Carbon dioxide heat pump system

Abstract

The utility model provides a carbon dioxide heat pump system which is provided with a water side supply end for working medium water to flow in and a water side load end for working medium water to flow out, and further comprises a compressor, an air cooler, an expansion valve, an evaporator and a water pump, the compressor, the first branch, the expansion valve and the evaporator are in fluid communication in sequence and form a carbon dioxide side loop allowing carbon dioxide fluid to flow circularly, the water side supply end, the second branch and the water side load end are in fluid communication in sequence and form a water supply path allowing working medium water to flow, and the water pump is arranged on the water supply path. The carbon dioxide heat pump system further comprises an electric heater and a backflow bypass capable of being selectively opened, the backflow bypass can allow working medium water located on the downstream of the second branch to flow back to the upstream of the second branch, the water pump, the second branch and the backflow bypass jointly form an inner circulation loop allowing the working medium water to circularly flow, and the electric heater is arranged on the inner circulation loop.

Description

Technical Field

[0001] The utility model relates to the technical field of heat pumps, in particular to a carbon dioxide heat pump system with a defrosting function. Background Art

[0002] Carbon dioxide heat pump, that is, a heat pump that uses carbon dioxide as a refrigerant, has many advantages such as large cooling capacity per unit volume, small compression ratio, environmental friendliness, low GWP value (global warming potential), and stable chemical properties. It is increasingly valued by the refrigeration and heating industries.

[0003] When the heat pump is running, the refrigerant absorbs heat and vaporizes at the evaporator, so the outside of the evaporator is prone to frost due to the drop in ambient air temperature. The frost on the evaporator hinders the convection heat exchange between the heat exchange tube and the ambient air, reducing the heat exchange coefficient of the evaporator and the thermal cycle efficiency of the heat pump system.

[0004] At present, how to effectively defrost is a proposition that has always troubled carbon dioxide heat pumps. Conventional refrigerant heat pumps generally use a four-way valve to switch the overall flow direction of the refrigerant to achieve the defrosting effect, but the fluid pressure inside the carbon dioxide heat pump is relatively high, and there is currently no four-way valve compatible with it on the market. Existing carbon dioxide heat pumps generally use hot gas bypass to defrost, that is, relying on the excess heat generated by the compressor itself to increase the temperature of the outer surface of the evaporator and the surrounding air in order to achieve the defrosting effect. However, in the case of low ambient temperature, high humidity, and thick frost, the heat generated by the compressor itself is relatively small, and it is impossible to completely remove the frost on the fins in a short time, resulting in a longer defrosting time. In addition, in the case of incomplete defrosting, there is residual snow water on the surface of the fins, which makes it easier to frost, and then the defrosting interval is shortened, affecting the overall efficiency of the unit. Utility Model Content

[0005] In view of the above technical problems, the purpose of the utility model is to provide a carbon dioxide heat pump system that can effectively defrost.

[0006] In order to achieve the above-mentioned purpose, the utility model provides the following technical solutions: a carbon dioxide heat pump system, having a water-side supply end for working medium water to flow in and a water-side load end for working medium water to flow out, the carbon dioxide heat pump also includes a compressor, an air cooler, an expansion valve, an evaporator and a water pump, the air cooler has a first branch and a second branch for heat exchange, the compressor, the first branch, the expansion valve and the evaporator are fluidly connected in sequence and constitute a carbon dioxide side loop for circulating carbon dioxide fluid, the water-side supply end, the second branch and the water-side load end are fluidly connected in sequence and constitute a water supply path for working medium water to flow, and the water pump is arranged on the water supply path; the carbon dioxide heat pump system also includes an electric heater and a selectively openable reflux bypass, the reflux bypass can allow working medium water located downstream of the second branch to flow back to the upstream of the second branch, the water pump, the second branch and the reflux bypass together form an internal circulation loop for circulating working medium water, and the electric heater is arranged on the internal circulation loop.

[0007] In the above technical solution, preferably, the water pump is arranged upstream of the second branch. Still more preferably, the electric heater is arranged between the water pump and the second branch.

[0008] In the above technical solution, preferably, it also includes a first thermometer located on both the inner circulation loop and the water supply path, and the first thermometer is adjacent to the downstream of the second branch. It is also possible that the heat pump system further includes a second thermometer located on the water supply path, and the second thermometer is adjacent to the upstream of the second branch.

