Liquid heat storage and heat pump coupling heat supply system for continuous grain drying

Abstract

The utility model discloses a liquid heat storage and heat pump coupling heat supply system for continuously drying grains, which consists of an electric heat storage hot water unit, an air source heat pump hot air unit and an accessory case, and the heat pump hot air unit is a full fresh air one-time heating unit. When the air source heat pump hot air unit supplies heat normally, the coupling system is closed, and the electric heat storage hot water unit stores heat; when the environment temperature detection sensor detects that the environment temperature is lower than the frosting temperature of the air source heat pump hot air unit, the coupling system operates, the electric heat storage hot water unit releases heat through the hot water heat exchanger by using the stored heat, the surrounding environment temperature of an evaporator of the air source heat pump hot air unit is increased, frosting is avoided, and continuous heat supply is achieved. The system provided by the utility model solves the problems that the existing air source heat pump hot air unit has the defects of frosting and defrosting, incapability of continuously supplying heat, reduced air outlet temperature and unstable air outlet, so that the grain drying temperature is uniform and continuous, the effect is good, and the purposes of reducing the power of the heat storage electric heater and reducing the load are also achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of hot air drying, and in particular relates to a liquid heat storage and heat pump coupled heating system for continuous grain drying. Background Art

[0002] Grain production area drying is an important link and key measure to ensure grain quality, reduce post-production and post-disaster losses, and ensure a bumper grain harvest. Accelerating the improvement of grain production area drying capacity is of great significance to ensuring national food security. In recent years, my country's grain production area drying capacity has made great progress, but there are still problems such as unbalanced and insufficient development, low mechanization, low technical level, incompatible facilities and equipment, and high energy consumption causing energy waste. Drying services cannot meet the needs of grain production.

[0003] Existing drying technologies are roughly divided into natural air drying, sun drying, fossil energy burning drying, electric heating, infrared, microwave drying, etc. These technologies have high energy consumption, low efficiency, heavy pollution, and are not in line with the trend of sustainable development. The heat pump hot air unit on the market is just in the promotion stage, and there are still many technologies that need innovation and breakthroughs. For example, in the low temperature and high humidity environment at night in autumn and winter, frosting and defrosting often occur, resulting in intermittent heating, lower temperature, uneven grain drying temperature, and poor drying effect in some periods. Summary of the invention

[0004] In order to overcome the shortcomings of the existing grain drying technology, the utility model provides a liquid heat storage and heat pump coupled heating system for continuous grain drying.

[0005] The utility model is realized by the following technical means:

[0006] A liquid heat storage and heat pump coupled heating system, comprising an electric heat storage hot water unit, an air source heat pump hot air unit and an accessory box;

[0007] The electric thermal storage hot water unit includes a heat storage tank, an inner tank is arranged inside the heat storage tank, an upper water distributor is arranged at the upper part of the inner tank, a lower water distributor is arranged at the lower part, an electric heater is arranged at the bottom end of the inner tank, and a water supply port and a water return port are arranged on one side of the electric thermal storage hot water unit, the water supply port is connected to the upper water distributor inside the inner tank through a pipeline, and the water return port is connected to the lower water distributor inside the inner tank through a pipeline.

[0008] Furthermore, the air source heat pump hot air unit includes a condenser arranged at the lower part of the body, a hot air outlet is arranged on the body on one side of the condenser, and a cold air inlet is arranged on the body on the other side, an evaporator and a hot water heat exchanger are arranged on the upper part of the body, a condensing fan is arranged on the top of the evaporator, and a water inlet and a water outlet are also arranged on the body, the water inlet is connected to a diverter through a pipe, the output end of the diverter is connected to the hot water inlet of the hot water heat exchanger through a diverter pipe, the water outlet is connected to a collector, and the collector is connected to the hot water outlet of the hot water heat exchanger.

[0009] Furthermore, an ambient temperature detection sensor is arranged outside the body of the air source heat pump hot air blower, and a preheating temperature detection sensor is arranged between the evaporator and the hot water heat exchanger.

