Reheating in gas turbine is done in order to increase the efficiency of the turbine. For this gas turbine is divided into number of stages and they are classified as high pressure turbine and low pressure turbine. At each stage power is produce based on the temperature and pressure of the gas. Procedure starts with the introduction of gasses at high temperature and high pressure into the turbine section having number of blades. Blades absorb power form gasses and after that gasses are eliminated from that section of gas turbine. When that gas at low temperature and pressure is received from the high pressure stage then it is reheated before it enters the low pressure turbine section. Is reheating is necessary because gas after existing the high pressure stage will be at such a low pressure that it cannot be used in second stage of gas turbine.
According to the working of the gas turbine the gasses for combustion are first get compresses in compressor and they move forwards for combustion. Temperature of gasses when they leave the compressor is lesser then the temperature of the gasses leaving the turbine after combustion and power production. Introduction of gasses in combustion chamber at high temperature will increase the efficiency of the turbine. To increase the temperature of gasses before they enter the combustion chamber, the gasses which are coming out of compressor are heat with the help of gasses which are coming out of the turbine outlet. For this heating purpose heat exchanger is used where hot gasses coming out of turbine flow in tubes and gasses coming out of compressor flow in shell of heat exchanger. During their flow in shell, gasses going into the combustion chamber gain heat through conduction and convection.