Heat Exchanger Unit and Air Conditioning System

This application claims benefit of Chinese Patent Application No. 202410323799.1, filed Mar. 20, 2024, and 202410641767.6, filed May 22, 2024, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in their entirety are herein incorporated by reference.

This disclosure relates to a field of refrigeration equipment, and in particular to a heat exchanger unit and an air conditioning system.

This disclosure provides a heat exchanger unit and an air conditioning system, which are used for at least solving or relieving problems in the prior art. A first aspect of this disclosure provides a heat exchanger unit, including: a first heat exchanger, including a first housing provided with a first refrigerant inlet and a first refrigerant outlet, a first refrigerant flow passage formed between the first refrigerant inlet and the first refrigerant outlet, and a first heat exchanging tube bundle disposed in the first housing; a second heat exchanger, including a second housing provided with a second refrigerant inlet and a second refrigerant outlet, a second refrigerant flow passage formed between the second refrigerant inlet and the second refrigerant outlet, and a third heat exchanging tube bundle disposed in the second housing, and having an inlet in communication with an outlet of the first heat exchanging tube bundle; a third heat exchanger, including a third refrigerant flow passage in communication with the first refrigerant flow passage, and a first heat exchanging flow passage; and a fourth heat exchanger, including a fourth refrigerant flow passage in communication with the second refrigerant flow passage, and a second heat exchanging flow passage having an inlet in communication with an outlet of the first heat exchanging flow passage.

In one or more embodiments, the third heat exchanger is disposed in the first housing, the first heat exchanging flow passage is a second heat exchanging tube bundle disposed in the first housing, the second heat exchanging tube bundle is disposed closer to the first refrigerant outlet than the first heat exchanging tube bundle, and the third refrigerant flow passage and the first refrigerant flow passage together form an empty space inside the first housing, and the fourth heat exchanger is disposed in the second housing, the second heat exchanging flow passage is a fourth heat exchanging tube bundle disposed in the second housing, the fourth heat exchanging tube bundle is disposed closer to the second refrigerant outlet than the third heat exchanging tube bundle, and the fourth refrigerant flow passage and the second refrigerant flow passage together form an empty space inside the second housing.

In one or more embodiments, the first heat exchanger further includes first housing tube sheets respectively disposed at two inner ends of the first housing and fixing the first heat exchanging tube bundle and the second heat exchanging tube bundle, first heat exchanger end covers respectively disposed at two ends of the first housing, first chambers enclosed by the first heat exchanger end covers and the first housing tube sheets disposed corresponding to the first heat exchanger end covers, and at least one first separator disposed in the first chamber and dividing the first chamber into a first heat exchanging tube bundle chamber in communication with the first heat exchanging tube bundle and a second heat exchanging tube bundle chamber in communication with the second heat exchanging tube bundle.

In one or more embodiments, the second heat exchanger further includes second housing tube sheets respectively disposed at two inner ends of the second housing and fixing the third heat exchanging tube bundle and the fourth heat exchanging tube bundle, second heat exchanger end covers respectively disposed at two ends of the second housing, second chambers enclosed by the second heat exchanger end covers and the second housing tube sheets disposed corresponding to the second heat exchanger end covers, and at least one second separator disposed in the second chamber and dividing the second chamber into a first accommodating chamber in communication with the third heat exchanging tube bundle and a second accommodating chamber in communication with the fourth heat exchanging tube bundle.

In one or more embodiments, the second heat exchanger further includes two third separators disposed in the second chamber and dividing the second chamber into a third accommodating chamber in communication with the third heat exchanging tube bundle, a fourth accommodating chamber in communication with the fourth heat exchanging tube bundle, and a fifth accommodating chamber between the third accommodating chamber and the fourth accommodating chamber.

In one or more embodiments, the fourth accommodating chamber is in communication with the first heat exchanging tube bundle chamber through a pipeline, the first heat exchanging tube bundle chamber is in communication with the fifth accommodating chamber through a pipeline, and the fifth accommodating chamber is in communication with the third accommodating chamber through the third heat exchanging tube bundle.

In one or more embodiments, the pipeline through which the fourth accommodating chamber is in communication with the first heat exchanging tube bundle chamber is provided with a first water pump.

