Heat supply system and heat supply method

Abstract

The embodiment of the invention discloses a heat supply system and a heat supply method. The system comprises a carbon dioxide heat pump located in an environment room; the heat supply terminal is located outside the environment as a heat supply source; and a recooler; in the system, a carbon dioxide heat pump forms a first heat cycle system; wherein the carbon dioxide heat pump evaporator is used for extracting heat in an environment room; the carbon dioxide heat pump air cooler is used for releasing heat; the heat supply terminal, the recooler and the carbon dioxide heat pump form a second heat cycle system; wherein the carbon dioxide heat pump air cooler is used for releasing heat to return water from a heat supply terminal after being subjected to heat exchange and cooling by the recooler in a heat exchange mode, and the temperature of the return water is increased after the return water obtains the heat provided by carbon dioxide; return water from the heat supply terminal exchanges heat with air passing through the evaporator in the environment chamber in the recooler so as to provide heat for carbon dioxide in the evaporator. The system can effectively improve the efficiency of the carbon dioxide heat pump, and the heat supply efficiency of the whole system is improved.

Description

Technical Field

[0001] The present application relates to the field of heating technology, and more specifically, to a heating system and a heating method. Background Art

[0002] With the conclusion of the Kigali Amendment, hydrofluorocarbon refrigerants (HFCs) have been included in the list of controlled substances, and the reduction schedule of HFCs has officially entered the agenda. Natural refrigerants have become the preferred alternative because of their safety and environmental friendliness. Among natural refrigerants, carbon dioxide has attracted widespread attention for its excellent environmental performance, refrigeration performance, safety and chemical stability, as well as its low price and easy access to economic performance. Especially in European countries, the research and application of carbon dioxide refrigeration and heat pump systems have developed very rapidly in the past 20 years. The unit volume refrigeration capacity of carbon dioxide is about 5 to 8 times that of refrigerants such as R22, NH3 and R134a, which greatly reduces the structural size of the compressor and makes the entire refrigeration system more compact and economical. Compared with conventional refrigerants, its more outstanding heat transfer performance and flow performance make the heat exchanger more efficient and conducive to the optimization of system performance.

[0003] Due to the unique temperature glide phenomenon of carbon dioxide in the high-temperature heat exchange process, transcritical carbon dioxide heat pumps have a natural advantage in providing high-temperature hot water. In order to make the room reach a comfortable heating temperature, the return water temperature should be above 45°C. However, experiments have shown that such a high return water temperature is not friendly to carbon dioxide heat pumps, causing their efficiency to drop sharply or even fail to operate normally. Summary of the invention

[0004] The object of the present invention is to provide a heating system and a heating method to solve at least one of the above technical problems.

[0005] In order to achieve at least one of the above purposes, the present application adopts the following technical solutions:

[0006] A first aspect of the present application provides a heating system, the system comprising:

[0007] A carbon dioxide heat pump located in an environmental chamber;

[0008] A heating terminal located outside the ambient room as a heating heat source; and

[0009] recooler;

[0010] In this system:

[0011] The carbon dioxide heat pump forms a first heat cycle system; wherein the carbon dioxide heat pump evaporator is used to extract heat from the environment room; the carbon dioxide heat pump air cooler is used to release the heat;

[0012] The heating terminal, the recooler and the carbon dioxide heat pump form a second heat cycle system; wherein the carbon dioxide heat pump air cooler is used to release heat to the return water from the heating terminal after heat exchange and cooling by the recooler through heat exchange, and the return water obtains the heat provided by the carbon dioxide and its temperature rises, and then enters the heating terminal again to provide heat for the room;

[0013] The return water from the heating terminal exchanges heat with the air in the environment room that has passed through the evaporator in the subcooler, lowering the return water temperature while raising the air temperature to provide heat for the carbon dioxide in the evaporator.

