4065 (RP-664) — Convective Heat Transfer in Building Energy and Thermal Load Calculations

Reports that valid enclosure film coefficients, required by hourly energy and thermal load programs, were experimentally determined for ventilative flow rates below 12 air changes per hour (ACH). 48 experiments were performed in a full-scale room from 3 to 12 ACH in order to determine film coefficients at low ventilative flow rates. Finds that for most room configurations, natural convection film coefficients significantly underpredict the rate of surface convective heat transfer. The new film coefficients were implemented in the BLAST program, an hourly heat balance based building energy simulation and the significance of the error incurred by using natural convection film coefficients in a ventilated space was estimated. Finds errors in calculated space cooling loads were in the order of 10%.

Units: Dual

KEYWORDS: year 1997, Heat flow, convection, buildings, cooling load, heat load, calculating, accuracy, computer programs, ventilation, air flow rate, space cooling