Abstract: The design method of heat pump air-conditioning system: air-conditioning load and capacity determination, unit type and number of units, heat pump position, pump selection and arrangement, heat pump air conditioning system terminal equipment selection. Keywords: air conditioning load heat pump air conditioning end equipment 1, air conditioning load and capacity to determine the air conditioning load, including air conditioning and cooling air conditioning heat load. Air conditioning cold (hot) load refers to the indoor air parameters to maintain the design parameters, the unit of time to be provided to the building cold (heat). This is a variable that is affected by many factors, such as interior design parameters, indoor personnel, equipment, etc., heat dissipation, water loss, nature of the envelope, outdoor air environment parameters (including temperature and humidity, airflow velocity, etc.) and solar radiation intensity. Air-conditioning cold (heat) load under indoor and outdoor design calculation parameters Calculate the cold (heat) load for the air conditioning design of a building. It is the fundamental purpose of air conditioning design that the air conditioning system appropriately provides the quantity of cold (heat) to meet the demand of the building under the design and calculation conditions and adapt to the cold (heat) load of the building air conditioning and its changes at any time. In the process of air-conditioning system design, air-conditioning load calculation is the first step, air-conditioning load calculation should include air-conditioning design calculation of load and load analysis of each period. Second, the capacity of the equipment must meet the requirements of cold (heat) load calculation of air conditioning design, while the other equipment configuration should be adapted to the characteristics of air conditioning load changes. In the air source heat pump type chiller unit for the cooling air conditioning system design heat pump unit capacity must take into account the building at the same time each part of the coefficient, should also take into account the actual heat pump heat capacity, the actual heat will be due to Equipment spacing restrictions and other causes of poor ventilation, part of the airflow short circuit (this part of the output loss of about 5%) are affected, and the outdoor heat exchanger due to surface ash, heat exchanger surface scaling, equipment attenuation and other factors Impact, so the choice of heat pump units should still consider the safety factor. Expressed by the formula: Q = β1 · β2 · QD. Where, Q - heat pump unit in the design conditions of the cooling (heating) KW QD - design calculation load, KW β1 - simultaneous use of coefficients, determined by the specific project, generally 0.75 ~ 1.0 β2 - safety Coefficient, generally take 1.05 ~ 1.10. In addition, heat pump units not only meet the cooling requirements of the system in summer, but also to meet the system requirements of winter air-conditioning heating. Different suppliers of heat pump rated cooling capacity, rated heating capacity of the different parameters, and outdoor air conditioning in various regions of the design parameters are not necessarily consistent. For Nanjing, the rated cooling conditions of the heat pump units provided by the general suppliers are the same as or close to those of the actual ones. Generally, the air dry-bulb temperature is 35 ° C and the air-conditioning refrigerant water inlet and outlet temperatures are respectively 12 ° C and 7 ° C. The winter heat pump rated working conditions for the outdoor air temperature 7 ~ 8 ℃, inlet and outlet water temperature is 50-55 ℃. This condition and Nanjing winter air conditioning design and calculation of the temperature is far from. Nanjing climate is characterized by cold winter and hot summer. For general office, hotel-based complex building, winter air conditioning heating design calculated thermal load of about 70-85% of the summer air conditioning design calculated cooling load. In the heat pump unit selection, you should see the heat pump unit corresponding to the local design and calculation of the actual conditions of the meteorological output. If the heat pump unit in the design and calculation of outdoor parameters of the cooling capacity is greater than the calculated design cooling load, and the heating capacity is equal to the thermal load, the heat load should be subject to select the heat pump. Conversely, if the cooling capacity to meet the design and calculation of cooling load requirements, while the heat is greater than the required heat, you may consider some of the selection of air-cooled chillers, some of the selection of heat pump units to reduce investment. Under normal circumstances, selected by the heat load in summer, to meet the requirements of winter heating. 2, the type and number of units to determine heat pump water chiller units can be divided according to different compressors scroll heat pump units, reciprocating heat pump units and screw heat pump units, according to the size of the unit structure, the combined size of different heat pump unit Divided into the overall heat pump units and modular heat pump units. The integral heat pump unit and the modular heat pump unit is no essential difference, the so-called modular heat pump refers to a heat pump unit by a number of heat pump unit (an independent refrigeration circuit, independent evaporation, condensation, independent framework, and even independent Control panel) made in parallel, the combination of various units flexible and convenient combination of any one unit failure does not affect the rest of the unit's work. The rated cooling capacity per unit is about 55KW. The domestic heat pump manufacturers to produce modular heat pump units as much, and the overall heat pump unit is a combination unit from the appearance, a whole framework, although there may be more than one compressor, and even more than two refrigeration circuits, However, they can not be further decomposed. The main advantages of modular heat pump unit is low noise, small vibration, due to the system of the total refrigeration circuit, the winter frost on the system temperature little effect. In addition, the heat pump unit is usually placed on the roof. The modular heat pump unit has the advantages of convenient transportation, convenient installation due to the flexible combination of various units and small size and light weight of each unit. If the project is large, modular heat pump unit will be due to the larger number of refrigeration units, but there are more points of failure, the maintenance of large capacity may be slightly lower than the rated efficiency of the overall unit. In addition, due to the modular heat pump plate heat exchanger is generally used, the higher the water quality requirements of the hydraulic equilibrium between the units is also higher. In summary, for smaller systems, or size, weight lifting and other special occasions, the modular heat pump has its advantages. The selected modular heat pump should pay attention to three issues: First, the water quality requirements, the entrance to set a higher filtration efficiency of the filter, and second, the hydraulic balance is better, the third is the number of pieces should not be