A numerical study on heat transfer enhancement and design of a heat exchanger with porous media in continuous hydrothermal flow synthesis system

The aim of this study is to use a new configuration of porous media in a heat exchanger in continuous hydrothermal flow synthesis(CHFS)system to enhance the heat transfer and minimize the required length of the heat exchanger.For this purpose,numerous numerical simulations are performed to investigate performance of the system with porous media.First,the numerical simulation for the heat exchanger in CHFS system is validated by experimental data.Then,porous media is added to the system and six different thicknesses for the porous media are examined to obtain the optimum thickness,based on the minimum required length of the heat exchanger.Finally,by changing the flow rate and inlet temperature of the product as well as the cooling water flow rate,the minimum required length of the heat exchanger with porous media for various inlet conditions is assessed.The investigations indicate that using porous media with the proper thickness in the heat exchanger increases the cooling rate of the product by almost 40% and reduces the required length of the heat exchanger by approximately 35%.The results also illustrate that the most proper thickness of the porous media is approximately equal to 90% of the product tube's thickness.Results of this study lead to design a porous heat exchanger in CHFS system for various inlet conditions.

Performance Analysis and Structural Optimization of Torsional Flow Heat Exchangers with Sinusoidal Corrugated Baffle

The thermal performance of the heat exchanger is strongly influenced by the supporting structure.Corrugated baffle enhances flow field disturbance and heat transfer through its complex and changeable flow channel.In order to enhance the thermal performance of the torsional flow heat exchanger(TFHX),the sinusoidal corrugated baffle(SCB)is used to replace the flat baffle(FB)and the full-section cycle model of the torsional flow heat exchanger with sinusoidal corrugated baffle(TFHX-SCB)is established.Computational fluid dynamics(CFD)method was used to discuss the flow resistance characteristics of the shell-side of heat exchangers.The results show that the SCB can improve the turbulence intensity and the uniformity of the flow field between the adjacent baffles.The combination of structural configurations on the shell-side of TFHX-SCB is analyzed by the central composite design(CCD)-response surface method(RSM).When the amplitude of the SCB is 1.37 mm,the cycles of the SCB are 4.42;the initial phase of the SCB is 112.73°,and the combination of heat transfer coefficient and comprehensive performance is optimal.Compared with the original structure,the heat transfer coefficient is increased by 11.58%,and the comprehensive performance is increased by 5.48%.The laser doppler velocimetry(LDV)experimental device irradiated the specified measurement point,and the dependability and accuracy of numerical simulation methods were verified.The research conclusion provides a basic theory for the structural development of the TFHX.