Gas discharge device, refrigeration and air conditioning system, and method for discharging non-condensable gas

TECHNICAL FIELD

The present invention generally refers to the field of refrigeration and air conditioning, in particular to a device for discharging non-condensable gas in a refrigeration and air conditioning system, and a discharge method.

Background Art

A conventional refrigeration and air conditioning system comprises four major components, namely a compressor, a condenser, a throttling device and an evaporator, which are used to make a refrigerant flow in circulation therein, so as to complete a refrigeration cycle through refrigerant state changes. A substance to be cooled is guided through the evaporator, and undergoes heat exchange with low-temperature refrigerant in the evaporator, so as to achieve the objective of being cooled.

In the case of certain refrigeration and air conditioning systems which employ low-pressure refrigerants (e.g. 123, R1233zd, etc.), some low-pressure regions lower than atmospheric pressure will form inside the system during operation thereof. Air might penetrate into these low-pressure regions inside the refrigeration and air conditioning system, and non-condensable gases in the air will accumulate in the condenser, causing a drop in the heat exchange performance of the condenser, and thereby reducing the refrigerating capacity of the refrigeration and air conditioning system. At the same time, the condensing pressure in the system will consequently increase, and the condensing temperature will increase, in turn leading to an increase in compressor exhaust temperature, an increase in electricity consumption, and a drop in the energy efficiency of the refrigeration and air conditioning system. Furthermore, the excessively high exhaust temperature might lead to carbonization of compressor lubricating oil, influencing the lubrication effect; in serious cases, the compressor may seize up or the compressor electric machine may be burnt out.

Hence, in the case of refrigeration and air conditioning systems which employ low-pressure refrigerants, it is necessary to isolate and discharge, at irregular intervals, non-condensable gases which enter the system, to solve the abovementioned technical problem.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, the present invention provides a gas discharge device, for discharging non-condensable gas in a refrigeration and air conditioning system, wherein the gas discharge device comprises: an evaporative condenser, which is a shell-and-tube heat exchanger and comprises a shell side and a tube side; a gas mixture of the non-condensable gas and gaseous refrigerant passes through the shell side/tube side of the evaporative condenser, and undergoes heat exchange with a cold source in the tube side/shell side, so that the gas mixture is separated into liquid refrigerant and non- condensable gas.

A gas discharge device according to the abovementioned first aspect, wherein the evaporative condenser comprises a gas mixture inlet, a liquid outlet and a gas outlet; the gas mixture inlet is used for leading in the gas mixture, the liquid outlet is used for leading the isolated liquid refrigerant into the refrigeration and air conditioning system, and the gas outlet is used for discharging the isolated non- condensable gas; the evaporative condenser also comprises a cold source inlet and a cold source outlet, the cold source inlet being used for leading in the cold source, and the cold source outlet being used for discharging the cold source. A gas discharge device according to the abovementioned first aspect, wherein the cold source inlet of the evaporative condenser is in communication with the refrigeration and air conditioning system, so as to lead a portion of low- temperature refrigerant in the refrigeration and air conditioning system into the evaporative condenser, to serve as the cold source of the gas discharge device; and the cold source outlet of the evaporative condenser is in communication with the refrigeration and air conditioning system, so as to lead the refrigerant entering the evaporative condenser back into the refrigeration and air conditioning system.

A gas discharge device according to the abovementioned first aspect, further comprising an ejector, the ejector comprising a high pressure source inlet, a liquid inlet and an ejector outlet, the high pressure source inlet being in communication with the refrigeration and air conditioning system, so as to lead a portion of high- pressure refrigerant in the refrigeration and air conditioning system into the ejector, the liquid inlet being in communication with the liquid outlet of the evaporative condenser, and the ejector outlet being in communication with the refrigeration and air conditioning system, such that the liquid refrigerant isolated by the evaporative condenser is led back into the refrigeration and air conditioning system via the ejector.

A gas discharge device according to the abovementioned first aspect, further comprising a cold source inlet control valve, connecting the cold source inlet of the evaporative condenser to the cold source; a gas mixture intake control valve, connecting the gas mixture inlet of the evaporative condenser to the refrigeration and air conditioning system; a liquid discharge control valve, establishing communication between the liquid outlet of the evaporative condenser and the refrigeration and air conditioning system; and a gas discharge control valve, disposed at the gas outlet of the evaporative condenser.

