Parametric investigation of a non-constant cross sectional area air to air heat exchanger

Abstract

5The present article addresses the design, mathematical modelling and analysis of a novel highly exergy-6 efficient air to air heat exchanger. An intricate design based on an hexagonal mesh is proposed for the cross-7 sectional area of the heat exchanger with aims to explore the performance gains that can be obtained by 8 exploiting the capabilities and benefits offered by modern fabrication techniques such as additive 9 manufacturing. Special attention is paid to understanding the relationship or trade-off that exists between the 10 overall exergy efficiency of the heat exchanger and its cost. 11The iterative algorithm used to find the geometrical parameters that yield the best performance in terms of 12 volume of material required per unit of exergy transfer at a certain level of efficiency, as well as the 13 assumptions and simplifications made, are comprehensively explained. 14 It has been found through the analyses carried out performed, which are thoroughly discussed throughout the 15 paper, that if the characteristic dimension of the heat exchanger is scaled up by a factor of n, the volume of 16 material per kW of exergy transfer at certain exergy efficiency will increase by a factor of n squared. This is a 17 very important observation, possibly applicable to other types of heat exchangers, that indicates that 18 performance improves dramatically at smaller scales. 19The overall performance of the case study presented is satisfactory, a volume of material as low as 84.8 cm 3 20 for one kW of exergy transfer can be achieved with a 99% exergy efficiency. 21 22 Keywords 23Gas to gas heat exchanger; high exergy efficiency heat exchanger; non-constant cross sectional area; heat 24 exchanger additive manufacturing; heat exchanger cost optimization 25 26

Techno-economic analysis of recuperated Joule-Brayton pumped thermal energy storage

“…The present work is limited to circular-tube heat exchangers, which have hydraulic diameters typically ranging from a few mm up to several cm [51], and a value of D = 5 mm is used in here. In general, small tubes are preferred because they lead to more compact devices [52], which is due to higher heat transfer coefficients and higher surface-tovolume ratios [34]. The sizing procedure assumes that the hydraulic diameters and flow areas of the two sides of the heat exchanger are the same, i.e.…”