Entropy production in the chemical reaction driven heat transformer

A chemical heat transformer uses a chemically reacting system for the inter nal cycle. Chemical conversions in a chemical heat transformer produce entr opy due to irreversibilities, which are taken into account in our derivatio n of a new, more realistic value for the thermal efficiency of this heat tr ansformer. We studied the example of the endothermic dehydrogenation of 2-p ropanol, yielding acetone and hydrogen, versus the exothermic hydrogenation of acetone yielding 2-propanol. Different from other papers we allow the d ehydrogenation temperature T-m to be higher than the boiling point T-b Of t he 2-propanol and we allow the isolation of 2-propanol from the mixture to be incomplete. The internal entropy production in the dehydrogenation and h ydrogenation reactor is calculated as a function of the hydrogenation tempe rature T-h with three different values of T-h - T-m and several incomplete separation values. The thermal efficiency is much lower than Carnot's effic iency for low-temperature lifts because of the high irreversibilities that are already present for these temperatures and because of the low efficienc y of the heat engine. A higher, but still low, efficiency is obtained for T -m > T-b and for the incomplete separation of 2-propanol from the mixture.