Cascade combined cooling and heating system and unit thereof

Abstract

The cascade type cold and heat cogeneration system comprises a high-temperature-stage circulation unit and a low-temperature-stage circulation unit, and the high-temperature-stage circulation unit and the low-temperature-stage circulation unit are coupled through an intermediate heat exchanger; a cooling heat exchanger is arranged in front of a refrigerant inlet of a high-temperature-stage valve in the high-temperature-stage circulating unit; a low-temperature fluid inlet / outlet of a low-temperature heat exchanger in the low-temperature circulation unit communicates with a low-temperature fluid inlet / outlet of the cooling heat exchanger to form a circulation path; and the cooling heat exchanger is used for reducing the temperature of the high-temperature refrigerant passing through the cooling heat exchanger according to heat exchange between the flowing-in low-temperature-stage fluid and the high-temperature-stage refrigerant. In this way, the temperature of the high-temperature-stage refrigerant passing through the cooling heat exchanger can be reduced, local temperature limiting cooling is conducted on the high-temperature-stage valve, it is guaranteed that the high-temperature-stage valve operates within the normal temperature range, the service life of the high-temperature-stage valve is prolonged, and the structural stability of the high-temperature-stage valve is improved.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and in particular to a cascade combined cooling and heating system and its unit. Background Technology

[0002] A cascade cogeneration system is a comprehensive energy supply system based on the principle of cascaded energy utilization. Its core is the combined production of cooling, heating, and electricity through cascade refrigeration technology. The cascade cogeneration system consists of a high-temperature stage and a low-temperature stage dual-cycle system, capable of handling high-temperature and low-temperature heat sources separately, dynamically matching cooling and heating load demands to achieve efficient energy utilization. The high-temperature stage cycle unit typically handles the high-temperature heat source or provides high-temperature heat output, while the low-temperature stage cycle unit handles the low-temperature heat source or provides low-temperature cooling output. Heat transfer between the two cycles is achieved through a heat exchanger. Simultaneously, intelligent control strategies dynamically adjust the operating parameters of each subsystem, such as compressor frequency and refrigerant flow rate, to ensure efficient and stable operation under different operating conditions, thereby significantly improving energy utilization efficiency and reducing operating costs.

[0003] However, high-temperature circulating units often reach temperatures exceeding 100℃ to 150℃, which will affect the material properties and structure of valve components in the high-temperature system. For example, at high temperatures, valve materials undergo thermal expansion, and the difference in the coefficient of thermal expansion between different materials may lead to increased clearances in internal components (such as valve stems and seats), affecting sealing performance and even causing leakage. The strength of metallic materials decreases at high temperatures, making valve structures more prone to deformation or damage, especially under pressure fluctuations, which may accelerate valve aging. High temperatures and continuous stress can cause creep in metallic materials, leading to loosening of connections, decreased sealing performance, and even leakage. High temperatures soften or decompose sealing materials (such as O-rings and gaskets), causing leakage and requiring replacement with high-temperature resistant sealing materials. This is especially true for the high-temperature throttling valves in high-temperature circulating units, which withstand transient thermal shocks exceeding 50K between the high-temperature refrigerant at the condenser outlet and the low-temperature refrigerant at the evaporator (heat exchanger) inlet.

[0004] Existing technology involves using special non-metallic materials to make valves in high-temperature circulating units to withstand transient thermal shocks above 50K. However, the lifespan of the valves is still shortened by high temperatures, affecting their structural stability. Summary of the Invention

[0005] This invention provides a cascade cogeneration system and unit to solve the problem that the lifespan of valve devices in high-temperature circulating units is shortened due to high temperatures, affecting the structural stability of the valve devices.

[0006] The technical solution of the present invention is a cascaded cogeneration system, comprising a high-temperature stage circulation unit and a low-temperature stage circulation unit, wherein the high-temperature stage circulation unit and the low-temperature stage circulation unit are coupled through an intermediate heat exchanger; a cooling heat exchanger is provided in front of the refrigerant inlet of the high-temperature stage valve in the high-temperature stage circulation unit.

[0007] The low-temperature fluid inlet and outlet of the low-temperature heat exchanger in the low-temperature stage circulation unit are respectively connected to the low-temperature fluid inlet and outlet of the cooling heat exchanger to form a circulation path;

[0008] The cooling heat exchanger is used to reduce the temperature of the high-temperature refrigerant passing through the cooling heat exchanger by exchanging heat between the incoming low-temperature fluid and the high-temperature refrigerant.

[0009] Furthermore, the low-temperature fluid inlet of the low-temperature heat exchanger is connected to the low-temperature fluid inlet of the cooling heat exchanger through a first pipe, and the low-temperature fluid outlet of the low-temperature heat exchanger is connected to the low-temperature fluid outlet of the cooling heat exchanger through a second pipe.

