General layout and main component configuration of

Analysis of the overall layout and main component configuration of heat pump chiller and water heater

1 preface

as the cold and heat source of central air conditioning, air-cooled heat pump chiller and water heater has its high equipment utilization rate, one machine can be used in winter and summer, eliminating the cooling water system and heating boiler required by the water-cooled chiller, and putting forward higher requirements for automobile manufacturers for water-saving and holiday friendly emission standards. It is of positive significance for energy and environmental protection, as well as convenient installation, It can be placed on the roof and does not occupy the building area. In recent years, it has been widely used in the Yangtze River Basin and the Yangtze River Delta region. This paper makes a comprehensive analysis of the overall layout and the configuration of main components of air-cooled heat pump cold and hot water units, which provides a reference for the design and selection of such units

2 type and overall layout of air side heat exchanger of air-cooled heat pump cold and hot water unit

air-cooled heat pump cold and hot water units with refrigerating capacity of about RT are generally called villa type small units, and the refrigerating capacity range of medium and large units is about RT

the types and air outlet modes of the air side heat exchanger of small villa type units are: (1) inclined side air outlet, and the compressor is at the lower part; (2) Flat side air outlet, compressor, etc. at the lower part; (3) Flat side air outlet, compressor on one side; (4) The finned tube stands upright to the bottom and the compressor is on the inside. For the flat side air outlet, when using two upper and lower fans, and each fan corresponds to an independent refrigeration system, it should be noted that in the case of alternative defrosting of the two systems, it is not conducive to the lower fin heat exchanger. When the upper defrosting, the defrosting water falls on the lower fin, which will cause serious icing of the lower fin

the air side heat exchanger type and unit layout of the integral unit are as follows: (1) upper vertical fin air side heat exchanger. Lower compressor, water side heat exchanger and other components; (2) The air side heat exchanger stands upright to the bottom, and the compressor and water side heat exchanger are inside, (3) the air side heat exchanger stands upright to the bottom, the water side heat exchanger is inside, and the compressor is at one or both ends; (4) The upper part is W-type air side exchanger, and the lower part is compressor and water side heat exchanger; (5) V-shaped air side heat exchanger and compressor are arranged outside the fins. Therefore, considering the maintainability of the unit, 2 There is nothing that big manufacturers cannot show customers. It is better to put the compressor on one or both ends

for modular units, most air side heat exchangers are V-shaped. The heat exchange effect of the middle heat exchanger is far less than that of both sides. The air inlet volume of the middle module is insufficient and the wind speed is small

the selection of fan for large air side fin heat exchanger is very important. In order to achieve the expected heat exchange effect, the uneven air inlet on the surface of the heat exchanger should be fully considered. Sufficient air intake is beneficial to high-temperature operation in summer and defrosting on the surface of fins in winter. If necessary, variable-speed fans can be considered to meet the requirements of different working conditions. The lower section of many air side heat exchangers is designed as a common supercooling (overheating) section, which is more beneficial to the stable operation of the whole machine

the types of air side heat exchangers include flat, corrugated and windowed fins. From the perspective of overall use efficiency; Corrugated fins are better for medium and large fin heat exchangers. The fin spacing shall generally not be less than 2mm. In order to strengthen the heat transfer inside the finned tube, the heat transfer coefficient can be greatly improved by replacing the smooth tube with the internally threaded tube. Fin tube surface treatment, such as coating hydrophilic film to reduce the wind resistance and corrosion prevention on the air side, coating antioxidant layer to prevent the air (especially used in the seaside) from corroding the aluminum fins, and coating the fins with black treatment, can enhance the surface heat transfer coefficient of the fins

the indoor heat exchanger of the small gas heat pump is optimized with the maximum cop as the objective function. Under the refrigeration condition, the number of loops of the heat exchanger is 6, the refrigeration and heating are optimized at the same time, and the number of loops of the heat exchanger is 4

3 water side heat exchanger

the types of water side heat exchangers of small villa type and modular air-cooled heat pump cold and hot water units are: sleeve type, plate type and vertical coil type

the corrugated internal thread pipe is suitable for the refrigerant water heat exchanger in the heat pump type cold and hot water unit

that is, to pay bank interest, bear depreciation and amortization, pay social security and living expenses of employees, and pay the drainage expenses of discontinued mines. All kinds of water side heat exchangers have their own characteristics. For casing and vertical coil heat exchangers, attention should be paid to solving their main problems in the design and manufacture. The use of plate heat exchangers should also enable users to understand their characteristics and pay attention to water quality problems. The water side heat exchanger has effective anti freezing protection

4 throttling device

the small air-cooled heat pump hot water unit uses a force expansion valve, which controls the direction of refrigeration and heating by four one-way valves. Capillary tubes are also used as auxiliary throttling during heating. Due to the large changes in refrigerant circulation under different working conditions of refrigeration and heating, two or more thermal expansion valves are required to meet the requirements of working conditions. In occasions with high resistance of liquid pipeline, such as high resistance of liquid separation head, Pay attention to appropriately increase the empty volume of the corresponding expansion valve to avoid insufficient liquid supply

manufacturers of air-cooled heat pumps should pay attention to the application research of electronic expansion valve. In terms of the characteristics of the electronic expansion valve itself, it can control the suction pressure and superheat of each circuit, control the refrigerant circulation, and adapt to the load changes more effectively than the thermal expansion valve, so that the partial load performance of the unit can be improved. In the defrosting cycle, the electronic expansion valve can also achieve the opening required for defrosting in time, so as to improve the defrosting performance of the unit

5 compressor type

small villa and modular units use fully enclosed reciprocating compressors or fully enclosed scroll compressors. Integral units generally use semi closed reciprocating compressors or semi closed screw compressors. At present, the most commonly used fully enclosed compressor is the reciprocating compressor. For the fully enclosed scroll compressor used in villa type units and modular units, the performance of the scroll compressor is better than that of the reciprocating compressor in all aspects. The scroll compressor has fewer parts, high energy efficiency ratio, and is not sensitive to wet compression. Liquid injection cooling can be used in places with high compression ratio. Compared with the reciprocating compressor, because of its small leakage, no clearance volume, and small flow loss, In November, the heat pump successfully transferred to Yanliang, Shaanxi Province to carry out a scientific research test flight. Under the high pressure ratio, it still has a higher volumetric efficiency. This model is more suitable for the operation of flower heat pump and will become a substitute model for reciprocating compressor in this range. For the integral unit, the performance of the semi closed screw compressor is also better than that of the reciprocating compressor. Its energy efficiency ratio in summer is higher than that of reciprocating compressor, and its heating performance coefficient in winter is% higher than that of reciprocating compressor. Screw compressors are suitable for cold regions with poor working conditions