Calculation method for along-duct resistance of spiral ducts based on experimental measurements

Using a nationally accredited laboratory airflow testing facility, the along-duct resistance for a fundamental series of 17 spiral duct samples is tested, and the measured values for the along-duct resistance of these 17 spiral ducts under different wind speeds are obtained. Referring to ANSI/ASHRAE Standard 120-2008, the measured values are fitted by the least square method, and 17 along-duct resistance formulas of spiral ducts are obtained. The correlations between these formulas are obtained by mathematical statistical methods. After further optimization and consolidation of the formula values, they are once again fitted using the least square method. Ultimately, these 17 formulas are fitted into a universal formula applicable for calculating along-duct resistance in spiral ducts of all specifications. The calculation results show that the average error of the along-duct resistance value of spiral ducts calculated by fitting the universal formula is less than 3% compared with the measured value, and the accuracy meets the design calculation requirements.