[0014] Optionally, the system also includes: a heat collection chamber; a third heat cycle system formed by the heat collection chamber and the environmental chamber; wherein the air in the environmental chamber that has been preliminarily preheated by the subcooler and passed through the evaporator exchanges heat with the air in the heat collection chamber to provide heat for the carbon dioxide in the evaporator.

[0015] Optionally, the system further comprises: an energy storage device; the energy storage device is configured to exchange heat with the air in the environmental room that has passed through the evaporator after being preliminarily preheated by the subcooler, so as to provide heat for the carbon dioxide in the evaporator.

[0016] Optionally, the energy storage device absorbs heat through the heat collection chamber and stores the heat in the energy storage device.

[0017] Optionally, an air return port and an air exhaust port are provided between the heat collection chamber and the environmental chamber;

[0018] The air in the environmental room enters the heat collecting room through the air outlet and exchanges heat with the air in the heat collecting room. The air after heat exchange enters the environmental room again through the air return outlet.

[0019] Optionally, the return air outlet and the exhaust air outlet both include a first switch and a second switch;

[0020] The first switch is used to control whether the environmental chamber is connected to the heat collection chamber;

[0021] The second switch is used to control whether the energy storage device exchanges heat with the air in the environmental room.

[0022] Optionally, the heat collection chamber is a solar heat collection chamber.

[0023] Optionally, the environmental chamber comprises a thermal insulation layer.

[0024] Optionally, the heat collecting chamber includes an exhaust valve;

[0025] The environmental chamber includes a fresh air valve.

[0026] The second aspect of the present application further provides a heating method implemented by using the heating system according to the first aspect, the method comprising:

[0027] The return water from the heating terminal exchanges heat with the air passing through the evaporator in the environment room in the subcooler, lowering the return water temperature and preheating the air passing through the evaporator in the environment room.

[0028] The carbon dioxide heat pump evaporator extracts the heat of the preliminarily preheated air in the environment room;

[0029] The carbon dioxide heat pump air cooler releases heat through heat exchange to the return water from the heating terminal after heat exchange and cooling in the recooler.

[0030] The beneficial effects of this application are as follows:

[0031] In view of the problems existing in the prior art, the present invention, on the one hand, exchanges heat between the return water from the heating terminal 10 and the air (i.e., the air discharged from the evaporator) in the environmental chamber 3 through the evaporator in the subcooler 4, so that the return water temperature after cooling is not higher than 45°C, so as to effectively improve the efficiency of the carbon dioxide heat pump, thereby improving the heating efficiency of the entire system. On the other hand, the subcooler can also be used to preheat the air in the environmental room, especially the low-temperature air in the environmental room that has passed through the evaporator, that is, to increase the temperature in the environmental room, so as to provide more heat for the carbon dioxide in the evaporator. The second heat cycle system in the present invention is used to release the heat released by the carbon dioxide heat pump air cooler to the return water from the heating terminal after heat exchange and cooling in the subcooler through heat exchange, so as to increase the temperature of the return water. The heated return water passes through the air cooler to obtain the heat of the carbon dioxide and then increases the temperature before entering the heating terminal again for heating. In summary, the heating system provided by the present application, through the return water from the heating terminal 10 in the subcooler 4 and the air in the environmental chamber 3 that has passed through the evaporator, effectively reduces the temperature of the return water from the heating terminal, improves the efficiency of the carbon dioxide heat pump, and does not have an adverse effect on the carbon dioxide heat pump, such as the problem of being unable to start due to the return water temperature being too high. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0033] Figure 1 A schematic structural diagram showing a heat collection chamber and an environmental chamber of a heat supply system in an embodiment of the present application when the heat collection chamber is connected.

[0034] Figure 2 A schematic diagram showing a structure in which an energy storage device of a heating system in an embodiment of the present application provides heating for an environmental chamber DETAILED DESCRIPTION

[0035] In the following description, for the purpose of explanation, in order to provide a thorough understanding of one or more embodiments, numerous specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details.

