Performance boost of a commercial air-to-air plate heat recovery unit by mesh-net insert; thermal-frictional, economic, and effectiveness-NTU analysis

This research proposes, tests, and comprehensively investigates the application of mesh-net to increase the efficiency of any air-to-air plate heat exchanger (mainly as a building heat recovery unit). The idea is tested through a commercial heat-recovery unit and all parameters including Nusselt number, pressure drop, friction factor, thermal performance factor, effectiveness, number of thermal units, pumping power and economical profitability are comprehensively investigated and reported with and without mesh-net insert. In economic evaluation the price of electricity and type of building heating system (resistance heater, heat pump and so on) are considered. In the maximum air flow rates, the overall heat transfer coefficient is enhanced from 24 to 36 W/m2K. Nusselt number increases up to 75 % depending on air flow rate. The economic results were found very interesting, and even by paying further fan power due to the higher pressure drop, the economic profitability is positive when the building heating system is resistance heater or heat pump with lower coefficient of performance. The profitability of the mesh net insert is higher for the region with higher electricity price. This means the gained recovered heat overcomes the further energy required for pumping power. Nonetheless, final decision making from pure economic viewpoint depends on the desired supply air flow rate, type of heating system and local price of electricity.