[0010] Furthermore, the low-temperature fluid outlet of the low-temperature heat exchanger is connected to the low-temperature fluid inlet of the cooling heat exchanger through a third pipe, and a water pump is provided on the third pipe;

[0011] The cryogenic fluid inlet of the cryogenic stage heat exchanger is connected to the cryogenic fluid outlet of the cooling heat exchanger via a fourth pipe.

[0012] Furthermore, the inlet and outlet of the cryogenic fluid in the cooling heat exchanger are connected by a fifth pipe, and a valve assembly is provided on the fifth pipe. The valve assembly is used to control the flow rate of the cryogenic fluid flowing into the cooling heat exchanger.

[0013] Furthermore, the cooling heat exchanger is any one of a shell-and-tube heat exchanger, a tube-and-tube heat exchanger, or a double tube sheet heat exchanger.

[0014] Furthermore, a first temperature sensing component is provided between the cooling heat exchanger and the high-temperature stage valve, the first temperature sensing component being used to detect the temperature of the high-temperature stage refrigerant flowing out of the cooling heat exchanger.

[0015] Furthermore, a cooling heat exchanger is connected to the bottom of the low-temperature stage heat exchanger.

[0016] Furthermore, the low-temperature stage heat exchanger, intermediate heat exchanger, and high-temperature stage heat exchanger are arranged side by side in a horizontal direction.

[0017] Furthermore, the low-temperature refrigerant in the low-temperature stage circulation unit circulates sequentially through the low-temperature stage heat exchanger, the low-temperature stage compressor, the intermediate heat exchanger, and the low-temperature stage valve;

[0018] The high-temperature refrigerant in the high-temperature circulating unit circulates sequentially through the high-temperature heat exchanger, cooling heat exchanger, high-temperature valve, intermediate heat exchanger, and high-temperature compressor.

[0019] The present invention also proposes a cascade unit, which includes the aforementioned cascade cogeneration system.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] This invention involves installing a cooling heat exchanger in front of the refrigerant inlet of a high-temperature valve, and connecting the low-temperature fluid inlet and outlet of the cooling heat exchanger with the low-temperature fluid inlet and outlet of the low-temperature stage heat exchanger to form a circulation path. This allows the low-temperature fluid flowing into the cooling heat exchanger to exchange heat with the high-temperature refrigerant, reducing the temperature of the high-temperature refrigerant passing through the cooling heat exchanger. This provides localized temperature-limiting cooling for the high-temperature valve, ensuring that the high-temperature valve operates within its normal temperature range, thereby extending its service life and improving its structural stability. Attached Figure Description

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects and not to describe a particular order.

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the first cascaded cogeneration system proposed in this invention;

[0025] Figure 2 This is a schematic diagram of the fluid flow in the first cascaded cogeneration system proposed in this invention.

[0026] Figure 3 This is a schematic diagram of the second type of cascaded combined cooling and heating system proposed in this invention;

[0027] Figure 4This is a schematic diagram of the fluid flow in the second type of cascaded combined cooling and heating system proposed in this invention.

[0028] Figure 5 This is a schematic diagram of the fluid flow in the third type of cascaded combined cooling and heating system proposed in this invention.

[0029] Figure 6 This is a schematic diagram of the fluid flow in the fourth type of cascaded combined cooling and heating system proposed in this invention.

[0030] Figure 7 This is a schematic diagram of the structure of the first cascaded combined cooling and heating system proposed in this invention.

[0031] Figure label:

[0032] 10. High-temperature circulation unit;

[0033] 101. High-temperature heat exchanger; 102. Cooling heat exchanger; 103. High-temperature valve; 104. First temperature sensing component; 105. High-temperature compressor; 106. High-temperature pressure sensor; 107. High-temperature water pump;

[0034] 20. Low-temperature stage circulation unit;

[0035] 201. Low-temperature stage heat exchanger; 202. First pipe; 203. Second pipe; 204. Third pipe; 205. Water pump; 206. Fourth pipe; 207. Fifth pipe; 208. Valve assembly; 209. Low-temperature stage compressor; 210. Low-temperature stage valve; 211. Low-temperature stage pressure sensor; 212. Low-temperature stage water pump; 213. Second temperature sensing component;

