Description

AIR CONDITIONING SYSTEM FOR COMMUNICATION EQUIPMENT AND METHOD OF PREVENTING THE SAME

FROM FREEZING

Technical Field

[1] The present invention relates to an air conditioning system for communication equipment and a method for controlling the same, and more particularly, to an air conditioning system for preventing components of the communication equipment from being damaged with cold by stopping an operation of an outdoor unit or operating a heat coil if refrigerant temperature, outdoor temperature, or both of them is lower than a predetermined temperature.

[2]

Background Art

[3] As is generally known in the art, an airconditioner employs evaporation heat which a refrigerant absorbs from surroundings when it evaporates. Typically, as refrigerant, liquids such as, ammonia, Freon, azeotropic refrigerant mixture, and chloromethyl which is easily evaporated at relatively low-temperatures.

[4] Typically, the air conditioner performs following processes: High-pressure vaporized refrigerant compressed by a compressor is changed into high-pressure refrigerant liquefied by heat exchange with outdoor air at a condenser; The high-pressure liquefied refrigerant is changed into low-pressure vaporized refrigerant by an expansion value and a capillary; and The low-pressure vaporized refrigerant flowed into an evaporator is evaporated by heat exchange with indoor air and the evaporated refrigerant is flowed back into the compressor. The refrigerant flowed into the compressor repeatedly circulates by the above processes. Air cooled by evaporation heat of the refrigerant occurred at the evaporator is blown into a predetermined space or objects to be cooled.

[5] As described above, a conventional air conditioner can cool objects by using characteristics of refrigerant to which a phase change, e.g.,condensation and evaporation easily occurs.

[6] In the meanwhile, there are many kinds of wire or wireless communication equipment in the base communication station or communication vehicles. Typically, heat resulted from the operation of the communication equipment may cause malfunction by breakdown of components in communication equipment or a contact error between two nodes in communication equipment. For this reason, it is necessary to cool the communication equipment all year round to minimize malfuction if the communication equipment due to heat generation therein.

[7] There is a problem that the conventional air conditioner for communication equipment does not appropriately use outdoor air or indoor air to cool the communication equipment according to surrounding temperature of the communication equipment. Also, there is another problem that since the conventional air conditioner is continueously operated by external power source, the power consumption of the conventional air conditioner is very high and the cooling efficiency of itself is very low.

[8] In order to solve the problem described above, Applicant invented an air conditioning system for communication equipment and a method for controlling the air conditioning system being able to reduce power consumption by operating selectively a outdoor unit and filed an application (Korea application number 10-2005-0014790) regarding the same. However, the application has a problem that if refrigerant temperature is lower than a predetermined temperatureon condition that the outdoor unit is operated for a long time or outdoor temperature is low below zero, components of the air conditioning system can be frozen. Especially, the refrigerant can be frozen. The frozen refrigerant may cause a pipe circulating the refrigerant to be broken. Then, the communication equipment can not be to be cooled.

[9]

Disclosure of Invention Technical Problem

[10] The present invention is directed to provide an air conditioning system for communication equipment to prevent components of the air conditioning system from being damaged with cold by stopping an operation of an outdoor unit or operating a heat coil if refrigerant temperature, outdoor temperature, or both of them is lower than a predetermined temperature.

[H]

Technical Solution

[12] In accordance with an aspect of the present invention, there is provided an air conditioning system for communication equipment including a first cooling unit, a second cooling unit and a third cooling unit.

[13] The first cooling unit includes an outdoor heat exchanger for exchanging heat with outdoor air, an indoor heat exchanger for exchanging heat with indoor air, a circulating pipe for circulating a first refrigerant, a circulation pump arranged on a predetermined position of the circulating pipe, a heat coil and a refrigerant temperature sensor arranged on an outdoor portion of the circulating pipe, a bypass pipe for circulating the first refrigerant to avoid passing through the outdoor heat exchanger, a first and a second bypass valves arranged on the circulating pipe and the bypass pipe, respectively, a first heat exchange tube arranged on the circulating pipe, a first brine heat

exchanger having the first heat exchange tube therein, an indoor temperature sensor for measuring indoor temperature of a base station, and an outdoor temperature sensor for measuring outdoor temperature of the base station.

