Self-defrosting energy-saving low-temperature air conditioning unit and control method

Abstract

The present invention relates to the technical field of air conditioner defrosting, and specifically to a self-defrosting energy-saving low-temperature air conditioner unit and a control method thereof. It includes an air conditioner unit box body, a fresh air inlet, a primary filter, a fresh air heat recovery coil, two low-temperature refrigeration evaporation coils connected in parallel through a bypass air valve, a heat recovery reheating coil, a fan motor, and an air supply outlet. The fresh air heat recovery coil and the heat recovery reheating coil are connected into a loop. The liquid outlet pipe of the fresh air heat recovery coil is respectively communicated with the liquid inlet pipes of the two low-temperature refrigeration evaporation coils through solenoid valve I. The liquid outlet pipes of the two low-temperature refrigeration evaporation coils are respectively connected to the liquid inlet pipe of the fresh air heat recovery coil through solenoid valve II and solenoid valve III. The liquid inlet side of the heat recovery reheating coil is communicated with the liquid inlet pipe of the fresh air heat recovery coil through a three-way valve. The present invention realizes automatic defrosting without an external heat source, and at the same time uses the fresh air heat for low-temperature reheating, reduces the reheating amount, and achieves a double-effect energy recovery effect.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioner defrosting, and specifically to a self-help defrosting energy-saving low-temperature air conditioner unit and a control method thereof. Background Art

[0002] More and more low-temperature industrial cold storages, cold chain food workshops and other environments have requirements for low-temperature constant temperature and humidity. The indoor temperature is generally ≤ 10 °C, and the dew point temperature is below zero. Therefore, low-temperature constant temperature and humidity air conditioning equipment is required to achieve a constant low-temperature environment. To achieve and maintain a constant low-temperature environment, the air conditioner unit needs to be equipped with a low-temperature refrigeration system for cooling and dehumidification. The evaporator coil of the indoor air conditioner unit is generally equipped with a low-temperature direct expansion outdoor unit for refrigeration. Since the air conditioner unit needs to have a relatively low outlet air temperature (usually below zero), the evaporation temperature of the compressor in the low-temperature refrigeration system is lower than that of the compressor used in a conventional air conditioner unit, usually below zero. When the evaporator operates in a low-temperature environment below zero for a long time, it is very easy to frost. Once the evaporator frosts, its resistance increases, the air volume of the air conditioner unit decreases, and the refrigeration capacity of the evaporator becomes worse. The more it frosts, a vicious cycle gradually forms, resulting in abnormal operation of the refrigeration system and inability to operate normally.

[0003] Therefore, to ensure the normal operation of the refrigeration system, the evaporator needs to be defrosted in time. The general defrosting measure for the evaporator is to stop refrigeration of the evaporator and use electric heating to melt the frost formed around the evaporator. When the evaporator is in the defrosting stage, it affects the temperature and humidity of the air discharged from the air conditioner unit, resulting in fluctuations in the temperature and humidity of the cold storage or cold chain food workshop. To keep the temperature and humidity constant in the air-conditioned area, the evaporators are usually set to be used alternately in two sets, that is, one set operates while the other set defrosts.

[0004] Existing air conditioner units successively include components such as an air conditioner unit box body, a fresh air inlet, a return air inlet (no return air in the case of a fresh air system), a primary filter, a low-temperature refrigeration evaporator coil used alternately for operation and defrosting, a defrost bypass air valve, an electric reheater or other reheating devices, a fan motor, and a supply air outlet. Traditional low-temperature evaporator coil defrosting usually adopts the form of electric defrosting, and electric heating tubes are arranged in the heat exchange tubes of the evaporator. When defrosting, the evaporator stops refrigeration, and the electric heating tubes are heated to melt the frost. Although the direct electric heating tube defrosting scheme has a simple system and good use effect, its operating energy consumption is very high. To ensure the temperature control effect, industrial air conditioner units generally operate for a long time, so the electricity consumption of air conditioning equipment is large, bringing a certain economic burden to the owner. Summary of the Invention

[0005] In view of the deficiencies of the above-mentioned prior art, the present invention provides a self-help defrosting energy-saving low-temperature air conditioner unit and a control method thereof, which have fast defrosting and low energy consumption.