[0010] Furthermore, the accessory box includes a first water circuit and a second water circuit, the first water circuit includes a first water inlet, a three-way regulating valve, a filter, a variable frequency pump and a first water outlet connected in sequence through a first pipeline; the second water circuit includes a second water outlet and a second water inlet connected in sequence through a second pipeline, wherein the three-way regulating valve is connected to the second pipeline through a pipe; the first water inlet is connected to the water supply port, the second water outlet is connected to the water inlet pipe port, the second water inlet is connected to the water outlet pipe port, and the second water outlet is connected to the return port.

[0011] Furthermore, a pressure relief port is arranged on the top of the heat storage tank, and a sewage outlet is arranged on the bottom.

[0012] Furthermore, a pressure relief port is arranged on the top of the heat storage tank, and a sewage outlet is arranged on the bottom.

[0013] Furthermore, the upper end of the hot water storage tank is provided with an overflow port, and the lower end is provided with a water replenishment port.

[0014] Furthermore, a drain valve is provided on the second pipeline connecting the first water outlet and the second water inlet.

[0015] Furthermore, a second water temperature detection sensor is provided on the connecting pipe between the filter and the three-way regulating valve.

[0016] Furthermore, the variable frequency pump and the first water outlet, as well as the variable frequency pump and the filter are connected via flexible connections.

[0017] Furthermore, the hot water heat exchanger is arranged outside the evaporator of the air source heat pump hot air unit.

[0018] Furthermore, the preheating temperature detection sensor is arranged outside the evaporator and inside the hot water heat exchanger. The sensor is a thermistor type.

[0019] Furthermore, the accessory box can be placed inside the air source heat pump hot air unit, or can be placed separately outside the unit.

[0020] Furthermore, the hot water circulation pump in the accessory box is a variable frequency pump, the three-way valve is an electric three-way regulating valve, and the water temperature detection sensor is a thermistor type.

[0021] Furthermore, the inner tank material of the electric heat storage water heater unit is a stainless steel plate, the heat storage medium can be water, the multiple temperature detection sensors arranged up and down are thermistor type, and the insulating layer is polyurethane.

[0022] Furthermore, a plurality of electric heaters arranged in parallel are arranged in the inner tank of the electric thermal storage water heater unit, which are connected with electric wires to form three sets of electrode loops and then connected to fuse protectors, and the loop connection method is triangle or star.

[0023] Furthermore, the electric thermal storage water heater unit controls the water temperature by feeding back a signal to an external PLC or computer system via a first water temperature detection sensor.

[0024] Furthermore, the electric heat storage water heater unit can provide heat either by the stored heat or by the stored heat and the electric heater being turned on simultaneously, so as to reduce the power of the electric heater and the power distribution capacity.

[0025] The liquid heat storage and heat pump coupled heating system provided by the utility model can be used for continuous drying of grains. The system consists of three parts: an electric heat storage hot water unit, an air source heat pump hot air unit and an accessory box. The heat pump hot air unit is a fresh air one-time heating unit. When the air source heat pump hot air unit is heating normally, the coupling system is closed, the electric heater of the electric heat storage hot water unit is turned on for heating, the frequency conversion pump in the accessory box is turned off, and the opening degree of the three-way regulating valve is reset. When the water temperature detection sensor detects that the water temperature reaches the design temperature, the electric heater is turned off and stops heating. The pressure generated inside the inner tank during the heating process is discharged through the pressure relief port to maintain normal pressure. When the ambient temperature detection sensor detects that the ambient temperature is lower than the frosting temperature of the heat pump hot air unit, the frequency conversion pump in the accessory box is turned on for frequency increase, the water flow switch detects the water flow, and the hot water on the upper part of the electric heat storage hot water unit flows into the upper water distributor and is connected through the water supply port. The water enters the accessory box through a pipe, and the opening degree of the three-way regulating valve is adjusted to adjust the water inlet of the second water channel connected to the third channel. The water temperature detection sensor detects the mixed water temperature, and after adjusting to the design temperature, it enters the water inlet of the heat pump hot air unit through a pipe connected to the water outlet. Through the diverter, the hot water is evenly distributed to the hot water heat exchanger, the preheated evaporator intake air, and the preheated hot water passes through the pipe connected to the collector outlet pipe, and returns to the second water return port of the accessory box through the lower water distributor to the lower part of the inner tank of the electric thermal storage hot water unit. As the hot water in the upper part gradually decreases, the cold water level in the lower part gradually increases, waiting for the next heating.

