EXPERIMENTAL AND NUMERICAL INVESTIGATION ON ABSORPTION-DIFFUSION REFRIGERATION MACHINE BASED ON LIGHT HYDROCARBONS N. Ben Ezzine (a) , R. Garma, A. Bellagi (b) (a) Department of Physics, Faculty of Sciences of Bizerte, University of Carthage, B.P.38 LaPoste 7000 Bizerte-Tunisia n_benezzine@yahoo.fr (b) U. R. Thermique & Thermodynamique des Procédés Industriels, National Engineering School at Monastir E.N.I.M, Av. Ibn Jazzar, 5060 Monastir, Tunisia, a.bellagi@enim.rnu.tn ABSTRACT Experimental and numerical investigations of an air cooled diffusion-absorption machine operating with a binary light hydrocarbon mixture (C 4 H 10 /C 9 H 20 ) as working fluid and helium as pressure equalizing inert gas are presented in this paper. The machine made of copper -an available and very good heat conducting metal- was designed, constructed and experimentally analysed. Its cooling capacity is 30-40 W. Cold is produced at temperatures between -10 and +10°C for a driving temperature in the range 120-150°C. The maximum COP approaches 0.175. A thermodynamic model for the machine is then developed. The cycle performance was parametrically studied by computer simulation for 1 kW cooling capacity design. Present experimental and simulation data are expected to provide useful information for determination of the design parameters for a solar powered machine. 1. INTRODUCTION The diffusion absorption technique invented by the Swedish engineers von Platen and Munters [1] in the 1920s is the best suited for solar applications. Its thermodynamic cycle is based on a refrigerant/ absorbent pair mixture as working fluids and an inert gas as pressure equalizing. A thermally driven bubble pump, which can be powered by either waste heat or solar thermal energy, is used to circle the liquid solution. The absence of any mechanical moving part allows a silent and very reliable machine [2] in addition to an economical and natural cycle. The use of ammonia/water mixture as working fluids and hydrogen as auxiliary inert gas [3,4] can provide cooling at very low temperature (-20 to -30°C depending on the diffusion absorption cycle configuration [2,5]) but it requires high driving temperature (more than 150°C) which is unsuited for solar heat. Furthermore ammonia is destructively corrosive with copper. A working fluid based on organic fluids was investigated [2,4] and it was concluded that a complete diffusion refrigerating system that uses this mixture may be powered by solar energy. The use of thermal solar energy is also possible with water/lithium bromide mixture fluids [6] (driving heat temperature below 100°C). Nevertheless, it presents some difficulties like to be operated under very low pressure and essentially problems related to the crystallisation of the salt. The search of other working fluids suitable to be used with diffusion absorption machine for solar applications continues to be the focus of active research in the air conditioning and refrigeration field. In this contest, a low capacity diffusion absorption machine operating with a binary mixture of light hydrocarbons is designed, constructed and experimentally investigated. We present in this paper the results of our investigation with a computer simulation for a similar machine with 1 kW cooling capacity. 329