A gas discharge device according to the abovementioned first aspect, further comprising an additional throttling device, disposed between the cold source inlet of the evaporative condenser and the refrigeration and air conditioning system; an ejector, comprising a high pressure source inlet, a liquid inlet and an ejector outlet, the high pressure source inlet being in communication with the refrigeration and air conditioning system, and the ejector outlet being in communication with the refrigeration and air conditioning system; a cold source outlet control valve, connecting the cold source outlet of the evaporative condenser to the liquid inlet of the ejector; a liquid discharge control valve, connecting the liquid outlet of the evaporative condenser to the liquid inlet of the ejector, thereby enabling the liquid refrigerant isolated in the evaporative condenser to be led back into the refrigeration and air conditioning system via the ejector.

A gas discharge device according to the abovementioned first aspect, further comprising a high pressure source control valve, disposed between the high pressure source inlet of the ejector and the refrigeration and air conditioning system.

According to a second aspect of the present invention, the present invention provides a refrigeration and air conditioning system, comprising: an evaporator, comprising an evaporator inlet and an evaporator outlet; a compressor, comprising a compressor inlet and a compressor outlet, the compressor inlet being in communication with the evaporator outlet; a condenser, comprising a condenser inlet and a condenser outlet, the condenser inlet being in communication with the compressor outlet; a throttling device, comprising a throttling device inlet and a throttling device outlet, the throttling device inlet being in communication with the condenser outlet, and the throttling device outlet being in communication with the evaporator inlet; wherein the refrigeration and air conditioning system further comprises the gas discharge device as claimed in any one of claims 1 - 7, wherein the gas mixture inlet of the evaporative condenser is in communication with the condenser, and the liquid outlet of the evaporative condenser is in communication with a low pressure side of the refrigeration and air conditioning system. A refrigeration and air conditioning system according to the abovementioned second aspect, wherein the gas mixture inlet of the evaporative condenser is connected to the top of the condenser, such that the gas mixture inlet of the evaporative condenser is in communication with the condenser.

A refrigeration and air conditioning system according to the abovementioned second aspect, wherein the cold source inlet of the evaporative condenser is in communication with the throttling device outlet; and the cold source outlet of the evaporative condenser is in communication with the compressor inlet or the evaporator.

According to a third aspect of the present invention, the present invention provides a method for discharging non-condensable gas in the refrigeration and air conditioning system according to the second aspect, the method comprising: an evaporative condensation process, in which a gas mixture composed of gaseous refrigerant and non-condensable gas in the condenser of the refrigeration and air conditioning system is led into the tube side/shell side of the evaporative condenser, and the cold source is led into the shell side/tube side of the evaporative condenser, thereby condensing the gaseous refrigerant in the gas mixture to liquid refrigerant by means of the evaporative condenser, and thereby isolating the non-condensable gas from the gas mixture; a liquid discharge process, in which the liquid refrigerant isolated by the evaporative condenser is discharged into a low pressure side of the refrigeration and air conditioning system; and a gas discharge process, in which the non-condensable gas isolated by the evaporative condenser is discharged.

A method according to the abovementioned third aspect, wherein the cold source is low-temperature refrigerant exiting the throttling device of the refrigeration and air conditioning system.

The gas discharge device and method thereof according to the present invention can lead a gas mixture of gaseous refrigerant and non-condensable gas out of a refrigeration and air conditioning system, and by condensing the gaseous refrigerant in the gas mixture to liquid refrigerant, can isolate the non-condensable gas from the gas mixture and discharge the non-condensable gas. Thus, the present invention can prevent the accumulation of non-condensable gas in a condenser of a refrigeration and air conditioning system, and thereby helps to maintain the condensing pressure in the condenser, to guarantee the refrigerating capacity and energy efficiency of the refrigeration and air conditioning system, such that it operates safely and efficiently.

Description of the accompanying drawings

Fig. 1 shows a schematic diagram of the main composition of a conventional refrigeration and air conditioning system.

Fig. 2 shows an embodiment of the gas discharge device of the present invention.

Fig. 3 shows a refrigeration and air conditioning system having the gas discharge device shown in fig. 2.

Figs. 4A - 4C show the process of discharging non-condensable gas from the refrigeration and air conditioning system in fig. 3.

Fig. 5 shows another embodiment of the gas discharge device of the present invention.

Fig. 6 shows a refrigeration and air conditioning system having the gas discharge device shown in fig. 5.

