Polymer Film Compact Heat Exchangers (PFCHEs)

The Process Intensification Group at Newcastle University has developed a novel concept of thin film polymer heat exchangers that offer high thermal efficiency, reduced fouling, significant reduction in weight and cost, resistance to chemically aggressive fluids and the ability to handle both liquids and gases (single and two phase duties). This provides PFCHEs, a competitive edge to their metal counterparts.

The units are of compact construction and can be of square or spiral configuration. An important feature of the heat exchangers that sets them apart from those on the current market, is the use in some variants, of a high temperature polymer, poly ether ether ketone (PEEK). PEEK has a continuous use temperature of up to 220°C. Although the thermal conductivity of the polymer is not as high as metals, the PFCHE made of 100 micron thick PEEK films offers negligible thermal resistance when the heat transfer coefficient is less than 4000 W/m²K.

Corrugated PEEK Sheets	Square PFCHE	Spiral PFCHE

The potential market opportunities are very wide ranging and include applications in the chemicals and food and drink industries, with possible applications in generic equipment such as condensing boilers and refrigeration plants. There are also opportunities in the aviation, fuel cell and automobile industries in the form of cabin air coolers, filter coolers and radiators. Case studies on the PFCHEs as a metal alternative in the aviation and fuel cell industries have been carried out using heat transfer and pressure drop correlations developed from different fluid systems. The fluid systems investigated are air/air, water/water and glycerol water mixtures/water for the square PFCHE whilst a water/air system was studied for the spiral PFCHE. The results are very positive as it involves huge cost and energy savings.

Studies on the effects of the corrugation angle and Prandtl number on the performance of the PFCHEs are also underway. Bonding issues have been addressed and among methods suggested are laser welding, co-extruding using different materials and using epoxy fillers/ thin sheets with screen printing. The issues of cheaper and more cost effective means of handling the heat exchanger polymer film are also being looked into.

With these benefits, it is hoped that, at a later stage, useful heat transfer and pressure drop correlations developed for different fluid systems obtained involving different PFCHE configurations over a range of Reynolds numbers would enable alternative compact industrial designs to be realised.

Table 1 below, shows a performance comparison of PFCHE with conventional metal heat exchangers for an air/air system using the heat transferred per unit matrix volume. It clearly shows that the PFCHE has a much higher heat transfer capacity than conventional metal units and highlights the advantage of the extreme compactness of the PFCHE.

Table 1 - Heat Transfer per Unit Matrix Volume (Air/Air)