[14] The second cooling unit includes a first compressor for changing a second refrigerant into a high-temperature and high-pressure second refrigerant, a first condenser for exchanging heat between outdoor air and the high-temperature and high-pressure second refrigerant, a first expansion valve for changing the second refrigerant supplied from the condenser into a low-temperature and low-pressure second refrigerant, and a first evaporator for exchanging heat with the first heat exchange tube wherein the first evaporator is arranged in the first brine heat exchanger installed between the first expansion valve and the first compressor.

[15] The third cooling unit includes a second compressor for changing a third refrigerant into a high-temperature and high-pressure third refrigerant; a second condenser for exchanging heat between outdoor air and the high-temperature and high-pressure third refrigerant; a second expansion valve for changing the third refrigerant supplied from the second condenser into a low-temperature and low-pressure third refrigerant; a second evaporator for exchanging heat with a second heat exchange tube wherein the second evaporator is arranged in a second brine heat exchanger installed between the second expansion valve and the second compressor. Also, the first cooling unit includes the second heat exchange tube arranged at one side of the first second heat exchange tube and the second brine heat exchanger having the second heat exchange tube and the second evaporator therein.

[16] In accordance with another aspect of the present invention, there is provided a method for preventing components of the air conditioning system from being broken with cold including a step of measuring outdoor temperature of the base station, a step of comparing the measured outdoor temperature with a first predetermined temperature, and carrying out a safety mode if the outdoor temperature is lower than the first predetermined temperature wherein the indoor heat exchanger is operated, the first and second valves is opened, and the circulation pump is operated on the safety mode.

Advantageous Effects

[17] An air conditioning system for communication equipment and a controlling method thereof according to the present invention can prevent components of the communication equipment from being damaged with cold by performing a safety mode in case that a refrigerant temperature is lower than a predetermined temperature by operating a cooling process for a long time or in case that refrigerant is easily frozen in a cold season such as winter when an indoor temperature is low. Since the safety mode

is regularly performed according to the refrigerant temperature and outdoor temperature, the present invention can prevent components of the air conditioning system from being damaged with cold regardless of surrounding temperature of the air conditioning system. [18]

Brief Description of the Drawings [19] Fig. 1 is a block diagram showing an air conditioning system for communication equipment in accordance with an embodiment of the present invention. [20] Fig. 2 is a block diagram showing a cooling operation using a first cooling unit in an air conditioning system for communication equipment in accordance with an embodiment of the present invention. [21] Fig. 3 is a block diagram showing a cooling operation using a first cooling unit and a second cooling unit in an air conditioning system for communication equipment in accordance with an embodiment of the present invention. [22] Fig. 4 is a block diagram showing a cooling operation using a first cooling unit to a third cooling unit in an air conditioning system for communication equipment in accordance with an embodiment of the present invention. [23] Figs. 5 and 6 are a flow chart illustrating a method for controlling an air conditioning system for communication equipment in accordance with an embodiment of the present invention. [24]

Best Mode for Carrying Out the Invention [25] Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to drawings provided according to the embodiment of the present invention. [26] Fig. 1 is a block diagram showing an air conditioning system for communication equipment in accordance with an embodiment of the present invention. [27] As shown, the air conditioning system for communication equipment in accordance with an embodiment of the present invention includes a first cooling unit 100 for directly cooling the communication equipment (not shown), and a second and a third cooling units 200 and 300 for indirectly cooling the communication equipment by cooling a first refrigerant of the first cooling unit 100. The first, second, and third cooling units 100, 200, 300 are arranged in an indoor unit 500 and an outdoor unit 600.

The indoor unit 500 is arranged with the communication equipment in a base station.

The outdoor unit 600 is arranged outside the base station. The indoor unit 500 includes a temperature sensor 510 for measuring indoor temperature and the outdoor unit 600 includes a temperature sensor 610 for measuring outdoor temperature.

[28] The first cooling unit 100 is first described hereinafter. An indoor heat exchanger 110 arranged in the indoor unit 500 carries out heat-exchanges between indoor air and the first refrigerant. A first temperature sensor 112 is arranged at the inlet of the indoor heat exchanger 110 and a second temperature sensor 114 is arranged at the outlet of the indoor heat exchanger 110. Indoor fans 116 are arranged at one side of the indoor heat exchanger 110 for transferring air cooled by heat exchange of the indoor heat exchanger 110. Outdoor heat exchangers 120 arranged in the outdoor unit 600 carry out heat-exchanges between outdoor air and the first refrigerant. The outdoor heat exchangers 120 are arranged in series or in parallel with reference to a position of outdoor fans 122. The indoor heat exchanger 110 and the outdoor heat exchangers 120 are connected by a circulating pipe 130 filled with the first refrigerant.

