BACKGROUND ART As shown in Fig. 3, in a refrigeration cycle using circulation of a refrigerant, the refrigerant moves in a closed circuit comprised of a compressor 211, a condenser 211, an expander 221 and an evaporator 233.

A low-pressure gaseous refrigerant is compressed into a high-pressure gaseous refrigerant by the compressor 211, and then the high-pressure gaseous refrigerant moves to the condenser 213 and is condensed into a liquid refrigerant, radiating heat to the outside. The condensed refrigerant is expanded by the expander 221, lowering the pressure thereof, and moves to the evaporator 233. The expanded refrigerant is evaporated by the evaporator 233, absorbing heat from the outside, and returns to the compressor 211.

In the refrigeration cycle, an endothermic operation of an evaporator is mostly used in a cooling system.

Further, an exothermic operation of a compressor is mostly used in a heating system, and that is particularly called a heat pump.

One refrigeration cycle can be used both as the

cooling system and the heating system, that is, the refrigerant can be selectively circulated in a forward direction or a reverse direction in one refrigeration cycle, and so the operations of the evaporator and the condenser can be mutually exchanged, thereby providing a heating and cooling system.

However, in the conventional refrigeration cycle, if the temperature around the condenser is excessively high, the refrigerant is incompletely cooled in the condenser and moves to the evaporator via the expander, so that the refrigerant cannot sufficiently absorb heat and incompletely evaporated in the evaporator, thereby lowering the evaporation efficiency. Further, if the temperature around the evaporator is excessively low, the refrigerant may be frosted on the evaporator because a temperature difference between the outside around the evaporator and the refrigerant is wide, and is incompletely evaporated in the evaporator and then moves to the compressor in a low dryness state, so that cavitation is created in the compressor when the refrigerant is wetly compressed in the compressor, thereby shortening a compressor's life. Thus, the refrigeration cycle separately requires a heater or a burner for improving the evaporation efficiency of the refrigerant.

DISCLOSURE OF INVENTION Accordingly, the present invention has been made keeping in mind the above-described shortcoming and user's need, and an object of the present invention is to provide a refrigeration cycle which can increase the dryness of a refrigerant flowing into a compressor, and sufficiently cool a refrigerant from a condenser, and prevent the refrigerant from being frosted on an evaporator.

This and other objects of the present invention may be accomplished by the provision of a refrigeration cycle comprising a compressor, a condenser, an expander and an evaporator, through which a refrigerant is circulated, further comprising a first auxiliary heat exchanger exchanging heat between the refrigerants from the expander and the evaporator; and a heat exchanger exchanging heat between the refrigerant flowing from the first auxiliary heat exchanger into the compressor and the refrigerant flowing out of the condenser.

Preferably, the expander is comprised of at least one capillary tube, and a. capillary heat exchanger in which heat is exchanged between the refrigerant inside the capillary tube and the refrigerant flowing from the first heat exchanger into the heat exchanger.

Preferably, the refrigeration cycle further comprises a second auxiliary heat exchanger exchanging heat between

the refrigerant flowing from the heat exchanger into the compressor and the refrigerant flowing out of the compressor.

BRIEF DESCRIPTION OF DRAWINGS The present invention will be better understood and its various objects and advantages will be more fully appreciated from the following description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic diagram of a refrigeration cycle according to a first embodiment of the present invention; Fig. 2 is a schematic diagram of a refrigeration cycle according to a second embodiment of the present invention; and Fig. 3 is a schematic diagram of a conventional refrigeration cycle.

MODES FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

As shown in Fig. 1, a refrigeration cycle according to a first embodiment of the present invention comprises a compressor 11 compressing a refrigerant, a condenser 13 condensing the compressed refrigerant, an evaporator 33 evaporating the refrigerant, and an expander 21 decompression-expanding the refrigerant flowing from the

condenser 13 into the evaporator 33, a first auxiliary heat exchanger 27 exchanging heat between the refrigerants from the expander 21 and the evaporator 33, and a heat exchanger 15 exchanging heat between the refrigerants flowing from the first auxiliary heat exchanger 27 into the compressor 11 and the refrigerant from the condenser 13, thereby forming a closed circuit through which the refrigerant is sequentially circulated.

The expander 21 is comprised of a capillary tube.

Further, the expander 25 may include an expanding valve.

The first auxiliary heat exchanger 27 is comprised of a casing 29 of an airtight container, a heat conductive coil pipe 31 accommodated in the casing 29 and passing the refrigerant from the expander 21 therethrough, and an inlet 29a and an outlet 29b for inflow and outflow of the refrigerant from the evaporator 33.

The heat exchanger 15 is comprised of a casing 17 of an airtight container, a heat conductive coil pipe 19 accommodated in the casing 17 and passing the refrigerant from the condenser 13 therethrough, and an inlet 17a and an outlet 17b for inflow and outflow of the refrigerant from the first auxiliary heat exchanger 27 into the compressor 11.

