Energy and exergy analyses of natural gas-fired boilers in a district heating system

In this study, energy and exergy analyses of natural gas fired boilers in a district heating system are performed. Mass, energy and exergy balance equations are formed for the boilers and its components. In the boilers, energy or heat losses are examinated, and the biggest of these is identified as the heat loss of flue gases. Energy and exergy efficiencies of the heating system are researched, and the energy, exergy flow diagrams are illustrated by specifying locations of irreversibilities. According to the results of the analyses, the ratio of flue gas energy and exergy losses in the boilers are 16.81% and 6.14%, respectively. The energy and exergy efficiencies of the boilers are found to be 82% and 32.78%. The location, where the maximum of the irreversibility in the boilers is noticed as combustion chamber, and adiabatic combustion temperature is calculated as 1846 °C.