[0036] 30. Intermediate heat exchanger. Detailed Implementation

[0037] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Therefore, a feature pointed out in this specification is used to illustrate one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0038] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0039] High-temperature circulating units often reach temperatures exceeding 100℃ to 150℃, impacting the material properties and structure of valve components in the high-temperature system. For example, at high temperatures, valve materials undergo thermal expansion, and differences in the coefficients of thermal expansion between different materials can lead to increased clearances in internal components (such as valve stems and seats), affecting sealing performance and potentially causing leaks. The strength of metallic materials decreases at high temperatures, making valve structures more prone to deformation or damage, especially under pressure fluctuations, which may accelerate valve aging. High temperatures and sustained stress can cause creep in metallic materials, leading to loosening of connections, decreased sealing performance, and even leaks. High temperatures soften or decompose sealing materials (such as O-rings and gaskets), causing leaks and necessitating replacement with high-temperature resistant sealing materials. This is particularly true for the high-temperature throttling valves in the high-temperature circulating unit, which withstand transient thermal shocks exceeding 50K between the high-temperature refrigerant at the condenser outlet and the low-temperature refrigerant at the evaporator (heat exchanger) inlet.

[0040] Existing technology involves using special non-metallic materials to make valves in high-temperature circulating units to withstand transient thermal shocks above 50K. However, the lifespan of the valves is still shortened by high temperatures, affecting their structural stability.

[0041] Therefore, in some embodiments, to address the problem that the lifespan of valve components in the high-temperature stage circulation unit is shortened due to high temperatures, thus affecting the structural stability of the valve components, such as... Figures 1-2 As shown, the present invention proposes a cascaded cogeneration system, including a high-temperature stage circulation unit 10 and a low-temperature stage circulation unit 20, wherein the high-temperature stage circulation unit 10 and the low-temperature stage circulation unit 20 are coupled through an intermediate heat exchanger 30; a cooling heat exchanger 102 is provided in front of the refrigerant inlet of the high-temperature stage valve 103 in the high-temperature stage circulation unit 10.

[0042] The low-temperature fluid inlet and outlet of the low-temperature heat exchanger 201 in the low-temperature circulation unit 20 are respectively connected to the low-temperature fluid inlet and outlet of the cooling heat exchanger 102 to form a circulation path.

[0043] The cooling heat exchanger 102 is used to reduce the temperature of the high-temperature refrigerant passing through the cooling heat exchanger 102 by exchanging heat between the incoming low-temperature fluid and the high-temperature refrigerant.

[0044] It should be noted that in this embodiment, water is preferred as the cryogenic fluid because its temperature is relatively easy to control, allowing for the production of water at the required temperature, and its cost is low. In this case, the cryogenic fluid inlet and outlet of the cryogenic heat exchanger 201 are equivalent to water inlets / outlets. The high-temperature valve 103 in this embodiment is illustrated using a high-temperature throttling valve as an example. The high-temperature heat exchanger 101 in this embodiment is preferably a condenser, and the cryogenic heat exchanger 201 in this embodiment is preferably an evaporator. This embodiment illustrates the placement of the high-temperature valve 103 on the pipeline between the high-temperature heat exchanger 101 and the intermediate heat exchanger 30, and in this case, the high-temperature valve 103 is preferably a throttling valve. Of course, the high-temperature valve 103 can also be placed in other locations within the high-temperature circulation unit 10, but in this case, the high-temperature valve 103 is not necessarily a throttling valve, and this is not a limitation.

[0045] Thus, when the cascade cogeneration system is running, the high-temperature refrigerant in the high-temperature circulating unit 10 circulates, and then the high-temperature water pump 107 inputs water that has not reached the specified temperature into the high-temperature heat exchanger 101, so that the water that has not reached the specified temperature exchanges heat with the high-temperature refrigerant in the high-temperature heat exchanger 101, thereby generating hot water (preferably at 85°C, but the temperature of the hot water can be increased or decreased according to the actual situation, which is not limited here) and output to the outside; similarly, the low-temperature water pump 212 inputs water that has not reached the specified temperature into the low-temperature heat exchanger 201, so that the water that has not reached the specified temperature exchanges heat with the low-temperature refrigerant in the low-temperature heat exchanger 201, thereby generating chilled water (preferably at 7°C, but the temperature of the chilled water can be increased or decreased according to the actual situation, which is not limited here) and output to the outside.

[0046] At this time, the high-temperature circulating unit 10 often reaches a high temperature of 100℃ to 150℃ or higher. However, this invention connects the low-temperature fluid inlet and outlet of the low-temperature heat exchanger 201 to the low-temperature fluid inlet and outlet of the cooling heat exchanger 102 to form a circulation path. In this way, some water from the inlet of the low-temperature heat exchanger 201 will flow through the pipe through the cooling heat exchanger 102 and then flow back to the outlet of the low-temperature heat exchanger 201, thereby reducing the temperature of the high-temperature refrigerant flowing through the cooling heat exchanger 102. This provides localized temperature-limited cooling for the high-temperature valve 103 in the high-temperature circulating unit 10, ensuring that the high-temperature valve 103 operates within the normal temperature range. This avoids thermal expansion of the high-temperature valve 103 at high temperatures, or deformation or damage of the high-temperature valve 103 at high temperatures, or creep of the material of the high-temperature valve 103 at high temperatures, which could lead to loosening of the connection, decreased sealing performance, or even leakage. This extends the service life of the high-temperature valve 103 and improves its structural stability.