There is further provided a second auxiliary heat exchanger 43 for exchanging heat between the refrigerants

flowing from the heat exchanger 15 into the compressor 11 and the refrigerant from the compressor 11. Further, there is provided a three-way valve 45 for controlling the refrigerant to flow from the heat exchanger 15 into the compressor 11 via the second auxiliary heat exchanger 43, depending upon the temperature of the refrigerant flowing into the compressor 11, detected by a temperature sensor 41 Further, there are provided a by-pass pipe 35 through which the refrigerant flowing from the heat exchanger 15 into the expander 21 partially joins the refrigerant flowing into the compressor 11, a by-pass valve 37 controlling the by- pass of the refrigerant depending upon the temperature of the refrigerant detected by the temperature sensor 41, and a by-pass expander 39 decompression-expanding the refrigerant flowing in the by-pass pipe 35. Herein, even if the second auxiliary heat exchanger 43, the three-way valve 45, the by-pass pipe 35, the by-pass valve 37, the by-pass expander 39 are not provided, the object of the present invention can be accomplished.

With this configuration, the refrigerant compressed by the compressor 11 is condensed by the condenser 13, and flows into the heat exchanger 15. That is, the refrigerant from the condenser 13 passes through the coil pipe 19 of the heat exchanger 15, and the refrigerant from the first auxiliary heat exchanger 27 flows into the inlet 17a of the

casing 17 and flows out of the outlet 17b. Thus, the refrigerant from the condenser 13 is first-cooled by heat exchange with the refrigerant from the first auxiliary heat exchanger 27, that is, by radiating heat to the refrigerant from the first heat exchanger 27. The refrigerant first- cooled in the heat exchanger 15 is second-cooled by being decompression-expanded in the expander 21, and flows into the first auxiliary heat exchanger 27. The refrigerant flowing from the expander 21 flows into the first auxiliary heat exchanger 27 through the coil pipe 31 thereof and into the evaporator 33. The refrigerant flowing from the evaporator 33 flows into the first auxiliary heat exchanger 27 through the inlet 29a and the outlet 29b, thereby exchanging heat between the refrigerants from the expander 21 and the evaporator 33, and then into the heat exchanger 15. That is, the refrigerant from the expander 21 is third- cooled by radiating heat to the refrigerant from the evaporator 33. The refrigerant from the evaporator 33 is first-heated in the first auxiliary heat exchanger 27 by heat exchange with the refrigerant from the expander 21, and flows into the heat exchanger 15. The refrigerant flowing from the first auxiliary heat exchanger 27 into the heat exchanger 15 exchanges heat with the refrigerant from the condenser 13 in the heat exchanger 15, that is, the refrigerant flowing from the first auxiliary exchanger 27

is second-heated in the heat exchanger 15 by absorbing heat from the refrigerant from the condenser 13, and flows to the compressor 11. Further, if the overheated refrigerant flows into the compressor 11, the refrigerant flowing from the heat exchanger 15 into the expander 21 is partially by- passed by the by-pass pipe 35, and decompression-expanded by the by-pass expander 39, and joins the refrigerant flowing into the compressor 11, thereby regulating the temperature of the refrigerant flowing to the compressor 11 within a predetermined temperature range. Further, if the overcooled refrigerant flows into the compressor 11, the three-way valve 45 controls the refrigerant flowing from the heat exchanger 15 into the compressor 11 to flow through the second auxiliary heat exchanger 43 depending upon the temperature detected by the temperature sensor 41, so that the refrigerant flowing into the compressor 11 is heated by heat exchange with the refrigerant flowing out the compressor 11 in the second auxiliary heat exchanger 43, thereby regulating the temperature of the refrigerant flowing to the compressor 11 within. a predetermined temperature range.

Thus, the refrigerant flowing from the condenser 13 flows into the evaporator 33 after being cooled in the heat exchanger 15 and then being sufficiently cooled via the expander 21. Therefore, if the temperature around the

evaporator 33 is excessively low, a temperature difference between the outside around the evaporator 33 and the refrigerant is narrow, thereby preventing the refrigerant from being frosted on the evaporator 33. Oppositely, if the temperature around the evaporator 33 is high, the refrigerant sufficiently absorbs heat from the outside around the evaporator 33, thereby cooling the outside around the evaporator 33.

The refrigerant flowing from the evaporator 33 into the compressor 11 has the high dryness by being heated by the first auxiliary heat exchanger 27 and the heat exchanger 15, thereby prolong a compressor's life by preventing the refrigerant from being wetly compressed in the compressor 11. Further, if the overheated refrigerant flows into the compressor 11, the refrigerant flowing from the heat exchanger 15 into the expander 21 is partially by- passed by the by-pass pipe 35, and decompression-expanded by the by-pass expander 39, and joins the refrigerant flowing into the compressor 11, so that the temperature of the refrigerant flowing to the compressor 11 is regulated within the predetermined temperature range, thereby preventing the compressor 11 from being overloaded and increasing the efficiency thereof. Further, if the overcooled refrigerant flows into the compressor 11, the refrigerant flowing into the compressor 11 is heated by

heat exchange with the refrigerant flowing out the compressor 11 in the second auxiliary heat exchanger 43, so that the temperature of the refrigerant flowing to the compressor 11 is regulated within the predetermined temperature range, thereby preventing the compressor 11 from being overloaded.