[0009] In the above technical solution, preferably, the heat pump system further comprises a first three-way valve located on the water supply path, the first three-way valve having a first water inlet for the working medium water to flow in, a first water outlet for the working medium water to flow out, and a first bypass port, the first water outlet and the first bypass port are configured to independently adjust the opening, and the first bypass port fluid is connected to one end of the reflux bypass. It is also further preferred that the heat pump system further comprises a second three-way valve, the first three-way valve is arranged upstream of the second branch, the second three-way valve is arranged downstream of the second branch and has a second water inlet for the working medium water to flow in, a second water outlet for the working medium water to flow out, and a second bypass port, the second water outlet and the second bypass port are configured to independently adjust the opening, and the second bypass port fluid is connected to the other end of the reflux bypass.

[0010] In the above technical solution, preferably, a heat bypass is formed between the compressor and the evaporator for the hot air discharged from the compressor to flow to the evaporator fins.

[0011] Compared with the traditional carbon dioxide heat pump, the carbon dioxide system provided by the technical solution of the utility model can open the reflux bypass, that is, open the internal circulation loop, when defrosting. The temperature of the working water on the internal circulation loop is then heated by an electric heater. As a result, the temperature of the carbon dioxide fluid when leaving the air cooler can be greatly increased. When this part of the carbon dioxide fluid flows to the evaporator, the temperature of the evaporator surface and the surrounding air can be greatly increased through heat transfer, thereby achieving a rapid defrosting effect. Thanks to the smaller compression ratio (2.5-3.5) of carbon dioxide refrigerant and the characteristics of the supercritical cycle (that is, carbon dioxide circulates in the heat pump system in the form of a supercritical fluid, and the physical properties of gaseous carbon dioxide and liquid carbon dioxide are close), this defrosting method does not cause damage to the various equipment in the carbon dioxide side loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a system diagram of the carbon dioxide heat pump system provided by the utility model; wherein the arrow direction in the figure indicates the flow direction of the carbon dioxide refrigerant;

[0013] Figure 2 This is a partial structural schematic diagram of the carbon dioxide heat pump system provided by the utility model.

[0014] 10. Water supply side; 20. Water load side;

[0015] 1. Compressor; 2. Air cooler; 3. Expansion valve; 4. Evaporator; 5. Heat bypass; 6. Water pump; 7. Electric heater; 8. Reflux bypass; 81. First three-way valve; 82. Second three-way valve; 91. First thermometer; 92. Second thermometer. DETAILED DESCRIPTION

[0016] In order to explain in detail the technical content, structural features, objectives and effects of the present application, the technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0017] In this application, spatially relative terms such as "under", "below", "under", "lower", "above", "upper", "above", "higher", "side" (for example, as in "sidewall"), etc., are used to describe the relationship of one element to another (other) element as shown in the accompanying drawings. The spatially relative terms are intended to include different orientations of the device in use, operation and / or manufacture in addition to the orientation depicted in the accompanying drawings. For example, if the device in the accompanying drawings is turned over, the elements described as "under" or "beneath" other elements or features will then be positioned as "above" the other elements or features. Therefore, the exemplary term "under" can include both above and below orientations. In addition, the device can be positioned otherwise (for example, rotated 90 degrees or at other orientations), so the spatially relative descriptors used herein are interpreted accordingly.

[0018] In the present utility model, the term "upstream" (or "downstream") means that one device or component is located upstream (or downstream) of another device or component in terms of the flow direction of the working medium water in the water supply path. For example, "the first three-way valve is located upstream of the second branch" means that in terms of the flow direction of the working medium water in the water supply path, the first three-way valve is located upstream of the second branch.

[0019] Figure 1 The carbon dioxide heat pump system (hereinafter referred to as the heat pump system) provided by the utility model is shown, which has a water-side supply end 10 for the inflow of working medium water and a water-side load end 20 for the outflow of working medium water. The heat pump system can heat the working medium water flowing in from the water-side supply end 10 to provide heat to various heat-using devices (not shown in the figure) located downstream of the water-side load end 20.

[0020] Combination Figure 2 The heat pump system includes a compressor 1, an air cooler 2, an expansion valve 3 and an evaporator 4. The air cooler 2 has a first branch and a second branch for heat exchange. The compressor 1, the first branch of the air cooler 2, the expansion valve 3 and the evaporator 4 are fluidly connected in sequence and form a carbon dioxide side loop for circulating carbon dioxide fluid.

