigerant, and discharge the compressed refrigerant. The refrigerant discharged from the compressors 241a, 241b, and 241c is guided to the refrigerant distribution units 270a, 270b, and 270c via the first refrigerant line 282.

[141] Meanwhile, the controller opens those of the first refrigerant control valves 272a,

272b, and 272c of the refrigerant distribution units 270a, 270b, and 270c, which correspond to the rooms selected to be heated by the user. For example, where it is

determined to operate the air handling unit and one indoor unit of each assembly, namely, the air handling units 201a, 201b, and 201c, and indoor units 260a, 260ς and 26Oe, in a heating mode, as shown in FIG. 6, the associated first refrigerant control valves 272a, 272b, and 272c are opened. In this case, the refrigerant passes through the first heat exchangers 216a, 216b, and 216c of the air handling units 201a, 201b, and 201c and the indoor heat exchangers 262a, 262ς and 262e of the indoor units 260a, 260c, and 26Oe, so that the refrigerant is condensed. Thus, the air handing units 201a, 201b, and 201c and indoor units 260a, 260ς and 26Oe operate in the heating mode. Of course, the second refrigerant control valves 274a, 274b, and 274c are closed, in order to prevent the refrigerant from flowing backwardly through the third refrigerant line 286.

[142] In this case, it is preferred that the first expansion valves 217a, 217b, and 217c and indoor expansion valves 264a, 264ς and 264e, which are connected to the first heat exchangers 216a, 216b, and 216c and indoor heat exchangers 262a, 262b, and 262e, and comprise EEVs, respectively, be fully opened.

[143] Thus, the refrigerant emerging from the air handling units 201a, 201b, and 201c and indoor units 260a, 260c, and 26Oe flows through the second refrigerant line 284. In this case, a part of the refrigerant is introduced into those of the indoor units 260a, 260b, 260c, 260c, 26Od, 26Oe, and 26Of, air handling units 201a, 201b, and 201c, and auxiliary units 250a, 250b, and 250ς which are determined to operate in the cooling mode. The remaining refrigerant is returned to the outdoor units 240a, 240b, and 240c via the second refrigerant line 284.

[144] Meanwhile, the auxiliary units 250a, 250b, and 250c operate in a reverse manner to the air handling units 201a, 201b, and 201c, in order to recover energy wasted through exhaust air discharged from the air handling units 201a, 201b, and 201c. For example, when the air handing units 201a, 201b, and 201c operate in the heating mode, as shown in FIG. 6, the auxiliary units 250a, 250b, and 250c should operate in the cooling mode. Accordingly, the controller determines the operation mode of the auxiliary units 250a, 250b, and 250c in accordance with the operation mode of the air handling units 201a, 201b, and 201c.

[145] As shown in FIG. 6, the second refrigerant control valves 274a, 274b, and 274c in the third refrigerant line 286, which are respectively connected to the indoor units 260a, 26Od, and 26Of operating in the cooling mode, and to the auxiliary units 250a, 250b, and 250c operating in the cooling mode, are opened. On the other hand, the first refrigerant control valves 27a, 272b, and 272c in the first refrigerant line 282 are

closed. As a result, the refrigerant emerging from the indoor units 260a, 260c, and 26Oe and air handling units 201a, 201b, and 201c operating in the heating mode flows to the indoor units 260b, 26Od, and 26Of and auxiliary units 250a, 250b, and 250c operating in the cooling mode, via the second refrigerant line 284. The refrigerant introduced into the auxiliary units 250a, 250b, and 250c is expanded while passing through the second expansion valves 254a, 254b, and 254ς and is then evaporated in the second heat exchangers 252a, 252b, and 252c. On the other hand, the refrigerant introduced into the indoor units 260a, 26Od, and 26Of is expanded while passing through the indoor expansion valves 264b, 264d, and 264f, and is then evaporated in the indoor heat exchangers 262b, 262d, and 262f. Thus, the auxiliary units 250a, 250b, and 250c and indoor units 260b, 26Od, and 26Of perform a cooling operation.

