Practical use of computational fluid dynamics (CFD) in improving the efficiency of domestic ventilation waste heat recovery systems

Efficiency of domestic ventilation waste heat recovery systems (WHRS) depends not only on the amount of waste heat recovered, but also on the energy involved in running fans to drive air through the system. Computational fluid dynamics (CFD) can be a powerful tool for analysing WHRS losses (thus predicting fan energy usage), but the computational effort involved can limit the value of CFD as a practical design tool. This study presents a range of assumptions and simplifications that can be applied to reduce the computational effort associated with the CFD analysis of a WHRS. The importance of experimental validation to assess the effect of errors introduced by the simplifying assumptions is discussed. In an example case, application of the methods presented have allowed total pressure losses (excluding the fixed losses through the heat exchanger) to be reduced by over 50 % in comparison with an initial prototype design, with proportional reduction in fan energy usage. This highlights the value of sufficiently simplified CFD analyses within a typical WHRS product development cycle. © 2014 The Author(s).