[0021] Among them, the compressor 1 can compress the high-temperature and low-pressure carbon dioxide fluid into a high-temperature and high-pressure carbon dioxide fluid, and provide the power for the carbon dioxide fluid to circulate in the loop; the air cooler 2 provides heat exchange between the carbon dioxide fluid and the working medium water, and allows the high-temperature and high-pressure carbon dioxide fluid to release heat to the outside and then be converted into a low-temperature and high-pressure carbon dioxide fluid; the expansion valve 3 can convert the low-temperature and high-pressure carbon dioxide fluid into a low-temperature and low-pressure carbon dioxide fluid through the throttling effect; finally, the evaporator 4 provides the low-temperature and low-pressure carbon dioxide fluid to exchange heat with the ambient air here, and converts it into a high-temperature and low-pressure carbon dioxide fluid. Therefore, through the above cycle, the carbon dioxide in the loop transfers part of the heat of the ambient air to the working medium water to heat the working medium water.

[0022] Furthermore, the heat pump system also forms a heat bypass 5 for the hot gas discharged from the compressor 1 to flow to the outside of the evaporator 4, so as to increase the temperature of the outer surface of the evaporator 4 and the ambient air to a certain extent, and reduce or alleviate frost on the evaporator 4.

[0023] The heat pump system also includes a water pump 6 that can provide flow power for the working medium water, an electric heater 7 that can heat the working medium water, and a selectively openable reflux bypass 8. The water side supply end 10, the second branch of the air cooler 2, and the water side load end 20 are fluidly connected in sequence and form a water supply path for the working medium water to flow.

[0024] The heat pump system also forms an internal circulation loop that can be selectively started. The internal circulation loop allows the working medium water to circulate, and the water pump 6, the electric heater 7 and the second branch of the air cooler 2 are all located on the internal circulation loop. Among them, the return bypass 8 constitutes a part of the internal circulation loop, and the working medium water is returned from the downstream of the second branch to the upstream of the second branch.

[0025] When the heat pump system needs to perform defrosting, the reflux bypass 8 is opened to allow at least part of the working medium water to circulate in the inner circulation loop. Thereafter, the working medium water in the inner circulation loop is heated by the electric heater 7, greatly increasing the temperature of the carbon dioxide fluid when it leaves the first branch. Thereafter, the carbon dioxide fluid with a higher temperature undergoes heat exchange at the evaporator 4, transferring part of the heat to the outside and causing the outer surface temperature of the evaporator 4 to rise, thereby achieving the effect of quickly removing frost on the outer surface of the evaporator 4. Thanks to the smaller compression ratio of carbon dioxide refrigerant and the characteristics of the supercritical cycle, this defrosting method does not cause damage to the various devices in the carbon dioxide side loop.

[0026] Furthermore, considering that the higher the working water temperature is, the higher the possibility of cavitation of the water pump 6 is. In order to extend the service life of the water pump 6, it is advisable to arrange it at a lower temperature. For this reason, the water pump 6 in this embodiment is arranged upstream of the second branch, and the electric heater 7 is arranged between the water pump 6 and the second branch.

[0027] Furthermore, the present embodiment is also provided with a first thermometer 91 adjacent to the downstream of the second branch to monitor the temperature of the working medium water leaving the second branch, and the heat pump system is configured to selectively open the return bypass 8 based on the signal of the first thermometer 91. It can be understood that if frost occurs on the outer surface of the evaporator 4, the heat absorbed by the carbon dioxide refrigerant from the evaporator 4 will be reduced, and the temperature of the working medium water when leaving the second branch will be reduced. Therefore, the return bypass 8 can be selectively opened and closed by the signal of the first thermometer 91 to perform defrosting operations. For example, when the first thermometer 91 monitors that the temperature of the working medium water leaving the second branch is below 35°C, the return bypass 8 is opened, and the heat pump system performs defrosting operations; when it is subsequently monitored that the temperature of the working medium water leaving the second branch is above 45°C, the return bypass 8 is closed, and the heat pump system ends the defrosting operation. Among them, the first thermometer 91 is located on both the water supply path and the internal circulation loop.

[0028] Furthermore, the present embodiment is further provided with a second thermometer 92 adjacent to the upstream of the second branch to monitor the temperature of the working medium water when it enters the second branch. The first and second thermometers can be used to monitor the inlet and outlet temperature difference of the working medium water in the second branch, and then determine whether there is scaling, leakage, etc. in the second branch.

