The Experimental Study On The Falling Film Water Source Heat Pump

As an energy-efficient equipment,the heat pump completes the refrigeration cycle of evaporation,compression,condensation,throttling and re-evaporation in the entire refrigeration system.Increasing the energy efficiency of the heat pump unit,the stability of the operation,and the degree of matching with the heat source and end are matters that the refrigeration industry must take action on.Improving the energy utilization and conversion of heat exchangers and developing energy-efficient and stable heat exchangers is undoubtedly a crucial means to improve the energy efficiency of heat pump units.This paper optimizes the falling film water source heat pump unit,analyzes the factors affecting the heat transfer efficiency of the horizontal tube falling film evaporator,proposes optimization measures for the falling film evaporator,and applies the optimized falling film evaporator to the new falling film type.On the water source heat pump unit,the optimized unit was tested to compare the performance of the falling film water source heat pump unit before and after optimization.In this paper,Fluent software is used to simulate the falling film flow heat transfer process outside the horizontal tube falling film evaporator tube.The effect of the flow state of the falling film outside the tube,the thickness of the formed liquid film and the local heat transfer coefficient outside the tube on the heat transfer efficiency of the horizontal tube falling film evaporator were studied.The following conclusions are drawn: when the spacing between the liquid droplets along the length of the tube is different,the variation of the thickness of the liquid film outside the tube is the same as that of the circumferential angle,and both of them show a rapid decrease with the increase of the circumferential angle.The smoothing is finally increasing.When the distance between the cloth liquid holes along the tube length direction is s=8 mm and 10 mm,the liquid film spreads more evenly outside the tube.When s=15mm,there is no liquid film flowing in a sheet shape outside the wall of the heat exchange tube,the liquid film is not continuous,and the dry area is large.When s=8m,the heat exchange efficiency is high.When the initial flow rate is increased from v=0.05 m/s to v=0.2 m/s,the liquid film thickness is gradually increased.When v=0.15m/s,the average heat transfer coefficient outside the tube is the largest,and the average heat transfer coefficient outside the tube is the smallest at v=0.05m/s.As the circumferential angle increases,the local heat transfer coefficient first decreases rapidly and then stabilizes and then decreases.In this paper,the tube bundle structure optimization of the falling film evaporator of the falling film water source heat pump unit is carried out.The Fluent software was used to simulate and optimize the arrangement of the inner tube bundle of the falling film evaporator,the height of the liquid,the spacing of the tubes,and whether the second liquid plate was added between the upper and lower tubes of the tube bundle.After the simulation analysis,the following conclusions are drawn: from the perspective of tube bundle arrangement,the tube bundle arrangement of the rotating triangle is better than the triangle tube bundle arrangement,the refrigerant liquid is more stable in the falling film outside the tube,and the tube wall is more stable.Liquid film;from the influence of the height of the cloth liquid,the thickness of the liquid film formed on the outer wall of the horizontal tube will gradually become thinner with the increase of the height of the liquid,and the liquid column between the tubes also follows the liquid.The height increase gradually becomes thinner.When the height of the cloth reaches a certain height,the lower tube shows a state of dripping flow.From the influence of the tube spacing,the film thickness of the outer tube of the horizontal tube gradually decreases with the increase of the tube spacing.The trend is that when the pipe spacing is equal to 25 mm,the heat transfer effect outside the pipe is the best;if the secondary liquid plate is added between the pipe lengths,the second liquid plate is added,and the falling film flow outside the pipe is more stable.The fluid between the tube bundles does not interfere with each other,and the tube wall forms a more stable liquid film.Finally,this paper applies the optimization measures to the new falling film water source heat pump unit,produces a new prototype and conducts performance tests according to national standards.The experimental results show that the evaporation temperature of the new prototype is obviously improved after the second liquid plate is added.The optimized performance of the new prototype under refrigeration conditions reaches 6.96,and the COP reaches 4.88 under heating conditions,and ICOP= 6.05 reached the national level of energy efficiency,and the performance of the new prototype improved significantly.