Referring to Fig. 2, a refrigeration cycle according to a second embodiment of the present invention, in an expander 121, heat is exchanged between the refrigerant flowing from a heat exchanger 115 into a first auxiliary heat exchanger 127 and the refrigerant flowing from the first auxiliary heat exchanger 127 into the heat exchanger 115.

The expander 121 is comprised of a casing 125 of an airtight container, a plurality of capillary tubes 123 accommodated in the casing 125 and passing the refrigerant from the heat exchanger 115 therethrough, an inlet 125a and an outlet 125b for inflow and outflow of the refrigerant from the first heat auxiliary exchanger 127, and a capillary heat exchanger (not shown) in which heat is exchanged between the refrigerant inside the capillary tubes 123 and the refrigerant flowing from the first auxiliary heat exchanger 127 into the heat exchanger 115.

Thus, the refrigerant flowing from the heat exchanger 115 into the first auxiliary heat exchanger 127 flows into the

capillary tubes 123 and exchanges heat with the refrigerant flowing from the first auxiliary heat exchanger into the heat exchanger 115, by being decompression-expanded by the capillary tubes 123. That is, the refrigerant decompression-expanded in the capillary tubes 123 is cooled by radiating heat thereof to the refrigerant flowing into the heat exchanger 115.

With this configuration, the refrigerant flowing from the heat exchanger 115 into the first auxiliary heat exchanger 127 is decompression-expanded in the expander 121, and simultaneously cooled by heat exchange with the refrigerant flowing from the first heat exchanger 127 into the heat exchanger 115, so that the refrigerant flowing from the expander 121 into the first auxiliary heat exchanger 127 is sufficiently cooled compared with the refrigerant flowing from the expander 21 into the first auxiliary heat exchanger 27 according to the first embodiment. Thus, the refrigerant flowing from the expander 121 into an evaporator 133 via the first auxiliary heat exchanger 127 is sufficiently cooled compared with the refrigerant flowing into the evaporator 33 according to the first embodiment. Therefore, if the temperature around the evaporator 133 is excessively low, a temperature difference between the outside around the evaporator 133 and the refrigerant is narrow, thereby preventing the refrigerant

from being frosted on the evaporator 133. Oppositely, if the temperature around the evaporator 133 is high, the refrigerant sufficiently absorbs heat from the outside around the evaporator 133, thereby cooling the outside around the evaporator 133. Further, the refrigerant flowing from the first auxiliary heat exchanger 127 into the heat exchanger 115 is heated by heat exchange with the refrigerant flowing into the capillary tubes 123 of the expander 121, thereby improving the dryness of the refrigerant flowing into the heat exchanger 115. Further, if the overheated refrigerant flows into a compressor 111, the refrigerant flowing from the heat exchanger 115 into the expander 121 is partially by-passed by a by-pass pipe 135, and decompression-expanded by a by-pass expander 139, and joins the refrigerant flowing into the compressor 111, so that the temperature of the refrigerant flowing to the compressor 111 is regulated within a predetermined temperature range, thereby preventing the compressor 111 from being overloaded and increasing the efficiency thereof.

Further, if the overcooled refrigerant flows into the compressor 111, the refrigerant flowing into the compressor 111 is heated by heat exchange with the refrigerant flowing out the compressor 111 in a second auxiliary heat exchanger 143, so that the temperature of the refrigerant flowing to the compressor 111 is regulated within a predetermined

temperature range, thereby preventing the compressor 111 from being overloaded and decreasing in efficiency.

As described above, the refrigeration cycle according to the present invention sufficiently cools a refrigerant flowing into an evaporator and increases the dryness of the refrigerant flowing into a compressor by exchanging heat between the refrigerants. Thus, the refrigerant evaporated in the evaporator can sufficiently absorb heat from the outside around the evaporator, thereby lowering the temperature of the outside around the evaporator. Further, if the temperature outside the evaporator is excessively low, the refrigerant is prevented from being frosted on the evaporator because a temperature difference between the outside around the evaporator and the refrigerant is narrow.

Further, because the refrigerant flowing into the compressor has the high dryness, the refrigerant is prevented from being wetly compressed in the compressor, thereby prolonging a compressor's life. Further, the temperature of the refrigerant flowing into the compressor is suitably regulated, thereby preventing the compressor from being overloaded and increasing the efficiency thereof.

In addition to the above configurations, an outlet may be positioned at the lower part of a heat exchanger, and an oil collection line may be provided for connecting the lower part of the heat exchanger with a compressor. Then, a

compression oil circulated together with a refrigerant may be gathered around the lower part of the heat exchanger, and directly supplied to the compressor.

Further, the refrigerating cycle according to the present invention can be applied to a cooling device, a heating device, a heating and cooling device, etc.

As described above, the present invention provides a refrigeration cycle which can increase the dryness of a refrigerant flowing into a compressor by heat exchange with the refrigerants and sufficiently cool the refrigerant from a condenser, thereby preventing refrigerant from being frosted on an evaporator.

Although the preferred embodiments of the present invention have been disclosed for illustrative purpose, 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.