Recuperator Energy and Exergy Analysis in the Application of Microturbine in Cogeneration of Heat and Power Systems

Micro turbines are indeed very small gas turbines (25-300 kW) that usually have thermal regenerator or recuperator to minimize the energy consumption. In currently working plants, the air entered into the compressor is compressed and then is preheated using the heat of turbine exhaust gases in a recuperator. One of the methods to enhance the performance of the gas turbine is using a heat exchanger to recover the energy of hot gases leaving from gas turbine. To recover heat in gas turbine industry different devices have been used. In general, heat recovery devices are divided into two groups i.e. i) regenerators and ii) recuperators. Regenerators act periodically and at the first time interval it absorbs the heat of turbine exhaust gas in the heat exchanger matrix and in the next time interval transfers heat to the cold dense air leaving the compressor. In contrast, Recuperators are heat exchangers that transfer heat into compressed air continuously and use the energy of exhaust hot gases. This paper investigates the thermodynamic of microturbine. The results show that adding a recuperator increases the cycle thermal efficiency significantly. Also this paper investigates the effect of recuperator materials on the micro-turbine performance and the turbine inlet temperature as the most effective factor to increase the performance. The thermodynamic equations were solved by an engineering software EES2013. Considering the results show that at the pressure ratio of 4.29 the thermal efficiency is maximum and adding a recuperator decreases the fuel consumption rate 45 percent in the combustion chamber.