HEAT TRANSFER ENHANCEMENT OF SENSIBLE ENERGY STORAGE FOR LOW TEMPERATURE APPLICATION

A shell and tube heat storage (1 MJ) has been designed computationally to enhance the heat transfer rate from heat transfer fluid (HTF) to the storage media. Concrete and water are considered as the sensible storage material and HTF, respectively. The system can be used to store the solar energy in the day time, which will be available in the absence of sunlight. Finite element based software, named COMSOL Multiphysics, is used for the study. The parameters analyzed, are tube outside diameter, radial distances between the tubes, number of tubes and inlet temperature of HTF. After a simulation time of 3000s, the increase of tube diameter from 1.03 to 1.71 cm is found to increase the average storage bed temperature by 6.3%. For the radial distances between the tubes to be 6 cm, the stored energy is maximum. The stored energies for 5 and 4 cm are 2.4 and 12.4% less than 6 cm, respectively, after duration of 6000s. The average bed temperature reaches to the steady state condition at 5147s with 19 tubes, whereas, with 25 tubes it takes 30.2% less time. Finally, the shell and tube heat storage has been optimized for higher heat transfer rate.