Storage Flue Gas Heat Recovery Systems SFGHRS
A Storage Flue Gas Heat Recovery Systems (SFGHRS) is a type of flue gas recovery system (FGRS), or more accurately flue gas heat recovery system (FGHRS) that capture and reuse waste heat from exhaust flue gases, these are used to preheat water or other fluids, improving energy efficiency by reducing demand and thus reducing emissions. If the FGHRS contains a volume of water (or condensate), it is known as a Storage Flue Gas Heat Recovery System (SFGHRS).
The UK government document "Review of the methodology for FGHRS in SAP. Final report" describes the systems thus:
"In such devices the store of water is heated by the flue gases via the heat exchanger. This volume of water may be contained in the same unit around the flue, or in a cylinder next to the primary FGHRS unit. The store may be insulated, depending on the store location and the manufacturer’s design. SFGHRS can transfer heat either when the boiler is operating in hot water mode or when the boiler is operating in space heating mode. When the boiler is operating in hot water mode the transfer of heat takes place directly from the flue gas to the incoming water.
"When the boiler is operating in space heating mode the energy must be stored and transferred at a later time, when the boiler switches over to DHW mode. This can either be achieved by residual heat in the body of the FGHRS, or more often via the stored water (acting as a thermal store) within the SFGHRS. The savings that are achieved through the transfer of heat directly to the incoming cold water are known as direct savings and the savings that can be transferred from the flue gas, via an internal store and then to the incoming cold water are known as deferred (or indirect) savings. SFGHRS can provide both direct energy savings and deferred savings whilst Instantaneous FGHRS (IFGHRS) provides predominantly direct savings (although there are still some indirect savings from the water and metal work comprising the IFGHRS)."
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