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The paper presents an absorption system with compact heat exchangers (micro-channels), working with ammonia water solution, driven by either solar or electrical energy. The construction of the solar panels includes heat pipes, and they are able to provide hot water with a maximum temperature of 130°C. The cooling capacity of the system ranges from 5 to 10 kW. The system is designed for comfort the technological air conditioning, providing inside air temperatures in the range of 10°C to 20°C. The project promotes ammonia as an ecological and natural refrigerant and aims to experimentally evaluate the thermal performances of each component of the system (condenser, evaporator, absorber and vapor generator) and of the entire system. The next step consists in a theoretical versus experimental comparison of data. The thermal performances refer to heat transfer coefficients in micro-channels on water ammonia side, as well as on the airside, and to the performance coefficient for various working conditions.

A mathematical model is formulated in this paper for the prediction of the heat rejection rate, assuming that the total heat transfer area of the mesochannel condenser is made up of 2 different areas, corresponding to superheated vapor state and the two-phase flow state. Each of these areas is considered as an independent heat exchanger (Mamani et al., 1999). The tested mesochannel condenser, manufactured by a Romanian company for automotive air-conditioning systems, is made of aluminum, based on an extrusion process; an oven brazing process was used for the headers to tubes joints. Maximum heat rejection rate represents the criteria used in order to optimize the geometrical configuration of the condenser. This theoretical study resulted in an optimized geometrical configuration of the mesochannel condenser (Heun et al., 1996a; Heun et al., 1996b). Experimental research has been carried out using a mesochannel condenser of optimized geometrical configuration. In order to ensure a quasi-state operating regime, the air-cooled mesochannel condenser was mounted inside an air loop, having multiple regulating and control means for the following parameters: inlet air dry bulb temperature, inlet air wet bulb temperature, and inlet air flow rate. The authors of the present paper develop a comparative analysis of theoretical vs. experimental heat rejection rate and heat transfer coefficient for an ammonia air-cooled mesochannel condenser.

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