[0047] Therefore, the present invention can provide a cooling heat exchanger 102 in front of the refrigerant inlet of the high-temperature valve 103, and connect the low-temperature fluid inlet and outlet of the cooling heat exchanger 102 with the low-temperature fluid inlet and outlet of the low-temperature heat exchanger 201 to form a circulation path. This allows the low-temperature fluid flowing into the cooling heat exchanger 102 to exchange heat with the high-temperature refrigerant, thereby reducing the temperature of the high-temperature refrigerant passing through the cooling heat exchanger 102. This provides localized temperature-limited cooling for the high-temperature valve 103, ensuring that the high-temperature valve 103 operates within the normal temperature range, thereby extending the service life of the high-temperature valve 103 and improving its structural stability.

[0048] In some embodiments, such as Figure 2 As shown, this embodiment proposes a first type of loop path, and the connection relationship of the loop path is as follows:

[0049] The low-temperature fluid inlet of the low-temperature heat exchanger 201 is connected to the low-temperature fluid inlet of the cooling heat exchanger 102 through the first pipe 202, and the low-temperature fluid outlet of the low-temperature heat exchanger 201 is connected to the low-temperature fluid outlet of the cooling heat exchanger 102 through the second pipe 203.

[0050] It is understood that the cooling heat exchanger 102 proposed in this embodiment includes a high-temperature refrigerant inlet, a high-temperature refrigerant outlet, a low-temperature fluid inlet, and a low-temperature fluid outlet; and the high-temperature refrigerant inlet and high-temperature refrigerant outlet of the cooling heat exchanger 102 are connected to the pipes in the high-temperature circulation unit 10; while the low-temperature fluid inlet and low-temperature fluid outlet of the cooling heat exchanger 102 are connected to the pipes in the low-temperature circulation unit 20.

[0051] It should be noted that even if the water does not enter the low-temperature stage heat exchanger 201 to exchange heat with the low-temperature stage refrigerant, the temperature is still lower than the temperature inside the high-temperature stage circulation unit 10, especially much lower than the temperature of the refrigerant flowing out of the refrigerant outlet of the high-temperature stage heat exchanger 101.

[0052] In this embodiment, the water in the low-temperature fluid inlet of the low-temperature heat exchanger 201 can be spontaneously driven by the pressure difference in the low-temperature circulation unit 20 to flow through the first pipe 202 to the low-temperature fluid inlet of the cooling heat exchanger 102, thereby entering the shell side of the cooling heat exchanger 102. After entering the cooling heat exchanger 102, the high-temperature refrigerant is evenly distributed in the heat exchange tubes so that the high-temperature refrigerant can exchange heat with the water outside the heat exchange tubes. After the heat exchange and cooling are completed, the tube-side refrigerant is mixed again inside. The high-temperature refrigerant, cooled to a suitable temperature, flows from the refrigerant outlet into the high-temperature valve 103, thereby completing local temperature-limited cooling and ensuring that the high-temperature valve 103 operates within the normal temperature range. At the same time, the water in the shell side will flow back from the low-temperature fluid outlet of the cooling heat exchanger 102 to the low-temperature fluid outlet of the low-temperature heat exchanger 201, so that the water in the circulation path can spontaneously circulate in the low-temperature circulation unit 20 by the pressure difference, reducing production costs.

[0053] Furthermore, the heat exchange capacity within the cooling heat exchanger 102 is relatively low, resulting in minimal impact on the temperature of the chilled water at the low-temperature fluid outlet of the low-temperature stage heat exchanger 201 when the water flowing out of the cooling heat exchanger 102 merges with the low-temperature fluid outlet of the low-temperature stage heat exchanger 201. This also facilitates the acquisition of a temperature-limited cooling source, ensuring a reduction in the temperature of the high-temperature stage refrigerant passing through the cooling heat exchanger 102, guaranteeing that the high-temperature stage valve 103 operates within its normal temperature range, extending the service life of the high-temperature stage valve 103, and improving the structural stability of the high-temperature stage valve 103.

