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) (where the electrolyte has a cooling role in the system) has been considered. Proper control volumes of system with specific qualifications have been chosen. Accordingly, heat and mass transfer in the control volumes have been assessed. Considerations of heat and mass transfer plus contributed models led to the use of a double tube heat exchanger as an energy sink. Design of this heat exchanger was dependent on heat transfer conditions and related equations. A composite system of alkaline fuel cells and peripheral equipment was used. Then the equations of all steps were integrated. Furthermore, the optimization codes were developed to propose the best operation point of the system, minimize total cost and determine the heat exchanger dimensions, flow rates and temperatures employing the ‘GAMS’ software. In the results, optimum electrolyte inlet and outlet temperature obtained were 73˚C and 40˚C, respectively; and the heat exchanger total area, minimizing the cost model, was rendered to 0.07 m2. Finally, parametric analysis for variation of temperature, length and diameter of the heat exchanger, pressure drop, total cost and performance of planned combined system were studied. It was concluded that system cooling is very important because system efficiency decreases with rising temperatures. A promising fact of increasing overall efficiency of the system with regards to reducing electrolyte temperature demonstrated reducing electrolyte temperature in the range of 70 to 40˚C, resulted in a 2% increase in overall system efficiency.

کلیدواژه ها:

Alkaline fuel cell ، Heat transfer ، Sensitivity analysis ، Energy efficiency ، Cost model