Numerical Simulation Of Flow And Heat Transfer Characteristics Of Smooth Tubes

The research methods of heat transfer enhancement technology are mainly to explore the optimal heat transfer efficiency of special-shaped tubes through the combination of theoretical research,experimental measurement and numerical simulation.In recent years,with the rapid development of computer technology,the research methods of heat transfer problems are inclined to numerical simulation with low cost and high efficiency.Because of the difficulty of setting measurement points and the limitation of visualization technology,it is necessary to simulate the flow and heat transfer characteristics.In this paper,in order to verify the accuracy of the numerical simulation,the single-phase simulation results of the smooth tube are compared with the experimental results.We choose stainless steel tube which outer diameter is 9.52 mm and the inner diameter is 8.32 mm and refrigerant R410 A to be working fluid which is coupled with water to transfer heat.The results show that the experimental and simulation results are in good agreement,it's error is within 0.2%.Experimental and numerical simulation results can be mutually verified.The working fluid for single-phase simulation of flower tube and twisted flower tube is R134 A,which is coupled with water for heat transfer.The mass flow rate is40~100 kg/(m2? K).The results show that the heat transfer performance of flower tube and twisted tube is enhanced along with the mass flow rate increases,so is the drag coefficient.Because of PEC > 1,the heat transfer performance of twisted flower tube is better than that of flower tube.With the increase of helix lead lengths,the heat transfer performance of twisted flower tube decreases gradually,and the flowresistance decreases.As helix lead lengths is125 mm the PEC is the highest and the overall performance is optimal.During the evaporation simulation,we choose R410 A as working fluid to couple with water for heat transfer.Which mass flow rate is 180-360 kg/(m2? K),evaporation saturation temperature is 279 K and inlet and outlet vapor quality is 0.8 and 0.2respectively.The results indicate that the working fluid is basically in annular flow during evaporation process.In order to obtain the heat transfer correlation of Nusselt number by non-linear regression which has a good fit and the error is within ±5%.During the condensation simulation,we choose R410 A as working fluid to couple with water for heat transfer.Which mass flow rate is 200-380 kg/(m2? K),condensation saturation temperature is 318 K and inlet and outlet vapor quality is 0.8 and 0.2respectively.The results indicate that the heat transfer coefficient and Nusselt number improve along with mass flow rate.In order to obtain the heat transfer correlation of Nusselt number by non-linear regression which fits well and the error is within ±5%.