[0054] The pressure difference in the low-temperature circulating unit 20 is equivalent to the water in the low-temperature fluid inlet of the low-temperature heat exchanger 201 being pressurized and flowing in through the low-temperature water pump 212. Therefore, the pressure at the low-temperature fluid inlet of the low-temperature heat exchanger 201 will be greater than the pressure at the low-temperature fluid outlet of the low-temperature heat exchanger 201, thus forming a pressure difference.

[0055] In some embodiments, such as Figures 3-4 As shown, this embodiment proposes a second loop path, the connection relationship of which is as follows:

[0056] The low-temperature fluid outlet of the low-temperature heat exchanger 201 is connected to the low-temperature fluid inlet of the cooling heat exchanger 102 through a third pipe 204, and a water pump 205 is provided on the third pipe 204.

[0057] The cryogenic fluid inlet of the cryogenic stage heat exchanger 201 is connected to the cryogenic fluid outlet of the cooling heat exchanger 102 via the fourth pipe 206.

[0058] To further improve the heat exchange effect, the water flowing into the cooling heat exchanger 102 is chilled water output from the low-temperature stage heat exchanger 201. The low-temperature fluid outlet of the low-temperature stage heat exchanger 201 flows to the low-temperature fluid inlet of the cooling heat exchanger 102 through the water pump 205 in the third pipe 204, thus entering the shell side of the cooling heat exchanger 102. The high-temperature stage refrigerant, after entering the cooling heat exchanger 102, is evenly distributed into the heat exchange tubes so that the high-temperature stage refrigerant can exchange heat with the water outside the heat exchange tubes. After completing the heat exchange and cooling, the tube-side refrigerant is mixed internally again. The high-temperature stage refrigerant, cooled to a suitable temperature, flows from the refrigerant outlet into the high-temperature stage valve. 103, thereby completing localized temperature-limited cooling and ensuring that the high-temperature stage valve 103 operates within the normal temperature range; at the same time, the water in the shell side will flow back from the low-temperature fluid outlet of the cooling heat exchanger 102 to the low-temperature fluid inlet of the low-temperature stage heat exchanger 201, so that the chilled water output from the low-temperature stage heat exchanger 201 flows into the circulation path, thereby improving the heat exchange efficiency of the cooling heat exchanger 102, further reducing the temperature of the high-temperature stage refrigerant passing through the cooling heat exchanger 102, further ensuring that the high-temperature stage valve 103 operates within the normal temperature range, extending the service life of the high-temperature stage valve 103, and improving the structural stability of the high-temperature stage valve 103.

[0059] In some embodiments, in order to ensure that the low-temperature fluid flowing into the cooling heat exchanger 102 and the high-temperature refrigerant exchange stably, the temperature of the high-temperature refrigerant passing through the cooling heat exchanger 102 is reduced, thereby performing local temperature-limited cooling on the high-temperature valve 103 and ensuring that the high-temperature valve 103 operates within the normal temperature range, the cooling heat exchanger 102 is any one of a shell-and-tube heat exchanger, a shell-and-tube heat exchanger, or a double tube sheet heat exchanger.

[0060] Of course, the cooling heat exchanger 102 can also be other heat exchangers with similar shell-and-tube or tube-and-tube structures, which are not limited here.

[0061] In other embodiments, such as Figures 5-6 As shown, this embodiment proposes other loop paths, and the connection relationship of these loop paths is as follows:

[0062] The refrigerant outlet of the low-temperature heat exchanger 201 is connected to the low-temperature fluid inlet of the cooling heat exchanger 102, and a water pump 205 is installed on the pipeline between the refrigerant outlet of the low-temperature heat exchanger 201 and the low-temperature fluid inlet of the cooling heat exchanger 102.

[0063] The refrigerant inlet of the low-temperature heat exchanger 201 (e.g.) Figure 5 (as shown) or the refrigerant inlet of the cryogenic valve 210 (such as...) Figure 6 (As shown) is connected to the cryogenic fluid outlet of the cooling heat exchanger 102.

[0064] As can be seen, in this embodiment, the shell side of the cooling heat exchanger 102 is filled with low-temperature refrigerant, and the tube side of the cooling heat exchanger 102 is filled with high-temperature refrigerant, thereby achieving heat exchange and reducing the temperature of the high-temperature refrigerant passing through the cooling heat exchanger 102. This allows for localized temperature-limited cooling of the high-temperature valve 103, ensuring that the high-temperature valve 103 operates within the normal temperature range, extending the service life of the high-temperature valve 103, and improving the structural stability of the high-temperature valve 103.

[0065] In some embodiments, such as Figure 1 As shown, a first temperature sensing component 104 is provided between the cooling heat exchanger 102 and the high-temperature valve 103. The first temperature sensing component 104 is used to detect the temperature of the high-temperature refrigerant flowing out of the cooling heat exchanger 102.