Figs. 7 A - 7C show the process of discharging non-condensable gas from the refrigeration and air conditioning system in fig. 6.

PARTICULAR EMBODIMENTS

Various particular embodiments of the present invention are described below with reference to the accompanying drawings, which form part of this Description. In possible cases, identical or similar reference labels used in the present invention denote identical or corresponding components.

First of all a conventional refrigeration and air conditioning system is presented with reference to fig. 1. As fig. 1 shows, the refrigeration and air conditioning system 100 mainly comprises an evaporator 110, a compressor 120, a condenser 130 and a throttling device 140, which are connected by pipelines to form a closed system filled with refrigerant. Specifically, as fig. 1 shows, the evaporator 110 comprises an inlet 110a and an outlet 110b, the compressor 120 comprises an inlet 120a and an outlet 120b, the condenser 130 comprises an inlet 130a and an outlet 130b, and the throttling device 140 comprises an inlet 140a and an outlet 140b. These components are connected by pipelines in the following manner: the inlet 120a of the compressor 120 is connected to the outlet 110b of the evaporator 110, the inlet 130a of the condenser 130 is connected to the outlet 120b of the compressor 120, the inlet 140a of the throttling device 140 is connected to the outlet 130b of the condenser 130, and the outlet 140b of the throttling device 140 is connected to the inlet 110a of the evaporator 110. The unshaded arrows in fig. 1 indicate the direction of travel of refrigerant in the refrigeration and air conditioning system. During refrigeration, the throttling device 140 throttles the flow of high-pressure liquid refrigerant coming from the condenser 130, causing the pressure thereof to fall; low-pressure refrigerant undergoes heat exchange with an object of cooling (in fig. 1, the arrow entering the evaporator 110 and the arrow exiting the evaporator 110 indicate the direction of travel of the object of cooling, e.g. chilled water) in the evaporator 110, absorbing heat from the object of cooling and thereby being vaporized and evaporating; refrigerant vapor produced by vaporization is sucked in by the compressor 120, and is discharged at high pressure after compression; high-temperature, high-pressure gaseous refrigerant discharged by the compressor 120 undergoes heat exchange with a surrounding medium (in fig. 1 , the arrows entering the condenser 130 and exiting the condenser 130 indicate the direction of travel of the surrounding medium, e.g. cooling water) in the condenser 130, releasing heat and thereby being liquefied and condensing; high-temperature refrigerant liquid flows through the throttling device 140 again and thereby undergoes a reduction in pressure. In this way, the cycle is repeated, creating a continuous refrigeration effect.

In the refrigeration and air conditioning system 100 shown in fig. 1, if the refrigerant used is a low-pressure refrigerant such as 123 or R1233zd, non- condensable gas from the air will accumulate in the condenser 130. For this reason, the gas discharge device of the present invention leads non-condensable gas out of the condenser 130. However, since gaseous refrigerant is also present in the condenser 130, gaseous refrigerant will be led out at the same time as non- condensable gas is led out. Thus, the gas discharge device of the present invention first of all separates a mixture of gaseous refrigerant and non-condensable gas, then sends the isolated refrigerant back to the refrigeration and air conditioning system, and leads the isolated non-condensable gas out of the gas discharge system and into the surrounding atmosphere.

Fig. 2 shows a gas discharge device according to an embodiment of the present invention, wherein the arrows indicate the direction of travel of a cold source. As fig. 2 shows, in this embodiment, the gas discharge device 200 comprises an evaporative condenser 210; the evaporative condenser 210 is a shell- and-tube heat exchanger, comprising a tube side 214 and a shell side 218. One of the tube side and shell side is used for accommodating a gas mixture of non- condensable gas and gaseous refrigerant in the refrigeration and air conditioning system, while the other of the tube side and shell side is used for accommodating a cold source, to enable the gas mixture to undergo heat exchange with the cold source, and thereby separate the gas mixture into liquid refrigerant and non- condensable gas, in order to discharge the non-condensable gas alone. To facilitate illustration and the following detailed description, in fig. 2 the shell side 218 is used to accommodate the cold source, while the tube side 214 is used to accommodate the gas mixture of non-condensable gas and gaseous refrigerant. However, those skilled in the art should understand that fig. 2 is merely an example; the function of the evaporative condenser could likewise be realized if the tube side were used to accommodate the cold source and the shell side were used to accommodate the gas mixture of non-condensable gas and gaseous refrigerant.

