Ultralow-temperature heat pump water heater and electronic expansion valve control method for same

Abstract

The invention provides an ultralow-temperature heat pump water heater and an electronic expansion valve control method for the same. The ultralow-temperature heat pump water heater is characterized bycomprising an enhanced vapor injection compressor, a four-way reversing valve, a shell type heat exchanger, an evaporator, a main electronic expansion valve, a secondary electronic expansion valve, an air and liquid separator and a middle heat exchanger; the middle heat exchanger comprises a medium-pressure coiled tube and a high-pressure coiled tube; gaseous and liquid refrigerants are stored inside the middle heat exchanger; an exhaust opening of the enhanced vapor injection compressor communicates with a first through hole of the four-way reversing valve; and a second through hole of the four-way reversing valve communicates with the inlet end of the shell type heat exchanger. The ultralow-temperature heat pump water heater provided by the invention has the beneficial effects that theelectronic expansion valve is used for replacing a mechanical expansion valve applied to the prior art; the application range is wide; the disadvantages such as delayed control of superheat degree dueto the heat capacity of the tube wall of the evaporator and a sensor of the traditional mechanical expansion valve and the like; the regulation quality of a system is improved; and the superheat degree is controlled within a target range in a quite wide evaporation temperature region.

Description

technical field [0001] The invention relates to a heat pump water heater, in particular to an ultra-low temperature heat pump water heater and a control method for an electronic expansion valve thereof. Background technique [0002] When the air source heat pump operates at a low temperature such as lower than -10°C, the compression ratio of the compressor will increase due to the drop in evaporation pressure, and the exhaust temperature will be too high, resulting in the unit not being able to operate effectively and normally. At the same time, the heating capacity will also be greatly attenuated, which cannot meet the user's hot water heating demand. [0003] The traditional air injection enthalpy increase and two-stage compression technology can increase the heating capacity of the unit to a certain extent and make the unit run stably. The conventional control logic of the electronic expansion valve, especially under the condition of low ambient temperature and high water...

AI Technical Summary

Problems solved by technology

[0002] When the air source heat pump operates at a low temperature such as lower than -10°C, the compression ratio of the compressor will increase due to the decrease in the evaporation pressure, and the exhaust temperature will be too high, resulting in the unit not being able to operate effectively and normally.

At the same time, the heating capacity will also be greatly attenuated, which cannot meet the user's hot water heating demand.

[0003] The traditional air injection enthalpy increase and two-stage compression technology can increase the heating capacity of the unit to a certain extent and make the unit run stably. The conventional control logic of the electronic expansion valve, especially under the condition of low ambient temperature and high water temperature, the two expansion valves cannot be effectively adjusted to the most suitable throttling state, and it is easy to fail to achieve a good evaporation process, resulting in the exhaust temperature of the unit being too high and unable to stabilize operation, which greatly limits the popularization and use of air source heat pumps in severe cold areas in my country, so it is necessary to make further improvements

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