In one or more embodiments, the second heat exchanging tube bundle chamber is in communication with the fifth accommodating chamber through a pipeline, the fourth heat exchanging tube bundle is in communication with the first heat exchanging tube bundle chamber through a pipeline, the first heat exchanging tube bundle chamber is in communication with the fifth accommodating chamber through a pipeline, and the fifth accommodating chamber is in communication with the third accommodating chamber through the third heat exchanging tube bundle.

In one or more embodiments, the pipeline through which the fourth heat exchanging tube bundle is in communication with the first heat exchanging tube bundle chamber is provided with a second water pump.

In one or more embodiments, each of the first heat exchanger and the second heat exchanger is a condenser.

In one or more embodiments, an outlet of the fourth heat exchanging tube bundle is in communication with an inlet of the third heat exchanging tube bundle through a pipeline.

In one or more embodiments, the pipeline through which the outlet of the fourth heat exchanging tube bundle is in communication with the inlet of the third heat exchanging tube bundle is provided with a third water pump.

In one or more embodiments, the third heat exchanger is disposed outside the first housing, and an inlet of the third refrigerant flow passage is in communication with the first refrigerant outlet. The fourth heat exchanger is disposed outside the second housing, and an inlet of the fourth refrigerant flow passage is in communication with the second refrigerant outlet.

In one or more embodiments, a pipeline through which the first heat exchanging flow passage is in communication with the second heat exchanging flow passage is provided with a fourth water pump.

In one or more embodiments, the outlet of the second heat exchanging flow passage is in communication with an inlet of the third heat exchanging tube bundle through a pipeline.

In one or more embodiments, the pipeline through which the outlet of the second heat exchanging flow passage is in communication with the inlet of the third heat exchanging tube bundle is provided with a fifth water pump.

Another aspect of this disclosure provides an air conditioning system, including the above heat exchanger unit as a condenser.

The technical solutions in the one or more embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings in the one or more embodiments of this disclosure, and obviously, any single technical feature illustrated or implicit in the drawings, this application still allows any combination or deletion between these technical features (or their equivalents) without any technical obstacles, thereby obtaining other embodiments of this application that may not be directly mentioned herein. Based on the one or more embodiments in this disclosure, all other embodiments obtained by a person skilled in the art without creative work fall within the protection scope of this disclosure.

For an air-conditioning chiller-heater unit or chiller unit, heat generated by a high-temperature and high-pressure gaseous refrigerant in a condenser during heat release can raise a temperature of the water to a higher temperature. In order to ensure good unit efficiency, it needs to be ensured that the refrigerant at an outlet of the condenser can have a certain degree of supercooling or a lower liquid refrigerant temperature. However, in heat exchangers of existing air conditioning systems, illustrated in, waterways of a first condenserand a second condenserare connected in series, and the entering water temperature of the second condenser(the exiting water temperature of the first condenser) is higher, so that the degree of supercooling of the second condenseris limited, and it is difficult for the refrigerant at the outlet of the second condenserto obtain a larger degree of supercooling or a lower liquid refrigerant temperature, which affects the overall heating performance of the air-conditioning chiller-heater unit or chiller unit.

As illustrated in, a first aspect of this disclosure provides a heat exchanger unit, including a first heat exchangerand a second heat exchangerthat are in communication with each other. The first heat exchangerincludes a first housingand a first heat exchanging tube bundleand a second heat exchanging tube bundlethat are disposed in the first housing. The first housingis provided with a first refrigerant inlet and a first refrigerant outlet. The second heat exchanging tube bundleis disposed closer to the first refrigerant outlet than the first heat exchanging tube bundle. The second heat exchangerincludes a second housingand a third heat exchanging tube bundleand a fourth heat exchanging tube bundledisposed in the second housing. The second housingis provided with a second refrigerant inlet and a second refrigerant outlet. The fourth heat exchanging tube bundleis disposed closer to the second refrigerant outlet than the third heat exchanging tube bundle. The first heat exchanging tube bundleis in communication with the third heat exchanging tube bundle, and the second heat exchanging tube bundleis in communication with the fourth heat exchanging tube bundle.

Specifically, a heat exchanging medium flowing in the first heat exchanging tube bundle, the second heat exchanging tube bundle, the third heat exchanging tube bundle, and the fourth heat exchanging tube bundleis preferably water. Water is used as an example below. Of course, the heat exchanging medium is not limited to water, and other fluids that can exchange heat with the refrigerant are applicable to this disclosure.

