Open Access

ARTICLE

NUMERICAL AND EXPERIMENTAL RESEARCH IN HEAT TRANSFER TO SCREW COMPRESSOR ROTORS*

Nikola Stosic^**, Ian K. Smith, Ahmed Kovacevic

Centre for Positive Displacement Compressor Technology, City University, London EC1V OHB, U.K.
* Parts of this paper have been presented in IMECE2004-60561 at 2004 ASME Congress, Anaheim, California. A permission to publish its parts in Frontiers in Heat and Mass Transfer was granted by ASME.
** Corresponding author. E-mail: n.stosic@city.ac.uk

Frontiers in Heat and Mass Transfer 2012, 3(2), 1-7. https://doi.org/10.5098/hmt.v3.2.3003

Abstract

Due to fast rotation of screw compressor rotors, temperature is uniform in the rotor cross section and temperature field is a function of the axial coordinate only. Apart of that the rotors in one cross section the rotors are simultaneously heated by hot gas on one side while cooled at another side by cold gas. As a result of identification of the main modes of heat transfer both in the rotors and between the rotors and their surroundings and the relative significance of each, a novel procedure is suggested to cool the rotors by injection of minute quantities of a volatile fluid. By this means the compressed gas should attain higher temperatures without rotor distortion. To confirm these concepts and quantify both the heat transfer rates and the rate of liquid injection required for rotor cooling, both a one dimensional flow study and a more complex 3-D numerical analysis were performed, the latter with the aid of a CFD code. The results indicated that the rotors could be maintained at a far lower temperature than that of the discharged gas by flash evaporative cooling, as a result of injecting a fractional percentage by mass of a volatile fluid. This was confirmed by experiment. This technique may be used to operate dry compressors at substantially higher pressure ratios than are currently possible in such machines. It is also shown that only minor design changes are needed to implement it.

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