A constant-temperature water supply system using a carbon dioxide heat pump and its control method

Abstract

The present invention discloses a constant-temperature water supply system using a carbon dioxide heat pump and its control method, which includes a primary side circuit, a secondary side water supply pipeline with a water inlet and a water outlet, a heat pump water heater arranged in the primary side circuit, and a heat exchanger arranged between the primary side circuit and the secondary side water supply pipeline. Since the present invention detects the water temperature through a return water temperature sensor and multiple return water tank temperature sensors, even if the return water temperature flowing out of the first heat exchange tube fluctuates, the return water can be input to the part of the return water tank with a close temperature, so that the water in the return water tank always maintains a stable stratified state, avoiding the water temperature fluctuation of the water flow sent from the return water tank to the heat pump water heater, thereby realizing constant-temperature water supply.

Description

Technical Field

[0001] The present invention relates to a constant temperature water supply system using a carbon dioxide heat pump and a control method thereof. Background Art

[0002] When a heat pump water heater is used in a secondary heat exchange system, the return water temperature on the primary side is greatly affected by the water temperature and flow rate changes on the secondary side. If the primary side return water is directly introduced into the heat pump water heater for reheating, due to the change of the primary side return water temperature, the outlet water temperature is likely to oscillate, and the system is unstable. Moreover, the energy efficiency of the heat pump system is greatly affected by the inlet water temperature on the air cooler side. When the inlet water temperature on the air cooler side is too high, the exhaust temperature and exhaust pressure are too high, and the compressor load is large and prone to overload, and the energy efficiency of the system decays significantly, and the system stability is affected to a certain extent.

[0003] Therefore, there is a need for a constant temperature water supply system using a carbon dioxide heat pump at present. Summary of the Invention

[0004] An object of the present invention is to provide a constant temperature water supply system using a carbon dioxide heat pump.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a constant temperature water supply system using a carbon dioxide heat pump, which includes a primary side circuit and a secondary side water supply pipeline having a water inlet and a water outlet, a heat pump water heater provided in the primary side circuit, and a heat exchanger provided between the primary side circuit and the secondary side water supply pipeline. The heat exchanger includes a first heat exchange tube and a second heat exchange tube that are arranged for heat exchange with each other. The first heat exchange tube is provided in the primary side circuit, and the second heat exchange tube is provided in the secondary side water supply pipeline. The primary side circuit and the secondary side water supply pipeline are heat exchange-connected through the heat exchanger. The primary side circuit further includes at least one vertically arranged return water tank. A return water outlet communicating with the heat pump water heater is provided at the bottom of the return water tank. A plurality of return water inlets connecting the heat exchanger are sequentially arranged in the vertical direction on the side of the return water tank. A return water valve is provided on each return water inlet. A plurality of return water tank temperature sensors for detecting the water temperature corresponding to the height of each return water inlet in the return water tank are provided on the return water tank. A return water temperature sensor for detecting the water temperature at the outlet of the first heat exchange tube is provided at the outlet of the first heat exchange tube.

[0006] Preferably, the return water outlets are uniformly distributed in sequence from the bottom to the top of the return water tank.

[0007] Preferably, the primary side circuit further includes a water supply tank. The upper ends of both sides of the water supply tank are respectively connected to the outlet of the heat pump water heater and the inlet of the first heat exchange tube.

[0008] Further preferably, the lower part of the water supply water tank and the upper part of the water return water tank are communicated with each other through a water pipe.

[0009] Further preferably, a water supply temperature sensor is arranged at the outlet end of the water supply water tank.

[0010] Preferably, a primary side water supply pump is arranged between the water return outlet and the heat pump water heater.

[0011] Preferably, a primary side circulation pump is further arranged in the primary side loop, and the primary side circulation pump is arranged between the water supply water tank and the inlet of the first heat exchange pipe.

[0012] Preferably, a secondary side inlet water temperature sensor and a secondary side outlet water temperature sensor are respectively arranged at the outlet end and the outlet end of the secondary side water supply pipeline.

[0013] Preferably, a water replenishing port is arranged at the bottom of the water return water tank.

[0014] A control method for a constant temperature water supply system using a carbon dioxide heat pump, which uses the above-mentioned constant temperature water supply system, detects the water temperature at the outlet of the first heat exchange pipe through the water return temperature sensor, and detects the water temperatures at different heights of the water return water tank through a plurality of water return water tank temperature sensors, and opens the water return valve corresponding to the water return water tank temperature sensor whose detected water temperature is close to the water temperature detected by the water return temperature sensor for water return.