As fig. 2 further shows, the tube side 214 comprises a gas mixture inlet 214a, a liquid outlet 214b and a gas outlet 214c; the gas mixture inlet 214a is used for leading in a gas mixture of non-condensable gas and gaseous refrigerant discharged from the refrigeration and air conditioning system, the liquid outlet 214b is used for conveying liquid refrigerant isolated in the tube side 214 back into the refrigeration and air conditioning system, and the gas outlet 214c is used for discharging non-condensable gas isolated in the tube side 214. The shell side 218 comprises a cold source inlet 218a and a cold source outlet 218b; the cold source inlet 218a is used for leading the cold source into the shell side 218, and the cold source outlet 218b is used for discharging from the shell side 218 the cold source that has been led in.

The gas discharge device 200 may also comprise an ejector 230; the ejector 230 can generate negative pressure at the liquid outlet 214b of the tube side 214, such that liquid refrigerant isolated in the tube side 214 is sucked into the ejector 230, and discharged by the ejector 230. However, it must be noted that the gas discharge device 200 need not be provided with the ejector 230; in the case where no ejector 230 is provided, liquid refrigerant isolated in the tube side 214 can likewise be discharged. The ejector 230 is merely used to accelerate the discharge of isolated liquid refrigerant in the tube side 214. As shown in fig. 2, the ejector 230 comprises a high pressure source inlet 231, a liquid inlet 232 and an ejector outlet 233; the high pressure source inlet 231 is used for leading a high pressure source into the ejector 230, the liquid inlet 232 is in communication with the liquid outlet 214b of the tube side 214, and the ejector outlet 233 is in communication with a low pressure side of the refrigeration and air conditioning system.

Fig. 2 also shows that a cold source control valve 270, a gas mixture intake control valve 240 and a high pressure source control valve 250 are provided upstream of the cold source inlet 218a of the evaporative condenser, the gas mixture inlet 214a and the high pressure source inlet 231 of the ejector 230 respectively, and are each used for controlling the entry of gas and/or liquid. A gas discharge control valve 260 is also provided at the gas outlet 214c of the evaporative condenser, and used for controlling the discharge of isolated non- condensable gas. In addition, a liquid discharge control valve 280 is also provided between the liquid inlet 232 of the ejector 230 and the liquid outlet 214b of the shell side 214.

According to one form of implementation of the embodiment shown in fig. 2, the cold source used to provide a quantity of cold for the evaporative condenser 210 is a portion of low-temperature refrigerant in the refrigeration and air conditioning system; fig. 3 shows the way in which the refrigeration and air conditioning system is connected to the gas discharge device implemented in such a way. It must be noted that when a portion of low-temperature refrigerant in the refrigeration and air conditioning system is used as the cold source of the evaporative condenser 210, this portion of refrigerant must ultimately be led back into the refrigeration and air conditioning system, to keep the total amount of refrigerant in the refrigeration and air conditioning system constant, so that the refrigeration and air conditioning system can operate normally. However, according to the principle of the present invention, the embodiment shown in fig. 2 may also be used to discharge non-condensable gas in the refrigeration and air conditioning system when a cold source outside the refrigeration and air conditioning system is used. The way in which the gas discharge device 200 is connected in a refrigeration and air conditioning system 100' is presented below with reference to the refrigeration and air conditioning system 100' shown in fig. 3, which system has the gas discharge device 200 shown in fig. 2. As fig. 3 shows, the cold source inlet 218a of the evaporative condenser 210 is in communication with an outlet 140b' of a throttling device 140' of the refrigeration and air conditioning system 100', and the cold source control valve 270 is connected therebetween. Refrigerant exiting the throttling device 140' is low-temperature refrigerant, and can provide a sufficient quantity of cold for the evaporative condenser 210. The gas mixture inlet 214a of the evaporative condenser 210 is in communication with a condenser 130' of the refrigeration and air conditioning system 100', and the gas mixture intake control valve 240 is connected therebetween. In a preferred embodiment, the gas mixture inlet 214a of the evaporative condenser 210 is in communication with the top of the condenser 130' of the refrigeration and air conditioning system 100'; since non-condensable gas accumulates at the top of the condenser 130', such a manner of connection is more favorable for discharging non-condensable gas from the condenser 130'. The cold source outlet 218b of the evaporative condenser 210 is in communication with an evaporator 110' of the refrigeration and air conditioning system, to convey refrigerant exiting the shell side 218 back into the refrigeration and air conditioning system. It is worth noting that the cold source outlet 218b of the evaporative condenser 210 could also be in communication with an inlet 120a' of a compressor 120', to convey refrigerant exiting the shell side 218 back into the refrigeration and air conditioning system. The high pressure source inlet 231 of the ejector 230 is in communication with a high pressure side (e.g. an outlet 120b' of the compressor 120') of the refrigeration and air conditioning system, for the purpose of leading a portion of high-pressure refrigerant exiting the compressor 120' into the ejector 230, and using this as a working gas of the ejector 230. The high pressure source control valve 250 is disposed between the high pressure source inlet 231 and the outlet 120b' of the compressor 120'. The ejector outlet 233 is in communication with a low pressure side (e.g. the evaporator 110') of the refrigeration and air conditioning system, to convey liquid refrigerant isolated by the evaporative condenser 210 back into the refrigeration and air conditioning system.

