Modelling of a Heat Recovery Ventilator Incorporating Thermoelectric Modules

Abstract

Heat recovery ventilation (HRV) involves the recovery of heat from exhaust air exiting the home. HRV works to both save energy and provide indoor air quality and comfort [1]. Focus has also been placed on alternatives to vapour-compression devices traditionally used as heat pumps, due to the harmfulness of refrigerants contained in these systems [2]. Thermoelectric modules (TEMs) are solid-state devices that can be used for converting electrical energy into thermal energy, effectively creating a heat pump. A thermoelectric module-based heat pump heat exchanger was modelled to determine performance when integrated into a heat recovery ventilation system. The model was developed as a node-based numerical system allowing the performance at various locations in the system to be analyzed. The model was developed further to evaluate HRV performance with and without thermoelectric modules included. Characteristics of the model geometry and configuration were based on a prototype developed by Natural Resources Canada, which includes a TEM-based crossflow heat transfer core in series with a LifeBreath model RNC5-ES HRV. The numerical model was implemented in Fortran90 and an open source compiler. A subsequent parametric evaluation of the heat sink selected by NRCan was completed and indicated that modifications to the current geometry would result in increased effectiveness and performance. Performance metrics were modified and evaluated for their suitability for producing meaningful results, including the development of the Heat Transfer Enhancement Factor (HTEF) metric. Based on the evaluation of different TEM models, the TEC127-14 thermoelectric module showed the greatest HTE for the hot-side heat transfer and is recommended for implementation. An analysis of flow configurations for integrating the TEM-HX into a conventional HRV indicated that a counterflow configuration with the exhaust inlet (from the house) directed through the TEM-based heat exchanger prior to entering the non-TEM heat exchanger core was the most effective configuration.