[0006] The technical solution adopted by the present invention to solve its technical problems is:

[0007] Self - defrosting energy - saving low - temperature air - conditioning unit, which includes an air - conditioning unit box, a fresh air inlet, a primary filter, a fresh air heat recovery coil, two low - temperature refrigeration evaporation coils connected in parallel through a bypass air valve, a heat recovery reheating coil, a fan motor, and an air supply outlet.

[0008] Among them, the fresh air heat recovery coil and the heat recovery reheating coil are connected into a loop. The liquid outlet pipe of the fresh air heat recovery coil is respectively connected to the liquid inlet pipes of the two low - temperature refrigeration evaporation coils through solenoid valve Ⅰ. The liquid outlet pipes of the two low - temperature refrigeration evaporation coils are respectively connected to the liquid inlet pipe of the fresh air heat recovery coil through solenoid valve Ⅱ and solenoid valve Ⅲ; the liquid inlet side of the heat recovery reheating coil is connected to the liquid inlet pipe of the fresh air heat recovery coil through a three - way valve; a solution circulation pump and a solution constant - pressure tank body are arranged on the liquid inlet pipe of the fresh air heat recovery coil.

[0009] Furthermore, the heat - exchange straight pipes of the low - temperature refrigeration evaporation coils include a low - temperature refrigerant pipe group and a high - temperature solution pipe group, and the low - temperature refrigerant pipe group and the high - temperature solution pipe group are arranged alternately.

[0010] Even further, a return air inlet is arranged on the side of the fresh air inlet.

[0011] Furthermore, it also includes an auxiliary heating device arranged at the liquid inlet pipes of the two low - temperature refrigeration evaporation coils.

[0012] The present invention also designs a control method for a self - defrosting energy - saving low - temperature air - conditioning unit, which includes a defrosting mode and a non - defrosting mode.

[0013] The control method of the defrosting mode is as follows:

[0014] Solenoid valve Ⅰ is opened, the three - way valve conducts the fresh air heat recovery coil and the heat recovery reheating coil, and the flow rates of the low - temperature refrigeration evaporation coil and the heat recovery reheating coil are controlled by adjusting the electric three - way valve.

[0015] The two low - temperature refrigeration evaporation coils realize the switching between the defrosting state and the normal operation state through the on - off states of solenoid valve Ⅱ and solenoid valve Ⅲ.

[0016] When it is necessary to accelerate defrosting, the three - way valve is closed, and all the high - temperature solution enters the low - temperature refrigeration evaporation coil for defrosting.

[0017] The control method of the non - defrosting mode is as follows: Solenoid valve Ⅰ, solenoid valve Ⅱ, and solenoid valve Ⅲ are all closed, the fresh air heat recovery coil and the heat recovery reheating coil loop is conducted, and the solution flow rate is adjusted by the three - way valve.

[0018] Furthermore, when it is necessary to accelerate defrosting, the auxiliary heating device is turned on.

[0019] The beneficial effects of the present invention are: It can realize the energy recovery between fresh air and the treated air after refrigeration and cooling, save the reheating energy, and achieve the energy - saving effect.

[0020] It can achieve self-help defrosting when the low-temperature refrigeration evaporation coil is frosted, without or with a small amount of external heat source (electric heating) for defrosting, greatly reducing the defrosting electric heating amount and achieving significant energy-saving effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the self-help defrosting energy-saving low-temperature constant temperature and humidity air conditioner unit of the present invention;

[0022] Figure 2 Schematic diagram of the defrosting system principle of the present invention;

[0023] Figure 3 Front view structural schematic diagram of the low-temperature refrigeration evaporation coil of the present invention;

[0024] Figure 4 Left-side structural schematic diagram of the low-temperature refrigeration evaporation coil of the present invention;

[0025] Figure 5 Right-side structural schematic diagram of the low-temperature refrigeration evaporation coil of the present invention;

[0026] Figure 6 Cross-sectional structural schematic diagram of the low-temperature refrigeration evaporation coil of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To better understand the present invention, the following combines the attached Figure 1-6 to explain the embodiments of the present invention in detail.