[0066] It should be noted that the cascaded cogeneration system proposed in this invention also includes a control unit, which is electrically connected to the first temperature sensing component 104.

[0067] In this way, the first temperature sensing component 104 detects the temperature of the high-temperature refrigerant flowing out of the cooling heat exchanger 102 in real time and uploads the detected temperature data to the control unit in real time. Then, the control unit compares the uploaded temperature data with the preset temperature. If the detected temperature data is higher than the preset temperature, it means that the temperature of the high-temperature refrigerant flowing out of the cooling heat exchanger 102 has not reached the specified requirement. Therefore, the control unit will increase the flow rate of the low-temperature fluid flowing into the cooling heat exchanger 102. If the detected temperature data is not higher than the preset temperature, the control unit will reduce the flow rate of the low-temperature fluid flowing into the cooling heat exchanger 102, thereby ensuring that the high-temperature valve 103 operates within the normal temperature range, thus extending the service life of the high-temperature valve 103 and improving the structural stability of the high-temperature valve 103.

[0068] In some embodiments, such as Figure 1 As shown, the inlet and outlet of the cryogenic fluid in the cooling heat exchanger 102 are connected by a fifth pipe 207, and a valve assembly 208 is provided on the fifth pipe 207. The valve assembly 208 is used to control the flow rate of the cryogenic fluid flowing into the cooling heat exchanger 102.

[0069] It should be noted that the valve assembly 208 is electrically connected to the control unit.

[0070] The control unit obtains the temperature of the high-temperature refrigerant flowing out of the cooling heat exchanger 102 in real time through the first temperature sensing component 104. If the refrigerant outlet temperature of the cooling heat exchanger 102 is higher than the preset temperature, the control unit will reduce the opening of the valve assembly 208 or even completely close the valve assembly 208 to allow most or all of the water to flow into the cooling heat exchanger 102, thereby increasing the cooling effect. If the refrigerant outlet temperature of the cooling heat exchanger 102 is lower than the preset temperature, the control unit will gradually increase the opening of the valve assembly 208 until it is fully open, so that some water will flow back through the fifth pipe 207 and follow the low-temperature fluid outlet of the cooling heat exchanger 102 to reduce the cooling effect. If the refrigerant outlet temperature of the cooling heat exchanger 102 is equal to the preset temperature, the original control is maintained.

[0071] Therefore, this embodiment can ensure that the high-temperature valve 103 operates within the normal temperature range according to the above control method, thereby extending the service life of the high-temperature valve 103 and improving the structural stability of the high-temperature valve 103.

[0072] In some embodiments, such as Figure 7 As shown, a cooling heat exchanger 102 is connected to the bottom of the low-temperature stage heat exchanger 201.

[0073] In this way, the cooling heat exchanger 102 is connected to the bottom of the low-temperature stage heat exchanger 201 by a bracket, which makes the cooling heat exchanger 102 closer to the low-temperature stage heat exchanger 201, facilitates pipe connection, shortens the heat exchange path, and reduces energy loss.

[0074] In some embodiments, such as Figure 7 As shown, the low-temperature stage heat exchanger 201, the intermediate heat exchanger 30, and the high-temperature stage heat exchanger 101 are arranged side by side in the horizontal direction.

[0075] It is understandable that the low-temperature heat exchanger 201, the intermediate heat exchanger 30, and the high-temperature heat exchanger 101 are at the same horizontal level and arranged side by side.

[0076] The low-temperature heat exchanger 201, intermediate heat exchanger 30 and high-temperature heat exchanger 101 arranged side by side in the horizontal direction can shorten the heat exchange path, reduce energy loss and improve the overall efficiency of the system; and this design can also improve the stability of the entire structure and save space.

[0077] In some embodiments, such as Figure 1 As shown, the low-temperature refrigerant in the low-temperature stage circulation unit 20 circulates sequentially through the low-temperature stage heat exchanger 201, the low-temperature stage compressor 209, the intermediate heat exchanger 30, and the low-temperature stage valve 210.

[0078] The high-temperature refrigerant in the high-temperature circulating unit 10 circulates sequentially through the high-temperature heat exchanger 101, the cooling heat exchanger 102, the high-temperature valve 103, the intermediate heat exchanger 30, and the high-temperature compressor 105.

[0079] The high-temperature compressor 105 compresses the high-temperature refrigerant into a high-temperature, high-pressure gas, which then enters the high-temperature heat exchanger 101 to release heat and condense into a high-pressure liquid for continuous hot water production. The refrigerant flowing out of the high-temperature heat exchanger 101 is then cooled by the cooling heat exchanger 102 before flowing into the high-temperature valve 103 for depressurization. The depressurized refrigerant then flows into the intermediate heat exchanger 30 to evaporate and absorb heat.