When each of the first heat exchangerand the second heat exchangeris a condenser, in the first heat exchanger, a high-temperature and high-pressure gaseous refrigerant enters from the first refrigerant inlet, and the heat of the high-temperature and high-pressure gaseous refrigerant in the first heat exchangeris absorbed by the water in the first heat exchanging tube bundleand the second heat exchanging tube bundle. During the heat exchange process, the high-temperature and high-pressure refrigerant is gradually condensed into high-pressure liquid and the temperature is gradually reduced, thus completing the condensation process. Since the second heat exchanging tube bundleis closer to the first refrigerant outlet, the refrigerant enters from the first refrigerant inlet, sequentially exchanges heat with the first heat exchanging tube bundleand the second heat exchanging tube bundle, and then is discharged from the first refrigerant outlet. Similarly, in the second heat exchanger, the high-temperature and high-pressure gaseous refrigerant enters from the second refrigerant inlet, sequentially exchanges heat with the third heat exchanging tube bundleand the fourth heat exchanging tube bundle, and then is discharged from the second refrigerant outlet.

It should be noted that “refrigerant in” and “refrigerant out” indicated intoare for illustration only and represent “a refrigerant entering” and “a refrigerant flowing out”, and do not represent actual positions of the first refrigerant inlet, the first refrigerant outlet, the second refrigerant inlet, and the second refrigerant outlet. Preferably, in directions illustrated into, in the first heat exchanger, the refrigerant enters from a top end of the first housingand flows out from a bottom end of the first housing. In the second heat exchanger, the refrigerant enters from a top end of the second housingand flows out from a bottom end of the second housing, where the top end and the bottom end may correspond to a top portion and a bottom portion in a radial direction of the housing.

Further, in the first heat exchanger, since the high-temperature and high-pressure refrigerant enters from the first refrigerant inlet and sequentially exchanges heat with the first heat exchanging tube bundleand the second heat exchanging tube bundle, the heat exchanging medium in the first heat exchanging tube bundlehas a relatively high temperature after absorbing the heat of the high-temperature and high-pressure gaseous refrigerant, but after the high-temperature and high-pressure gaseous refrigerant exchanges heat with the first heat exchanging tube bundle, most or all of the gaseous refrigerant is condensed into liquid, and the condensed liquid refrigerant further exchanges heat with the second heat exchanging tube bundle, so that the part of the liquid refrigerant has a further reduced temperature after exchanging heat with the second heat exchanging tube bundle, and the heat exchanging medium in the second heat exchanging tube bundleabsorbs the heat of the refrigerant after flowing through the first heat exchanging tube bundleand has a relatively low temperature (compared with a case in which the first heat exchanging tube bundledirectly exchanges heat with the high-temperature gaseous refrigerant). That is, when the configurations of the first heat exchanging tube bundleand the second heat exchanging tube bundleare substantially the same, the temperature rise of the heat exchanging medium in the first heat exchanging tube bundleis higher than the temperature rise of the heat exchanging medium in the second heat exchanging tube bundle.

In the prior art, the first condenseronly includes one heat exchanging medium outlet. The heat exchanging medium after exchanging heat with the refrigerant in the first condenserabsorbs the heat released by the refrigerant in the first condenser, and then all enters the second condenserto exchange heat with the refrigerant in the second condenser, resulting in a small temperature difference between the heat exchanging medium and the refrigerant in the second condenser, a small degree of supercooling at the condenser outlet of the second condenser, and a poor heat exchange effect. This disclosure utilizes the fact that in the flow direction of the refrigerant, the second heat exchanging tube bundleis close to the first refrigerant outlet, and the heat exchanging medium in the second heat exchanging tube bundlehas a lower outlet temperature than the heat exchanging medium in the first heat exchanging tube bundle, and communicates the second heat exchanging tube bundlewith the fourth heat exchanging tube bundleof the second heat exchanger, so that the inlet temperature of the heat exchanging medium entering the fourth heat exchanging tube bundleof the second heat exchangeris reduced, the temperature difference between the heat exchanging medium in the fourth heat exchanging tube bundleand the refrigerant in the second heat exchangeris increased, the heat exchange effect is improved, and a greater degree of supercooling is ensured for the refrigerant at the outlet of the second heat exchanger, which is beneficial to improving the overall heating efficiency and heating capacity of the heat exchanger unit.

