Comparative Thermodynamic Study of Five Couples Used in Solar Cooling with Adsorption by Simulation

Aims: The aim of this work was to develop a thermodynamic model that applies to several couples, for determining the COPth of a cycle of adsorption and to compare these couples of adsorption.

Methodology: Five couples were considered: Silica gel-water, Zeolite-water, Activated Carbon-methanol, Activated Carbon-ethanol, and Activated Carbon-Ammonia.

From a thermodynamic cycle, heats exchanged was determined using Dubinin-Astakhov equation for adsorption and a COP is calculated.

We studied the influence of some physical quantities on the performance of these couples mainly the effect of operating temperatures and the effect of parameter n of Dubinin-Astakhov.

Results: The results showed that the silica gel-water and zeolite-water couples show better performance for evaporation temperature higher than 5°C in the climatic conditions of Burkina Faso.

On the opposite, for evaporation temperatures lower than 5°C the activated carbon-methanol and activated carbon-ethanol couples have the best thermal performance. The results show that for each couple, there is an optimal value of Dubinin Astakhov parameter n:

For silica gel-water n = 1.78, for zeolite-water n = 2.3, for activated carbon-methanol n = 2.15, for activated carbon-ethanol n = 2.25 and for activated carbon-ammoniac n = 1.55.

Finding(s): An interesting and useful finding was that the proposed thermodynamic model allow calculation of the COP of others refrigeration pairs knowing their thermophysicals properties and Dubinin Parameters.

We also found that silica gel-water and zeolite-water pair although not reliable in ice making purpose have higher cold production due to the high latent heat of vaporization of water

Conclusion: Silica gel-water pair is recommendable for refrigeration (food conservation) and activated carbon-methanol for ice making (Vaccine conservation).

The various results which are obtained by simulation need to be validated experimentally.