How can we increase the efficiency of a heat engine?

Hint:A heat engine consists of a cold sink and a hot source. The process to determine the efficiency of the engine is dependent upon the temperature of the hot source and the cold sink.

Complete step by step solution:
A heat engine is described as a machine that converts the heat energy into mechanical work and its efficiency is fundamentally related to Carnot’s theorem. This engine can be used to do the mechanical work and it works by bringing a working substance from its higher state temperature to its lower state temperature.

The working substance generates the heat in the working body of the engine and transfers the heat produced to the cold sink till it reaches a lower state temperature. During this process, there is a conversion of thermal energy into work and this happens by exploiting the properties of the working substance.

The efficiency of the heat engine can be given by the following formula;
\[\eta = 1 - ({T_L}/{T_H})\]
Where \[{T_L}\] represents the temperature of the cold sink and \[{T_H}\] is the temperature of the hot source.
By the equation mentioned above, we can conclude that the efficiency of the heat engine can be increased by decreasing the temperature of the cold sink.

Hence, it can be increased by increasing the temperature of the hot source.

Note: A working substance in the heat engine can be any system that has a non-zero heat capacity but is in the form of a gas or a liquid. During the process of converting heat into work, some amount of heat is also lost into the surroundings and is not converted into work and also some heat is lost during frictional forces.