DefinePK

Abstract

Heat storages are essential elements of renewable solar energy systems as well as conventional industry applications. Their performance and cost are detrimental to the concerned systems. Carbon foam material excels as heat storage medium due to its high thermal conductivity coupled with its high heat capacity, and light weight, allowing design of smaller, more efficient, cheaper, and lighter heat storages. To optimize the design of small sized carbon foam heat storage, ANOVA analysis was employed to determine significances of heat transfer controlling factors such as pore size, porosity, length and diameter of the bed, and mass flow rate of charging hot air. Also, Surface Response Method was employed to construct a statistical model that describes the energy/volume as a function of the above parameters. The model employs one-dimensional continuity, momentum and energy equations to simulate the heat transfer process within a volume of carbon foam material with pore diameter of 0.003 m, and porosity (e) ranging from 0.08 to 0.385. The investigation shows that coefficient of determination (R2)=0.84 of the statistical model. With ambient and charging temperatures of 25ºC and 85ºC, bed length of 0.4 m, bed diameter of 0.1 m, mass flow rate per area of 0.25 kg/sm¬2, and e of 0.19, the maximum heat energy/volume (82000kj/m3) is achieved at about 1.3 hours of charging time. At mass flow rate per area of 0.125 kg/sm¬2 and e of 0.175 the maximum energy stored is achieved at about 1.7 hours of charging time.