[0080] The low-temperature compressor 209 discharges high-temperature refrigerant gas to the intermediate heat exchanger 30, where it exchanges heat with the high-temperature refrigerant flowing into the intermediate heat exchanger 30. Then, it passes through the low-temperature valve 210 and flows into the low-temperature heat exchanger 201 for heat absorption and refrigeration to continuously produce chilled water. Finally, it flows back to the low-temperature compressor 209. The low-temperature valve 210 can regulate the flow rate of the low-temperature refrigerant to ensure the heat balance between the low-temperature heat exchanger 201 and the intermediate heat exchanger 30.

[0081] In some embodiments, such as Figure 1 As shown, a low-temperature stage pressure sensor 211 electrically connected to the control unit is installed in the pipeline between the low-temperature stage heat exchanger 201 and the low-temperature stage compressor 209. In this way, when the low-temperature stage refrigerant in the low-temperature stage circulation unit 20 leaks or gets blocked, causing the inlet pressure of the low-temperature stage compressor 209 to fall below the safety threshold, the control unit will trigger a shutdown accordingly to prevent the low-temperature stage compressor 209 from burning out due to lack of oil or idling; or to prevent the inlet pressure of the low-temperature stage compressor 209 from rising abnormally, thus preventing the pipeline from bursting.

[0082] Similarly, a high-temperature pressure sensor 106 electrically connected to the control unit is installed in the pipeline between the intermediate heat exchanger 30 and the high-temperature compressor 105. In this way, when the high-temperature refrigerant in the high-temperature circulation unit 10 leaks or gets blocked, causing the inlet pressure of the high-temperature compressor 105 to fall below the safety threshold, the control unit will trigger a shutdown accordingly to prevent the high-temperature compressor 105 from burning out due to lack of oil or idling; or to prevent the inlet pressure of the high-temperature compressor 105 from rising abnormally, thus preventing the pipeline from bursting.

[0083] In some embodiments, such as Figure 1 As shown, the outlet of the low-temperature heat exchanger 201 is equipped with a second temperature sensing component 213 that is electrically connected to the control unit. The second temperature sensing component 213 is used to detect the temperature of the chilled water output by the low-temperature heat exchanger 201 so that the control unit can control the heat exchange efficiency of the low-temperature heat exchanger 201 according to the temperature of the chilled water output to the outside.

[0084] In some embodiments, the present invention also provides a cascade unit, which includes the cascade cogeneration system described above.

[0085] Specifically, the high-temperature compressor 105 compresses the high-temperature refrigerant into a high-temperature, high-pressure gas, which then enters the high-temperature heat exchanger 101 to release heat and condense into a high-pressure liquid. The high-temperature water pump 107 then inputs water that has not reached the specified temperature into the high-temperature heat exchanger 101 to exchange heat with the high-temperature refrigerant, continuously generating hot water. The hot water is then output to the outside (user side) and exchanges heat with the terminal equipment on the user side to meet the user's heating needs. The refrigerant flowing out of the high-temperature heat exchanger 101 is then cooled by the cooling heat exchanger 102 before flowing into the high-temperature valve 103 for depressurization. The depressurized refrigerant then flows into the intermediate heat exchanger 30 to evaporate and absorb heat, and finally flows back to the high-temperature compressor 105 for a new cycle.

[0086] The low-temperature compressor 209 discharges high-temperature refrigerant gas to the intermediate heat exchanger 30, where it exchanges heat with the high-temperature refrigerant flowing into the intermediate heat exchanger 30. Then, it passes through the low-temperature valve 210 and flows into the low-temperature heat exchanger 201 for heat absorption and cooling. At the same time, the low-temperature water pump 212 inputs water that has not reached the specified temperature into the low-temperature heat exchanger 201 to exchange heat with the low-temperature refrigerant, thereby continuously generating chilled water. The hot chilled water is then output to the outside (user side) and exchanges heat with the terminal equipment on the user side to meet the user's cooling needs. Finally, it flows back to the low-temperature compressor 209 for a new cycle.

[0087] Furthermore, when the cascade unit is shut down, the control unit shuts off the high-temperature stage water pump 107 while the low-temperature stage water pump 212 continues to run. This ensures that the temperature of the high-temperature stage refrigerant flowing into the high-temperature stage valve 103 drops to the preset temperature before shutting off the low-temperature stage water pump 212. This prevents refrigerant migration caused by high and low pressure balance after the cascade unit is shut down, thus avoiding the refrigerant from being repeatedly carried into the high-temperature stage valve 103. This ensures that the high-temperature stage valve 103 operates within the normal temperature range, extending the service life of the high-temperature stage valve 103 and the entire unit.

