Jp. Meyer et al., The influence of return loop flow rate on stratification in a vertical hotwater storage tank connected to a heat pump water heater, HEAT TR ENG, 21(2), 2000, pp. 67-73
A temperature-controlled hot water heat pump was simulated using heating in
a vertical, domestic hot water storage tank. The influence of the return l
oop flow rate on stratification was investigated experimentally. The return
loop is the water line that supplies a long line of consumers with hot wat
er and returns colder water to the middle of the hot water storage tank. Th
e return temperature is a function of the length of the loop, insulation, a
nd ambient conditions. Temperatures were measured as a function of time at
different vertical locations on the centerline of the storage tank. The tem
perature distributions in the tank were compared for different return flow
rates. A return flow rate of three tank volumes per day was identified as p
referable, although good results were also obtained for less than three tan
k volumes per day.