Pressure Drop Characteristics in Flexible Ducting in Exhaust system

摘要

This paper describes experimental and analytical research of the pressure drop characteristics of flexible ducting which is used in extraction ventilation systems for working environmental protection. The aim of the approach is to determine the pressure drop in flexible ducting by laboratory tests. Pressure drop in flexible ducting in its extended mode, compressed mode and normal mode was studied. The equation used to calculate the friction factor was that proposed by Jain which was developed from the Colebrook-White formula. Friction charts are presented in this paper for the pressure drop properties in different modes of flexible ducting. The obtained results indicated that the absolute roughness k_s of polyester ducting in the fully extended mode is smaller than the aluminium ducting in the same mode. The k_s value of polyester ducting in compressed mode is greater than aluminium ducting in the same mode. By comparing the results with the data of ASHRAE Handbook Fundamentals, the k_s value of polyester ducting is in the lower position of the range of ASHRAE data, and the k_s value of aluminium ducting is bigger than the data of ASHRAE.