[0026] After heating, the hot air temperature is detected by the preheating temperature detection sensor. When the temperature is still lower than the frosting temperature, the third passage of the three-way regulating valve reduces the water flow of the second water passage, and the frequency conversion pump increases the water flow of the first water passage, gradually increasing the water supply temperature until the hot air temperature is higher than the frosting temperature to prevent frosting; when the ambient temperature detection sensor detects that the ambient temperature is higher than the frosting temperature of the heat pump hot air unit, the frequency conversion pump in the accessory box is reduced and closed, the opening degree of the three-way regulating valve is reset, the electric heat storage hot water unit stops heating, and the electric heater is turned on to heat and store heat. The upper and lower water distributors in the inner tank of the electric heat storage hot water unit are key components of the electric heat storage hot water unit. They adopt a relatively efficient radial disc structure and are connected to the supply and return water pipes. The main function is to reduce the thickness of the inclined temperature layer. The upper part is hot water with a higher temperature, and the lower part is hot water with a lower temperature. They are not mixed at first, which improves the utilization rate of hot water. As the amount of hot water used increases, the inclined temperature layer increases step by step. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the electric thermal storage water heater unit provided by the utility model.

[0028] Figure 2 This is a schematic diagram of the overall structure of the electric thermal storage water heater unit provided by the utility model.

[0029] Figure 3 This is a schematic diagram of the heat pump hot air unit provided by the utility model.

[0030] Figure 4 This is a side schematic diagram of the heat pump hot air unit provided by the utility model.

[0031] Figure 5 This is a schematic diagram of the interior of the accessory box provided by the utility model.

[0032] Figure 6 The utility model provides a connection diagram of an electric heat storage hot water unit, an accessory box, and a heat pump hot air unit.

[0033] above Figure 1-Figure 6Among them, 4 is an air source heat pump hot air blower, 4-1 is a hot air outlet, 4-2 is a condenser, 4-3 is an evaporator, 4-4 is a condensing fan, 4-5 is a cold air inlet, 4-6 is a water inlet, 4-7 is a water outlet, 4-8 is a diverter, 4-9 is a collector, 4-10 is an ambient temperature detection sensor, 4-11 is a preheating temperature detection sensor, 4-12 is a hot water heat exchanger, 5 is an electric heat storage hot water unit, 5-1 is a hot water storage tank, 5-2 is an inner tank, 5-3 is an insulating layer, 5-4 is a base, 5-5 is a ground wire terminal, 5-6 is a water supply port , 5-7 water return port, 5-8 overflow port, 5-9 water replenishment port, 5-10 sewage outlet, 5-11 pressure relief port, 5-12 upper water distributor, 5-13 lower water distributor, 5-14 electric heater, 5-15 the first water temperature detection sensor, 5-16 liquid level sensor, 6 accessory box, 6-1 frequency conversion pump, 6-2 filter, 6-3 three-way regulating valve, 6-4 sewage valve, 6-5 soft joint, 6-61 is the first water inlet, 6-62 is the second water inlet, 6-71 is the second water outlet, 6-72 is the second water outlet, 6-8 the second water temperature detection sensor. DETAILED DESCRIPTION

[0034] The utility model provides a liquid heat storage and heat pump coupled heating system for continuous grain drying. The system includes three parts: an electric heat storage hot water unit, an air source heat pump hot air unit and an accessory box. When the air source heat pump hot air unit is heating normally, the coupling system is closed and the electric heat storage hot water unit stores heat; when the ambient temperature detection sensor detects that the ambient temperature is lower than the frosting temperature of the air source heat pump hot air unit, the coupling system is operated, and the electric heat storage hot water unit uses the stored heat to release heat through the hot water heat exchanger to increase the ambient temperature around the evaporator of the air source heat pump hot air unit, avoid frosting, and continuously supply heat. The system of the utility model solves the pain points of the existing air source heat pump hot air unit that cannot continuously supply heat due to frosting and defrosting, the outlet air temperature is reduced, and the outlet air is unstable, so that the grain drying temperature is uniform and continuous with good effect, and the purpose of reducing the power of the heat storage electric heater and reducing the load is achieved.