[29] As described above, the circulating pipe 130 is filled with the first refrigerant and the first refrigerant circulates through the circulating pipe 130. A circulation pump 132 compulsively circulates the first refrigerant through the circulating pipe 130. A pressure switch 134 measures pressure of the first refrigerant at the inlet of the indoor heat exchanger 110. A flow switch 136 measures the flow amount of the first refrigerant at the outlet of the indoor heat exchanger 110.

[30] A heat coil 180 and a refrigerant temperature sensor 190 are arranged on the portion of the circulating pipe 130 installed in the out door unit 600, and the heat coil 180 prevents the circulation pipe 130 from being broken by cold weather. Also, a first heat exchange tube 162 and a second heat exchanged tube 164 are arranged in series on the circulating pipe 130 wherein the first heat exchange tube 162 is for exchanging heat with a first evaporator 240 of the second cooling unit 200 and the second heat exchange tube 164 is for exchanging heat with a second evaporator 340 of the third cooling unit 300. The first brine heat exchanger 172 has the first heat exchange tube 162 therein and the second brine heat exchanger 174 has the second heat exchange tube 164 therein.

[31] A bypass pipe 140 is arranged for circulating the first refrigerant so that the first refrigerant avoid passing through the outdoor heat exchangers 120. A first bypass valve 152 is provided on the circulation pipe 130 and a second bypass valve 154 is provided on the bypass pipe 140. The first bypass valve 152 and the second bypass valve 154 can be opened at the same time or a selected one of the two valves 152 and 154 can be opened.

[32] The circulation pump 132 includes a pair of pumping units which are connected in parallel. Although one of the pair of pumping units is out of order, since the other can be normally operated, the circulation of the first refrigerant can be carried out. Thus, the cooling operation of the first cooling unit 100 can be regularly performed. Herein, as described above, the heat coil 180 is for preventing components of the air con-

ditioning system from being damaged with cold.

[33] The second cooling unit 200 includes a first compressor 210 for changing a second refrigerant into a high-temperature and high-pressure second refrigerant, a first condenser 220 for exchanging heat between outdoor air and the high-temperature and high-pressure second refrigerant, a first expansion valve 230 for changing the second refrigerant supplied from the first condenser 220 into a low-temperature and low- pressure second refrigerant, the first evaporator 240 arranged in the first brine heat exchanger 172 exchanges heat with the first heat exchange tube 162. Herein, the first evaporator 240 is arranged between the first expansion valve 230 and the first compressor 210.

[34] The third cooling unit 300 includes a second compressor 310 for changing a third refrigerant into a high-temperature and high-pressure third refrigerant, a second condenser 320 for exchanging heat between outdoor air and the high-temperature and high-pressure third refrigerant, a second expansion valve 330 for changing the third refrigerant supplied from the condenser into a low-temperature and low-pressure third refrigerant, and the second evaporator 340 arranged between the second expansion valve 330 and the second compressor 310. Herein, the second evaporator 340 is for exchanging heat with a second heat exchange tube 164 and is arranged in a second brine heat exchanger 174.

[35] The first refrigerant used in the first cooling unit 100 according to the present invention includes water. The second refrigerant used in the second cooling unit 200 and the third refrigerant used in the third cooling unit 300 includes one selected from the group consisting of ammonia, azeotropic refrigerant and chloride methyl, or combinations thereof.

[36] A cooling operation of the air conditioning system according to the present invention is described hereinafter. The cooling operation is controlled according to indoor temperature and the outdoor heat exchangers 120 is controlled according to outdoor temperature and the temperature of the first refrigerant. Herein, the first refrigerant may include brine.

[37] First, the indoor temperature of the base station is measured. If the measured indoor temperature is higher than a first reference temperature, e.g., 25 degrees, the first cooling unit 100 is operated (Referring to Fig. 2). This case is called a first cooling operation. In this case, if outdoor temperature is lower than that of the first refrigerant, the first bypass valve 152 is opened and the outdoor heat exchangers 120 is operated. Herein, the second bypass valve 154 is closed. If outdoor temperature is higher than that of the first refrigerant, the second bypass valve 154 is opened and the operation of the outdoor heat exchangers 120 is stopped. Herein the first bypass valve 152 is closed.

