Heat recovery
Also known as: waste heat recovery, desuperheater
Short definitionUsing part or all of the heat a refrigeration system rejects at the condenser for hot water, space heating or underfloor heating. It lowers the fuel bill of the plant.
The heat taken from the room and the electricity used by the compressor leave together at the condenser. A plant delivering 60 kW of cooling while drawing 25 kW of electricity rejects 85 kW of heat. A heat exchanger in the discharge line transfers this heat to water. A desuperheater takes 10–25% of the total heat but gives water at 55–65 °C. The full-condensing type takes all of the heat, with water at 35–45 °C.
In a cold store the most common use is heating under the floor of frozen rooms; glycol at 10–20 °C is enough against frost heave. Preheating wash water and heating offices also fit well. Since production and demand do not happen at the same hours, an insulated tank is needed. Raising the condensing pressure to get hotter water is a trap: each 1 K increase adds 2–3% to compressor consumption. The condenser must stay large enough to reject all the heat when recovery is off.