[0036] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0037] It should also be noted that, in the description of the present application, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the statement "comprise one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0038] In order to solve the problems existing in the prior art, an embodiment of the present application provides a heating system, such as Figure 1-2As shown, the system includes: a carbon dioxide heat pump 1 located in an environmental room 3; a heating terminal 10 located outside the environmental room as a heating heat source, the heating terminal 10 includes but is not limited to, for example, heating, which is used as a heat source to increase the temperature in the room; and a recooler 4; in this system: a first heat cycle system formed by the carbon dioxide heat pump 1; wherein the carbon dioxide heat pump evaporator is used to extract heat from the environmental room 3; the carbon dioxide heat pump 1 air cooler is used to release heat; a second heat cycle system formed by the heating terminal 10, the recooler 4 and the carbon dioxide heat pump 1; wherein, The air cooler of the carbon dioxide heat pump 1 is used to release heat to the return water from the heating terminal 10 after heat exchange and cooling in the subcooler 4 through heat exchange. The temperature of the return water increases after obtaining the heat provided by the carbon dioxide. Specifically, the temperature of the return water increases after obtaining the heat provided by the carbon dioxide in the air cooler, and enters the heating terminal 10 again to provide heat for the room; the return water from the heating terminal 10 exchanges heat with the air passing through the evaporator (i.e., the evaporator exhaust air) in the subcooler 4, reducing the return water temperature while increasing the air temperature to provide heat for the carbon dioxide in the evaporator. Specifically, the air passing through the evaporator after preliminary preheating can exchange heat with the low-temperature air of the carbon dioxide heat pump evaporator to provide heat for the carbon dioxide in the carbon dioxide heat pump evaporator.

[0039] Compared with the prior art, the technical solution provided by the present application, on the one hand, the return water from the heating terminal 10 exchanges heat with the air passing through the evaporator in the environmental chamber 3 in the subcooler 4 to reduce the temperature of the return water from the heating terminal 10, so that the return water temperature after cooling is not higher than 45°C, so as to effectively improve the efficiency of the carbon dioxide heat pump 1, and thus improve the heating efficiency of the entire system. On the other hand, the subcooler 4 can also be used to preheat the air in the environmental chamber 3, especially the low-temperature air passing through the evaporator in the environmental chamber 3, that is, to increase the temperature in the environmental chamber 3 to provide more heat for the carbon dioxide in the evaporator. By exchanging heat between the return water from the heating terminal 10 and the air passing through the evaporator in the environmental chamber 3 in the subcooler 4, the temperature of the return water from the heating terminal 10 is effectively reduced, the efficiency of the carbon dioxide heat pump 1 is improved, and no adverse effect is produced on the carbon dioxide heat pump. In a specific embodiment, the system further includes: a heat collection chamber 6; a third heat cycle system formed by the heat collection chamber 6 and the environment chamber 3; wherein the air in the environment chamber 3 that has been preheated by the subcooler 4 and has passed through the evaporator can exchange heat with the air in the heat collection chamber 6 to provide heat for the carbon dioxide in the evaporator. Specifically, the return water from the heating terminal 10 exchanges heat with the air in the environment chamber 3 that has passed through the evaporator in the subcooler 4 to preheat the air in the environment chamber 3, and the air that has been preheated by the subcooler 4 and has passed through the evaporator exchanges heat with the air in the heat collection chamber 6 to increase the temperature of the air that has been preheated by the subcooler 4, and the air returns to the air inlet of the evaporator to provide heat for the carbon dioxide therein. The third heat cycle system can further increase the temperature of the air in the environment chamber 3 that has been preheated by the subcooler 4, providing more heat for the carbon dioxide in the evaporator, thereby increasing the evaporation temperature of the carbon dioxide heat pump 1 and further improving the efficiency of the entire heating system.

[0040] Optionally, the heat collection chamber 6 may be a solar heat collection chamber. When the sunlight is sufficient, the solar energy absorbs the heat of the sun, raising the temperature of the heat collection chamber 6. In practical applications, the outer wall of the heat collection chamber 6 may be transparent glass to improve the efficiency of absorbing solar energy.