[0028] The technical solution adopted by the present invention to solve the problem of energy waste is: a set of self-help defrosting system is set on the traditional low-temperature constant temperature and humidity air conditioner unit. ① When the low-temperature refrigeration evaporation coil in the air conditioner unit is defrosting, the heat in the high-temperature fresh air is transferred to the low-temperature refrigeration evaporation coil for heating, the temperature of the low-temperature coil rises, and the ice and frost on the coil melt to achieve the purpose of defrosting. At the same time, a part of the high-temperature solution coming from the high-temperature fresh air enters the reheating coil for reheating, so that the air supply temperature of the air conditioner unit is increased to a suitable air supply state, reducing or canceling the electric reheating after low temperature. ② When the air conditioner unit is operating normally for refrigeration and does not require defrosting, the self-help defrosting system is converted into an independent energy recovery system, that is, the defrosting mode is converted into a full energy recovery mode. The heat in the high-temperature fresh air system is recovered by reheating, and the high-temperature fresh air transfers the heat to the low-temperature refrigeration coil for heating, so that the air supply temperature of the air conditioner unit is increased to a suitable air supply state, reducing or canceling the electric reheating after low temperature.

[0029] The self-help defrosting energy-saving low-temperature air conditioner unit is as Figure 1As shown in the figure, the unit sequentially includes the air conditioner unit housing 1, fresh air inlet 8, primary filter 2, fresh air heat recovery coil 3 (ethylene glycol solution), return air inlet 9 (no return air inlet in a fresh air only system), low-temperature refrigeration evaporator coils 41 and 42 used alternately for operation and defrosting, bypass air valves 101 and 102, heat recovery reheating coil 5 (ethylene glycol solution), fan motor 7, and air supply outlet 11, etc. An auxiliary heating device 6 (which can use electric heating or other heating methods) is also provided. When the recovered reheating amount is insufficient, the auxiliary heating device 6 is activated.

[0030] The system operation plan is as follows: When the unit is operating, the fresh air inlet 8 is opened, and the high-temperature fresh air is filtered by the primary filter 2, then exchanges heat with the fresh air heat recovery coil 3 to cool down, and is mixed with the return air (no return air in a fresh air only system). If the low-temperature refrigeration evaporator coil 41 is set as the operating coil, the two air valves 101 are opened, and the two air valves 102 are closed. The air flow passes through the low-temperature refrigeration evaporator coil 41 for cooling and dehumidification. Since the cold storage refrigeration environment requires a relatively low temperature, generally in a sub-zero ambient temperature, the outlet air temperature of the refrigeration evaporator coil 41 is also very low (below zero). After operating for a period of time, frost forms on the surface of the evaporator coil, affecting the heat exchange effect, and defrosting is required. At this time, the low-temperature refrigeration evaporator coil 41 stops operating and enters the defrosting mode, and the unit switches to the operating mode with the low-temperature refrigeration evaporator coil 41 turned on. After the air is cooled and dehumidified by the refrigeration evaporator coil, it is reheated by the heat recovery coil to a suitable air supply temperature and sent to the air conditioning area through the air supply valve of the supply fan 7. The self-service defrosting and energy recovery system structure is as Figure 2 shown, and includes: fresh air heat recovery coil 3, circulating ethylene glycol solution pipeline 21, circulating water pump 22, low-temperature refrigeration evaporator coil 41 operating alternately with the defrosting mode, low-temperature refrigeration evaporator coil 42, solenoid valve I 23, electric three-way valve 24, solenoid valve II 25, solenoid valve III 26, heat recovery reheating coil 5, auxiliary heating device 28, and ethylene glycol solution and solution constant pressure tank 27 used for heat exchange in the connecting pipes.

