Frost formation in membrane based flat plate heat exchangers

Abstract

The objective of the Research Centre ZEB is to eliminate greenhouse gas emissions from buildings. Reducing the energy consumption in buildings is a means to that end. The use of membrane based plate heat exchangers can allow for recycling of energy in exhaust air, thereby reducing the overall energy spent on heating and regulating humidity of supply air. Such heat exchangers have been studied in warm, humid climates to a much greater extent than in cold climates. The objectives of this study was to build a rig for testing of heat exchangers in cold climates, build a membrane based quasi-counter flow heat exchanger and investigate if frost formation would occur in this heat exchanger. The rig was built in accordance with relevant standards for testing of heat exchangers. The heat exchanger was built with durability, mechanical stability and low cross contamination in mind. One membrane material was utilized through three different tests. In all tests freezing did occur. The frost was found only in the exhaust air channels, whereas the supply air channels were dry and frost free. Although the whole membrane surface had frost formation, the densest frost was found in the areas with the lowest temperatures and air flow rates. The tested material was therefore found unsuitable for use in cold climates.