The Analysis Of Coupled Heat Transfer In A Type Of Plate Heat Exchangers

Energy issues and environmental issues caused by the extensive use of fossil energy are still the focus of the international community.As a high-efficiency heat exchange equipment,plate heat exchangers are widely used in various industries involving heat energy exchange.The structure of the corrugated plate of the detachable plate heat exchanger has an important influence on the flow and heat transfer performance of the plate heat exchanger.Analyzing the flow and heat transfer characteristics of the existing plate heat exchanger,optimizing the structure of the corrugated plate,and improving the overall performance of the plate heat exchanger are of great significance to improving energy utilization and reducing energy loss.The simplified plate heat exchanger model is difficult to accurately reflect the overall flow and heat transfer characteristics of the plate heat exchanger,so this paper establishes a dualchannel coupled heat transfer calculation model for cold and hot fluids with inlet and outlet and complete diversion areas,using the software Fluent 2021 R1 Numerical simulation and analysis of fluid flow and heat transfer characteristics in plate heat exchangers.Using numerical methods to analyze the temperature and pressure drop of the inlet and outlet of cold and hot fluids when the flow velocity between the plates is 0.3 m/s,0.5 m/s,0.7m/s,and 0.9 m/s,and comparing with the experimental results,the temperature difference between the inlet and outlet is obtained The difference between the numerical simulation results and the experimental calculation results is within 2%,and the difference between the numerical simulation results of the inlet and outlet pressure drop and the experimental calculation results is within 15%.Therefore,the numerical method can accurately reflect the flow and heat transfer characteristics of the fluid in the plate heat exchanger,and can be used in the study of the plate heat exchanger.After post-processing the numerical calculation results when the flow velocity between the plates is 0.8 m/s,comparing the pressure cloud diagram,temperature cloud diagram and velocity vector diagram at different positions,it is found that the flow distribution of the fluid in the diversion area is uneven,resulting in the fluid flow in the heat exchange area.There is an obvious hysteresis area of temperature change near the side connecting the inlet and outlet.Calculated when the flow velocity between plates is 0.4 m/s,0.8 m/s,1.2 m/s,1.6 m/s,2.0 m/s,2.4 m/s The velocity distribution of the 14 small sections on the section connected by the area,and the average velocity and volume flow of the 1～7 section and the 8～14 section are calculated,and it is found that the fluid on this section is more from the 1 near the inlet and outlet connection line side ～7 section flow,the volume flow rate of hot side fluid inlet side 1～7 section is 1.32 times of 8～14 section,and the volume flow rate of outlet side 1～7 section is 1.22 times of 8～14 section.The heat exchange area improves the uneven flow distribution,and the maximum uneven rate of the outlet side section is significantly lower than that of the inlet side.The average ξ value of the cold fluid outlet side is 11.0% lower than that of the inlet side,and the average ξ value of the hot fluid outlet side is 31.5% lower than that of the inlet side.The single-channel model and the dual-channel coupled heat transfer model were compared and analyzed.Calculated the change of the surface heat transfer coefficient of the single-channel model and the total heat transfer coefficient of the dual-channel model in the range of Re number 1910.8 to 11464.9,and found that when the Re number was 1910.8,the K value of the dual-channel coupled heat transfer model was higher than that of the single-channel model.The model conversion K value is 6.50% larger;when the Re number is 11464.9,the K value of the dual-channel coupling heat transfer model is 2.20% larger than the single-channel model conversion K value,so when the Re number is small,in order to accurately reflect the flow of the plate heat exchanger and heat transfer characteristics,a dual-channel coupled heat transfer model is required.The influence of the structure of the diversion zone on the flow and heat transfer performance of the plate heat exchanger was investigated.A dual-channel coupled heat exchange fluid model of a plate heat exchanger with a simplified diversion zone was established.Through numerical simulation,the K value and ΔP of the Re number in the range of 1910.8 to11464.9,as well as the K value and ΔP of the original model,were found by comparison.The K value of the simplified diversion zone model is 14.63%～29.66% higher than that of the original model at the above flow rate,and the ΔP is 13%～15% higher than the original model,which shows that the structure of the diversion zone of the plate heat exchanger has a great impact on the flow of the plate heat exchanger.significantly affect the heat transfer performance.Structural optimization is carried out for the uneven distribution of flow in the flow channel caused by the structure of the diversion area of the plate heat exchanger.By changing the angle of the diversion groove,three new structures with diversion groove angles of 20°,40°and 60° were established.By comparing the K values and ΔP of the three structures in the range of Re numbers from 1910.8 to 11464.9,it was found that the conductivity When the launder angle is 60°,the K value increases the most,and the average improvement rate under different Re numbers is 12.22%.Install one set,two sets,and three sets of seals in the upper,middle,and lower positions of the diversion area on the inlet and outlet sides of the cold and hot runners of the plate heat exchanger.By comparing the K values of the three structures in the range of Re number from 1910.8 to 11464.9,it is found that when the Re number is small,adding a seal in the diversion area can improve the heat transfer capacity of the plate heat exchanger the most.Under different Re numbers,when three sets of seals are added,the K value is improved the most.The average improvement rate under different Re numbers is 11.11%.