Analytical modeling of oscillatory heat transfer in coated sorption beds

Abstract

A novel analytical model that considers the thermal contact resistance (TCR) at the interface between the sorbent layer and heat exchanger (HEX) is developed to investigate the oscillatory heat transfer and performance of coated sorption beds. The governing energy equation is solved using an orthogonal expansion technique and closed-form relationships are obtained to calculate the temperature distribution inside the sorbent coating and HEX. In addition, a new gravimetric large pressure jump (GLAP) test bed is designed to measure the uptake of sorption material. Novel graphite coated sorption beds were prepared and tested in the GLAP test bed. The model was successfully validated with the measurements performed in the GLAP test bed. It is found that specific cooling power (SCP) of a sorption cooling system (SCS) enhances by increasing the sorbent thermal diffusivity and decreasing the TCR. For example, SCP of the sorption cooling system (SCS) can be enhanced from 90 to 900 (W/kg) by increasing the sorbent thermal diffusivity from 2.5e−7 to 5.25e−6 (m2/s) and decreasing the TCR from 4 to 0.3 (K/W). Moreover, the results show that SCP increases by reducing the HEX to sorbent thickness ratio (HSTR). Therefore, the proposed graphite coated sorption beds with high thermal diffusivity and low thickness are suitable for sorption cooling applications.