Dynamic Simulation of Absorber for Solar Adsorption Refrigerator: A Validated Numerical Model

Abstract

In this work, a numerical model is presented that describes the transfer of heat and mass inside a cylindrical regenerator of a solar adsorption refrigerator that uses the methanol/activated-carbon refrigerant pair. This model is based on the equations of mass conservation, energy conservation, Darcy's law and the balance model between sorbate and sorbent given by the Dubinin-Astakhov's equation. On the other hand, the linear driving force (LDF) model is used to describe the rate of desorption. In the developed model, the spatial variation of methanol vapor pressure within the activated carbon bed is taken into account and, as one of the boundary conditions, the temperature is used at the external surface of the absorber measured experimentally along the day. Using the developed model, the temperature, pressure and concentration of methanol were calculated; both inside the grains of carbon and in the space between the grains, as a function of time. The algorithm was validated comparing the numerical results with the experimental data, obtaining a satisfactory concordance.

Thermal Analysis and Experimental Validation of Parabolic Trough Collector for Solar Adsorption Refrigerator

“…As previously stated, in order to validate the thermal model, it is coupled to the numerical model of an absorber of a solar adsorption refrigerator [12]. The validation of the model is carried out by comparing the temperature of the absorber's surface of two different prototypes of SARs.…”

“…Since all the heat fluxes are known, the absorbed heat is calculated and given as a boundary condition to the absorber model developed by Echarri et al [12], which determines how much of that heat is consumed by the desorption process and how much is responsible for the temperature raise in the surface of the absorber. These two models (collector and absorber) are coupled and from the "absorber model" block and the new absorber's temperature is obtained.…”

“…Some research have been done concerning the dynamic of sorption; Luo and Tounder [10] developed a mathematical model in which the pressure on the system is supposed to remain constant, while Zao et al [11] present a model in which is considered as a constant the temperature in the absorber's surface. Echarri et al [12] developed a numerical model in which the temperature in the surface of the absorber and the pressure inside the vapor canal are considered variables.…”

“…The model includes an algorithm to obtain the solar irradiation as a function of time, which also depends on the geographic location of the prototype and the sorber of a solar adsorption refrigerator developed by Echarri et al [12] as a boundary condition in order to iteratively obtain the desorption heat intake, as well as the evolution of the temperature in the surface of the absorber and the rest of the collector's components. This model is satisfactorily validated with experimental data.…”