The reaction time of hydrogen in metal hydride vessels (MHVs for short) is strongly influenced by the heat transfer from/to the hydride bed. In the present work an experimental study of the geometric and the operating parameters of a finned spiral heat exchanger has been carried out to identify their influence on the performance of the charging process of the MHV. The experimental results show that the charge time of the reactor is considerably reduced, when finned spiral heat exchanger is used. in addition, the effect of different parameters (flow mass and temperature of the cooling fluid, applied pressure, and hydrogen tank volume) has been discussed and obtained results show that a good choice of these parameters is important. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.