[0035] The liquid heat storage and heat pump coupled heating system provided by the utility model is described in detail below in conjunction with the accompanying drawings.

[0036] In one embodiment of the utility model, a grain drying system of a liquid heat storage and heat pump coupled heating system is provided, such as Figure 1-6As shown, it includes a heat pump hot air blower 4, an electric heat storage hot water unit 5 and an accessory box 6. A condenser 4-2 is arranged at the lower part of the body of the heat pump hot air blower 4, a hot air outlet 4-1 is arranged on the body on one side of the condenser 4-2, and a cold air inlet 4-5 is arranged on the body on the other side, an evaporator 4-3 is arranged at the upper part of the body, a fan 4-4 is arranged on the top of the evaporator 4-3, and a water inlet pipe 4-6 and a water outlet pipe 4-7 are also arranged on the body, the water inlet pipe 4-6 is connected to the diverter 4-8 through a pipeline, the output end of the diverter 4-8 is connected to the heat exchange inlet of the hot water heat exchanger 4-12 through a diverter pipe, the water outlet pipe 4-7 is connected to the collector 4-9, and the collector 4-9 is connected to the heat exchange outlet of the hot water heat exchanger 4-12. The electric thermal storage hot water unit 5 includes a hot water storage tank 5-1, an inner tank 5-2 is arranged inside the hot water storage tank 5-1, an upper water distributor 5-12 is arranged at the upper part of the inner tank 5-2, and a lower water distributor 5-13 is arranged at the lower part, an electric heater 5-14 is arranged at the bottom end of the inner tank 5-2, and a water supply port 5-6 and a water return port 5-7 are arranged on one side of the electric thermal storage hot water unit 5, the water supply port 5-6 is connected to the upper water distributor 5-12 inside the inner tank 5-2 through a pipeline, and the water return port 5-7 is connected to the lower water distributor 5-13 inside the inner tank 5-2 through a pipeline. The accessory box 6 includes a first water circuit and a second water circuit. The first water circuit includes a first water inlet 6-61, a three-way regulating valve 6-3, a filter 6-2, a variable frequency pump 6-1 and a first water outlet 6-71 connected in sequence through a first pipeline; the second water circuit includes a second water outlet 6-72 and a second water inlet 6-62 connected in sequence through a second pipeline, wherein the three-way regulating valve 6-3 is connected to the second pipeline through a pipeline; the first water inlet 6-61 is connected to the water supply port 5-6, the first water outlet 6-71 is connected to the water inlet pipe 4-6, the second water inlet 6-62 is connected to the water outlet pipe 4-7, and the second water outlet 6-72 is connected to the return water port 5-7. A drain valve 6-4 is provided on the second pipeline connecting the first water outlet 6-71 and the second water inlet 6-62, and a second water temperature detection sensor 6-8 is provided on the connecting pipeline between the filter 6-2 and the three-way regulating valve 6-3. The variable frequency pump 6-1 and the first water outlet 6-71, as well as the variable frequency pump 6-1 and the filter 6-2 are connected via a flexible connection 6-5.

[0037] like Figure 2 As shown, it is a schematic diagram of a heat pump hot air blower, an ambient temperature detection sensor 4-10 is arranged outside the body of the heat pump hot air blower 4, a preheating temperature detection sensor 4-11 is arranged between the evaporator 4-3 and the hot water heat exchanger 4-12, and the preheating temperature detection sensor 4-11 is installed in mid-air.

[0038] like Figure 3 As shown, this is a schematic diagram of an electric thermal storage water heater unit. Figure 4 As shown, it is a schematic diagram of the overall structure of the electric thermal storage water heater unit, the inner wall of the water storage tank 5-1 is provided with an insulating layer 5-3, the bottom of the water storage tank 5-1 is provided with a base 5-4, the base 5-4 is provided with a ground wire terminal 5-5, the top of the water storage tank 5-1 is provided with a pressure relief port 5-11, the bottom is provided with a sewage outlet 5-10, the upper end of the water storage tank 5-1 is provided with an overflow port 5-8, and the lower end is provided with a water replenishment port 5-9, and the other side of the electric thermal storage water heater unit 5 is provided with a first water temperature detection sensor 5-15 for detecting the internal water temperature of the inner tank 5-2 and a liquid level sensor 5-16 for detecting the internal water level of the inner tank 5-2.

