Heat Transfer Analysis And Numerical Simulation Of Gravity Heat Pipe Heat Exchanger

In recent years, with the continuous use of resource, waste heat recycling has become one of the effective ways of energy conservation and environmental protection. Normal and medium temperature heat pipe heat exchanger in the application of waste heat recovery, can greatly improve the energy efficiency. Based on the normal and medium temperature in the gravity heat pipe heat exchanger as the research object, The conventional design method is adopted to design the heat pipe heat exchanger. The Fluent software is used for heat exchangers to simulate the fluid flow field, temperature field and heat pipe working state simulation; To study the different operation parameters and the fin parameters on the thermal performance of heat exchanger, and carries on the optimization, optimal operation parameters and corresponding fin structure. The main research contents and conclusions were as follows:(1) Do the numerical simulation study on the normal temperature gravity heat pipe heat exchanger, the heat pipe is set to the boundary conditions of constant heat flux density. Simulate the flow field and temperature field analysis of the heat exchanger under different operation parameters. The experience formula calculation results were compared with simulation results to verify the correctness of the simulation method in this paper, comparing the simulation results show that choose the calculation method is reasonable.(2) In this paper, do the numerical simulation research on the medium temperature gravity heat pipe heat exchanger, and analyzed the flow field, temperature field and heat pipe working condition in evaporator and condenser of the heat exchanger. Research results show that thermal fluid inlet velocity is larger, and the heat exchanger heat transfer effect is improved. But the speed is too large, the heat pipe can produce resonance phenomenon, so the speed of the fluid is to be kept in a reasonable range; When the flue gas inlet temperature changes within the range of 733~753k. With the increase of flue gas inlet temperature, heat transfer performance of heat exchanger is improved. But relative to the flue gas inlet velocity within the evaporator and condenser on the influence of the fluid temperature, the fluid temperature under the influence of inlet temperature is small. When the inlet velocity or temperature of the flue gas is too large, The heat pipe steam temperature in the transition zone will be higher than the working limit temperature of the heat pipe and the explosin phenomenon of tube will happens. Therefore, according to the working state of the heat pipe, we can change the setting of the heat pipe, such as increasing the temperature of the period of heat pipe tube row number, change the heat pipe spacing and the heat pipe fin tube spacing parameters, etc.(3) In order to the optimum operation parameters and structure parameters of the gravity heat pipe heat exchanger, we do the optimization research the heat pipe fin parameters. Analysis of different fluid inlet velocity in the evaporation, different heat pipe fin spacing, fin height, horizontal tube spacing and longitudinal tube spacing on the average convective heat transfer coefficient, the total heat transfer, finned heat exchanger efficiency, pressure drop and the PEC in the heat exchanger. The results show when the fin spacing value range is 5~6mm, the heat pipe fin height values of 12~13mm, the optimal value range of horizontal tube spacing is 65~70 mm, the optimal value range of longitudinal tube spacing is 55 mm to 65 mm, and the flue gas inlet velocity in 2.5~3m/s, the gravity heat pipe heat exchanger heat transfer performance is the best.