Background Art Typically, cooling devices or room coolers are used in summer season, while heating devices or hot air heaters are used in winter season.

In recent years, an integrated system, capable of selectively functioning as a room cooler or a hot air heater when necessary, has been proposed and effectively used. Such an integrated system is so-called a heating and cooling system.

In typical heating and cooling systems, refrigerant is processed through four successive processes: compression, condensation, expansion and evaporation.

During a heating or cooling operation of such a system, the refrigerant is compressed at the compression process, thus becoming a pressurized gas refrigerant having a temperature of about 55°C. The gas refrigerant from the compression process is, thereafter, condensed at the condensation process, thus becoming liquid refrigerant having latent heat of about 20°C prior to flowing into an

expansion valve. Such latent heat undesirably reduces the thermal efficiency of the heating and cooling system.

In an effort to improve the thermal efficiency of the heating and cooling system during a heating operation, a conventional electric heater may be used along with the system. When using such an electric heater along with the system, the thermal efficiency of the system may be somewhat improved. However, this forces a user to pay additional money for the electric heater and increases consumption of electric power due to the use of such a heater. In addition, the heating and cooling system and the electric heater have to be separately turned on and off by a user and this is inconvenient to the user.

Another problem experienced in the typical heating and cooling systems resides in that the systems fail to accomplish the desired thermal efficiency and so the systems have to be operated for a lengthy period of time so as to heat or cool the room air to a desired temperature. This wastes electric power.

Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above probiems occurring in the prior art, and an object of the present invention is to provide a heating and cooling system, which is designed to selectively heat or cool room air to a desired temperature and to allow refrigerant during a cooling operation and refrigerant during a heating operation to respectively flow in different expansion valves, thus improving the thermal efficiency during such a heating or cooling operation.

In order to accomplish the above object, the present

invention provides a heating and cooling system, comprising: indoor and outdoor units connected to each other with a compressor being mounted on a refrigerant line extending between the two units; a first expansion valve being positioned on the line in a way such that refrigerant flows in the order of the outdoor unit, the first expansion valve, the indoor unit, the first expansion valve, the compressor, and the outdoor unit during a cooling operation; and a second expansion valve being positioned on the line in a way such that the refrigerant flows in the order of the outdoor unit, the second expansion valve, the compressor, the indoor unit, the second expansion valve, and the outdoor unit during a heating operation.

Each of the first and second expansion valves comprises a capillary tube encased by a case having a predetermined size, the capillary tubes of the first and second expansion valves having different diameters.

During a cooling operation, liquid refrigerant from the outdoor unit passes through the capillary tube of the first expansion valve prior to reaching the indoor unit, and passes through the case of the first expansion valve prior to returning to the outdoor unit.

During a heating operation, gas refrigerant from the outdoor unit passes through the case of the second expansion valve prior to reaching the indoor unit, and passes through the capillary tube of the second expansion valve prior to returning to the outdoor unit.

In the present invention, the diameter of the capillary tube of the first expansion valve is smaller than that of the capillary tube of said second expansion valve.

Brief Description of the Drawings The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a circuit diagram of a heating and cooling system in accordance with the preferred embodiment of the present invention; Fig. 2 is a circuit diagram of a cooling part included in the above system; Fig. 3 is a sectional view showing the construction of a first expansion valve included in the cooling part of Fig. 2; Fig. 4 is a circuit diagram of a heating part included in the above system; and Fig. 5 is a sectional view showing the construction of a second expansion valve included in the heating part of Fig. 4.

Best Mode for Carrying Out the Invention Fig. 1 is a circuit diagram of a heating and cooling system in accordance with the preferred embodiment of this invention. Fig. 2 is a circuit diagram of a cooling part included in the above system. Fig. 3 is a sectional view showing the construction of a first expansion valve included in the cooling part of Fig. 2. Fig. 4 is a circuit diagram of a heating part included in the above system. Fig. 5 is a sectional view showing the construction of a second expansion valve included in the heating part of Fig. 4. As shown in the drawings, the system of this invention comprises two units: outdoor and

indoor units 10 and 30. The above system also has a compressor 40 provided on a refrigerant line extending between the two units 10 and 30. In order to allow the system to selectively heat or cool room air as desired, the system is divided into two parts: a cooling part and a heating part.

As shown in Figs. 1 and 2, the cooling part comprises a first expansion valve 21, of which one end is connected to the outdoor unit 10 through a first supply pipe 11.

The other end of the first expansion valve 21 is connected to the indoor unit 30 through a second supply pipe 23.

A valve 23a is mounted on the second supply pipe 23. The above first expansion valve 20 comprises a first capillary tube 22 encased by a first case 21 as shown in Fig. 3.

