Description

AIR CONDITIONER HAVING COOLING AND HEATING

FUNCTION

Technical Field

[1] The present invention relates to an air conditioner having cooling and heating functions (hereinafter, referred to as 'cooling and heating air conditioner'). More particularly, the present invention relates to a cooling and heating air conditioner capable of performing heating more stably, while preventing frost formation on coils of an outdoor unit even at subzero temperature in winter by using first and second heat exchangers and an auxiliary expansion valve. Background Art

[2] Hereinafter, a conventional cooling and heating air conditioner will be described.

[3] FIG. 1 schematically shows the conventional cooling and heating air conditioner.

[4] The conventional cooling and heating air conditioner comprises an indoor unit 1 for heating up the indoor air through heat exchange between the indoor air and high- temperature high-pressure coolant flowing in during heating, an outdoor unit 2 for emitting heat to the atmosphere through heat exchange between the outside air and the expanded coolant flowing in during heating, an outdoor unit coil 3, and a compressor 4 for compressing the coolant by high temperature and high pressure in an insulated state and supplying the compressed coolant to the indoor unit 1.

[5] When operating a heating mode, the high-temperature high-pressure coolant compressed by the compressor 4 is condensed to liquid in the indoor unit 1. The liquefied coolant is expanded by an expansion valve 5. The expanded coolant is evaporated in the outdoor unit 2 through the outdoor unit coil 3, and drawn back into the compressor 4.

[6] When the air conditioner is operated for heating, if the air flowing into the outdoor unit 2 has low temperature, the evaporation is not favorably performed due to the insufficient temperature difference between the air and the coolant at the outdoor unit coil 3. Occasionally, frost may form on the outdoor unit coil 3, deteriorating the function of the outdoor unit 2 as the heat exchanger.

[7] In order to remove the frost from the outdoor unit 3, generally, the air conditioner is operated in a frost removal mode, one of cooling modes, so that the liquid coolant of high temperature and high pressure flows into the outdoor unit 2. During this, however, since the indoor unit 1 serves as an evaporator, the heating cannot be performed any more.

[8] To solve this problem, use of an auxiliary heater has been tried in the frost removal

mode. However, this abruptly increases power consumption. Disclosure of Invention

Technical Problem

[9] The present invention has been made in view of the above-mentioned problems generally occurring in winter, that is, frost formation on the surface of an outdoor unit under subzero temperature and unstable heating operation caused by poor evaporation due to insufficient temperature difference between the low-temperature outside air and coolant. Therefore, it is an object of the present invention to provide a cooling and heating air conditioner capable of stably performing the heating cycle although subzero air flows in an evaporator from the outside in winter.

[10] It is another object of the present invention to provide a cooling and heating air conditioner capable of stably operating a heating cycle without causing frost formation even when the outside temperature drops to below zero in winter, by using first and second heat exchangers and an auxiliary expansion valve. Technical Solution

[11] According to an aspect of the present invention, there is provided a cooling and heating air conditioner having an indoor unit, an outdoor unit, a compressor, and an expansion valve, further comprising a thermometer for detecting temperature of the outdoor unit; an electronic control valve opened and closed according to the temperature detected by the electronic control valve; a first heat exchanger performing heat exchange between high-temperature high-pressure liquid coolant flowing in through the electronic control valve and low-temperature low-pressure coolant passed through an auxiliary expansion valve; a second heat exchanger mounted around the outdoor unit to heat the ambient air of the outdoor unit through heat exchange between the coolant flowing in through the first heat exchanger and the outside air; and the auxiliary expansion valve for decompressing the coolant passed through the second heat exchanger and supplying the decompressed coolant to the first heat exchanger.

Advantageous Effects

[12] According to the present invention, when coolant is not actively evaporated due to low temperature of the outside air, a thermometer installed at an entrance and an exit of an outdoor unit detects this through temperature difference between the entrance and the exit of the outdoor unit and generates a signal. According to the signal, an electronic control valve is opened so that the coolant can flow to a second heat exchanger. The temperature of the outside air being supplied to the outdoor unit is increased. Therefore, evaporation of the coolant is favorably performed. As a result, the air conditioner is able to work stably even in winter, constantly performing heating of the indoor space.

