Weak current College】 【air-cooled heat pump overall layout and the analysis of the main part configuration.

1 preface

Air-cooled heat pump as central air conditioning and heating source has its equipment utilization is high, a machine of winter-eliminates water cooled chiller the required cooling water system and heating boilers, water saving, energy saving and environmental protection are positive, as well as easy installation, can be placed on the roof, not the construction area, and other characteristics, in recent years on the Yangtze River basin and the long southern areas of widespread use. This article on the air-cooled heat pump overall layout and main part of the configuration for a more comprehensive analysis, as this type of design and selection of the unit.

2 air-cooled heat pump air heat exchanger-types and overall layout

Cooling capacity at around 3-15RT air-cooled heat pump commonly known as villa-style of small units, large unit refrigeration capacity range is around 20-400RT.

Small villa-style unit wind side heat exchangers of type and method are: the wind
(1) oblique side outlet, compressors, etc in the lower;
(2)-ping side outlet, compressors, etc in the lower;
(3) the flat side of the wind, the compressor in the side;
(4) goes against the wind, finned tube up to the end, the compressor on the inside. For the flat side of the wind using the up and down two fans, each of which corresponds to a separate fan cooling system, it should be noted that in two alternating defrosting system, on the lower part of the fin heat exchanger, when the upper part of the defrosting, defrosting water fell on the lower part of the fin, can cause serious icing at fin.

Integral unit air side heat exchanger type and unit layout include the following:
(1) upper vertical fin-air heat exchanger. The lower part of the water side of the compressor and heat exchanger, etc;
(2) air side heat exchanger up to the end, compressors and water heat exchanger, the internal
(3) air side heat exchanger up to the end, the water side of the heat exchanger in internal, compressor at one end or both ends;
(4) the upper side of the w-type air exchanger, lower part is a compressor and water heat exchanger;
(5) V-shaped air side heat exchangers, compressors in fin lateral arrangement. Because of this, maintainability unit to compressor on one end or both ends.

For modular units, air side heat exchanger most v-shaped structure. Central heat exchanger for heat exchange efficiency is far behind the central module on both sides, into the wind, the wind speed.

Large air side fin heat exchanger fan selection is very important to achieve the desired effect of heat, should take full account of the heat exchanger surface wind is not uniform. Adequate intake air volume run on high temperature in summer and winter for fin surface frosting is good, if necessary, consider using a variable speed fan to fit different operating requirements. Many air heat exchanger design into the lower part of a common cold (hot), on the whole more favourable and stable operation.

Air side heat exchanger type have plain film, ripple Tablet and fenestration fin. Overall efficiency in large fin; heat exchanger to use ripple Tablet as well. Fin spacing should be not less than 2mm. For enhanced finned tubes inside the heat, with internal thread pipe instead of fluorescent tubes, can significantly increase the heat transfer coefficient. Finned tube surface treatment, such as coated hydrophilic membrane to reduce wind resistance and air side of corrosion protection, oxidation layer to prevent air (especially sea) on corrosion of aluminum fins and the fin black handling, enhanced finned surface heat transfer coefficients.

On small---gas heat pump of indoor heat exchanger to COP a maximum target function has been optimized calculation, in the refrigeration mode optimization, heat exchanger circuit number is 6, refrigeration, heating while optimizing the heat exchanger circuit number is 4.

3 water heat exchanger

Small villa-style and modular air-cooled heat pump water side heat exchanger type: telescopic, plate and vertical coil.

Heat pump chiller-refrigerant-in-water heat exchanger to adopt corrugated inner thread pipe is appropriate.

Various water side of the heat exchanger has its own characteristics, telescopic and vertical coil heat exchanger and pay attention in the design and manufacturing time solutions to their problems, use the plate heat exchanger should enable users to understand its features and attention to water quality problems. Water side of the heat exchanger has valid antifreeze protection.

4 throttle devices

Small air-cooled heat pump hot water unit with a power expansion valve, four-valve control of refrigeration, heating, also useful when the capillary do heating, auxiliary throttle used in refrigeration, heating unit due to the different conditions of refrigerant cycle variation, having two or more thermal expansion valves to accommodate the work condition, in liquid piping resistance big occasions, such as liquid head resistance, it is necessary to pay attention to the right to increase the amount of empty expansion valve, to avoid for liquid shortage.

Air-cooled heat pump manufacturers should pay attention to the application of electronic expansion valves. It features electronic expansion valve itself is concerned, it is possible to control the loop of the suction pressure and superheat, control the amount of refrigerant circulation than thermal expansion valves more effectively adapt to changes in load, so that the unit part load performance is improved. The defrost cycle, electronic expansion valve can also be timely to defrost the desired opening, improve the performance of defrosting unit.

5 compressors type

Small villa-style and modular unit using closed reciprocating compressor or hermetic scroll compressor. Integral units generally use semi-hermetic reciprocating or semi-hermetic screw compressors compressors. Currently use more hermetic compressor is a reciprocating compressor. In the Villa and its units and modular units use the hermetic scroll compressor, scroll compressors in all aspects of performance that surpasses the reciprocating compressor, scroll compressor parts, high-efficiency ratio, not sensitive to wet compressed, high compression ratio and may use the spray liquid cooling, compared with reciprocating compressors, because its disclosure contrary to the space capacity, flow loss is small, in heat pump running high pressure ratio.