The present study examines the effect of flow and geometric parameters on the performance of solar thermal collector provided with impinging air jets. The investigation has been carried out in terms of performance defining criterions which are pertinent to determine the optimal design of impinging jet solar thermal collector. The experimental investigation indicated that the impinging air jets enhances the thermal performance but at the same time the friction power penalty also increases which depress the overall performance of the system. In view of this the preference selection index (PSI) approach based methodology has been applied using various performance criterions in order to determine the optimal design of the parameters which deliver maximum thermal performance with minimal increase in friction factor inside the collector duct. The optimum configuration of the parameters obtained as a result of proposed method is: streamwise pitch ratio of 0.435; spanwise pitch ratio of 0.869; jet diameter ratio of 0.065 and flow Reynolds number of 16,000. (C) 2016 Published by Elsevier Ltd.