In addition, in this disclosure, the ratio of the flow capacity of the heat exchanging medium flowing through the second heat exchanging tube bundleto the flow capacity of the heat exchanging medium flowing through the first heat exchanging tube bundleis not particularly limited, and may be appropriately adjusted according to the capacity load and the like of the heat exchanger.

However, the flow capacity of the heat exchanging medium flowing through the second heat exchanging tube bundlemay be less than the flow capacity of the heat exchanging medium in the first heat exchanging tube bundle, and the flow capacity of the heat exchanging medium flowing through the third heat exchanging tube bundleis greater than the flow capacity of the heat exchanging medium in the fourth heat exchanging tube bundle(for example, the amount of water flowing through the first heat exchanging tube bundleand the third heat exchanging tube bundleis 90%, and the amount of water flowing through the second heat exchanging tube bundleand the fourth heat exchanging tube bundleis 10%).

Still referring to, in some embodiments of this disclosure, the first heat exchangerfurther includes two first housing tube sheets, two first heat exchanger end covers, two first chambers, and at least one first separator. The two first housing tube sheetsare respectively disposed at two inner ends of the first housingand are used for fixing the first heat exchanging tube bundleand the second heat exchanging tube bundle. The two first heat exchanger end coversare respectively disposed at two ends of the first housing, and the two first housing tube sheetsare respectively disposed corresponding to the two first heat exchanger end coversand enclose two first chamberswith the first heat exchanger end covers. At least one first separatoris disposed in the first chambersand divides the first chambersinto a first heat exchanging tube bundle chamberin communication with the first heat exchanging tube bundleand a second heat exchanging tube bundle chamberin communication with the second heat exchanging tube bundle.

The second heat exchangerfurther includes two second housing tube sheets, two second heat exchanger end covers, two second chambers, and at least one second separator. The two second housing tube sheetsare respectively disposed at two inner ends of the second housingand are used for fixing the third heat exchanging tube bundleand the fourth heat exchanging tube bundle. The two second heat exchanger end coversare respectively disposed at two ends of the second housing, and the two second housing tube sheetsare respectively disposed corresponding to the two second heat exchanger end coversand enclose two second chamberswith the second heat exchanger end covers. At least one second separatoris disposed in the second chambersand divides the second chambersinto a first accommodating chamberin communication with the third heat exchanging tube bundleand a second accommodating chamberin communication with the fourth heat exchanging tube bundle.

Specifically, as illustrated in, when the first heat exchangerand the second heat exchangerare connected in series, only one first separatoris disposed on the outlet side of the first heat exchanger, one second separatoris disposed on the inlet side of the second heat exchanger, the first heat exchanging tube bundleis in communication with the third heat exchanging tube bundle, and the second heat exchanging tube bundleis in communication with the fourth heat exchanging tube bundle.

In this way, only one outlet of the two first chambersof the first heat exchanger(the water exit side of the first heat exchanger) and one inlet of the two second chambersof the second heat exchanger(the entering water side of the second heat exchanger) need to be changed slightly in structure, so that the temperature of part of the heat exchanging medium entering the second heat exchangeris reduced, the overall heating capacity and heating efficiency of the heat exchanger unit is improved, and costs are saved.

In some embodiments of this disclosure, in the heat exchanger unit disposed in series, the first heat exchanging tube bundle, the second heat exchanging tube bundle, the third heat exchanging tube bundle, and the fourth heat exchanging tube bundleare all single-pass heat exchanging tube bundles. The single-pass heat exchanging tube bundle has the advantage of large flow capacity. A person skilled in the art could select heat exchanging tube bundles of different passes according to actual needs, as long as the connection relationship between different heat exchanging tube bundles follows the above connection relationship.

Another aspect of this disclosure provides an air conditioning system, including the above heat exchanger unit as a condenser. By using the above heat exchanger unit as a condenser, under the same working conditions (the same refrigerant temperature and pressure at the outlet of the compressor unit) of a compressor unit of the air conditioning system, the outlet temperature of the refrigerant in the second heat exchangercan be reduced to a lower temperature, thereby ensuring a large degree of supercooling of the second heat exchanger, and improving the overall heating capacity and heating efficiency of the heat exchanger unit and the air conditioning system.

One or more embodiments of this disclosure will be described by taking an example in which the entering water temperature of the first chamberon the entering water side of the first heat exchangeris 50° C. and the exiting water temperature of the second chamberon the exiting water side of the second heat exchangeris 70° C.