[0039] The utility model provides an electric heat storage hot water unit to prevent frost from forming. When the water storage amount of the electric heat storage hot water unit 5 is lower than the position of the liquid level sensor 5-16, water can be automatically replenished through the water replenishment port 5-9. When the heat pump hot air unit 4 is supplying heat normally, the electric heater 5-14 of the electric heat storage hot water unit 5 is turned on for heating, the frequency conversion pump 6-1 of the accessory box 6 is turned off, and the opening degree of the three-way regulating valve 6-3 is reset. When the first water temperature detection sensor 5-15 detects that the water temperature has reached the design temperature, the electric heater 5-14 is turned off and stops heating. During the heating process, the pressure generated inside the inner tank 5-2 is discharged through the pressure relief port 5-11 to maintain normal pressure. When the ambient temperature detection sensor 4-10 detects that the ambient temperature is lower than the frosting temperature of the heat pump hot air unit 4, the frequency conversion pump 6-1 of the accessory box 6 is turned on for frequency increase operation, the water flow switch 6-9 detects the water flow, and the hot water on the upper part of the electric heat storage hot water unit 5 flows into the upper water distributor 5-12, passes through the pipe connected to the water supply port 5-6, and enters the first water inlet 6-61 of the accessory box 6. The opening degree of valve 6-3 is adjusted to regulate the water inlet of the second water channel connected to the third passage. The second water temperature detection sensor 6-8 detects the mixed water temperature. After adjusting to the design temperature, the mixed water enters the water inlet port 4-6 of the heat pump hot air unit 4 through the pipe connected to the first water outlet 6-71. Through the diverter 4-8, the hot water is evenly distributed to the hot water heat exchanger 4-12, the preheating evaporator 4-3 intakes air, and the hot water that releases heat and cools down passes through the pipe connected to the outlet port 4-7 of the collector 4-9, and flows back to the second water inlet 6-62 of the second water channel of the accessory box 6 through the pipe connected to the second water outlet 6-72, enters the return port 5-7 of the electric thermal storage hot water unit 5, and flows back to the lower part of the inner tank 5-2 of the electric thermal storage hot water unit 5 through the lower water distributor 5-13. As the upper hot water gradually decreases, the lower cold water level gradually increases, waiting for the next heating.

[0040] After heating, the hot air temperature is detected by the preheating temperature detection sensor 4-11. When the temperature is still lower than the frosting temperature, the third passage of the three-way regulating valve 6-3 reduces the water flow of the second water passage, and the frequency conversion pump 6-1 increases the water flow of the first water passage, gradually increasing the water supply temperature until the hot air temperature is higher than the frosting temperature to prevent frosting; when the ambient temperature detection sensor 4-10 detects that the ambient temperature is higher than the frosting temperature of the heat pump hot air unit 4, the frequency conversion pump 6-1 in the accessory box 6 is reduced and closed, the opening degree of the three-way regulating valve 6-3 is reset, the electric heat storage hot water unit 5 stops heating, and the electric heater 5-14 is turned on to heat and store heat. The upper water distributor 5-12 and the lower water distributor 5-13 in the inner tank 5-2 of the electric heat storage hot water unit 5 are key components of the electric heat storage hot water unit 5, and adopt a relatively high-efficiency radial disc structure, which is connected to the supply and return water pipes. The main function is to reduce the thickness of the thermocline layer. The upper part is hot water with a higher temperature, and the lower part is hot water with a lower temperature. They are not mixed at the beginning, which improves the utilization rate of hot water. As the amount of hot water used increases, the thermocline layer rises step by step.

[0041] The utility model provides a liquid heat storage and heat pump coupled heating system for grain drying, which solves the problem that the existing heat pump hot air unit needs to defrost in reverse during defrosting, resulting in lower air outlet temperature and unstable air outlet, thus leading to uneven grain drying temperature and poor effect.

