Statistical Modeling of Head Loss through Duct Fittings in Conditioned Air Distribution Systems

Fractions of the total head loss which constitute the loss through duct fittings, obtained in an earlier study, for varying numbers of supply outlets and lengths of index duct run were used in a regression analysis to obtain second order equations which gave a general increase of the fraction from 0.598 to 0.713 for an increase in number of outlets from 3 to 19 and for a corresponding increase of 11.2 m to 43.2 m in index duct length. The correlation coefficient between the fraction of loss through duct fittings and each of the variables of number of supply outlets and length of index duct run was 0.823, which was found to be acceptable for a 95% confidence level. The ratios are useful for quick estimate of total pressure losses in conditioned air distribution systems which are needed in determining the fan pressure requirements.