In order to guide the processed refrigerant or gas refrigerant from the indoor unit 30 to the outdoor unit 10 during such a cooling operation, a first return pipe 31 extends from the indoor unit 30 to the case 21 of the first expansion valve 20. In the above cooling part, the compressor 40 is connected to the case 21 of the first expansion valve 20 through a second return pipe 32. The above compressor 40 has two pressure gauges 41 and 42 at its inlet and outlet sides, respectively.

The compressor 40 is also connected to the outdoor unit 10 through a third return pipe 43. Said return pipe 43 has a valve 43a.

On the other hand, the heating part comprises a third supply pipe 12. The above third supply pipe 12, provided with a valve 12a, extends from the outdoor unit 10 to a second expansion valve 24. The second expansion valve 24 is also connected to the compressor 40 through a fourth supply pipe 27. The above second expansion valve 24 comprises a second capillary tube 26 encased by a second

case 25 as shown in Fig. 5.

A fifth supply pipe 44, provided with a valve 44a, is branched from the third return pipe 43 and extends to the indoor unit 30. A fifth return pipe 33, provided with a valve 33a, extends from the indoor unit 30 to the case 25 of the second expansion valve 24. The above fifth return pipe 33 is also jointed to the second supply pipe 23. A sixth return pipe 13 extends from the case 25 of the second expansion valve 24 to the outdoor unit 10. The sixth return pipe 13 is also jointed to the first supply pipe 11.

The operational effect of the above heating and cooling system will be described hereinbelow.

In a cooling operation, the above system is operated as follows. As shown in Fig. 2, low temperature liquid refrigerant from the outdoor unit 10 passes through the first supply pipe 11 prior to being introduced into the capillary tube 22 of the first expansion valve 20. The refrigerant is, thereafter, applied to the indoor unit 30 through the second supply pipe 23, thus cooling room air.

After being processed at the indoor unit 30, the refrigerant becomes gas refrigerant.

Thereafter, the gas refrigerant returns from the indoor unit 30 to the outdoor unit 10 as follows. That is, the gas refrigerant flows from the indoor unit 30 into the case 21 of the first expansion valve 20 through the first return pipe 31, thus being preheated in the case 21.

The preheated gas refrigerant is, thereafter, introduced into the compressor 40 through the second return pipe 32.

In the above compressor 40, the gas refrigerant is pressurized and cooled prior to being introduced into the condenser or the outdoor unit 10 through the third return pipe 43. The outdoor unit 10 condenses the gas

refrigerant, thus providing low temperature liquid refrigerant used in a continued cycle. The system thus repeats the cooling operation.

In a heating operation, the above system is operated as shown in Fig. 4. That is, gas refrigerant from the outdoor unit 10 passes through the third supply pipe 12 prior to being introduced into the case 25 of the second expansion valve 24 where the refrigerant is preheated.

The preheated gas refrigerant is, thereafter, applied to the compressor 40 through the fourth supply pipe 27, thus being pressurized. The pressurized gas refrigerant, thereafter, flows to the indoor unit 30 where the refrigerant heats room air while becoming liquid refrigerant.

After heating the room air, the liquid refrigerant returns from the indoor unit 30 to the outdoor unit 10 as follows. That is, the liquid refrigerant flows from the indoor unit 30 to the capillary tube 26 of the second expansion valve 24 through the fourth return pipe 13. The refrigerant is, thereafter, introduced into the outdoor unit 10 through the fifth return pipe 33. At the outdoor unit 10, the liquid refrigerant is evaporated, thus becoming gas refrigerant which is used in a continued cycle. The above cycle is repeated during a cooling operation of the system.

During a cooling operation of the system, the valves, provided on the refrigerant pipes of the heating part, are closed. On the other hand, the valves, provided on the refrigerant pipes of the cooling part, are closed during a heating operation of the system.

In the above system, liquid refrigerant, flowing in the capillary tube 22 of the first expansion valve 20 during a cooling operation has a low temperature and a low

pressure, while liquid refrigerant, flowing in the capillary tube 26 of the second expansion valve 24 during a heating operation, has a high pressure. Therefore, the system is designed in that the diameter of the capillary tube 22 of the first expansion valve 20 is smaller than that of the capillary tube 26 of the second expansion valve 24.

In each of the first and second expansion valves 20 and 24, the capillary tube 22,26 is encased by the case 21,25, and so gas refrigerant passes through the case 21, 25 while being preheated during a cooling or heating operation. This effectively reduces energy loss during the operation of the system.

The pressure gauges 41 and 42, provided at the inlet and outlet sides of the compressor 40, appropriately regulate the inlet and outlet pressures of refrigerant passing through the compressor 40 during the operation of the system.

Industrial Applicability As described above, the present invention provides a heating and cooling system. The system selectively heats or cools room air to a desired temperature and allows refrigerant during a cooling operation and refrigerant during a heating operation to respectively flow in different expansion valves. The system thus improves the thermal efficiency during such a heating or cooling operation.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.