Experimental study of air-to-air heat exchangers for use in arctic housing

During the operation of heat recovery systems in Arctic housing, the heat transfer effectiveness of air-to-air heat exchangers diminishes due to the frost formation, and as a consequence the potential for energy savings due to the heat recovery is lost. If the frost formation is not detected, it might damage the HEE core. There is no standard technique for the detection of required starting time of the defrost operation. Manufacturers of such HEE units use a pre-set duration of normal operation that is followed by defrost period. This paper presents the experimental results under laboratory-controlled environment of an air-to-air heat/energy exchanger (HEE), tested with four different cores, to assess the performance under Arctic climate conditions. The frost formation is not directly measured, but indirectly through the evaluation of the effect of frost formation and management on the exhaust air flow rate, and the sensible and latent heat transfer effectiveness. Correlation-based models are developed that predict the change in exhaust air mass flow rate in terms of heat transfer effectiveness, and core type. The practical usage of those correlations for the ongoing commissioning of existing residential ventilation systems stays with the estimation of the starting of core defrosting. Thus the use of factory-set defrost schedule can be replaced by a schedule that is adapted to the operating conditions of the cores. The paper also proposes the use of a heat recovery system with two HEE units, and evaluates the heat transfer effectiveness and supply air flow rate of that system during the operation. (C) 2017 Elsevier Ltd. All rights reserved.