Hot Water Management of DHW Storage Tank: Supply Features

The current study is directed to analyze the mixing nature of cold and hot water inside storage tank, and the corresponding effects on the total usable and delivered energy to consumers. The analyses are done for two different supply features bottom and side supply of cold water. An experimental rig consisting of hot water reservoir, cold water reservoir, water pump, flow meter, hot water storage tank (HWST), and a PC with Lab-View data acquisition system, was constructed to collect the necessary data for analyses. Four different flow rates ranging from 1.9 to 10 L/min have been taken under consideration. The results were in a good agreement with the published expectations. As it is well known, low flow rates save more energy in both bottom and side cold water supply (CWS). The comparison between the two supply features showed that the side CWS has higher amount of usable hot water than the bottom CWS at the same flow rate. Side CWS also minimizes the turbulent mixing within the HWST which by its turn supply higher energy for consumers. The bottom supply feature which is easier for assembly, has a bad effect on the total usable hot water and the total amount of energy delivered to the customers. A special mechanism to distribute the water as a uniform layer from the bottom of the tank is currently under investigations.