Heating fresh air by hot exhaust air of HVAC systems

The present work concerns heating fresh air by the hot exhaust air of all-air heating ventilating and air conditioning HVAC systems. To proceed, a prototype is implemented and a parametric analysis is carried out to test the effect of temperatures and mass flow rates on the performance of the heat recovery system. Experiments are performed under typical conditions simulating the HVAC operation in cold climates. On the other hand, a generalized procedure of calculation is suggested based on the experimental results. It allows to simulate heat recovery designs and to perform parametric study without need to perform new experimental studies. It was shown that powers up to 110 W can be economized in cold climates and for low air flow rates of around 0.1 kg/s and 0.005 kg/s for respectively the hot exhaust air and the fresh cold air. Extrapolation shows that economized power can exceed 1 kW for a room of heating load 4 kW if all of the supply air is exhausted.