When a portion of low-temperature refrigerant of the refrigeration and air conditioning system 100' itself is used as the cold source of the gas discharge device 200 as shown in fig. 3, there is no longer a need to separately configure an independent cooling system for the gas discharge device 200, hence the number of components in the gas discharge system can be reduced, so that the structure of the refrigeration and air conditioning system as a whole is more compact.

There follows a detailed description, referring to figs. 4A - 4C, of how the gas discharge device 200 is used to discharge non-condensable gas from the refrigeration and air conditioning system 100' shown in fig. 3; in each drawing, unshaded arrows indicate the direction of travel of refrigerant in the refrigeration and air conditioning system and the gas discharge device. Roughly speaking, an operating process of the gas discharge device is divided into three stages, namely an evaporative condensation process, a liquid discharge process and a gas discharge process, wherein the evaporative condensation process is intended to isolate non-condensable gas from a gas mixture of said non-condensable gas and gaseous refrigerant, the liquid discharge process is intended to convey isolated refrigerant back into the refrigeration and air conditioning system, and the gas discharge process is intended to discharge isolated non-condensable gas into the surrounding atmosphere. The method of the present invention by which non- condensable gas is discharged from the refrigeration and air conditioning system using the gas discharge device is also embodied in the operating process described below. Fig. 4 A shows the evaporative condensation process. In the evaporative condensation process, the cold source control valve 270 and the gas mixture intake control valve 240 are open, but the remaining valves, i.e. the high pressure source control valve 250, the gas discharge control valve 260 and the liquid discharge control valve 280, are all closed. Low-temperature refrigerant exiting the outlet 140b' of the throttling device 140' is split into two streams. One stream of refrigerant enters the evaporator 110' and is evaporated; the other stream of refrigerant enters the shell side 218 as the cold source via the cold source control valve 270. Non-condensable gas accumulated in the condenser 130' will enter the tube side 214 together with gaseous refrigerant in the condenser 130' as a gas mixture, and undergo heat exchange with the low-temperature refrigerant in the shell side 218, such that the gaseous refrigerant in the gas mixture is condensed to liquid refrigerant. Liquid refrigerant isolated by condensation is stored at the bottom of the tube side 214, whereas isolated non-condensable gas is stored at the top of the tube side 214; non-condensable gas is thereby separated from refrigerant. The low-temperature refrigerant in the shell side 218 evaporates and changes to a gas in the course of the abovementioned heat exchange, and enters the evaporator 110' via the cold source outlet 218b of the shell side 218.

Fig. 4B shows the liquid discharge process. When the liquid refrigerant in the tube side 214 reaches a certain height, the liquid discharge process is started. In the liquid discharge process, the high pressure source control valve 250 and the liquid discharge control valve 280 are open, but the remaining valves, i.e. the cold source control valve 270, the gas mixture intake control valve 240 and the gas discharge control valve 260, are all closed. At this time, high-pressure refrigerant exiting the outlet 120b' of the compressor 120' enters the ejector 230 via the high pressure source control valve 250, draws out liquid refrigerant stored in the tube side 214 by the ejection effect of the ejector 230, and is discharged into the evaporator 110' via the ejector 230. Fig. 4C shows the gas discharge process. In the gas discharge process, the gas discharge control valve 260 is open, but the remaining valves, i.e. the cold source control valve 270, the gas mixture intake control valve 240, the high pressure source control valve 250 and the liquid discharge control valve 280, are all closed. At this time, non-condensable gas in the tube side 214 is discharged into the surrounding atmosphere by means of the gas discharge control valve 260.

