Combined Thermodynamic Cycles for Heat Recovery from Secondary Sources

Heat pumps (refrigerating plants included) are usually designed either to raise the thermal potential of some working agent from a lower temperature T 2 of a secondary (residual) source to a higher temperature T 1 becoming further a useful heating source for warming enclosures or producing mechanical work, or to cool down a secondary chilling / freezing agent (brine) used further for refrigerating chambers or to freeze perishable products at ordinary temperature [1 ÷ 5]. In both cases, mechanical energy from other sources has to be consumed to recycle the working agent from temperature T 2 to temperature T 1 . Some heat recover y plants were imagined and are described below, together with their ideal functioning cycles, combining inverse cycles with the production of at least a part of the needed pumping work from a direct cycle which is based also on the same secondary (or residual) source heat available.