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Augmentation of heat transfer and pressure drop during laminar flow of oil inside one smooth tube and seven wire-coil inserted tubes of varying wire diameter and
pitch have been investigated experimentally. The experimental set-up which was used in this investigation was an oil system equipped with all necessary instruments. The heater of this system was a double pipe counter flow heat exchanger in which oil is heated inside inner tube by the steam flowing in the annulus. All together 120 test runs with various flow rates were performed for plain and roughed tubes (tubes with coiled wire inserts). Results show that increase in the friction factor is comparatively low at lower Reynolds number and at higher values it is very large due to some induced turbulence. Also heat transfer coefficients of tubes with coiled wire insert are significantly higher than
plain tube and it is a function of Reynolds
number, helix angle and Prandtl number.
The maximum obtained enhancement in heat transfer coefficient was as high as 230 percent.
On the basis of the experimental data of
this investigation, a correlation was developed for predicting of heat transfer coefficient during heating of oil flowing inside tubes with coiled wire inserts. The heat transfer coefficients calculated by this correlation were within :1:20% of the experimental values for most of the data. So there is a good compliance between this correlation and experimental values.