[38] If the measured indoor temperature is higher than a second reference temperature,

e.g., 26.5 degrees, the first cooling operation is not sufficient to cool the indoor space of the base station. In this case, both of the first cooling unit 100 and the second cooling unit 200 are operated. This case is called a second cooling operation (Referring to Fig. 3). While the first cooling unit 100 and the second cooling unit 200 are operated, heat exchange between the first refrigerant and the second refrigerant is performed in the first brine heat exchanger 172. The first refrigerant cooled by the above heat exchange is used to cool communication equipment in the base station.

[39] Also, if the measured indoor temperature is higher than a third reference temperature, e.g., 27.5 degrees, the second cooling operation is not sufficient to cool the indoor space of the base station. In this case, all of the first, second, and third cooling units 100, 200, 300 are operated. This case is called a third cooling operation. During the third cooling operation, heat exchange between the first refrigerant and the second refrigerant is first performed in the first brine heat exchanger 172 and heat exchange between the first refrigerant and the third refrigerant is secondly performed in the second brine heat exchanger 174. The first refrigerant cooled by the above heat exchanges is used to cool communication equipment in the base station.

[40] As described above, if outdoor temperature is lower than that of the first refrigerant during the second cooling operation and the third cooling operation, the first bypass valve 152 is opened and the outdoor heat exchangers 120 is operated. If outdoor temperature is higher than that of the first refrigerant during the second cooling operation and the third cooling operation, the second bypass valve 154 is opened and the operation of the outdoor heat exchangers 120 is stopped.

[41] Referring to Figs 1, 5 and 6, a method for preventing components of the air conditioning system from being broken with cold according to the present invention is described hereinafter.

[42] Referring to Figs 1 and 5, it is described a method for preventing the air conditioning system from being broken with cold in cold season such as winter when indoor temperature is low. First, the outdoor temperature of the base station 400 is measured with using the outdoor temperature sensor 610 (S 102) and the measured outdoor temperature is compared with a predetermined temperature T , e.g., 5 degrees (S 104). If the measured outdoor temperature is lower than the predetermined temperature T , the safety mode is performed. On the safety mode, the first and second valves 152 and 154 are opened, and the indoor heat exchanger 110 and the circulation pump 134 are operated on condition that the outdoor fan 122 is not operated. In that case, if the outdoor temperature T is higher than a second predetermined temperature T , e.g., 10 degrees, the safety mode is exited and a normal cooling operation is performed (Sl 10). As the outdoor fans 122 may be frequently turned on or off if the predetermined temperature T is a reference temperature, the air conditioning system may be out of

order. Thus, the second predetermined temperature T is a reference temperature to exit the safety mode. [43] The temperature of the first refrigerant T is measured with using the refrigerant flow temperature sensor 190 (Sl 12) and the measured temperature T is compared with a flow third predetermined temperature T , e.g., 2 degrees (Sl 14). Then, if the measured f3 temperature T is lower than the third predetermined temperature T , the heat coil 180 and the circulation pump 132 is operated (Sl 16). In this case, if the air conditioning system is on the normal cooling operation, the outdoor fans 122 is stopped to operate. If the temperature of the first refrigerant T is higher than a fourth pre- flow determined temperature T , e.g., 5 degrees (Sl 18), the operation of the heat coil 180 is stopped and the normal cooling operation is performed (S 120). [44] As shown in Fig. 6, if the measured outdoor temperature T is below a first setting out temperature, e.g., -25 degrees (S202), the safety mode is performed for 1 minute in 15 minutes cycle (S204). The safety mode is performed for 1 minute in 30 minutes cycle (S208) if the outdoor temperature T out is between the first setting temperature and a second setting temperature, e.g., -15 degrees (S206). The safety mode is performed for 1 minute in 45 minutes cycle (S212) if the outdoor temperature Tout is between the second setting temperature and a third setting temperature, e.g., -5 degrees (S210). The safety mode is performed for 1 minute in 60 minutes cycle (S216) if the outdoor temperature T out is between the third setting temperature and a fourth setting temperature, e.g., 5 degrees (S214). Also, if the outdoor temperature T is higher than out the fourth setting temperature, the safety mode is exited (S218).

[45] Although the safety mode is exemplified to be performed for one minute according to the above embodiment, a predetermined time for performing the safety mode can be various depending on a user's requirement. For instance, the predetermined time can be above 1 minute or below 1 minute.

[46] While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

[47]