Numerical and Experimental Research in Heat Transfer to Screw Compressor Rotors

Due to fast rotation of screw compressor rotors, temperature is uniform in a cross section and temperature field is a function of the axial coordinate only. 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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Estimation and Control of Heat Transfer in Screw Compressor Rotors

Advanced Energy Systems ◽

10.1115/imece2004-60516 ◽

2004 ◽

Cited By ~ 2

Author(s):

N. Stosic ◽

I. K. Smith ◽

A. Kovacevic

Keyword(s):

Heat Transfer ◽

Relative Significance ◽

Transfer Rates ◽

Design Changes ◽

Liquid Injection ◽

Compressed Gas ◽

Estimation And Control ◽

Lower Temperature ◽

Oil Injection ◽

And Control

Stage pressure ratios in screw compressors, operating without oil injection, are limited by deformation of the rotors, caused by the temperature rise of the compressed gas. Rotor cooling would reduce this restriction. 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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Performance analysis of screw compressors – numerical simulation and experimental verification

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406211417961 ◽

2011 ◽

Vol 226 (4) ◽

pp. 968-980 ◽

Cited By ~ 2

Author(s):

S H Hsieh ◽

Y C Shih ◽

W-H Hsieh ◽

F Y Lin ◽

M J Tsai

Keyword(s):

Heat Transfer ◽

Screw Compressor ◽

Pressure Curve ◽

Discharge Process ◽

Transfer Rates ◽

Outlet Port ◽

Total Process ◽

The Difference ◽

Verification Process ◽

Empirical Constants

This article describes a theoretical model and computer program for calculating the pressure–volume ( PV ) diagram and the efficiency of an oil-injected screw compressor. The proposed model considers the mass and energy conservation laws, the heat transfer between air and oil, the leakages through various paths, and the discharges of air and oil. The proposed program, which uses seven empirical constants to account for the difference between the flow and the heat-transfer rates in the screw compressor and those estimated by available correlations, solves for the efficiency and the pressure curve of the compressed air. A systematic methodology for the determination of the seven empirical constants is presented in this article. Optimization is carried out to determine the seven empirical constants. With the empirical constants, which are determined with four sets of experiments, the maximum difference between the calculated and measured results in the training process, the verification process and the total process is 2.0 per cent for the volumetric and isentropic efficiencies and 5 per cent for the pressure curve. In the discharge process, the pressure in the compression chamber is noted to be affected by the area of the outlet port and the pressure in the neighbouring chambers.

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Numerical investigation on mass and heat transfer in an ammonia oil-free twin-screw compressor with liquid injection

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2017.06.007 ◽

2017 ◽

Vol 120 ◽

pp. 175-184 ◽

Cited By ~ 6

Author(s):

Yafen Tian ◽

Hao Yuan ◽

Chuang Wang ◽

Huagen Wu ◽

Ziwen Xing

Keyword(s):

Heat Transfer ◽

Numerical Investigation ◽

Screw Compressor ◽

Liquid Injection ◽

Twin Screw ◽

Mass And Heat Transfer

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Flow Field Around Dimpled Pin-Fins in a Staggered Array

Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B ◽

10.1115/imece2011-63485 ◽

2011 ◽

Author(s):

R. K. Nagar ◽

J. P. Meyer ◽

Md. MahbubAlam ◽

G. Spedding

Keyword(s):

Heat Transfer ◽

Cross Section ◽

Turbine Blades ◽

Circular Cross Section ◽

Enhanced Heat Transfer ◽

Enhance Heat Transfer ◽

Transfer Rates ◽

Pin Fin ◽

Low Aspect Ratio ◽

Pin Fins

Pin fins are low aspect ratio rods of circular cross section that are used to enhance heat transfer inside turbine blades. Although modifying the basic circular geometry with numerous shallow depressions (dimples) has been linked with enhanced heat transfer rates, the fluid mechanical mechanisms have remained speculative. Here we investigate numerically the effects of dimples onthe mean and turbulence velocities that lead to increased heat transfer. It has been found that dimples result in an increased turbulence intensity which may possess a greater potential to extract and transport more heat from the pin-fin.

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Experiments on a Crossflow Heat Exchanger With Tubes of Lenticular Shape

Journal of Heat Transfer ◽

10.1115/1.3245623 ◽

1983 ◽

Vol 105 (3) ◽

pp. 571-575 ◽

Cited By ~ 20

Author(s):

E. K. Ruth

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Cross Section ◽

Reynolds Numbers ◽

Transfer Rates ◽

Tube Heat Exchanger ◽

Pressure Losses ◽

Circular Tubes

Measurements of pressure losses and heat transfer rates were made for an unconventional crossflow heat exchanger with tubes of lenticular cross section so spaced to reduce variation in the velocity of the fluid outside the tubes, thus reducing separation and drag. The results of these experiments are reported for various tube spacing and demonstrate that the performance of the lenticular tube heat exchanger is superior to that of conventional circular tubes by 20 percent at Reynolds numbers of 20,000 to 50,000.

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