Bed configuration effects on the finned flat-tube adsorption heat exchanger performance: Numerical modeling and experimental validation

A three dimensional numerical scheme has been developed to examine geometrical configuration effects on the performance of a single bed adsorption chiller with a trapezoidal aluminum finned flat-tube heat exchanger (FFT HEx). A mathematical distributed model along with the linear driving force (LDF) model and Darcy's law have been considered to take into account the effects of heat and both intra/inter-grain mass transfer resistances. The developed numerical scheme has also been validated experimentally by using a composite sorbent SWS-1L and water as a working pair. Additionally, rectangular beds with identical working conditions and bed dimensions as the tested trapezoidal beds have been examined in similar details to identify, which type of the fin geometry provides a superior performance. It was found that in this particular HEx, the heat transfer resistance is mainly influenced by both of the fin pitch and height, while the inter-grain mass transfer resistance is independently controlled by the bed length. This fact makes the role of the fin pitch and fin height almost interchangeable with respect to the cycle time and specific cooling power (SCP) especially in rectangular beds. However, the coefficient of performance (COP) is more influenced by the fin height than the fin pitch. In addition, higher SCP can be achieved at smaller bed dimensions at the expense of lower COP. Moreover, it was found that using rectangular bed is more appropriate, since its SCP is either the same or higher than its corresponding trapezoidal bed especially at shorter bed lengths, while COP remains almost the same for both bed types in all considered ranges of bed dimensions. Finally, a bed designing procedure has been proposed for proper designing of effective adsorption HExs based on the performed parametric studies.