Claims

1. A liquid heat storage and heat pump coupled heating system for continuous grain drying, characterized in that: The invention comprises an air source heat pump hot air unit (4), an electric heat storage hot water unit (5) and an accessory box (6); a condenser (4-2) is arranged at the lower part of the body of the air source heat pump hot air unit (4); a hot air outlet (4-1) is arranged on the body on one side of the condenser (4-2); a cold air inlet (4-5) is arranged on the body on the other side; an evaporator (4-3) is arranged at the upper part of the body; a condensing fan (4-4) is arranged on the top of the evaporator (4-3); a water inlet pipe (4-6) and a water outlet pipe (4-7) are also arranged on the body; the water inlet pipe (4-6) The flow divider (4-8) is connected via a pipeline; the output end of the flow divider (4-8) is connected to the heat exchange inlet of the hot water heat exchanger (4-12) via the flow divider pipeline; the water outlet pipe (4-7) is connected to the collector (4-9); the collector (4-9) is connected to the heat exchange outlet of the hot water heat exchanger (4-12); the electric thermal storage hot water unit (5) comprises a hot water storage tank (5-1); an inner tank (5-2) is arranged inside the hot water storage tank (5-1); an upper water distributor (5-12) is arranged at the upper part of the inner tank (5-2); a lower water distributor (5-13) is arranged at the lower part of the inner tank (5-2); the inner tank ( An electric heater (5-14) is arranged at the bottom end of the inner tank (5-2); a water supply port (5-6) and a water return port (5-7) are arranged on one side of the electric thermal storage hot water unit (5); the water supply port (5-6) is connected to an upper water distributor (5-12) inside the inner tank (5-2) through a pipeline; the water return port (5-7) is connected to a lower water distributor (5-13) inside the inner tank (5-2) through a pipeline; the accessory box (6) includes a first water path and a second water path; the first water path includes a first water inlet (6-61), a three-way regulating valve (6-3), a filter (6-4) and a filter (6-5) connected in sequence through a first pipeline. (6-2), a variable frequency pump (6-1) and a first water outlet (6-71), the second water circuit comprises a second water inlet (6-62) and a second water outlet (6-72) connected in sequence through a second pipeline, wherein the three-way regulating valve (6-3) is connected to the second pipeline through a pipeline; the first water inlet (6-61) is connected to the water supply port (5-6), the first water outlet (6-71) is connected to the water inlet pipe port (4-6), the second water inlet (6-62) is connected to the water outlet pipe port (4-7), and the second water outlet (6-72) is connected to the water return port (5-7).

2. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: An ambient temperature detection sensor (4-10) is arranged outside the body of the air source heat pump hot air unit (4), and a preheating temperature detection sensor (4-11) is arranged between the evaporator (4-3) and the hot water heat exchanger (4-12).

3. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: The inner wall of the hot water storage tank (5-1) is provided with an insulating heat-insulating layer (5-3), the bottom of the hot water storage tank (5-1) is provided with a base (5-4), and the base (5-4) is provided with a ground wire terminal (5-5).

4. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: A pressure relief port (5-11) is provided above the hot water storage tank (5-1), and a sewage outlet (5-10) is provided at the bottom.

5. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: The upper end of the hot water storage tank (5-1) is provided with an overflow port (5-8), and the lower end is provided with a water replenishment port (5-9).

6. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: A sewage valve (6-4) is provided on the second pipeline connecting the first water outlet (6-71) and the second water inlet (6-62).

7. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: A second water temperature detection sensor (6-8) is provided on the connecting pipe between the filter (6-2) and the three-way regulating valve (6-3).

8. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: The other side of the electric thermal storage water heater unit (5) is provided with a first water temperature detection sensor (5-15) for detecting the water temperature inside the inner tank (5-2) and a liquid level sensor (5-16) for detecting the water level inside the inner tank (5-2).

9. The liquid heat storage and heat pump coupled heating system according to claim 1, characterized in that: The variable frequency pump (6-1) and the first water outlet (6-71), as well as the variable frequency pump (6-1) and the filter (6-2) are connected via a flexible connection (6-5).

10. The liquid heat storage and heat pump coupled heating system according to claim 2, characterized in that: The preheating temperature detection sensor (4-11) is installed in the air between the evaporator and the hot water heat exchanger.

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