Maybe, but I clearly remember that it is not possible to have a reversible process wich only transfers heat from a colder body to a warmer one. The third law also gives quantitative bounds to the reversibility of such processes.
Heat pumps with efficiency above 1 rely on heat transfer between external bodies (e.g. from a subterranean water source to the atmosphere forhome heating systems), but this does not seem to be the system described by Malta.
>It provides an upper limit on the efficiency that any classical thermodynamic engine can achieve during the conversion of heat into work
The word 'efficiency' here is misleading... If one reverses the process, converting work back into heat, you get back all the original energy in an ideal machine (and real machines, for example gas turbines, are within ~15% of ideal for the temperature & pressure change between input and output)
Thanks for the clarification. I still have issues understanding the intermediate stage, where the world is entirely and reversibly converted into a temperature differential. I might have to go back to drawing T-S diagrams.
An ideal heat pump is fully reversible with no energy loss.