Ecological problems and energy crisis in a globalized world have motivated scientists to develop energy systems more sustainable, having as one of the possible alternative the use of solar energy as source for cooling systems. In the field of the sorption cooling, there are three kinds of system: liquid absorption, solid absorption (chemical reaction) and adsorption. The great advantage of adsorption systems over absorption ones is that they can operate without moving parts, having then lower costs of maintenance. Other advantages in comparison with the compression systems are: simple construction, environmentally benign and noiseless. A lot of applications for adsorption cooling systems have been viewed in both developed and developing countries such as: storage and conservation of vaccine, medical products, food conservation (vegetable, meat, fish, etc), refrigeration, air conditioning, chillers and ice production.

This paper presents the modelization of heat and mass transfer in tubular adsorber of solar adsorption cooling machine. The modelling and the analysis of the adsorber are the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the working cycle. The adsorber is heated by solar energy and contains a porous medium constituted of activated carbon AC-35 reacting by adsorption with methanol.

The developed model is based on the energy equation of the adsorbent layers, the energy balance equation of the adsorber tube wall and the state equation of the bivariant solid- vapour equilibrium using the Dubinin-Astakhov model to describe the adsorption phenomena.

A FORTRAN computer program is written to solve the proposed numerical model using an implicit finite difference technique.

The obtained solution allows to know the daily thermal behaviour of the tubular adsorber.

The performance of the machine has been discussed in the studied case of 1m² surface area of flat plate collector integrated with an eight copper tubes containing the activated carbon AC35/methanol pair, where the thickness adsorbent bed in each tube is 55.5 cm.

The dimensioning of the solar reactor (internal adsorber radius and collector surface area) is done after an optimization study, which is discussed in the present work. It has been found that the solar and the thermal performance coefficient of the system are 0.135 and 0.308, respectively.

Key words: Solar refrigeration machine; Adsorption; Heat and mass transfer; Activated carbon AC-35/methanol; Numerical simulation.