Abstract

ABSTRACT
Experimental study of air-to-air heat/energy exchangers for use in Arctic housing
Colin J. Beattie
The thesis presents the experimental results of an air-to-air heat/energy exchanger (HEE), tested with four different cores, to assess the performance under Arctic climate conditions. Four per-formance indicators are presented: (i) the outlet supply air temperature; (ii) the exhaust air flow rate; (iii) the sensible and latent heat transfer effectiveness; and (iv) UV-value. The mass of ice formed within the core was also measured at the end of each experiment. The experiments are separated into three phases: Phase 1 with one HEE without recirculation defrost, Phase 2 with one HEE with recirculation defrost, and Phase 3 with two HEEs in parallel with alternating recir-culation defrost. Correlation−based models were developed that predict the change in heat transfer effectiveness in terms of the change in exhaust air mass flow rate, inlet supply air temperature and core type. The experiments with recirculation defrost proved that the factory-set defrost times are a conservative approach that manages the formation of frost. Because of the reduced operating time as controlled by the timer, all cores have almost the same sensible heat transfer effectiveness. The use of vapour-permeable cores reduced the rate of frost growth and the amount of frost at inlet supply air temperatures where core frosting was a concern. The rate of core frosting was dependant on the inlet supply air temperature. Frost formation impeded the transfer of heat between the two airstreams and reduced the adjusted sensible and latent heat transfer effectiveness for all cores. Recirculation defrost effectively managed the formation of frost in all tested exchanger cores for the duration of the tests at inlet supply air temperature down to −35°C. However, the use of recirculation defrost intermittently interrupts the supply of outdoor air resulting in reduced ventilation rates. The use of two heat/energy exchangers with alternating recirculation defrost adequately managed core frosting while providing a continuous supply of outdoor air.