Ammoniac-Water absorption system are studied in this work, our aim is to look for new method having improved performance coefficient, without adding novel component in the conventional configuration. We present a thermodynamic study of the machine. A particular interest is tuned to the rich solution’s flow influence on the machine’s COP. The refrigerating system is then associated with a plane solar collector. The computational heat transfer simulation shows the existence of an optimal flow for which the COP is optimum. Considering the numerical results, we have established a relationship giving the optimal flow according to the climate data. The numerical investigation reveals a great importance in the conception of an optimal refrigeration solar absorption system, where we propose to integrate a rich solution’s circulating pump, provided with a variable speed transmission, ordered by a control law giving the optimal flow for the desired operating conditions.