| The lack of fresh water have affected the development of social economy and theimprovement of living standards, in order to relieve the strain on freshwater, thegovernments are actively looking for effective way to solve this problem. As iswell-known, the sea water resources are inexhaustible. So if can turn sea water intofresh water, it will be one of the important ways to solve water crisis.Thus, seawaterdesalination technology arises at the historic moment, effectively alleviate the watershortage crisis. As a kind of high efficiency and energy-saving technology in theapplication of seawater desalination, heat pump low temperature evaporationwith itscharacteristics of high efficiency and energy saving, has a broad development space.Therefore, the research onthis technology is of great significance to promote thedevelopment of desalination.The low-temperature saturated steam is compressed into a high-temperaturesuperheated state by a compressor, the high-temperature superheated steam is thencondensed in a condenser. While the saturated salt water is heated by the latent releaseso that the salt water can be partially evaporated to saturated steam in an evaporator. Itis operated in the condition of negative pressure, so that the process can effectivelylessen brine fouling and corrosion problems and result in a higher thermal efficiency.To study the performance of heat pump low temperature evaporation system, thispaper constructed the physical and mathematical model, and the seawater isdetermined as the working medium in desalination process. Based on this model, acomputer code is made to emphatically analyze the influence of three importantindependent parameters including-compression ratio of the compressor, evaporationtemperature and discharging concentration on the system performance. The resultsshow that water production rate and the power consumption rise as the compression ratio and the evaporation temperature get higher, but the COP becomes lower; thedischarging concentration of brine has a mild effect on system performance.On the basis of the theoretical model, this paper established the heat pump lowtemperature evaporation desalination experiment platform, using roots compressor,and the horizontal tube falling film evaporation technology to find out the influence ofcompression ratio, evaporation temperature and discharging concentration on waterproduction rate and the parameters of the energy consumption. Due to fouling andcorrosion factors and the performance of the compressor influencing the practicaloperation, the suitable range of evaporation temperature is chosen62-79℃, thecompression ratio is1.2-1.5and that of discharge concentration is0.04to0.06.The compressor efficiency is turned out to be only0.318which is used to revisetheory model after the experiment, and a calculation curve under the experimentcondition is introduced as a comparison to analyze. The results indicate that thecompression ratio increases from1.2to1.5, brings about the power consumption torise from37.97kW h/m3to97.85kW h/m3, and COP decreased from4.74to1.84,about61.2%, system’s energy saving falls by more than half; The water productionrate is increased from13.8kg/h to16.89kg/h, rose by22.4%when evaporationtemperature ranges from62℃to79℃, however the energy-saving performance fallsby around4%. Therefore, under the premise of meeting the water production rate andrequirements of scaling prevention, choosing a lower compression ratio and higherevaporation temperature can make contributions to increasing the rate of waterproduction and saving energy consumption. In this experiment, it can achieve theoptimal performance when compression ratio remains1.2, and evaporationtemperature stays79℃, with discharging concentration keeping0.05. With theoptimal condition, water production rate can be16.89kg/h, the power consumption41.14kW h/m3, heat pump’s COP4.33. |
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