Optimisation of a recirculating domestic hot water system to minimise wait time and heat loss

Many houses suffer from a delay in hot water arrival, after opening the tap, due to length of pipe work boiler or thermal store. Measurements three properties showed delays up 46 s. A recirculation system could maintain at suitable temperature and for 15 m is expected use 30 W less electrical power than local store delivery point. Time-steady eigenvector solutions linked equations allow optimisation flow rate, diameters insulation thickness. The pumping <1 mW pumpless thermo-syphon should be possible some installations. Heat loss coefficients have been calculated pair pipes common sleeve minimise losses. plug transient advection model based on sliding 1-D grid has developed validated single pipe, then extended also recirculating systems. losses pumped may reduced using timer so can cool overnight. predicts relationship between warm-up rate optimise pump size timing.