Thermal Performance and Energy Efficiency Analysis of a Natural Gas Boiler Under Variable Load Conditions

Abstract

This study analyzes the thermal and economic performance of a natural gas-fired boiler system operating at loads ranging from 30% to 100%. Key parameters include energy input and output, thermal efficiency, specific fuel consumption (SFC), and the contribution of the economizer to energy and cost savings. Results show that thermal efficiency increases with load, peaking at 51.97% at 90% capacity before slightly declining at full load. SFC decreases from 0.1931 MJ/kg steam at 30% load to 0.1295 MJ/kg steam at 90%, indicating better fuel utilization. The total operating cost rises from USD 23.00/h at 30% load to USD 37.80/h at 100%, with the most economical performance observed at 90% load (USD 34.96/h). The economizer also plays a consistent role in reducing fuel-related costs, with savings potential increasing from USD 11.04/h at 30% load to USD 16.24/h at full load. These findings indicate that operating the boiler within the 80%–90% load range offers an optimal balance between thermal efficiency and economic performance.