Development of Thermal Performance Metrics for Direct Gas-Fired Circulating Heaters

Many climate-controlled agricultural buildings use direct gas-fired circulating heaters (DGFCH) for supplement heat. There is no standardized test to calculate thermal efficiency these heaters. This study aimed develop a measurement system and analytical analysis efficiency, quantify the uncertainty, assess economics of DGFCH efficiency. The developed was similar ASHRAE 103 standard stand with adaptations connect apparatus DGFCH. Two different propane systems were used: input ratings < 30 kW used mass flow > volumetric gas meter. Three DGFCHs (21.9, 29.3, 73.3 kW) tested evaluate system. Thermal efficiencies ranged from 92.4% 100.9%. resulting uncertainty (coverage factor 2; ~95% Confidence Interval) 13.1% 30.7% 56.3 11.4 kW. Key sources air measurement. economic impact 1% difference in USD $61.3 $72.0 per heating season. Refinement testing procedures are needed reduce uncertainty. application this will aid building designers selection various applications.