HEAT AND MASS TRANSFER BY NAFION® GAS HUMIDIFIERS

Abstract

Heat and mass transfer by nafion gas humidifiers The present research aim is to investigate the performance of a PermaPure humidifier (PPH) device, that is able to transfer heat and moisture from the PEM fuel cell cathode exhaust to the inlet air stream and is similar to an air/air shell tube counter current flow heat exchanger, with 1660, 0.345 m long, tubes. The experimental apparatus consists essentially of two variable speed air compressors, a temperature controlled large water tank, in order to get saturated the primary line air, and the humidifier to be tested; in the secondary air line the gas flows from the compressor to the PPH tubes, increasing its humidity along its path. The instrumentation consists of two air flow meters, four hygrometers for the measurements of either the relative humidity or the temperature, several chromel-alumel thermocouples and pressure transducers to measure the ambient and loop temperature and pressure and pressure drop across the PPH shell and tube sides. The experimental results, obtained within a wide range of air temperature, flow rate and inlet humidity, of the same order of the real fuel cell parameters, are reported in order to investigate the water vapour transfer from a moisture saturated air stream to a dry and cold air stream. The direct transport of vapour is from shell to tube-side flow. Data are discussed on the ground of models that have been presented recently and a simplified model is also presented, to predict the outlet PPH conditions for different inlet conditions; the test data comparison with the prediction seems fairly good