1 heat pump system economic operation of the basic requirements: 1) as far as possible the use of high temperature heat source. 2) The actual temperature difference between heat source and heat medium is the lowest. 3) The heat source shall meet the following requirements: --- Provide the required heat at the highest possible heating temperature. --- The cost of using the heat source is lower. --- Whether in the chemical or physical, heat exchange equipment does not have a negative impact. --- Heat conditions change, better adaptability. --- Conveying equipment such as fans, pumps and other energy consumption as low as possible. 2. The heat pump system compressor should meet the following requirements: 1) For air source heat pump, in the tz = -35 ~ +15 oC and tl ≤ 65oC range should be able to operate normally; compression ratio up to 9, there should be satisfactory efficiency At the same time, there should be no excessive overheating temperature. 2) The compressor is not affected by the quality of the inspiratory air when it is superheated and unsaturated. 3) Can withstand rapid changes in working pressure, no oil foam; oil should be returned to the crankcase with steam, and in the box with immersion heaters. 4) There should be good, reliable over-temperature, over-voltage protection device. Trouble-free operation time in more than 25000h. 5) Larger heat pumps should be equipped with a smooth and loss-free energy conditioner. 6) Compressor equipped with a motor, with a flat efficiency curve. Based on the above requirements, put forward the following recommendations: Heating Q = 0.5 ~ 500KW, the use of positive displacement. Heating Q> 500KW, the use of centrifugal. 3. Refrigerant flow control to the use of thermal expansion valve is appropriate, and should be "balanced hole" type, in order to maintain the pressure does not change with the change, but in the case of smaller pressure drop the normal operation. 4. Economic judgments For a heat pump system with a certain performance, it is usually considered economical when used under the following conditions: There is a good heat source like groundwater. The annual running time is not less than 2000h. COP values> 3 No heating is required for heating cycles based on summer cooling. Refrigeration equipment has been used in the occasion, such as cold storage, skating rink, supermarkets and so on. Waste heat available for use. Large internal waste heat within the building, it is possible to use the internal heat source to heat the building when the ambient temperature is below zero, such as department stores, theaters, computer rooms. Conversely, the economics of a heat pump in the following situations are not certain: for heating only. COP <3. Heat pump capacity is much larger than the heating load.