Heat energy is expensive both financially and for the biosphere regardless of its source. It therefore makes great sense to hold onto it for as long as possible once it has been purchased and take all practical steps to prevent or slow down its escape. For heat loss through the walls of buildings or process plant, the easiest way to prevent heat loss is with the use of insulation. However, this is not a panacea and there are circumstances where insulation would not be applicable. One such example would be the necessity to sufficiently ventilate our buildings to provide the necessary oxygen for the occupants and for odour control. In which case, the ventilation system bypasses the insulation around the building envelope. Cold, fresh, ambient air is drawn in to the building and the warmed, stale air is exhausted from the building. The energy flow of such an air exchange can be easily quantified.
Since there is a negative temperature gradient between the warm outgoing air and the cold incoming air there is an opportunity to transfer some of the heat which would otherwise leave the building to the incoming air stream. This is achieved by the use of Heat Exchange devices placed simultaneously in the fresh air and exhaust air paths. Common examples include air to air plate heat exchangers, thermal wheels and run-around circuits (hydraulic circuit connecting two duct mounted coils). In the case of the air to air plate heat exchanger and thermal wheel, the transfer of heat occurs naturally with minimal mechanical enhancement and any energy thus transferred reduces the requirement for it to be provided by the heating system. The installation cost of the Heat Exchange devices is therefore repaid over time from the resulting energy savings.
Where the energy flow is part of a process the same situation can apply. The product or waste stream of the process may leave at a higher temperature and raw material or feedstock stream may enter at a lower temperature. In which case, an air-to-air, air-to-liquid or liquid-to-liquid heat exchanger may be used to transfer the heat energy accordingly, again providing energy savings to offset the capital cost of the heat exchanger installation.
Due to the high cost of heat energy, the payback time of Heat Recovery systems are often quite short and make perfect economic sense.
Callidus Design offer a number of services for Heat Recovery systems including design and specification of entire heat transfer systems, system modifications and extensions, condition surveys, refurbishment and troubleshooting.