assembled too much, so as not to affect the heat exchanger into the wind area. In general, a group of not more than 6 units. In the selection of integral heat pump units, air conditioners should take into account the characteristics of load changes and equipment interoperability between equipment, taking into account the winter heat pump defrost minimize the impact on water temperature. Generally, the number of heat pump units of an air-conditioning system should not be less than 2-3 units, and the total number of refrigeration circuits of the heat pump units configured for each air-conditioning system should not be less than 4-6. Of course, the number of heat pump should also consider the building functions, user unit division, measurement, management and other comprehensive factors. To the reciprocating heat pump units and screw heat pump units, in theory, screw-type heat pump less moving parts, less maintenance, high efficiency, low noise. However, due to the heat pump is a large part of the noise from the fan, and compressor noise can be reduced by adding noise enclosures, etc., so in fact screw-type heat pump noise slightly lower than the piston-type heat pump noise (about 3-5dB (A) ). In addition, the heat pump unit heat resistance is mainly in the outdoor heat exchanger side, the heat pump efficiency is also affected by the two-area and other factors, so from the engineering point of view, screw-type heat pump and piston-type heat pump in the difference in efficiency is limited. However, the price of screw heat pump than the reciprocating heat pump. On the refrigerant issue, when possible, as far as possible the choice of environment-friendly refrigerators, such as R134a, R407C, which should be preferred R407C followed by R134a, from the price of the refrigerant, the cheapest is R22. 3, the location of the heat pump The location of the heat pump has the following types, one is placed in the top of the podium, the second is placed in the top of the tower, the third is placed on the windowsill, the fourth is placed in a high net indoor height. Taking into account the lifting and replacement of other reasons, the heat pump is more placed in the top of the podium. When the heat pump is placed on the top of the podium, it is necessary to evaluate its impact on the main building and the surrounding environment. Larger heat pump units (≥200RT) and stand-alone noise of 75 ~ 85db (A) or so. If necessary, add noise barriers, or in the main building by heat pump to avoid the door to do double-glazed windows or high-quality hollow glass instead of ordinary single-pane glass. Heat pumps arranged on the windowsills are often independent configuration of each floor, separate measurement of places, only limited to the smaller capacity of the heat pump, the exhaust side should be used in the form of side into the wind. Selection of exhaust heat pump should be installed when the diversion duct, into the side of the exhaust. Even if there is a high clearance in the room, it is not advisable to place the heat pump in the room. When the conditions are limited, the indoor air should be used in the hallway. There should be enough air inlet area and ventilation through the air duct To the outdoor, to prevent short-circuit airflow. When adding exhaust pipe, the fan should be adjusted accordingly to avoid the increase of resistance and reduce the ventilation. Ideally, heat pumps should be placed on top of the tower so that the heat pump has good ventilation and minimizes noise impact. . However, it should be noted that the heat pump can not be located near residential or other noise-demanding rooms. Heat pumps and water pumps should not be placed above or below the residence (guest room). Heat pump unit should adopt spring shock absorber vibration isolation, shock absorber model and layout points are determined by calculation. Heat pump by the daughter of the wall and the main building distance greater than 3m, heat pump spacing should not be less than 3m, when the distance should be increased. In addition to consider the layout of the heat pump around the small, good ventilation, but also consider the pipeline layout, lifting equipment and subsequent replacement and other factors, when conditions set aside 1 to 2 heat pump position, leaving room for development and equipment Install and replace Consider adequate load conditions. 4, the choice and arrangement of pumps The number of pumps should correspond to the number of heat pumps. Heat pump and pump connection should adopt a one-on-one way, heat pump and pump linkage. When the number of heat pumps is more, the pump can be affixed to the heat pump arrangement, the water pump should have a waterproof performance and add the rain cover, when the heat pump is small, the pump should be arranged in the room. Standby pumps can be used without first installing a temporary replacement method. If the pump is connected in parallel with the parallel first heat pump in series, the number of parallel heat pumps should not exceed 6 and there should be reliable hydraulic balance measures. This connection should be arranged in the pump near the heat pump room can also be placed in the basement, the number of pumps should be considered 1 to 2 spare pump. In the selection of pump specifications, as far as possible choose a low speed pump, to reduce noise, the pump flow rate can be selected according to the system 1.1 times, the pump lift should be equal to the system to overcome the total resistance. Pump power consumption should be controlled within the heat pump output within 1/30. The layout of the pump to have a certain distance, when conditions reserved for the installation of 1 to 2 pumps for development needs. Pumps should also have reliable vibration isolation measures. 5, heat pump air conditioning system end equipment options Under summer conditions, the heat pump rated supply and return water temperatures were 7 ℃ and 12 ℃, which is consistent with the rated condition of the general air conditioner, air conditioner selection and other forms of calculation The same air-conditioning system. Winter working conditions, heat pump air conditioning system rated conditions (outdoor air 8 ℃), heat pump rated supply and return water temperature are generally 47 ℃, 42 ℃. When the outdoor temperature is low, the heat pump air conditioning system, the water temperature is generally maintained at 39 ~ 40 ℃. The water temperature is obviously lower than the rated heating and cooling water supply system temperature (60 ℃ and 50 ℃, respectively), which is lower than the rated inlet and outlet water temperature of the general air conditioner performance parameters (also respectively 60 ℃ and 50 ℃), due to water temperature is not the same, there is a significant difference between the amount of heat the air conditioner. Some scholars think that heat pump air conditioning system end equipment should be calculated based on the results of the summer conditions based on the results have been enlarged. However, according to our calculations, the end of the heat pump air-conditioning system in Nanjing can be calculated using the results of the calculation under summer cooling conditions. This is due to the fact that the heat load of general buildings in Nanjing area is less than that of summer cooling load. In addition,
