| The open exchange tower is modified from traditional airconditioning open cooling tower which generally used as evaporative cooling equipment, using which inversely as the heating equipment especially the heat source of heat pump has a wide application prospect and many advantages and it can realize cooling-heating-domestic hot water triple generation. Under the heat exchange condition, there will be complicated heat and mass transfer process between the air and water in open exchange tower, most of the research on this process sees the tower as cooling tower, the theoretical research of the tower which is seen as the source of heat is not sufficient. Open exchange tower can extract heat from air and it also can extract low temperature waste heat from industrial waste gas, which is energy-efficient and can lower environment pollution. The technique of open exchange tower is based on the research result of cooling tower, whose theoretical research time and practical application time are short and the research of whose inside heat and mass transfer theory is not thorough. On account of that, this thesis adopts the methods of theoretical analysis, numerical simulation and experimental study to discuss the heat and mass transfer process of the air and water in open exchange tower and the heat transfer characteristics of its mass coupling.(1) The analysis and conclusion of heat and mass transfer mechanism inside of heat source tower were made. First, the air change process in heat source tower was analyzed in details, then the three possible results of air change process(Warming humidification?Cooling dehumidification + Cooling humidification?Cooling dehumidification) were concluded. Then the differences of latent heat transfer capacity, heat-transfer resistance at water side, physical property of water flow change at water side between open exchange tower and cooling tower were analyzed and concluded colligating with research results of previous studies.(2) The theoretical and experimental research on system performance of open exchange tower were carried out in this thesis, the experiment on heat and mass transfer performance of open countercurrent exchange tower which adopts PVC film packing was carried out and the experimental results were analyzed and processed, the varying pattern of heat exchange capacity, inlet and outlet temperature, air enthalpy etc. under the influence of water-air ratio were obtained; When the product of heat exchange capacity and increasing velocity of heat exchange capacity reachs maximum the water-air ratio reachs optimum value. Through the process of experimental data the fairly ideal scope of water-air ratio in cooling and heating condition were obtained.(3)The FLUENT was applied to make numerical simulation of open exchange tower, the physical model of open exchange tower was made, the porous medium model was added in Packing area accordingly, to which the proper mesh generation was applied, and then the three dimensional numerical simulation was applied to the inside heat and mass transfer process in open exchange tower; The distribution diagram of velocity, pressure, temperature, density etc. of open exchange tower in cooling condition and heating condition were obtained respectively through numerical simulation and the correlation analysis was made.Through the analysis of FLUENT simulation results and the incorporation with relative experimental data, the reference can be provided for engineer practice.(4) Thermal comprehensive performance of open exchange tower was analyzed through the first and second law of thermodynamics, the detailed analysis was made on heat absorption capacity, sensible heat ratio, exergy efficiency and exergy loss of open countercurrent exchange tower. At last, the optimized water-air ratio was derived and calculated by the method of heat transfer unit on the basis of analysis. |
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