Heat transfer characteristics of a high temperature sensible heat storage water heater using cast iron as a storage material

This paper describes the heat transfer characteristics of high temperature sensible heat storage in cast iron for water heating applications. An experimental setup consisting of a cast iron cylinder and a tube running through its center was fabricated and tested. The experimental data were compared with the theoretical model. It was observed that the contact resistance between the cast iron and the tube plays a dominant role in extracting the heat. An approximate contact resistance prediction was obtained by assuming the resistance due to the air gap modulated by a correction factor, which accounts for the contacting surface area. Based on the results from the experimental setup and theoretical modeling a prototype storage water heater using cast iron blocks as the storage material was designed, fabricated and tested.