[0088] Therefore, this invention provides a cooling heat exchanger 102 in front of the refrigerant inlet of the high-temperature valve 103, and connects the low-temperature fluid inlet and outlet of the cooling heat exchanger 102 with the low-temperature fluid inlet and outlet of the low-temperature heat exchanger 201 to form a circulation path. This allows the low-temperature fluid flowing into the cooling heat exchanger 102 to exchange heat with the high-temperature refrigerant, reducing the temperature of the high-temperature refrigerant passing through the cooling heat exchanger 102. This provides localized temperature-limited cooling for the high-temperature valve 103, ensuring that the high-temperature valve 103 operates within the normal temperature range. This extends the service life of the high-temperature valve 103 and the entire unit, improves the structural stability of the high-temperature valve 103, and ensures the safety and long-term operation of the cascade unit.

[0089] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A cascaded cogeneration system, comprising a high-temperature stage circulation unit (10) and a low-temperature stage circulation unit (20), wherein the high-temperature stage circulation unit (10) and the low-temperature stage circulation unit (20) are coupled together via an intermediate heat exchanger (30); characterized in that, A cooling heat exchanger (102) is provided in front of the refrigerant inlet of the high-temperature valve (103) in the high-temperature circulating unit (10); The low-temperature fluid inlet and outlet of the low-temperature heat exchanger (201) in the low-temperature circulation unit (20) are connected to the low-temperature fluid inlet and outlet of the cooling heat exchanger (102) to form a circulation path; The cooling heat exchanger (102) is used to reduce the temperature of the high-temperature refrigerant passing through the cooling heat exchanger (102) by exchanging heat between the incoming low-temperature fluid and the high-temperature refrigerant.

2. The cascade cogeneration system according to claim 1, characterized in that, The low-temperature fluid inlet of the low-temperature heat exchanger (201) is connected to the low-temperature fluid inlet of the cooling heat exchanger (102) through a first pipe (202), and the low-temperature fluid outlet of the low-temperature heat exchanger (201) is connected to the low-temperature fluid outlet of the cooling heat exchanger (102) through a second pipe (203).

3. The cascade cogeneration system according to claim 1, characterized in that, The low-temperature fluid outlet of the low-temperature heat exchanger (201) is connected to the low-temperature fluid inlet of the cooling heat exchanger (102) through a third pipe (204), and a water pump (205) is provided on the third pipe (204). The cryogenic fluid inlet of the cryogenic stage heat exchanger (201) is connected to the cryogenic fluid outlet of the cooling heat exchanger (102) through a fourth pipe (206).

4. The cascade cogeneration system according to any one of claims 1 to 3, characterized in that, The inlet and outlet of the cooling heat exchanger (102) are connected by a fifth pipe (207), and a valve assembly (208) is provided on the fifth pipe (207). The valve assembly (208) is used to control the flow rate of the low-temperature fluid flowing into the cooling heat exchanger (102).

5. The cascade cogeneration system according to claim 4, characterized in that, The cooling heat exchanger (102) is any one of a shell-and-tube heat exchanger, a tube-and-shell heat exchanger, or a double tube sheet heat exchanger.

6. The cascade cogeneration system according to claim 1, characterized in that, A first temperature sensing component (104) is provided between the cooling heat exchanger (102) and the high-temperature valve (103), and the first temperature sensing component (104) is used to detect the temperature of the high-temperature refrigerant flowing out of the cooling heat exchanger (102).

7. The cascade cogeneration system according to claim 1, characterized in that, The bottom of the low-temperature stage heat exchanger (201) is connected to a cooling heat exchanger (102).

8. The cascade cogeneration system according to claim 1, characterized in that, The low-temperature stage heat exchanger (201), intermediate heat exchanger (30) and high-temperature stage heat exchanger (101) are arranged side by side in the horizontal direction.

9. The cascade cogeneration system according to claim 1, characterized in that, The low-temperature refrigerant in the low-temperature stage circulation unit (20) circulates sequentially through the low-temperature stage heat exchanger (201), the low-temperature stage compressor (209), the intermediate heat exchanger (30), and the low-temperature stage valve (210). The high-temperature refrigerant in the high-temperature circulating unit (10) circulates sequentially through the high-temperature heat exchanger (101), the cooling heat exchanger (102), the high-temperature valve (103), the intermediate heat exchanger (30), and the high-temperature compressor (105).

10. A cascade generator unit, characterized in that, The cascade unit includes the cascade cogeneration system as described in any one of claims 1 to 9.

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