Prof. Ramadan Youssef Sakr Moustafa :: Publications:

A numerical study is carried out to predict the transient response of a packed bed thermal storage system containing a phase change material (PCM) as a packing material. A vertical cylindrical heat storage packed bed containing PCM encapsulated in spherical pebbles with air as a working fluid is investigated. Three different PCMs in addition to rock grains are tested. The present problem is modeled using two dimensional axisymmertric time-dependent coupled partial differential equations for energy conservation of the working fluid and the PCM. The energy equation for the working fluid is transformed by finite difference approximation and solved by Alternating Direction Implicit scheme (ADI) while the PCM energy equations are solved using fully explicit schemes. The temperature distributions for both the working fluid and PCM and the liquid mass fraction of the PCM are predicted in radial and axial directions for both charging and recovery modes at different operating parameters. The present predictions are compared with previous experimental data to check the validity of the present model. Also, the influence of the flowing fluid mass flow rate, inlet fluid temperature, heat storage volume and the PCM thermophysical properties are investigated. An enhancement in the thermal energy stored with a maximum value of about 500% is predicted when using beds containing PCMs instead of using rock grains.