Design Features of High Temperature Service Air Conditioners High temperature service air conditioners use the most commonly used vapor compression refrigeration. The design features of the main components of the system are as follows: compressor selection. At present, there are two main types of compressors for high temperature driving air conditioners: reciprocating piston compressors and scroll compressors. Because the scroll compressor has the advantages of small size, light weight, simultaneous compression of multiple chambers, less leakage, high efficiency, almost continuous suction and exhaust process, low noise, small torque change, stable and reliable operation, it has become a driving air conditioner. The preferred compressor form in the design of the unit. The compressors selected must also meet the special requirements of high temperature refrigerants and their corresponding lubricants.
The form and characteristics of the condenser. The condensers for high-temperature driving air conditioners are mainly water-cooled and air-cooled. They are mainly air-cooled. This is determined by the production process requirements of the operating environment of the running air conditioner. In many cases, no water is allowed. Leaks can cause immeasurable losses to production. Air-cooled condensers generally use finned tube condensers, and their design requirements are strict. First, the fin spacing must be reasonably determined. Because the ambient air contains a large amount of dust, the dust particles will be in the fins in a short time. Deposition between, so the fin spacing is required to be larger than conventional air conditioners, but too large is obviously not conducive to heat transfer. Therefore, it is necessary to comprehensively consider various factors such as wind speed, environmental pollution process, cleaning time, heat exchanger volume, heat transfer effect and reasonable branching. In the condenser design, due to the high outdoor ambient temperature, the choice of thermal load factor will be higher than that of the general air conditioner. According to relevant empirical data: the pressure ratio is 3.07.0, and the thermal load factor is in the range of 1.11.8. To the actual working condition of the driving air conditioner, the thermal load factor is 1.
The form and characteristics of the evaporator. The evaporator for high-temperature driving air conditioners also adopts fin-and-tube type, and the design problem of condensed water should be considered in design. How to deal with condensate is a very important issue in the design of driving air conditioners. At present, three main methods are adopted: 1) introducing condensed water into a fixed container outside the air conditioner; 2) designing a water storage tank inside the air conditioner, and then discharging it regularly; 3) evaporating the condensed water by electric heating. The former two are low cost, but the risk is high, the latter wastes energy, but can be used for certain special occasions.
The choice of throttling components. This is one of the key technologies in the design of high temperature driving air conditioners. The running air conditioner has a lot of operating conditions. Therefore, the thermal expansion valve is generally used as a throttling element in its design. In addition to selecting a certain size of thermal expansion valve according to the theoretical design, it must be based on the actual work after the assembly is completed. The static opening of the regulating valve.
The theoretical design of high-temperature driving air conditioners includes: thermal calculation, compressor selection, design calculation of the two devices, selection of other auxiliary equipment, determination of refrigerant charge, and design of electrical control.
This article is mainly for the thermal calculation and two-piece design for a brief description. The high temperature refrigerant used is R142b, and the designed cooling capacity is 9.5kW. The design conditions are as follows: evaporation temperature 10, condensation temperature 80, superheat degree 15, subcooling degree 2, indoor side dry bulb temperature 30, indoor side wet bulb temperature 23 , outdoor side dry bulb temperature 60. The thermal calculation of the refrigeration cycle <3> is calculated by pressure: unit cooling capacity g0 = 154.
91kJ/kg, refrigerant flow rate gv=0.061326kJ/s, volume cooling capacity q0=1408.29kJ/m3, theoretical compressor gas VP=25.3m3/h, and a suitable compressor is selected accordingly. The design of the condenser is calculated as <4> The load of the condenser is: Kk=KQ0, K heat load coefficient, taking K=1.7.
Conclusion (1) In the design of high temperature driving air conditioner, the designed evaporation temperature and condensation temperature, superheat degree and supercooling degree should be reasonably selected. In the design of the evaporator, the enthalpy difference of the air treatment is generally 3kcal/kg dry, and the static expansion degree of the thermal expansion valve in the commissioning is 812 laps; (2) the supercooling device such as the regenerator is installed at the outlet of the condenser. The cooling capacity is increased by increasing the degree of subcooling; (3) when the ambient temperature is higher than 90, the cold storage device is used for cooling, so that the air conditioner realizes automatic switching between steam compression refrigeration and cold storage and cooling. In the normal temperature zone air conditioner works normally, in addition to providing indoor cooling capacity, it is also responsible for cold storage.
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