The definition and composition of the pressure drop over a tangential inlet, reverse flow cyclone have been analyzed. It is assumed that two factors mainly contribute to the pressure drop, i.e., the local loss and the loss along the distance. The former includes the expansion loss at the cyclone inlet and the contraction loss at the entrance of the outlet tube (or vortex finder). The latter consists of the swirling loss resulting from friction at the cyclone walls and the dissipation of gas dynamic energy in the outlet tube. By use of the measured results of the flow field in cyclones, the calculation methods for each loss have been developed. And a universal model to predict the cyclone pressure drop is thus obtained simply by summing each loss. A detailed comparison between the calculated and experimental results shows that this accurate model is suitable either for pure or for dust laden gases at normal or high temperatures and can meet the requirement of most cyclone designs.

In order to predict the influence of operating temperature on cyclone performance, an experimental investigation on particle separation was conducted in a 300 mm diameter, tangential volute-inlet and reverse flow cyclone separator with air heated up to 973 K. The test powder silica has a mass median diameter of 10 microns and the inlet velocity ranges from 12 m.s–1 to 36 m.s–1. Both the overall efficiency and fractional efficiency of the cyclone were measured as a function of the inlet velocity and operating temperature. It is shown that at the same inlet velocity both the overall efficiency and fractional efficiency decrease with an increase of temperature. An analysis of our own data and published results has shown that the fractional efficiency of a cyclone is a definite function of such dimensionless numbers as Stokes number, Reynolds number, Froude number and dimensionless cyclone inlet area and dimensionless outlet diameter. A nondimensional experimental correlation of the cyclone performance, including the influence of the temperature, was obtained on the basis of our own previous work. The prediction of the influence of temperature on separation efficiencies is in fairly good agreement with experimental results.