[0041] Furthermore, a return air port 12 and an exhaust air port 13 are provided between the heat collection chamber 6 and the environment chamber 3. The air in the environment chamber 3 enters the heat collection chamber 6 through the exhaust air port 13 and exchanges heat with the air in the heat collection chamber 6. The air after heat exchange enters the environment chamber 3 again through the return air port 12. In other words, the environment chamber 3 can be connected with the heat collection chamber 6 through the return air port 12 and the exhaust air port 13. In practical applications, the heat collection chamber 6 and the environment chamber 3 share a side wall, and the return air port 12 and the exhaust air port 13 respectively penetrate the side wall, which has a simple structure.

[0042] In a specific embodiment, the system further includes: an energy storage device 11, which is configured to exchange heat with the air passing through the evaporator in the environmental chamber 3 and preliminarily preheated by the subcooler 4 to provide heat for the carbon dioxide in the evaporator. Specifically, the return water from the heating terminal 10 exchanges heat with the air passing through the evaporator in the environmental chamber 3 in the subcooler 4, and preliminarily preheats the air in the environmental chamber 3. The air passing through the evaporator after the preliminarily preheated by the subcooler 4 exchanges heat with the energy storage device 11 to increase the temperature of the air preliminarily preheated by the subcooler 4, and the air returns to the air inlet of the evaporator to provide heat for the carbon dioxide therein. Here, when the temperature of the heat collection chamber 6 is not higher than the temperature in the environmental chamber 3, the energy storage device 11 is turned on to exchange heat with the environmental chamber 3 to increase the temperature in the environmental chamber 3.

[0043] In a specific embodiment, the energy storage device 11 absorbs heat from the heat collection chamber 6 and stores the heat in the energy storage device 11. Specifically, the energy storage device 11 can absorb heat from the heat collection chamber 6 when the temperature of the heat collection chamber 6 is high and store the heat therein. In practical applications, heat can of course also be stored in other ways.

[0044] Optionally, the energy storage device 11 includes a phase change material, which refers to a substance that changes its state and provides latent heat without changing its temperature. The process of changing physical properties is called a phase change process. At this time, the phase change material will absorb or release a large amount of latent heat.

[0045] In a specific example, the energy storage device 11 can be installed between the return air outlet 12 and the exhaust air outlet 13. In this way, the energy storage device is adjacent to the heat collection chamber, which is convenient for storing heat and can also be used as a common side wall of the heat collection chamber 6 and the environmental chamber 3, thereby reducing the occupied space of the entire heating system.

[0046] In a specific embodiment, the return air inlet 12 and the exhaust air outlet 13 both include a first switch 9 and a second switch 8; the first switch 9 is used to control whether the environmental chamber 3 is connected to the heat collection chamber 6; the second switch 8 is used to control whether the energy storage device 11 exchanges heat with the air preheated by the subcooler in the environmental chamber 3. When the first switch 9 is turned on and the second switch 8 is closed, the return air inlet 12 and the exhaust air outlet 13 between the heat collection chamber 6 and the environmental chamber 3 are both opened, so that the heat collection chamber 6 is connected to the environmental chamber 3, and the air preheated by the subcooler in the environmental chamber 3 exchanges heat with the air in the heat collection chamber 6, and the heat storage device 11 does not exchange heat with the air in the environmental chamber 3; when the first switch 9 is closed and the second switch 8 is turned on, the return air inlet 12 and the exhaust air outlet 13 between the heat collection chamber 6 and the environmental chamber 3 are both closed, and the two are separate spaces and do not exchange heat; the energy storage device 11 exchanges heat with the air in the environmental chamber 3 to increase the temperature in the environmental chamber 3.