[0015] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0016] Since the present invention detects the water temperature through the water return temperature sensor and a plurality of water return water tank temperature sensors, even if the water temperature of the water return flowing out of the first heat exchange pipe fluctuates, the water return can be input into the part of the water return tank with a temperature close to it, so that the water in the water return tank always maintains a stable stratified state, avoiding the water temperature fluctuation of the water flow sent from the water return tank to the heat pump water heater, thereby realizing constant temperature water supply. Brief Description of the Drawings

[0017] Attached Figure 1 is a structural schematic diagram of the present invention.

[0018] In the above drawings: 1. Carbon dioxide heat pump water heater; 2. Heat exchanger; 21. First heat exchange tube; 22. Second heat exchange tube; 31. Secondary side circulation pump; 32. Secondary side inlet water temperature sensor; 33. Secondary side outlet water temperature sensor; 4. Return water tank; 41. Return water outlet; 42. Return water inlet; 43. Return water valve; 44. Return water tank temperature sensor; 45. Water replenishment port; 5. Return water temperature sensor; 6. Water supply tank; 61. Water supply inlet; 62. Water supply outlet; 63. Water supply temperature sensor; 64. Water supply bottom temperature sensor; 7. Primary side water supply pump; 8. Primary side circulation pump. Detailed implementation mode

[0019] The present invention will be further described below in conjunction with the embodiments shown in the drawings:

[0020] See the appendix Figure 1 As shown, a constant temperature water supply system using a carbon dioxide heat pump includes a primary side loop, a secondary side water supply pipeline with a water inlet and a water outlet, a carbon dioxide heat pump water heater 1 arranged in the primary side loop, and a heat exchanger 2 arranged between the primary side loop and the secondary side water supply pipeline.

[0021] Specifically, the heat exchanger 2 includes a first heat exchange tube 21 and a second heat exchange tube 22 that are arranged for heat exchange with each other. The first heat exchange tube 21 is arranged in the primary side loop, and the second heat exchange tube 22 is arranged in the secondary side water supply pipeline. The primary side loop and the secondary side water supply pipeline are heat exchange-connected through the heat exchanger 2.

[0022] The primary side loop includes n parallel-connected return water tanks 4 (only one is shown in the figure) arranged vertically. The bottom of the return water tank 4 is provided with a return water outlet 41 communicating with the carbon dioxide heat pump water heater 1. On the side of the return water tank 4, m return water inlets 42 connecting to the heat exchanger 2 are arranged in sequence in the vertical direction. A return water valve 43 is arranged on each return water inlet 42. The return water tank 4 is provided with a plurality of return water tank temperature sensors 44 for detecting the water temperature at the height corresponding to each return water inlet 42 in the return water tank 4. Therefore, there are n*m groups of return water tank temperature sensors 44 on the return water tank. A return water temperature sensor 5 for detecting the water temperature at the outlet of the first heat exchange tube 21 is arranged at the outlet of the first heat exchange tube 21.

[0023] The specific control method of the constant temperature water supply system in this embodiment is as follows:

[0024] 1. Detect the return water temperature through the return water temperature sensor 5 , and detect the temperature T of the return water tank 4 through n*m groups of return water tank temperature sensors 44 Ni ;

[0025] 2. Compare with T Ni for comparison, and there are three situations 1) Between two adjacent Ts Ni At this time, open the return water valve 43 corresponding to the return water tank temperature sensor 44 with the lower temperature among the adjacent Ts; the primary side return water returns here; 2) Ni ≥T ≥T Ni Maximum value; at this time, open the return water valve 43 corresponding to the return water tank temperature sensor 44 of T Ni Maximum value; the primary side return water returns here; 3) ≤T Ni Minimum value; at this time, open the return water valve 43 corresponding to the return water tank temperature sensor 44 of T Ni Minimum value; the primary side return water returns here.

[0026] In the hot water of a static container, since the water with a higher temperature has a smaller density and is in the upper layer, while the hot water with a lower temperature has a larger density and is in the lower layer. Even when the water flow temperature flowing out of the first heat exchange tube 21 fluctuates, in this embodiment, the water flow entering the return water tank 4 is sent to the water layer with a temperature close to it according to the temperature, so that the hot water in the return water tank 4 always maintains a state of temperature stratification. When water is injected from the return water inlet 42, the hot water with a lower temperature at the lowermost end in the return water tank 4 enters the carbon dioxide heat pump water heater 1 from the return water outlet 41, thus avoiding the temperature fluctuation of the water flow entering the carbon dioxide heat pump water heater 1, so that the water flow heated by the carbon dioxide heat pump water heater 1 will not have a temperature fluctuation either. Finally, the water flow entering the first heat exchange tube 21 can also maintain a stable temperature, and the heat exchanger 2 outputs relatively stable heat to the secondary side water supply pipeline, and finally the water flow temperature output by the secondary side water supply pipeline is stable.