[146] The refrigerant emerging from the auxiliary units 250a, 250b, and 250c and indoor units 260b, 26Od, and 26Of is glided to the outdoor units 240a, 240b, and 240c via the third refrigerant line 286 because the second refrigerant control valves 274a, 274b, and 274c are in an opened state. In detail, the refrigerant is introduced into the compressors 241a, 241b, and 241c via the accumulators 244a, 244b, and 244c.

[147] Now, the case, in which the air conditioning system operates in the cooling- predominant mode, will be described.

[148] When the air conditioning system operates in the cooling-predominant mode, the controller controls the switching operations of the four-way valves 243a, 243b, and 243c of the outdoor units 240a, 240b, and 240c to establish a flow path allowing the refrigerant discharged from the compressors 241a, 241b, and 241c to flow through the first and second refrigerant lines 282 and 284. That is, the refrigerant discharged from the compressors 241a, 241b, and 241c is branched at the outlets of the compressors 241a, 241b, and 241c such that a part of the refrigerant flows to the second refrigerant line 284 via the outdoor heat exchangers 242a, 242b, and 242c, and the remaining refrigerant flows to the first refrigerant line 282.

[149] The refrigerant, which is introduced into the outdoor heat exchangers 242a, 242b, and 242ς is condensed while passing through the outdoor heat exchangers 242a, 242b, and 242c. The condensed refrigerant is guided to the refrigerant distribution units 270a, 270b, and 270c via the seoond refrigerant line 284 after passing through the outdoor expansion valves 246a, 246b, and 246c. In this case, the outdoor expansion valves 246a, 246b, and 246c are in a fully-opened state.

[150] The controller controls the refrigerant distribution units 270a, 270b, and 270c to open those of the second refrigerant control valves 274a, 274b, and 274c connected to

those of the indoor units 260a, 260b, 260ς 26Od, 26Oe, and 26Of, air handling units 201a, 201b, and 201c, and auxiliary units 250a, 250b, and 250c, which operate in the cooling mode, and to close the first refrigerant control valves 272a, 272b, and 272c. For example, where it is determined to operate the air handling unit and one indoor unit of each assembly, namely, the air handling units 201a, 201b, and 201c, and indoor units 260a, 260ς and 26Oe, in a cooling mode, as shown in FIG. 7, the first refrigerant control valves 272a, 272b, and 272c arranged in the first refrigerant line 282, and respectively connected to the air handling units 201a, 201b, and 201c, and indoor units 260a, 260c, and 26Oe are closed. On the other hand, the second refrigerant control valves 272a, 272b, and 272c arranged in the third refrigerant line 286, and respectively connected to the air handling units 201a, 201b, and 20 Ic, and indoor units 260a, 260c, and 26Oe are opened.

[151] In this case, the refrigerant flowing through the second refrigerant line 284 flows toward the air handling units 201a, 201b, and 20 lς and indoor units 260a, 260c, and 26Oe operating in the cooling mode.

[152] The refrigerant flowing toward the air handling units 201a, 201b is guided to the first expansion valves 217a, 217b, and 217c of the air handling units 201a, 201b, and 201c via the second refrigerant line 284. In this case, the first expansion valves 217a, 217b, and 217c are controlled to expand the refrigerant. The expanded refrigerant enters the first heat exchangers 216a, 216b, and 216ς and absorbs heat around the first heat exchangers 216a, 216b, and 216c while passing through the first heat exchangers 216a, 216b, and 216c. Thus, the first heat exchangers 216a, 216b, and 216c function as a cooling source. The evaporated refrigerant flows toward the third refrigerant line 286 because the first refrigerant control valves 272a, 272b, and 272c are in a closed state, and the seoond refrigerant control valves 274a, 274b, and 274c arranged in the third refrigerant line 286 are in an opened state. Thus, the refrigerant is guided to the outdoor units 240a, 240b, and 240c via the third refrigerant line 286.