[0029] Finally, this embodiment provides a technical solution that can realize the selective opening of the reflux bypass 8 (ie, the selective opening of the internal circulation loop). Figure 1-2 As shown, the heat pump system of this embodiment is also equipped with a first three-way valve 81, which is located on the water supply path and has a first water inlet for the working medium water to flow in, a first water outlet for the working medium water to flow out, and a first bypass port at one end of the fluid connected to the reflux bypass 8. The first water inlet, the first water outlet and the first bypass port are all configured to have independently adjustable openings. When the reflux bypass 8 needs to be opened, the heat pump system can reduce (or completely close) the opening of the first water inlet and increase (or completely open) the opening of the first bypass port. The water inlet of the water pump 6 forms a negative pressure. Under the action of the negative pressure, at least part of the working medium water flowing out of the second branch flows back to the water inlet of the water pump 6 through the reflux bypass 8, thereby forming a circulating flow. Among them, the first three-way valve 81 can be arranged upstream of the second branch, or downstream of the second branch. In other embodiments, the selective opening of the reflux bypass can also be achieved by forming a solenoid valve group with multiple solenoid valves that can independently control the opening.

[0030] Furthermore, the present embodiment also provides a second three-way valve 82. Similarly, the second three-way valve 82 has a second water inlet for the working medium water to flow in, a second water outlet for the working medium water to flow out, and a second bypass port connected to the other end of the fluid return bypass 8 (i.e., the side away from the first three-way valve 81). The second water inlet, the second water outlet and the second bypass port are all configured to have independently adjustable openings. Compared with the case of using only one three-way valve, the advantage of the three-way valve group composed of two three-way valves is that it can cut off the water supply path and allow the working medium water to circulate completely in the internal circulation loop, thereby quickly increasing the temperature of this part of the working medium water. Specifically, in the present embodiment, the first three-way valve 81 is arranged upstream of the second branch, and the second three-way valve 82 is arranged downstream of the second branch. When the heat pump system is performing defrosting operation, the first water inlet of the first three-way valve 81 can be closed and the first bypass port can be opened, and the second water outlet of the second three-way valve 82 can be closed and the second bypass port can be opened, so that the working water in the internal circulation loop can be quickly heated up and the duration of the defrosting operation can be reduced.

[0031] The above embodiments are only for illustrating the technical concept and features of the present application, and their purpose is to enable people familiar with the technology to understand the content of the present application and implement it accordingly, and they cannot be used to limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A carbon dioxide heat pump system, comprising a water supply end for inflow of working medium water and a water load end for outflow of working medium water, characterized in that: It also includes a compressor, an air cooler, an expansion valve, an evaporator and a water pump. The air cooler has a first branch and a second branch for heat exchange. The compressor, the first branch, the expansion valve and the evaporator are fluidly connected in sequence and form a carbon dioxide side loop for circulating carbon dioxide fluid. The water side supply end, the second branch and the water side load end are fluidly connected in sequence and form a water supply path for flowing working medium water. The water pump is arranged on the water supply path. The carbon dioxide heat pump system also has an electric heater and a selectively openable reflux bypass. The reflux bypass can allow the working medium water located downstream of the second branch to flow back to the upstream of the second branch. The water pump, the second branch and the reflux bypass together form an internal circulation loop for circulating working medium water. The electric heater is arranged on the internal circulation loop.

2. The carbon dioxide heat pump system according to claim 1, characterized in that: The water pump is arranged upstream of the second branch.

3. The carbon dioxide heat pump system according to claim 2, characterized in that: The electric heater is arranged between the water pump and the second branch.

4. The carbon dioxide heat pump system according to claim 1, characterized in that: It also includes a first thermometer located on both the internal circulation loop and the water supply path, and the first thermometer is adjacent to the downstream of the second branch.

5. The carbon dioxide heat pump system according to claim 4, characterized in that: It also includes a second thermometer located on the water supply path, wherein the second thermometer is adjacent to the upstream of the second branch.

6. The carbon dioxide heat pump system according to claim 1, characterized in that: It also includes a first three-way valve located on the water supply path, the first three-way valve has a first water inlet for the working medium water to flow in, a first water outlet for the working medium water to flow out, and a first bypass port, the first water inlet, the first water outlet and the first bypass port are constructed to independently adjust the opening, and the first bypass port fluid is connected to one side end of the reflux bypass.

7. The carbon dioxide heat pump system according to claim 6, characterized in that: It also includes a second three-way valve, wherein the first three-way valve is arranged upstream of the second branch, and the second three-way valve is arranged downstream of the second branch and has a second water inlet for the working medium water to flow in, a second water outlet for the working medium water to flow out, and a second bypass port, the second water inlet, the second water outlet and the second bypass port are constructed to have independently adjustable openings, and the second bypass port fluid is connected to the other side end of the reflux bypass.

8. The carbon dioxide heat pump system according to claim 1, characterized in that: A heat bypass is formed between the compressor and the evaporator for hot air discharged from the compressor to flow to the evaporator fins.

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