[0031] Operation and control scheme of constant temperature and humidity air conditioning unit: (1) Defrosting mode during unit operation: Solenoid valve I 23 is opened, and the electric three-way valve 24 is adjusted. The high-temperature ethylene glycol solution flowing out of the fresh air heat recovery coil 3 for heat exchange enters the low-temperature refrigeration evaporation coil (41 or 42) and the heat recovery reheating coil 5 respectively. The solution flowing into the low-temperature refrigeration evaporation coil is for defrosting function, and the solution flowing into the heat recovery reheating coil 5 is for heat recovery function. The flow rates of the two paths are controlled by adjusting the electric three-way valve 24. The high-temperature solution for defrosting enters the required defrosting coil 41 or 42 for defrosting. After defrosting, it becomes low-temperature ethylene glycol solution and flows back to the fresh air heat recovery coil through the pipeline. Since the low-temperature refrigeration evaporation coil 41 and the low-temperature refrigeration evaporation coil 42 are used alternately, one for operation and the other for defrosting, the control of the ethylene glycol solution in the solution pipe depends on the usage functions of the two low-temperature refrigeration evaporation coils. When the low-temperature refrigeration evaporation coil 41 stops operating and enters the defrosting state, the low-temperature refrigeration evaporation coil 42 is operating normally. At this time, solenoid valve II 25 is opened, solenoid valve III 26 is closed, and the solution flows into the low-temperature refrigeration evaporation coil 41 for heat exchange defrosting. The low-temperature ethylene glycol solution after defrosting flows back to the fresh air heat recovery coil through the pipeline for heat exchange. On the contrary, when the low-temperature refrigeration evaporation coil 42 stops operating and enters the defrosting state, the low-temperature refrigeration evaporation coil 41 is operating normally. At this time, solenoid valve III 26 is opened, solenoid valve II 25 is closed, and the solution flows into the low-temperature refrigeration evaporation coil 42 for heat exchange defrosting. The low-temperature ethylene glycol solution after defrosting flows back to the fresh air heat recovery coil through the pipeline for heat exchange. The defrosting speed of the low-temperature refrigeration evaporation coil 41 or the low-temperature refrigeration evaporation coil 42 depends on the operation time of the other coil. If the frosting of the normally operating coil is fast, the defrosting time of the other coil will be short. If it is necessary to urgently shorten the defrosting time, the electric three-way valve 24 can be closed to make all the high-temperature solution flow into the defrosting coil, increasing the solution flow rate to improve the defrosting efficiency. Or the auxiliary heating device 28 can be started to heat the ethylene glycol solution in the pipe to raise the temperature and achieve rapid defrosting. (2) Non-defrosting mode during normal unit operation: Solenoid valve I, solenoid valve II and solenoid valve III are all closed. The high-temperature ethylene glycol solution for heat exchange in the fresh air heat recovery coil 3 adjusts the solution flow rate through the electric three-way valve 24, controls the solution to enter the heat recovery reheating coil 5 for heat recovery, and the low-temperature ethylene glycol solution after recovery flows back to the fresh air heat recovery coil 3 by the circulating water pump to complete the full energy recovery in the non-defrosting mode.

[0032] Such as Figure 3-6As shown, the heat exchange straight pipes in the refrigeration coil are divided into two major parts. In a large part of the pipes, low-temperature refrigerant flows in for refrigeration and cooling, and in a small part of the pipes, high-temperature solution flows in for defrosting in the defrosting mode. The intake pipe 12 (refrigerant inlet pipe) and the return pipe 13 (refrigerant outlet pipe) of the low-temperature refrigeration evaporation coil are on one side, and the inlet pipe 14 and the outlet pipe 15 of the high-temperature ethylene glycol solution are on the other side, which is convenient for production, installation and pipeline connection. The high-temperature solution pipeline and the low-temperature refrigeration pipeline are separated by one row of defrosting pipes every 1 to 2 rows to achieve a uniform defrosting effect, and at the same time, it is convenient for the solution header arrangement according to the arrangement of each row. Figure 6 The pipes with cross-hatching in the figure are the high-temperature solution pipelines 16, and those without cross-hatching are the low-temperature refrigeration pipelines 17.

[0033] The present invention realizes automatic defrosting without an external heat source, and at the same time uses the heat of fresh air for low-temperature reheating, reduces the reheating amount, and achieves a double-effect energy recovery effect.

