3-D Transient Heat Transfer in a simulated Solar-Heated Adsorption Panel

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Rizalinda L. de Leon

Dissertation (PhD Chemical Engineering)-University of the Philippines Diliman-2006


Adsorption panels are used for refrigeration and heat pump applications. These are operated in a cycle of desorption and adsorption. Desorption may be done by heating the adsorption panel using solar heat. Cycle performance is significantly affected by the thermal characteristics of the system and design of panel. This thesis presents a 3-D mathematical model of transient heat transfer in a solar heated silica gel-water adsorption panel with cylindrical fins. The model is based on the assumption that conduction heat transfer is controlling and that the amount adsorbed at any time is equal to the equilibrium uptake dependent only on temperature and pressure. Correction factors are used to account for thermal currents that contribute to heat transfer and for deviation from the equilibrium assumption. A computer simulation program is developed to integrate the partial differential equations using the Method of Lines and the second order Runge-Kutta method. The simulation program is used for parametric studies to explore the influence of the effective thermal conductivity, the rate of internal generation of heat, wind velocity, bed depth and distance between fins. The effective thermal conductivity and the rate of internal generation are seen to have a significant effect on the calculated temperature progressions.

An adsorption experiment apparatus is built composed of an adsorption panel filled with silica gel connected to a reservoir of water. The system is operated under vacuum. The top of the adsorption panel serves as the solar collector heated by a set of halogen lamps to simulate solar radiation. Temperature progressions at different locations in the bed were measured using different simulated solar radiation intensities. The model agrees will measured temperature progressions and is found useful for parametric studies in adsorption panel design.