Investigation of Different Cathode Path Topologies for Water Recovery in a Heavy-Duty Polymer Electrolyte Membrane Fuel Cell Vehicle

Heavy-duty vehicles equipped with polymer electrolyte membrane fuel cells (PEM-FC) are an environmentally friendly alternative to vehicles powered by internal combustion engines. A major challenge for heavy-duty fuel cell vehicles is the potential cooling deficit under high load conditions at high ambient temperatures. To solve this problem, a spray cooling system can be utilized, in which liquid water is sprayed on the main cooler at the front end of the vehicle. The evaporation of the sprayed liquid water results in an increased cooling power. In this paper, the recovery of liquid water within the cathode loop of a mobile PEM-FC system is presented and discussed. For this purpose, three different topologies of the cathode subsystem of the PEM-FC are investigated for recovering liquid water directly from the fuel cell exhaust gas. To obtain liquid water, vapor in the exhaust gas is cooled below the saturation temperature in an additional heat exchanger. Three possible positions of such a heat exchanger in the exhaust gas system are analyzed and discussed in this study. The first investigated position is at the outlet of the turbine and the other two are either upstream or downstream of the membrane humidifier. For the position upstream of the humidifier, a control and operating strategy is established. To investigate the water recovery of the three topologies, a simulation study is conducted using a validated physics-based model of the entire fuel cell system. The result of the study is a recommendation that the additional cooler should be placed upstream of the membrane humidifier.