Study On Performance Of Closed Surface Water Source Heat Pump Forced Circulation Heat Exchanger

This paper proposes a new type of closed surface water source heat pump forced circulation heat exchanger suitable for cold regions in the north and some hot summer and cold winter regions.Due to the low temperature of surface water in winter in northern China,even the bottom of the water with the highest density is only 4 °C.Water temperature,if using surface water source heat pump,it is necessary to reduce the heat exchange temperature difference of surface water.Under the same heat exchange quantity,it is necessary to increase the flow of surface water.This study mainly uses the idea of "large flow rate,small temperature difference" to the new type of closed Performance analysis and numerical calculation of surface water source heat pump forced circulation heat exchanger.Firstly,according to the basic environmental conditions at 4 °C in the bottom of the winter water body,the numerical calculation of the spiral coil heat exchanger and the new forced circulation heat exchanger of the conventional closed surface water source heat pump system respectively,the heat exchange area of the two heat exchangers,The flow resistance is compared with the energy consumption of the pump.The heat exchange area required for the heat exchange area of the forced circulation heat exchanger under the same heat exchange amount is 14.3 m2 and is smaller than the heat exchange area of the spiral coil heat exchanger of 47.1 m2.The forced circulation heat exchanger system has a flow resistance of 13.17 kPa which is smaller than the conventional closed surface water source heat pump heat exchange system of 49.1 kPa.It shows that the heat transfer performance and energy consumption of the new closed system forced circulation heat exchanger is superior to the conventional spiral coil heat exchanger.Secondly,considering the comprehensive influence of physical factors on the heat transfer performance of the forced circulation heat exchanger,the heat exchanger inlet and outlet average temperature,heat transfer temperature difference,shell and tube flow velocity and heat transfer pipe parameters are changed respectively.The numerical calculation is carried out;in the most unfavorable case at 4 °C,reducing the heat transfer temperature difference and increasing the water flow rate will increase the system energy consumption.In this study,the shell flow velocity is appropriately reduced by three different calculation schemes(respectively 1m/s,0.8m/s,0.67m/s)can reduce the system resistance to some extent.At the same time,it also changes the influence of the common three kinds of metal pipes(stainless steel pipe,copper pipe,galvanized steel pipe)on the performance of the heat exchanger,because its thermal resistance is a small proportion of the total thermal resistance(three metal pipes)The thermal resistance of thermal conductivity is 2.56%,0.31%,and 1.92%,respectively.It can be concluded that the thermal conductivity of metal pipes does not need to be placed in the primary consideration.Finally,because the geometric factors(integrated geometric factors,baffle number,baffle spacing and heat transfer pipe diameter,etc.)also affect the performance of the heat exchanger,different heat exchangers are used for the heat exchanger under the same heat transfer rate.The choice of size and size,calculation and analysis of its heat transfer performance and energy consumption.From the results,it is concluded that the flow resistance of the heat exchanger is not longer and longer due to the influence of the integrated geometrical factors(the heat exchanger of L=4.5 m under given environmental conditions is more heat exchange than L=3 m).The flow resistance should be small);also in the system energy consumption,try to reduce the number of baffles and increase the baffle spacing,which can effectively reduce the flow resistance of the heat exchanger;under the same heat exchange area,the large heat exchange tube The heat exchanger of the radial direction has a small flow resistance;therefore,the geometric factors should also be considered when selecting the heat exchanger.