A Double Pipe Heat Exchanger Design and Optimization for Cooling an Alkaline Fuel Cell System

In the presented research, heat transfer of a mobile electrolyte alkaline fuel cell (AFC) (which the electrolyte has cooling role of system) has been considered. Proper control volumes of system with specific qualification have been chosen. Consequently, heat and mass transfer in control volumes have been assessed. Considerations on them and contributed models lead to approve a double tube heat exchanger as energy sink. Design of this heat exchanger is dependent on heat transfer conditions and related equations. A composite system of alkaline fuel cell and peripheral equipment has been used. Then the equations of all steps have been integrated. Furthermore, the optimization codes have been developed to propose best operation point of system, minimizing total cost and determining the heat exchanger dimensions, flow rates and temperatures and in this manner the software ‘GAMS’ was employed. In the results, optimum electrolyte inlet and outlet temperature obtained 73˚C and 40˚C respectively; and the heat exchanger total area with minimizing the cost model is rendered to 0.07 m2. Finally, parametric analysis for variation of temperature, length and diameter of heat exchanger, pressure drop, total cost and performance of planned combined system has been studied. It can be concluded that cooling of system is very important because the efficiency of system reduces with temperatures rising. A promising fact of increasing overall efficiency of system regards to reducing electrolyte temperature demonstrate reducing electrolyte temperature in the range of 70 to 40 oC, concluded 2% overall system efficiency increasing.