Energy Return Wheel

A Energy Return wheel consists of a circular honeycomb matrix of heat-absorbing material, which is slowly rotated within the supply and exhaust air streams of an air handling system. As the thermal wheel rotates heat is picked up from the exhaust air stream in one half of the rotation, and given up to the fresh air stream in the other half of the rotation. Thus waste heat energy from the exhaust air stream is transferred to the matrix material and then from the matrix material to the fresh air stream, raising the temperature of the supply air stream by an amount proportional to the temperature differential between air streams, or 'thermal gradient', and depending upon the efficiency of the device. Heat exchange is most efficient when the streams flow in opposite direction, since this causes a favorable temperature gradient across the thickness of the wheel. The principle of course works in reverse and 'coolth' energy can be recovered to the supply air stream if so desired and the temperature differential allows.