[13] In addition, formation of frost can be prevented although the outside temperature drops to below zero in winter, by using first and second heat exchangers and an auxiliary expansion valve. As a consequence, a heating cycle can be operated stably. Brief Description of the Drawings

[14] The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

[15] FIG. 1 is a schematic view of a conventional cooling and heating air conditioner;

[16] FIG. 2 is a schematic view of a cooling and heating air conditioner according to an embodiment of the present invention; and

[17] FIG. 3 is a flowchart illustrating the operation principle of the cooling and heating air conditioner according to the embodiment of the present invention. Best Mode for Carrying Out the Invention

[18] Hereinafter, a cooling and heating air conditioner and the operation process according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[19] FIG. 2 schematically shows a cooling and heating air conditioner according to an embodiment of the present invention.

[20] Referring to FIG. 2, the cooling and heating air conditioner having an expansion valve 5, an indoor unit 100, an outdoor unit 200, and a compressor 400, further comprises an electronic control valve 500 such as a solenoid valve, a first heat exchanger 510, a second heat exchanger 520, and an auxiliary expansion valve 530. The electronic control valve 500 is opened when the ambient temperature of the outdoor unit 200 drops to lower than a preset value, thereby controlling high- temperature high-pressure liquid coolant to flow into the first heat exchanger 510. The first heat exchanger 510 performs heat exchange between the high-temperature high- pressure liquid coolant flowing in through the electronic control valve 500 and low- temperature low-pressure coolant passed through the second heat exchanger 520 and the auxiliary expansion valve 530. The second heat exchanger 520 helps stable evaporation in the outdoor unit 200 during heating, and heats the ambient air of the outdoor unit 200 to prevent formation of frost on the outdoor unit coil 300. The auxiliary expansion valve 530 decompresses the coolant so that the liquid coolant passed through the second heat exchanger 520 can easily convert to gas coolant in the first heat exchanger 510. The air temperature outside the outdoor unit 200 is measured through the temperature difference between an entrance and an exit of the outdoor unit 200. A thermometer (not shown) is provided to detect the temperatures at the entrance and the exit of the outdoor unit 200.

[21]

[22] The operation of the cooling and heating air conditioner of FIG. 2 will be described with reference to FIG. 3 which is a flowchart illustrating the operation principle of the cooling and heating air conditioner according to the embodiment of the present invention.

[23] As shown in FIG. 3, temperatures at the entrance and the exit of the outdoor unit

200 are detected by the thermometer (not shown), so as to determine whether the temperature difference between the entrance and the exit is less than a preset value (S600).

[24] When the temperature difference is not less than the preset value, the electronic control valve 500 is not opened because it is determined that the outdoor unit 200 is normally working (S605). In this case, the liquid coolant is flowed into the outdoor unit 200 from the indoor unit 100, passing through the expansion valve 5, in the same manner as in a general air conditioner.

[25] On the contrary, when the temperature difference is less than the preset value, it is determined that the outdoor unit 200 is not performing the heat exchange with the outside air. Therefore, evaporation of the coolant is not favorably performed. Occasionally, removal of frost may be required. In this state, the electronic control valve 500 is opened (S610) so that part of the high-temperature high-pressure liquid coolant can flow into the first heat exchanger 510 (S620).

[26] The liquid coolant is flowed from the first heat exchanger 510 to the second heat exchanger 520 disposed in front of the outdoor unit 200 (S630). As the high- temperature coolant flows in the second heat exchanger 520, the outside air passing through the second heat exchanger 520 is heated up. When the heated outside air is inducted into the outdoor unit 200, the outdoor unit coil 300 can be protected from frost formation and the outdoor unit 200 can work stably.

[27] The coolant passed through the second heat exchanger 520 is in liquid form.

Therefore, before being supplied to the compressor 400, the liquid coolant needs to be converted to gas form by the auxiliary expansion valve 530 and the first heat exchanger 510.

[28] First, the liquid coolant is decompressed while passing through the auxiliary expansion valve 530 to be evaporated more easily (S640). The liquid coolant is then converted to gas coolant through heat exchange in the first heat exchanger 510 (S650).

[29] Next, the gas coolant is flowed into a return line 540 (S660) and united in the outdoor unit 200 to a main flow of coolant heading for the indoor unit 100 (S670).

[30] As described above, by being provided with the electronic control valve opened and closed based on the temperature difference between the entrance and the exit of the outdoor unit 200, the cooling and heating air conditioner according to the present

invention is capable of overcoming it when the outdoor unit 200 cannot favorably evaporate the coolant, by supplying high temperature coolant to the second heat exchanger and performing heat exchange between the high temperature coolant and the outside air so that the heated outside air is supplied to the outdoor unit 200, accordingly promoting the evaporation.

[31] While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Industrial Applicability

[32] A cooling and heating air conditioner according to the present invention can be applied to stably perform heating without generating frost formation on an outdoor unit coil even in cold winter.