The present invention also provides another embodiment of a gas discharge device, as shown in fig. 5, wherein the arrows indicate the direction of travel of a cold source. In this embodiment, a gas discharge device 300 comprises an evaporative condenser 310 similar to that in the gas discharge device 200, the main difference between the gas discharge device 300 and the gas discharge device 200 shown in fig. 2 being that in the gas discharge device 300, an additional throttling device 370 is provided upstream of a cold source inlet 318a of a shell side 318, for the purpose of further lowering the temperature of the cold source before the cold source enters the shell side 318, and thereby increasing the condensing capacity of the evaporative condenser.

As was the case with the gas discharge device 200, an ejector 330 may also be used in the gas discharge device 300 to accelerate the discharge of liquid refrigerant from the evaporative condenser 310. Refrigerant of the refrigeration and air conditioning system itself may also be used as the cold source of the gas discharge device 300, i.e. a portion of refrigerant exiting a throttling device of the refrigeration and air conditioning system is used as the cold source of the gas discharge device. When refrigerant of the refrigeration and air conditioning system itself is used as the cold source, since the cold source refrigerant entering the shell side 318 has passed through two throttling devices (i.e. the throttling device of the refrigeration and air conditioning system and the additional throttling device 370 in the gas discharge device 300), the pressure thereof is lower than the pressure of refrigerant in a low pressure side of the refrigeration and air conditioning system. In such a case, if it is desired to send the refrigerant serving as the cold source in the shell side 318 back into the low pressure side (e.g. the inlet of the the compressor or the evaporator) of the refrigeration and air conditioning system, it is necessary to add an auxiliary liquid discharge device. The ejector 330 shown in fig. 5 may be used as the auxiliary liquid discharge device. At this time, the ejector 330 may be used to realize two functions simultaneously, i.e. used as the auxiliary liquid discharge device of the shell side 318, and also used to accelerate the discharge of liquid from a tube side 314. In order to realize these two functions, it is necessary to provide a control valve between the shell side 318 and the ejector 330, and to provide a control valve between the tube side 314 and the ejector 330, i.e. a cold source outlet control valve 390 and a liquid discharge control valve 380; only then can an evaporative condensation process and a liquid discharge process of the gas discharge device 300 be separated from one another (this can also be seen from the operating process of the gas discharge device 300 described below).

In addition, similarly to the gas discharge device 200 shown in fig. 2, a gas discharge control valve 360, a gas mixture intake control valve 340 and a high pressure source control valve 350 are also provided in the gas discharge device 300 shown in fig. 5.

Fig. 6 shows a refrigeration and air conditioning system 100" having the gas discharge device 300 shown in fig. 5; the way in which the gas discharge device 300 is connected to the refrigeration and air conditioning system 100" is similar to the way in which the gas discharge device 200 is connected to the refrigeration and air conditioning system 100', and is not repeated in detail here.

Since the gas discharge device 300 has two more control valves than the gas discharge device 200 (i.e. the cold source outlet control valve 390 and the liquid discharge control valve 380), there are slight differences in the open/closed states of the various control valves in the operating process in which the refrigeration and air conditioning system 100" uses the gas discharge device 300 to discharge non- condensable gas, and the operating process in which the refrigeration and air conditioning system 100' uses the gas discharge device 200 to discharge non- condensable gas; therefore, for the sake of clarity, the operating process in which the refrigeration and air conditioning system 100" uses the gas discharge device 300 to discharge non-condensable gas is presented in detail below with reference to figs. 7A - 7C. As before, in each drawing, unshaded arrows indicate the direction of travel of refrigerant in the refrigeration and air conditioning system and the gas discharge device, and the operating process of the gas discharge device is divided into three stages, namely an evaporative condensation process, a liquid discharge process and a gas discharge process.

