This paper presents a steady-state analysis of fluid flow and heat transfer in a zero boil-off cryogenic liquid hydrogen storage tank in microgravity environment. The storage tank is equipped with an assembly of an inlet tube and a nozzle head that contains many nozzles on its front face. Liquid hydrogen is cooled by an external cryocooler, flows along the nozzle head assembly, penetrates into the bulk liquid through the nozzles in order to prevent the boiling off due to heat leak from the surroundings through the tank wall insulation, exits the tank through an annular outlet opening coaxial with the inlet, and then goes back to the external cooling system. Eleven cases for different geometry settings were analyzed. Typical distributions of velocity and temperature are presented. The results show that thermal performance of the system can be improved by increasing the inlet diameter and properly selecting the depth and the span of the nozzle head. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.