A channel reactor arrangement and a process uses a heat exchange fluid with a high thermal density to indirectly heat or cool the reactants by indirect heat exchange. The system brings the efficiency of plate reactor arrangements to the effectiveness of high heat capacity heat exchange fluids such as molten salts and liquid metals. The channel reactor arrangement maintains a limited temperature gradient through the channels at all points to improve process selectivity. This type of arrangement is of a particular advantage where the reaction zone uses a heterogeneous catalyst system within a heat exchanging reaction section. The plate and channel heat transfer arrangement is particularly beneficial because of its high surface area provided per unit volume of channels. The high surface area of plates is particularly beneficial for heat transfer fluids having a high thermal density since the mass flow of the fluid, for lower thermal density fluids, will often end up being the limiting heat input variable where the approach temperature between the heat exchange channels and reaction channels is limited. Highly exothermic processes such as oxidation reactions or endothermic processes such as dehydrogenation achieve the most benefit from this invention.