Study On Heat Transfer Characteristics Of Plate Heat Exchanger Strengthened By Nanofluids And Turbulence Structures

The current trend towards sustainable development is to reduce emissions from industrial production,and how to improve the utilization rate of energy to reduce carbon emissions has gradually attracted the attention of scholars.Both high-tech fields and traditional industrial production have put forward new and higher requirements for enhanced heat exchange.Plate heat exchanger,as an important link between machine tools and cooling systems,are directly related to energy consumption and machining accuracy.Therefore,it is essential to investigate the heat transfer performance of plate heat exchangers.This paper realizes the research on strengthening the heat transfer performance of plate heat exchanger from two aspects:improving the thermophysical property of the heat transfer medium and changing the structure of the heat transfer surface,based on the investigation of the heat transfer performance of plate heat exchanger.A combination of numerical simulation and experimental validation was used to investigate the heat transfer performance of plate heat exchanger using No.5 spindle oil as the heat transfer medium.Analysis of the effect of different inlet flow rates and temperatures on the heat transfer performance of plate heat exchanger.The results show that low inlet temperatures and high flow rates are conducive to heat transfer and the deviation between the numerical and experimental results is less than 10%.It provides a methodological basis for conducting research into the heat transfer performance of enhanced plate heat exchanger.The effect of nanofluid enhanced heat transfer performance of plate heat exchanger was investigated.The stability,thermophysical properties,and heat transfer performance of Si O₂-No.5 spindle oil nanofluids with different concentrations in the plate heat exchanger of CNC machine tools were investigated experimentally.The Si O₂-No.5 spindle oil nanofluids with different volume concentrations（0.1-1 vol%）were prepared by a two-step method,and sedimentation experiments,Zeta potential analysis,and particle size distribution experiments were completed.The experimental results show that the Si O₂-No.5 spindle oil nanofluids are stable systems.The thermal conductivity and viscosity of nanofluids of different volume concentrations were measured in the temperature range of 15°C to 40°C as important thermal properties.The data indicate that the thermal conductivity and viscosity of the nanofluids increase with increasing nanofluid concentration,while a decreasing trend is found with increasing temperature.Experimental analysis of heat transfer in a plate heat exchanger in the volume flow rate range of 5-10 L/min revealed that the nanofluids can significantly increase the heat transfer performance.The convective heat transfer coefficient of nanofluid,as the medium,with a volume fraction of 1 vol%was increased by 18.7%at a flow rate of 10 L/min.A predictive correlation equation based on the Reynolds number and Nusselt number of the plate heat exchanger was obtained based on the experimental data.Study of the effect of turbulence structures to enhance the heat transfer performance of a plate heat exchanger.Design of 3D models of different turbulence structures.Study of the effect of different locations,shapes,numbers and sizes of turbulence structures on the flow characteristics of plate heat exchanger,heat transfer performance and the combined nanofluid and turbulence structures on heat transfer performance by using a combination of numerical simulation calculations and experiments.The results show that different shapes of structures have different effects on the heat transfer performance.The difference between the numbers and sizes of turbulence structures on the heat transfer performance of the enhanced plate heat exchanger is not significant.The plate heat exchanger with seven 8×4 mm rectangular turbulence structures has the best heat transfer performance.The heat transfer performance is improved by 133%and the overall heat transfer performance is enhanced by maximum,at an inlet temperature of 20°C and 5 L/min.Finally,the effect of nanofluid and turbulence structure on improving the heat transfer performance of plate heat exchanger was analyzed.The heat transfer performance is enhanced by 150%,and the overall heat transfer performance is improved to maximum,at an inlet temperature of 20°C and 10 L/min.