Part of water entering the first chamberat 50° C. flows through the second heat exchanging tube bundleto exchange heat with the refrigerant and then flows out of the second heat exchanging tube bundle chamber. At this time, for example, the exiting water temperature is 51.5° C., that is, the temperature of the part of the entering water of the second heat exchangeris significantly reduced. Further, the temperature of the refrigerant flowing out of the first heat exchangeris 53° C., and the temperature of the refrigerant flowing out of the second heat exchangeris 54.5° C., which is slightly higher than the temperature of the refrigerant flowing out of the first heat exchanger, that is, the temperature of the refrigerant at the outlet of the second heat exchangercan be reduced and the degree of supercooling of the refrigerant at the outlet of the second heat exchangerand the heating effect can be improved by introducing the water in the second heat exchanging tube bundleinto the fourth heat exchanging tube bundleto exchange heat with the refrigerant in the second heat exchanger.

In some embodiments, the above air conditioning system may be a series counter-flow chiller unit. It should be noted that other structures and connection relationships of the air conditioning system are not limited in this disclosure, as long as they can form a complete refrigerant circulation loop.

As illustrated in, some embodiments of this disclosure provide a heat exchanger unit, which differs from other embodiments in the waterway connection between the first heat exchangerand the second heat exchangerand the structure of the first chamberof the first heat exchangeror the second chamberof the second heat exchanger. Further, the first heat exchangerfurther includes one fourth separator, which is disposed in the first chamberon the entering water side of the first heat exchangerand divides the first chamber(the first chamberon the right side in the drawing direction) into a third heat exchanging tube bundle chamberand a fourth heat exchanging tube bundle chamber. Since the first separatoris disposed, the first chamberon the left side of the drawing direction is divided into the first heat exchanging tube bundle chamberand the second heat exchanging tube bundle chamber. The third heat exchanging tube bundle chamberis in communication with the first heat exchanging tube bundle, and the fourth heat exchanging tube bundle chamberis in communication with the first heat exchanging tube bundleand the second heat exchanging tube bundleat the same time. The first heat exchanging tube bundleis a double-pass tube bundle, and includes a first tube bodyand a second tube bodywhich are disposed in parallel and in communication with each other through the first heat exchanging tube bundle chamber. Two ends of the first tube bodyare in communication with the first heat exchanging tube bundle chamberand the third heat exchanging tube bundle chamberrespectively, and two ends of the second tube bodyare in communication with the first heat exchanging tube bundle chamberand the fourth heat exchanging tube bundle chamberrespectively. Two ends of the second heat exchanging tube bundleare in communication with the second heat exchanging tube bundle chamberand the fourth heat exchanging tube bundle chamberrespectively.

As illustrated in, the second heat exchangerfurther includes two third separatorsdisposed in one of the second chambersof the second heat exchanger. The two third separatorsdivide the second chamber(the second chamberon the right side of the drawing direction) into a third accommodating chamberin communication with the third heat exchanging tube bundle, a fourth accommodating chamberin communication with the fourth heat exchanging tube bundle, and a fifth accommodating chamberbetween the third accommodating chamberand the fourth accommodating chamber. The fifth accommodating chamberis disposed corresponding to the third heat exchanging tube bundle. The third heat exchanging tube bundleis a double-pass tube bundle, including a third tube bodyand a fourth tube bodywhich are disposed in parallel and in communication with each other through the first accommodating chamber. Two ends of the third tube bodyare in communication with the first accommodating chamberand the third accommodating chamberrespectively, and two ends of the fourth tube bodyare in communication with the first accommodating chamberand the fifth accommodating chamberrespectively. Two ends of the fourth heat exchanging tube bundleare in communication with the second accommodating chamberand the fourth accommodating chamberrespectively.

In some embodiments, the waterway connection between the first heat exchangerand the second heat exchangeris that the fourth accommodating chamberof the second heat exchangeris in communication with the first heat exchanging tube bundle chamberof the first heat exchangerthrough an external pipeline. The first heat exchanging tube bundle chamberis in communication with the third heat exchanging tube bundle chamberthrough the first tube body, and then is in communication with the fifth accommodating chamberof the second heat exchangerthrough an external pipeline. The fifth accommodating chamberis in communication with the third accommodating chamberthrough the third heat exchanging tube bundleand the first accommodating chamber.

