Analytical Study on Thermal and Mechanical Design of Printed Circuit Heat Exchanger

Abstract

The analytical methodologies for the thermal design, mechanical design, and cost estimation of printed circuit heat exchanger are presented in this study. Three flow arrangements for PCHE of parallel flow, countercurrent flow and crossflow are taken into account. For each flow arrangement, the analytical solution of temperature profile of heat exchanger is introduced. The size and cost of printed circuit heat exchangers for advanced small modular reactors are also presented using various coolants such as sodium, molten salts, helium, and water. viii ix SUMMARYPrinted Circuit Heat Exchanger (PCHE) is one of the candidate designs of Very High Temperature Reactor (VHTR) or Advanced High Temperature Reactor (AHTR) heat exchanger (HX). Fine grooves in the plate of PCHE are made by using the technique that is employed for making printed circuit board. This heat exchanger is formed by the diffusion bonding of stacked plates whose grooved surfaces are the flow paths. Thermal design of heat exchanger is required to determine the size and effectiveness of heat exchanger. To evaluate the structural integrity, mechanical design of heat exchanger must be investigated. In a previous study, the parallel/counter flow PCHE analysis code was developed. The methodologies for the thermal and mechanical design of parallel/counter flow PCHE used in previous study are also summarized in this report.The objective of this work is to develop the analysis code for the crossflow PCHE to determine the size and cost of crossflow PCHE for AHTR. The size of the crossflow PCHE is determined through thermal design process of heat exchanger. Two dimensional temperature profiles in primary and secondary sides of crossflow PCHE are obtained from the solution of analytical model of crossflow PCHE assuming a single pass, both with unmixed fluid, and no contribution from longitudinal heat conduction. The mechanical design of crossflow PCHE is to determine the criteria of geometric parameters of structure for maintaining the integrity of the heat exchanger. The method for mechanical design of crossflow PCHE is developed based on that of parallel/counter flow PCHE.To verify the developed code, the grid sensitivity test and effectiveness-number of transfer units (NTU) analysis were carried out. The grid sensitivity test for the developed code was performed to evaluate the effect of grid number on the result. The result of grid sensitivity test shows that the effect of grid number is negligible. The effectiveness-NTU analysis was carried out to verify the developed code. The calculated effectiveness by the code and -NTU correlation for crossflow heat exchanger shows a good agreement with each other.As a parametric study, uncertainty analyses for fluid properties and heat transfer correlation were performed. The uncertainty of fluid properties was investigated by assuming ±30% of uncertainty in fluid material properties. The result of uncertainty analysis shows that the uncertainty of fluid property was negligible in the thermal design of crossflow...

Advanced power cycle modelling

“…An analytical solution for a PCHE channel pair, such as the one modelled in this thesis, was developed by the Idaho National Laboratory [34]. The solution developed was for a counterflow configuration.…”

“…The derivation is based off an energy balance of fluid control volumes, accounting for the overall heat transfer resistance between the streams, as presented in figure 21. [34] The equations developed for fluids 1 and 2 are as follows [34]: The indices i1 and i2 can have values of +1 or -1 and modify the equation set depending on whether a counterflow or parallel flow configuration is being analysed [34]. A positive value indicates flow in the same direction as the x axis, and vice versa.…”

“…By defining the variables θ and X, a non-dimensional form of these equations is derived [34]: where NTU and R refer to Number of Transfer Units and the heat capacity rate ratio respectively:…”

Design and modeling of printed - circuit heat exchangers and centrifugal compressors for supercritical carbon dioxide

“…The numerical results showed that the transition is observed at Reynolds numbers of 2300 for the circular and 3100 semicircular channels, while the heat transfer and pressure drop characteristics were also investigated. Yoon et al [52] from Idaho National Laboratory (INL) presented general methods for thermal design and cost estimation in order to determine the size, the thermalhydraulic characteristics and the cost of a crossflow PCHE. The effectiveness calculated by the developed code showed a good agreement with the results obtained with the ε-NTU method.…”