Claims

1. Self - defrosting energy - saving low - temperature air - conditioning unit, characterized in that: It includes an air-conditioning unit box, a fresh air inlet, a primary filter, a fresh air heat recovery coil, two low-temperature refrigeration evaporation coils connected in parallel through a bypass air valve, a heat recovery reheating coil, a fan motor, and an air supply outlet. Among them, the fresh air heat recovery coil and the heat recovery reheating coil are connected into a loop. The liquid outlet pipe of the fresh air heat recovery coil is respectively connected to the liquid inlet pipes of the two low-temperature refrigeration evaporation coils through solenoid valve Ⅰ. The liquid outlet pipes of the two low-temperature refrigeration evaporation coils are respectively connected to the liquid inlet pipe of the fresh air heat recovery coil through solenoid valve Ⅱ and solenoid valve Ⅲ; the liquid inlet side of the heat recovery reheating coil is connected to the liquid inlet pipe of the fresh air heat recovery coil through a three-way valve; a solution circulation pump and a solution constant pressure tank are arranged on the liquid inlet pipe of the fresh air heat recovery coil. In the defrosting mode, solenoid valve Ⅰ is opened, the three-way valve conducts the fresh air heat recovery coil and the heat recovery reheating coil, and the flow rates of the low-temperature refrigeration evaporation coil and the heat recovery reheating coil are controlled by adjusting the electric three-way valve. The two low-temperature refrigeration evaporation coils realize the switching between the defrosting state and the normal operation state through the on-off states of solenoid valve Ⅱ and solenoid valve Ⅲ. When it is necessary to accelerate defrosting, the three-way valve is closed, and all the high-temperature solution enters the low-temperature refrigeration evaporation coil for defrosting. In the non-defrosting mode, solenoid valve Ⅰ, solenoid valve Ⅱ, and solenoid valve Ⅲ are all closed, the fresh air heat recovery coil and the heat recovery reheating coil loop is conducted, and the solution flow rate is adjusted by the three-way valve.

2. The self-defrosting energy-saving low-temperature air-conditioning unit according to claim 1, characterized in that, The heat exchange straight pipes of the low-temperature refrigeration evaporation coil include a low-temperature refrigerant pipe group and a high-temperature solution pipe group, and the low-temperature refrigerant pipe group and the high-temperature solution pipe group are arranged alternately.

3. The self-defrosting energy-saving low-temperature air-conditioning unit according to claim 2, wherein, An air return opening is arranged on the side of the fresh air inlet.

4. The self-defrosting energy-saving low-temperature air-conditioning unit according to claim 2, characterized in that, It also includes an auxiliary heating device arranged at the liquid inlet pipes of the two low-temperature refrigeration evaporation coils.

5. The control method of the self-defrosting energy-saving low-temperature air-conditioning unit according to any one of claims 1-4, characterized in that, It includes a defrosting mode and a non-defrosting mode. The control method of the defrosting mode is as follows: Solenoid valve Ⅰ is opened, the three-way valve conducts the fresh air heat recovery coil and the heat recovery reheating coil, and the flow rates of the low-temperature refrigeration evaporation coil and the heat recovery reheating coil are controlled by adjusting the electric three-way valve. The two low-temperature refrigeration evaporation coils realize the switching between the defrosting state and the normal operation state through the on-off states of solenoid valve Ⅱ and solenoid valve Ⅲ. When it is necessary to accelerate defrosting, the three-way valve is closed, and all the high-temperature solution enters the low-temperature refrigeration evaporation coil for defrosting. The control method of the non-defrosting mode is as follows: Solenoid valve Ⅰ, solenoid valve Ⅱ, and solenoid valve Ⅲ are all closed, the fresh air heat recovery coil and the heat recovery reheating coil loop is conducted, and the solution flow rate is adjusted by the three-way valve.

6. The control method of the self-defrosting energy-saving low-temperature air-conditioning unit as described in claim 5, characterized in that, When it is necessary to accelerate defrosting, the auxiliary heating device is turned on.

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