Fig. 7 A shows the evaporative condensation process. In the evaporative condensation process, the additional throttling device 370 is open, the gas mixture intake control valve 340, high pressure source control valve 350 and cold source outlet control valve 390 are also open, but the liquid discharge control valve 380 and gas discharge control valve 360 are closed. Low-temperature refrigerant exiting an outlet 140b" of a throttling device 140" is split into two streams. One stream of refrigerant enters an evaporator 110" to evaporate; the other stream of refrigerant undergoes further throttling and pressure reduction via the additional throttling device 370, consequently changing to two-phase refrigerant at a lower temperature, and enters the shell side 318 to serve as the cold source. Non- condensable gas accumulated in a condenser 130" will enter the tube side 314 together with gaseous refrigerant in the condenser 130" as a gas mixture, and undergo heat exchange with the low-temperature refrigerant in the shell side 318, such that the gaseous refrigerant in the gas mixture is condensed to liquid refrigerant. Liquid refrigerant isolated by condensation is stored at the bottom of the tube side 314, whereas isolated non-condensable gas is stored at the top of the tube side 314; non-condensable gas is thereby separated from refrigerant. Low- temperature refrigerant in the shell side 318 evaporates and changes to a gas in the course of the abovementioned heat exchange, and high-pressure refrigerant exiting an outlet 120b" of a compressor 120" then enters the ejector 330 via the high pressure source control valve 350; under the ejection effect of the ejector 330, gaseous refrigerant in the shell side 318 enters the evaporator 110" of the refrigeration and air conditioning system via the ejector 330, thus returning to the refrigeration and air conditioning system.

Fig. 7B shows the liquid discharge process. When the liquid refrigerant in the tube side 314 reaches a certain height, the liquid discharge process is started. In the liquid discharge process, the high pressure source control valve 350, the cold source outlet control valve 390 and the liquid discharge control valve 380 are open, but the additional throttling device 370, the gas mixture intake control valve 340 and the gas discharge control valve 360 are all closed. At this time, high-pressure refrigerant exiting the outlet 120b" of the compressor 120" enters the ejector 330 via the high pressure source control valve 350, draws out liquid refrigerant stored in the tube side 314 by the ejection effect of the ejector 330, and is discharged into the evaporator 110" via the ejector 330.

Fig. 7C shows the gas discharge process. In the gas discharge process, the gas discharge control valve 360 is open, but the remaining valves, i.e. the additional throttling device 370, the gas mixture intake control valve 340, the high pressure source control valve 350, the cold source outlet control valve 390 and the liquid discharge control valve 380, are all closed. At this time, non-condensable gas in the tube side 314 is discharged into the surrounding atmosphere by means of the gas discharge control valve 360.

The temperature of the cold source entering the evaporative condenser is further reduced in the gas discharge device 300 shown in fig. 5 in comparison with the gas discharge device 200 shown in fig. 2; this is more favorable for increasing the efficiency of the gas discharge device. It can be seen from the operating processes of the gas discharge devices 200 and 300 described above that the gas discharge device and the refrigeration and air conditioning system of the refrigeration and air conditioning system itself together form a closed system; the refrigerant in the refrigeration and air conditioning system not only performs a refrigeration cycle of the refrigeration and air conditioning system, but at the same time serves as the cold source of the gas discharge device, providing a quantity of cold for isolating non-condensable gas. Furthermore, high-pressure refrigerant in the refrigeration and air conditioning system can also serve as a high pressure source, helping refrigerant that has entered the gas discharge device to return to the refrigeration and air conditioning system. When such gas discharge devices are used, the entire refrigeration and air conditioning system is not only relatively compact in structure, but can also realize centralized control.

It is worth noting that the gas discharge device does not need to operate continuously during operation of the refrigeration and air conditioning system, but need only begin operating when the accumulated amount of non-condensable gas in the condenser reaches a certain level. The liquid discharge process and gas discharge process of the gas discharge device also do not need to proceed continuously during operation of the gas discharge device; these two processes need only be started when liquid refrigerant and non-condensable gas in the evaporative condenser are stored to a certain level.

In addition, the present invention also provides a method for discharging non- condensable gas from a condenser of a refrigeration and air conditioning system. The method is realized using a gas discharge device exemplified by figs. 2 and 5, and has been explained in the operating processes, presented in detail above, of the gas discharge devices shown in figs. 2 and 5.

Although the present invention has been described with reference to particular embodiments shown in the accompanying drawings, it should be understood that many variant forms of the gas discharge device of the present invention and the gas discharge method thereof are possible without departing from the spirit, scope and background of the teaching of the present invention. Those skilled in the art will also realize that there are different ways of changing structural details in the embodiments disclosed in the present invention, but these changes all fall within the spirit and scope of the present invention and claims.