[0047] In actual application, during the day, the two first switches 9 are both turned on, the two second switches 8 are both turned off, the heat collection chamber 6 is connected to the environmental chamber 3, the return water from the heating terminal 10 exchanges heat with the air in the environmental chamber 3 that has passed through the evaporator in the subcooler 4, and preliminarily preheats the low-temperature air in the environmental chamber 3 that has passed through the evaporator, the air that has been preliminarily preheated by the subcooler 4 exchanges heat with the air in the heat collection chamber 6, and the temperature of the low-temperature air that has been preliminarily preheated by the subcooler 4 is increased, and the air returns to the evaporator air inlet to provide heat for the carbon dioxide therein. The energy storage device 11 absorbs heat through the heat collection chamber and stores it therein.

[0048] At night, the two first switches 9 are closed, the two second switches 8 are opened, the return air inlet 12 and the exhaust air outlet 13 between the heat collecting chamber 6 and the environmental chamber 3 are closed, and the energy storage device 11 is opened and releases heat; specifically, the return water from the heating terminal 10 is heat-exchanged with the air passing through the evaporator in the environmental chamber 3 in the subcooler 4, and the low-temperature air in the environmental chamber 3 passing through the evaporator is preliminarily preheated, and the air preliminarily preheated by the subcooler 4 exchanges heat with the energy storage device 11 to increase the temperature of the low-temperature air after the preheating by the subcooler 4, and the heated air returns to the evaporator air inlet to provide heat for the carbon dioxide therein.

[0049] In a specific embodiment, the heat collection chamber 6 includes an exhaust valve 7, and the exhaust valve 7 is used to connect the heat collection chamber 6 with the outside world. The exhaust valve 7 is arranged on the side wall of the heat collection chamber 6, and the side wall is not the same side wall as the side wall shared by the environment chamber 3 and the heat collection chamber 6. When the exhaust valve 7 is opened, the heat collection chamber 6 is connected with the outside world, and can be used to exhaust the air therein, or allow the outside air to enter the heat collection chamber 6.

[0050] In a preferred embodiment, the environmental chamber 3 includes a fresh air valve 2; the fresh air valve 2 is used to control whether the outside air enters the environmental chamber 3. The fresh air valve 2 can be arranged on the side wall of the environmental chamber 3, which is not the same side wall as the side wall shared by the environmental chamber 3 and the heat collecting chamber 6. When the fresh air valve 2 is opened, the environmental chamber 3 can be connected with the outside, so that the outside air can enter the environmental chamber 3 or the air in the environmental chamber 3 can be discharged to the outside.

[0051] In a specific embodiment, the environmental chamber 3 includes a heat-insulating layer 5 . The material of the heat-insulating layer 5 includes but is not limited to a polyurethane foam board, which can reduce heat loss in the environmental chamber 3 .

[0052] The present application also provides a heating method implemented by using the above-mentioned heating system, comprising:

[0053] Step S1: the return water from the heating terminal exchanges heat with the air passing through the evaporator in the environmental room in the recooler to reduce the return water temperature and preliminarily preheat the air passing through the evaporator in the environmental room 3;

[0054] Step S2: the evaporator of the carbon dioxide heat pump 1 extracts heat from the preliminarily preheated air in the environmental chamber 3;

[0055] Step S3: the air cooler of the carbon dioxide heat pump 1 releases heat to the return water from the heating terminal 10 after heat exchange and temperature reduction in the subcooler 4 through heat exchange.

[0056] In one embodiment, the step S1 further comprises:

[0057] The air passing through the evaporator after preliminary preheating by the subcooler 4 exchanges heat with the air in the heat collecting chamber 6 to increase the temperature of the air preheated by the subcooler, and the air returns to the air inlet of the evaporator to provide heat for the carbon dioxide therein. Specifically, the air passing through the evaporator after preliminary preheating by the subcooler 4 exchanges heat with the air in the heat collecting chamber 6, so that the temperature of the air passing through the evaporator is further increased, providing more heat for the carbon dioxide in the evaporator, thereby increasing the evaporation temperature of the carbon dioxide heat pump 1 and further improving the efficiency of the heating system.