[0027] In this embodiment, the return water outlets 41 are evenly distributed in sequence from the bottom to the top of the return water tank 4 to reduce the temperature difference between the incoming water flow and the water in the return water tank 4.

[0028] The primary side loop further includes a water supply tank 6. The upper two ends of the water supply tank 6 are respectively connected to the water supply inlet 61 of the carbon dioxide heat pump water heater 1 and the water supply outlet 62 of the first heat exchange tube 21. The lower part of the water supply tank 6 is communicated with the upper part of the return water tank 4 through a water pipe. When the water temperature of the hot water flowing out of the carbon dioxide heat pump water heater 1 fluctuates, the water supply tank 6 can play a buffering role. After the hot water with a fluctuating water temperature is mixed with the original hot water in the water supply tank 6, the fluctuation range becomes smaller, further reducing the water temperature fluctuation of the water flow flowing out of the water supply outlet 62.

[0029] A water supply temperature sensor 63 is arranged near the water supply outlet 62 on the water supply tank 6, and a water supply bottom temperature sensor 64 is arranged at the bottom of the water supply tank 6. To respectively monitor the water temperature difference between the top and the bottom of the water supply tank 6.

[0030] A primary side water supply pump 7 is provided between the return water outlet 41 and the carbon dioxide heat pump water heater 1. A primary side circulation pump 8 is provided between the water supply tank 6 and the inlet of the first heat exchange tube 21. The primary side water supply pump 7 is used to send the water flow at the bottom of the return water tank to the carbon dioxide heat pump water heater 1 for heating, and the primary side circulation pump 8 can assist the water flow circulation of the primary side loop.

[0031] In addition, a water replenishment port 45 is provided in the primary side loop. In order to prevent the water temperature fluctuation caused by water replenishment, the water replenishment port 45 is arranged at the bottom of the return water tank 4, so that the cold water replenished can enter the carbon dioxide heat pump water heater 1 and be quickly heated after entering the primary side loop.

[0032] In addition, a secondary side circulation pump 31 is provided on the secondary side water supply pipeline of this embodiment, and a secondary side inlet water temperature sensor 32 and a secondary side outlet water temperature sensor 33 are respectively arranged at the inlet end and the outlet end of the secondary side water supply pipeline. The secondary side circulation pump 31 is arranged close to the inlet end, which can prevent the secondary side circulation pump 31 from idling and being damaged when the heat exchanger 2 is blocked.

[0033] The control method of the secondary side water supply pipe is to adjust the working frequency V of the secondary side circulation pump 31 according to the relationship between the temperature difference Δt between the secondary side inlet water temperature detected by the secondary side inlet water temperature sensor 32 and the return water temperature detected by the return water temperature sensor 5 so as to output hot water with a stable water temperature.

[0034] Specifically:

[0035] ;

[0036] ;

[0037] where a and b are empirical parameters.

[0038] When ΔT - c ≤ Δt ≤ ΔT + c, the frequency of the primary side circulation pump remains unchanged. When Δt < ΔT - c, the frequency of the primary side circulation pump is reduced. When Δt > ΔT + c, the frequency of the primary side circulation pump is increased until ΔT - c ≤ Δt ≤ ΔT + c, where c is the temperature tolerance, which is taken as an integer according to the actual situation, and the recommended value range is 2 - 5, or it can also be customized by those skilled in the art according to the actual situation.

[0039] Thus, the working frequency V of the secondary side circulation pump 31 can be adjusted according to the water temperature fluctuation at the inlet of the secondary side water supply pipeline, so as to further reduce the water temperature fluctuation at the outlet of the secondary side water supply pipeline.

