Unsteady Temperature Distributions in Vertical Storage Tanks Heated with Heat Pumps

摘要

In this article, four methods of heating hot water in domestic storage tanks are investigated experimentally to determine the unsteady temperature gradients formed in the storage tank. These four methods involved heating the water with an electric hot water heater, a heat pump parallel to the storage tank, a temperature-controlled heat pump, and a temperature-controlled heat pump with return water. The first heating method was studied on a real electric hot water heater system, while the other three heating systems were experimentally simulated. Temperatures were measured as a function of time at different vertical locations on the centerline of a vertical storage tank. The temperature distributions and, more important, the availability of hot water for the different types of consumptions were compared. It was concluded that the four heating methods may be ranked from the most favorable to the least favorable as follows: temperature-controlled heat pump, electric hot water heater system, temperature-controlled heat pump with a return loop, and lastly the heat pump parallel to the storage tank without any temperature control.