[0058] Alternatively, in one embodiment, the step S1 further includes: the air preheated by the subcooler 4 exchanges heat with the energy storage device 11 to increase the temperature of the air preheated by the subcooler 4, and the air returns to the air inlet of the evaporator to provide heat for the carbon dioxide therein. Specifically, the air preheated by the subcooler 4 and passing through the evaporator further increases the temperature of the air passing through the evaporator by exchanging heat with the energy storage device 11, providing more heat for the carbon dioxide in the evaporator, thereby increasing the evaporation temperature of the carbon dioxide heat pump 1 and further improving the efficiency of the heating system.

[0059] In the heating method provided by the present application, the return water from the heating terminal 10 exchanges heat with the air passing through the evaporator in the environmental chamber 3 in the recooler 4, thereby effectively reducing the temperature of the return water from the heating terminal 10, improving the heat conversion efficiency of the carbon dioxide heat pump, and avoiding the problem of adverse effects on the carbon dioxide heat pump due to the high return water temperature of the heating terminal 10.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A heating system, characterized in that: The system comprises: A carbon dioxide heat pump located in an environmental chamber; A heating terminal located outside the ambient room as a heating heat source; and recooler; In this system: The carbon dioxide heat pump forms a first heat cycle system; wherein the carbon dioxide heat pump evaporator is used to extract heat from the environment room; the carbon dioxide heat pump air cooler is used to release the heat; The heating terminal, the recooler and the carbon dioxide heat pump form a second heat cycle system; wherein the carbon dioxide heat pump air cooler is used to release heat to the return water from the heating terminal after heat exchange and cooling by the recooler through heat exchange, and the return water obtains the heat provided by the carbon dioxide and its temperature rises, and then enters the heating terminal again to provide heat for the room; The return water from the heating terminal exchanges heat with the air in the environmental room that has passed through the evaporator in the subcooler, lowering the return water temperature while raising the air temperature to provide heat for the carbon dioxide in the evaporator.

2. The heating system according to claim 1, characterized in that: The system also includes: a heat collection chamber; a third heat cycle system formed by the heat collection chamber and the environmental chamber; wherein the air in the environmental chamber that has been preliminarily preheated by the subcooler and passed through the evaporator exchanges heat with the air in the heat collection chamber to provide heat for the carbon dioxide in the evaporator.

3. The heating system according to claim 2, characterized in that: The system further includes: an energy storage device; the energy storage device is configured to exchange heat with the air in the environmental room that has been preliminarily preheated by the subcooler and passed through the evaporator to provide heat for the carbon dioxide in the evaporator.

4. The heating system according to claim 3, characterized in that: The energy storage device absorbs heat through the heat collection chamber and stores the heat in the energy storage device.

5. The heating system according to claim 3, characterized in that: An air return port and an air exhaust port are provided between the heat collection chamber and the environmental chamber; The air in the environmental room enters the heat collecting room through the air outlet and exchanges heat with the air in the heat collecting room. The air after heat exchange enters the environmental room again through the air return outlet.

6. The heating system according to claim 5, characterized in that: The return air outlet and the exhaust air outlet both include a first switch and a second switch; The first switch is used to control whether the environmental chamber is connected to the heat collection chamber; The second switch is used to control whether the energy storage device exchanges heat with the air in the environmental room.

7. The heating system according to claim 2, characterized in that: The heat collection chamber is a solar heat collection chamber.

8. The heating system according to claim 1, characterized in that: The environmental chamber includes a thermal insulation layer.

9. The heating system according to claim 2, characterized in that: The heat collecting chamber includes an exhaust valve; The environmental chamber includes a fresh air valve.

10. A heating method implemented by using the heating system according to any one of claims 1 to 9, characterized in that: The method includes: The return water from the heating terminal exchanges heat with the air passing through the evaporator in the environment room in the subcooler, lowering the return water temperature and preheating the air passing through the evaporator in the environment room. The carbon dioxide heat pump evaporator extracts the heat of the preliminarily preheated air in the environment room; The carbon dioxide heat pump air cooler releases heat through heat exchange to the return water from the heating terminal after heat exchange and cooling in the recooler.

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