[153] Similarly, the refrigerant flowing toward the indoor units 260a, 260ς and 26Oe is guided to the indoor expansion valves 264a, 264c, and 264e of the indoor units 260a, 260c, and 26Oe via the seoond refrigerant line 284. In this case, the indoor expansion valves 264a, 264c, and 264e are controlled to expand the refrigerant. The expanded refrigerant enters the indoor heat exchangers 262a, 262b, and 262ς and absorbs heat around the indoor heat exchangers 262a, 262b, and 262c while passing through the indoor heat exchangers 262a, 262b, and 262c. Thus, the indoor heat exchangers 262a, 262b, and 262c function as a cooling source. The evaporated refrigerant flows toward

the third refrigerant line 286 because the second refrigerant control valves 274a, 274b, and 274c arranged in the third refrigerant line 286 are in an opened state. Thus, the refrigerant is glided to the outdoor units 240a, 240b, and 240c via the third refrigerant line 286.

[154] The refrigerant glided to the outdoor units 240a, 240b, and 240c is introduced into the compressors 241a, 241b, and 241c after passing through the accumulators 244a, 244b, and 244c, so that the refrigerant is compressed.

[155] On the other hand, the refrigerant flowing through the first refrigerant line 282 is guided to the refrigerant distribution units 270a, 270b, and 270c. In this case, the controller controls the refrigerant distribution units 270a, 270b, and 270c to open those of the first refrigerant control valves 272a, 272b, and 272ς which correspond to those of the rooms selected to be heated by the user, in order to enable the refrigerant to flow to the selected rooms.

[156] As described above, the auxiliary units 250a, 250b, and 250c operate in a reverse manner to the air handling units 201a, 201b, and 201c, in order to recover energy wasted through exhaust air discharged from the air handling units 201a, 201b, and 201c. When the air handling units 201a, 201b, and 201c operate in the cooling mode, as shown in FIG. 7, accordingly, the auxiliary units 250a, 250b, and 250c should operate in the heating mode. In this case, accordingly, the controller controls the refrigerant distribution units 270a, 270b, and 270c to appropriately open or close the first refrigerant control valves 272a, 272b, and 272c and second refrigerant control valves 274a, 274b, and 274c, in order to enable the auxiliary units 250a, 250b, and 250c to perform a heating operation.

[157] When the auxiliary unit and one indoor unit of each assembly, namely, the auxiliary units 250a, 250b, and 250c and indoor units 260b, 26Od, and 26Of, operate in the heating mode, as shown in FIG. 7, the associated first refrigerant control valves 272a, 272b, and 272c are opened. As a result, the refrigerant passes through the second heat exchangers 252a, 252b, and 252c of the auxiliary units 250a, 250b, and 250c and the indoor heat exchangers 262b, 262d, and 262f of the indoor units 260b, 26Od, and 26Of via the first refrigerant line 282, so that the refrigerant is condensed. Thus, each of the auxiliary units 250a, 250b, and 250c and indoor units 260b, 26Od, and 26Of performs a heating operation. Of course, in this case, the second refrigerant control valves 274a, 274b, and 274c should be closed in order to prevent the refrigerant from flowing badcwardly through the third refrigerant line 286.

[158] In this case, it is preferred that the second expansion valves 254a, 254b, and 254c

and indoor expansion valves 264b, 264d, and 264f, which are connected to the second heat exchangers 252a, 252b, and 252c and indoor heat exchangers 262b, 262d, and 262f, and comprise EEVs, respectively, be fully opened, as described above.

[159] Thus, the refrigerant emerging from the auxiliary units 250a, 250b, and 250c and indoor units 260b, 26Od, and 26Of operating in the heating mode flows through the second refrigerant line 284. In this case, the refrigerant is introduced into the indoor units 260a, 260ς and 26Oe and air handling units 201a, 201b, and 201c operating in the cooling mode, and is evaporated. Thus, each of the indoor units 260a, 260c, and 26Oe and air handling units 201a, 201b, and 201c performs a cooling operation. The refrigerant is subsequently returned to the outdoor units 240a, 240b, and 240c via the third refrigerant line 286.

[160] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Industrial Applicability

[161] The present invention provides an air conditioning system capable of recovering energy wasted through exhaust gas discharged from air handling units. The present invention can be applied to the manufacture and installation of various air conditioning systems.