[0040] The above embodiments are only used to illustrate the technical concept and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A constant temperature water supply system using a carbon dioxide heat pump, characterized in that: The constant temperature water supply system includes a primary side circuit, a secondary side water supply pipeline with a water inlet and a water outlet, a heat pump water heater arranged in the primary side circuit, and a heat exchanger arranged between the primary side circuit and the secondary side water supply pipeline. The heat exchanger includes a first heat exchange pipe and a second heat exchange pipe which are arranged for heat exchange with each other. The first heat exchange pipe is arranged in the primary side circuit, and the second heat exchange pipe is arranged in the secondary side water supply pipeline. The primary side circuit and the secondary side water supply pipeline are heat exchange connected through the heat exchanger; The primary side circuit further includes at least one vertically arranged return water tank. A return water outlet communicating with the heat pump water heater is arranged at the bottom of the return water tank. A plurality of return water inlets connecting the heat exchanger are sequentially arranged in the vertical direction on the side of the return water tank. A return water valve is arranged on each return water inlet. A return water tank temperature sensor for detecting the water temperature at the height corresponding to each return water inlet in the return water tank is arranged on the return water tank. A return water temperature sensor for detecting the water temperature at the outlet of the first heat exchange pipe is arranged at the outlet of the first heat exchange pipe; The primary side circuit further includes a water supply tank. Two ends of the upper part of the water supply tank are respectively connected to the outlet of the heat pump water heater and the inlet of the first heat exchange pipe. The lower part of the water supply tank is communicated with the upper part of the return water tank through a water pipe; A secondary side circulation pump is arranged on the secondary side water supply pipeline. A secondary side inlet water temperature sensor and a secondary side outlet water temperature sensor are respectively arranged at the inlet end and the outlet end of the secondary side water supply pipeline; The control method of the constant temperature water supply system is as follows: Detect the return water temperature T through the return water temperature sensor 10 , and detect the water temperature T of the water at the height corresponding to each of the return water inlets in the return water tank through a plurality of the return water tank temperature sensors Ni ; Compare T 10 with T Ni When T 10 is between two adjacent Ts Ni ; at this time, open the return water valve corresponding to the return water tank temperature sensor with the lower temperature among the adjacent Ts Ni , and the primary side return water returns here; when T 10 ≥ the maximum value in T Ni , at this time, open the return water valve corresponding to the return water tank temperature sensor with the maximum value in T Ni , and the primary side return water returns here; when T 10 ≤ the minimum value in T Ni , at this time, open the return water valve corresponding to the return water tank temperature sensor with the minimum value in T Ni , and the primary side return water returns here; The control method of the secondary side water supply pipe adjusts the operating frequency of the secondary side circulation pump according to the relationship between the temperature difference △t between the water temperature T of the secondary side inlet water detected by the secondary side inlet water temperature sensor and the water temperature T of the return water detected by the return water temperature sensor and the target difference △T, so as to output hot water with a stable water temperature; 2i and the water temperature T of the return water detected by the return water temperature sensor 10 to output hot water with a stable water temperature; Specifically: △t = T 10 -T 2i ; △T = a×T 20 / T 2i + b; Where a and b are empirical parameters; When △T - c ≤ △t ≤ △T + c, keep the frequency of the primary side circulation pump unchanged. When △t < △T - c, decrease the frequency of the primary side circulation pump. When △t > △T + c, increase the frequency of the primary side circulation pump until △T - c ≤ △t ≤ △T + c, where c is 2 - 5.

2. The constant-temperature water supply system using a carbon dioxide heat pump according to claim 1, characterized in that: The plurality of return water inlets are uniformly distributed in sequence from the bottom to the top of the return water tank.

3. The constant temperature water supply system using a carbon dioxide heat pump according to claim 1, characterized in that: A water supply temperature sensor is arranged at the outlet end of the water supply tank.

4. The constant temperature water supply system using a carbon dioxide heat pump according to claim 1, characterized in that: A primary side water supply pump is arranged between the return water outlet and the heat pump water heater.

5. The constant-temperature water supply system using a carbon dioxide heat pump according to claim 1, characterized in that: A primary side circulation pump is further arranged in the primary side circuit. The primary side circulation pump is arranged between the water supply tank and the inlet of the first heat exchange pipe.

6. The constant temperature water supply system using a carbon dioxide heat pump according to claim 1, characterized in that: A water replenishing port is arranged at the bottom of the return water tank.

7. A control method of a constant temperature water supply system using a carbon dioxide heat pump, which uses the constant temperature water supply system using a heat pump according to any one of claims 1 - 6. The water temperature at the outlet of the first heat exchange pipe is detected through the return water temperature sensor, and the water temperatures at different heights of the return water tank are detected through a plurality of return water tank temperature sensors. The return water valve corresponding to the return water tank temperature sensor whose detected water temperature is close to the water temperature detected by the return water temperature sensor is opened for return water.

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