The present invention provides an adsorbent vessel adapted to contain an adsorbent and form an adsorbent bed for use in adsorbing a component of a multicomponent gas mixture during a pressure swing adsorption process. In accordance with such process the adsorbent bed is regenerated by desorbing the adsorbed component. The adsorption capacity of the adsorbent decreases with decreasing temperature and the pressure swing adsorption process produces a cold spot of reduced temperature within a region of the adsorbent bed. In order to combat the resulting decreased adsorption capacity, a convective heat exchanger extends into the cold spot to raise the temperature of the cold spot. The convective heat exchanger is provided with at least two passes for the entering multi-component gas mixture or the outward bound desorbed component to transverse and thereby transfer heat to the cold spot. Additionally, the heat exchanger can also serve to supply a sufficiently long straight run for the entering multi-component gas mixture to fully develop. The full development of the entering flow prevents unequal distribution of the multi-component gas mixture within the adsorbent bed.