In some embodiments, the above separators disposed in the first chambermay be collectively referred to as first separators, and the above separators disposed in the second chambermay be collectively referred to as second separators. The chambers in communication with the first heat exchanging tube bundlemay be collectively referred to as first heat exchanging tube bundle chambers, and the chambers in communication with the second heat exchanging tube bundle may be collectively referred to as second heat exchanging tube bundle chambers. The chambers in communication with the third heat exchanging tube bundlemay be collectively referred to as first accommodating chambers, and the chambers in communication with the fourth heat exchanging tube bundlemay be collectively referred to as second accommodating chambers. From the perspective of easy reading and understanding, the above first separators, the second separators, the heat exchanging tube bundle chambers, and the accommodating chambers are renamed according to different positions thereof (mainly, the chamber on the inlet side (the entering water side) of the first heat exchangeris named, and the accommodating chamber on the outlet side (the water exit side) of the second heat exchangeris named).

The structures of the first heat exchangerand the second heat exchangerare described in detail above, and the flow directions of the waterways thereof are described below.

In some embodiments, water as the heat exchanging medium enters the first heat exchanging tube bundleand the second heat exchanging tube bundlefrom the fourth heat exchanging tube bundle chamberof the first heat exchanger.

The water entering the second heat exchanging tube bundleenters the second accommodating chamberof the second heat exchangerthrough the second heat exchanging tube bundle chamber, exchanges heat in the fourth heat exchanging tube bundle, flows out through the fourth accommodating chamberand enters the first heat exchanging tube bundle chamberof the first heat exchanger, mixes with the water flowing through the second tube body, flows through the first tube bodyand flows out through the third heat exchanging tube bundle chamber, enters the fifth accommodating chamberof the second heat exchangerthrough an external pipeline, flows through the fourth tube body, the first accommodating chamber, and the third tube body, and finally is discharged from the third accommodating chamber, thus completing heat exchange and flowing out of the second heat exchanger.

As described above, the first heat exchanging tube bundleis a double-pass tube bundle including the first tube bodyand the second tube body. The water entering the second tube bodyof the first heat exchanging tube bundlemerges with the water from the fourth accommodating chamberafter entering the first heat exchanging tube bundle chamber, which will not be repeated here.

In some embodiments, after the entering water of the heat exchanger unit enters the heat exchanger unit from the fourth heat exchanging tube bundle chamberof the first heat exchanger, part of the entering water firstly flows through the second heat exchanging tube bundleof the first heat exchangerand then flows through the fourth heat exchanging tube bundleof the second heat exchanger, exchanges heat with the refrigerant that has been partially cooled and condensed in the first heat exchangerand the second heat exchangerrespectively, enters the first heat exchanging tube bundle chamberof the first heat exchangerthrough an external pipeline, and exchanges heat with the high-temperature and high-pressure refrigerant entering the first heat exchangerfrom the outlet of the compressor to further increase its temperature. The water entering the first heat exchanging tube bundle chamberfrom the fourth heat exchanging tube bundlecan cool the refrigerant in the first heat exchanger, so that the refrigerant maintains an appropriate temperature difference with the water from the second heat exchanger, thereby ensuring the heating effect of the first heat exchanger.

In some embodiments, for example, as a housing-and-tube heat exchanger, there is no need to make a large structural change to the first heat exchangerand the second heat exchanger, and only corresponding separators need to be disposed at ends of a respective housing and proper external pipelines need to be configured, thereby simplifying waterway arrangement of the heat exchanger unit. In some embodiments, on the premise of ensuring that the flow directions of the waterways are unchanged or the positions of the inlets and the outlets of the waterways are unchanged, the number of waterway passes of the first heat exchanging tube bundleand the third heat exchanging tube bundlemay also be adjusted and corresponding separators may be added, which is not limited in this disclosure.

Preferably, the external pipeline through which the fourth accommodating chamberis in communication with the first heat exchanging tube bundle chamberis provided with a first water pump. The first water pumpcan pump the heat exchanging medium in the fourth accommodating chamberto the first heat exchanging tube bundle chamber, thereby overcoming the flow resistance caused by this part of water passing through the second heat exchanging tube bundle, the fourth heat exchanging tube bundle, and the external pipeline, and is beneficial to achieve pressure balance and full mix with the water from the second tube bodyin the first heat exchanging tube bundle chamberto ensure the water flow capacity requirement of the first tube body.