The Research Of Integrated Air Conditioning Combined With Evaporative Cooling And Mechanical Refrigeration

With the use of natural cooling source, low energy consumption, low pollution, etc.The existing evaporative cooling and mechanical refrigeration hybrid air conditioning units, have been widely used in practical engineering.However, during the practical engineering application there still exist some problems,such as large covering of the equipment, divided cold source and air conditioning units cause the system a large area, secondary exhaust air is directly discharged, and this part of the cooling capacity is not fully utilized.To solve these problems, we use the tube-type indirect evaporative cooler, the characteristics of low resistance, stable heat exchange efficiency, low cost and easy production process, combined with small refrigeration system constituted by scroll compressor, the characteristics of small size, stable performance and long service life, and put forward the integrated air conditioning combined with evaporative cooling and mechanical refrigeration.Firstly, compared the principle, structure and operation mode of the overseas existing hybrid integrated air conditioning.And, according to with the climate characteristics and the situation of the evaporative cooling technology in our country,we determined the structure scheme of the experimental prototype, adopted three kinds of operation modes,DEC, IDEC, and IEC+DX, and designed the position of each equipment.With study and analyze to the outside air and secondary exhaust air laws of Heat Interchange in the indirect cooling air cooler, we obtained the method of determining the secondary exhaust air parameters by the formula derivation. And use the 5000m3/h modular tube-type indirect evaporative cooler as a test rig, to test and calculate the method of determining the secondary exhaust air.And through this method, we derived the secondary exhaust air parameters of some cities in China, and analyzed using the secondary exhaust air as the condenser air flow theoretically.Choose the 5000m3/h modular tube-type indirect evaporative cooler as design criteria to calculate the experimental prototype designing. After select the outdoor design parameters, according to the empirical heat exchange efficiency of the tube-typeindirect evaporative cooling, analyzed Pressure-enthalpy diagram、Enthalpy wet chart together, to calculate the cooling relationship between mechanical refrigeration cooling and mechanical refrigeration,and the determining the secondary exhaust air.On this basis, we selected the mechanical refrigeration evaporation temperature, condensation temperature, the cooling capacity of the compressor, and calculated the proportion of each air flow, the wind turbine, pump selection, then completed unit design.In the end,we designed the automatic control scheme for it, and assemble the experimental prototype with the help of cooperative enterprise.Each of temperature drop of each functional section was tested in Baoji, Shaanxi,may to July.and analyzed the evaporative cooling equipment heat exchange efficiency and the refrigeration cycle efficiency by calculation. Test shows:(1) Using the mode of DEC, or IDEC can meet the requirements temperature and humidity of the supply air in the transition season, using the mode of IEC+DX can also meet the requirements temperature and humidity of the supply air in the air conditioning season.(2) Because the air volume is slightly lower than the design value, the wet bulb efficiency of the indirect evaporative cooling section is 58%, and the wet bulb efficiency of the cooling section is 89%,both are lower than the design value.(3) In the air conditioning season,compared and analyzed the IEC+DX operating mode with the pure mechanical refrigeration, the result shows that using the indirect evaporative cooling as pre-cooling for the mechanical refrigeration and using secondary exhaust air flow to cooling the condenser, and the cooling temperature can be reduced by of 8.7 at averaged, and EER can be increased 17.79%;(4) Automatic control system runs normally, it can according to the outdoor conditions to complete the operation mode of the switch, but the waiting time is too long and need to be improved further.In the end, we analyzed operating mode hours, air handling process, the selection of the two air, and the cold source ratio of the air conditioning system that based on this experimental prototype.