Model-based sensitivity analysis of barometric pressure on cooling capacity measurement of hydronic room fan coil units

Abstract

The goal of this paper is to quantify the impact of weather-induced and altitude-induced barometric pressure variations on the cooling capacity measurement of hydronic coils in room fan coil units. Based on an AHRI-certified coil simulation model and the Monte Carlo sampling method, capacity measurement data were simulated for three hydronic cooling coils at a fixed testing condition with different barometric pressures. The model outputs were statistically analyzed to determine the standardized regression coefficient for sensitivity evaluation. Results show that the total and sensible capacity measurements at a fixed location are less sensitive to weather-induced barometric pressure fluctuation compared with the impacts of entering air dry- and wet-bulb temperatures, airflow rate, and leaving water temperature. While marginal impact on the sensible capacity measurement, the altitude-induced barometric pressure variation from 101.635 kPa (14.741 psia) to 81.210 kPa (11.779 psia) leads to over 10% increase in the total capacity measurement with the fixed entering air and water temperatures and airflow rate. A procedure to adjust the entering air wet-bulb temperature based on local barometric pressure was proposed and validated. The mitigation procedure contributes to the consistency improvement of standard testing and enables the cooling capacity conversion between sea level and elevated altitudes.