Process intensification :cross-corrugated polymer film compact heat exchanger (PFCHE)

Abstract

Until recently, work on compact metallic heat exchangers has sparked interest amongst heat exchanger manufacturers due to its enhanced thermal performance and energy saving benefits in comparison to conventional heat exchangers. Nevertheless, the limitations of these metallic heat exchangers which involve corrosion, weight and cost issues have created the need to develop alternative units. Much of the initial interest in the development of polymer compact heat exchangers was stimulated by their ability to handle both liquids and gases (single and two phase duties); their resistance to fouling and corrosion and their possible use in humidification and dehumidification duties. But, most importantly, the use of polymers offers substantial weight, volume, space and cost savings which give them a competitive edge over exchangers manufactured from more exotic alloys. This research focuses on the development and performance investigation of a polymer heat exchanger using thin films (PFCHE). The design incorporates the use of thin 100/-lm PEEK films, to combat the low thermal conductivity of the polymer and adopts laminar flows to avoid high pressure drops. Performance testing using industrial conditions was carried out for square and spiral PFCHE configurations, leading to the development of design correlations for various fluid systems (0.7<Pr<192), tested in the respective units. These correlations have been used in case studies, to develop alternative designs to metallic heat exchangers for suitable applications where weight and cost issues are a primary concern. Other design aspects of the PFCHE such as the effect of the corrugation angle, surface geometry and the material of construction have also been investigated to obtain a better understanding of the unit and more importantly, to optimise the performance capability and extend its potential. Performance comparisons with compact metallic heat exchangers are also carried out to highlight the advantages of the PFCHE design. In this thesis, scientific contributions in the form of design correlations involving different PFCHE configurations, fluid systems, corrugation angles and the influence of the Pr number have been established. Tests to investigate the mechanical robustness of the heat exchanger were not carried out as part of this study, as this thesis highlights the thermal performance of the PFCHE. A detailed mechanical testing of the prototype is being considered in collaboration with an industrial partner.