Abstract
The present work experimental and numerical investigations have been carried out to study friction factor and heat transfer characteristics of twisted square ducts. Experiments were conducted for different velocities of air under constant heat flux condition, twist ratio is equal to 6.12 and also Reynolds number varied from 8000 to 30000. The experimental analysis has been carried out and the experimentation is completely based upon design of experiments to get the optimum heat transfer rate and minimize pressure drop. The results of friction factor, Nusselt number and thermal performance factor are presented. Twisted square duct shows relatively higher heat transfer and optimum pressure drop compared to plain square duct. The experimental results shows that Nusselt number for the twisted square duct is about 1.89 times above that for the plain square duct while friction factor is 2.29 times higher (f/fo= 2.29). Thermal performance (enhancement ratio) of the twisted square duct is 1.41. In this work Numeric simulations were calculated by using the CFD software package ANSYS 18.2 FLUENT has been used. Heat transfer and numerical flow behaviors such as temperature, friction factor contours of the are also reported. Hence it is concluded that square duct with twist ratio 6.12 gives highest heat transfer and thermal performance due to lowest friction loss indicating promising device of the twisted square duct.
Highlights
Non circular cross section of ducts are extensively used in many heat exchangers
The experimental results of Nusselt number and friction factor of the present plain Square duct are compared with those from correlations of Dittus–Boelter, Blasius and Petukhov found for turbulent flow in ducts
The heat transfer coefficient increased with Reynolds number increases in twisted square duct and Te highest heat transfer coefficient is obtained at velocity of air flow is equal to 8.6 m/sec
Summary
Non circular cross section of ducts are extensively used in many heat exchangers. Generally, design of any industrial process plants is influenced by need for optimum utilization of energy as effective usage of heat for economic design and operation. The need for effective utilization and recovery of heat has been prompted the development of various heat transfer enhancement techniques for heat exchangers. Augmentation techniques increase convective heat transfer by reducing thermal resistance in heat exchanger. Amar RajSingh Suri [1] studied heat transfer and fluid flow behaviors of multiple square perforated twisted tapes in heat exchanger. The experimental investigations are carried out at twist ratio of 2.5 , Reynolds number varied from 5000 to 27000. And numerically investigations analysis has carriedout for three twisted square ducts with uniform cross section, divergent cross section and convergent cross section along the duct length. It was concluded that for range of parameter studied divergent duct always enhance heat transfer, convergent duct always deteriorate heat transfer and straight duct may enhance or deteriorate performance depending upon comparison conditions
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