Thermal design of the reformer in reformer-fuel cell systems for onboard hydrogen production in LNG-fueled ships

• Thermal design of the reformer, a subsystem of reformer-fuel cell systems addressed. • Tube-side heat transfer coefficients from the correlation proposed by Wakao et al. considered. • Tube-side friction factor from the correlation developed by Erdim et al. considered. • The reformer length is 1.72 m at a temperature difference ( T h,o – T c,i ) of ∼ 70 ℃. This study focuses on the thermal design of a reformer that produces hydrogen by extracting a portion of the boil-off gas generated from the fuel tank of an LNG-fueled ship. The reformer is a subsystem of a reformer-fuel cell system and is designed as a shell-and-tube heat exchanger, with a fixed lump of catalyst particles within the tubes and a bundle of these tubes installed within the shell. Designing the reformer requires determining the heat transfer coefficients and pressure drops inside and outside the tubes. For the thermal design of the particle bed in the tube, the heat transfer coefficient on the tube side is calculated using the correlation proposed by Wakao et al., which is widely used in the design of heat exchangers with spherical or cylindrical particle beds. The pressure drop across the particle bed packed in the tube is calculated using the correlation reported by Erdim et al. Based on the thermal design, the length of the reformer is predicted to be 1.72 m when the temperature difference between the shell-side outlet and tube-side inlet is approximately 70 ℃. This estimate aligns with the length (approximately 1.7 m) obtained from the demethanation reaction model of the reformer. The reforming process achieves a hydrogen yield of approximately 43 % with a methane conversion rate of approximately 98 %.