A heat engine having an efficiency of $$70\% $$ is used to drive a refrigerator having a coefficient of performance of $$5.$$ The energy absorbed from low temperature reservoir by the refrigerator for each $$kJ$$ of energy absorbed from high temperature source by the engine is

A Carnot cycle is having an efficiency of $$0.75.$$ If the temperature of the high temperature reservoir is $${727^ \circ }C,$$ what is the temperature of low temperature reservoir?

A cyclic heat engine does $$50$$ $$kJ$$ of work per cycle. If the efficiency of the heat engine is $$75\% $$, then heat rejected per cycle is

For two cycles coupled in series, the topping cycle has an efficiency of $$30\% $$ and the bottoming cycle has an efficiency of $$20\% $$. The overall combined cycle efficiency is