دانلود رایگان مقاله انگلیسی بهینه سازی مبدل حرارتی لوله مارپیچ پیپ دوتایی و مقایسه آن با مبدل حرارتی لوله راست دوتایی- اشپرینگر 2017

Abstract

Optimization of double pipe helical coil heat exchanger with various optimizing parameters and its comparison with double pipe straight tube are the prime objectives of this paper. Numerical studies were performed with the aid of a commercial computational fluid dynamics package ANSYS FLUENT 14. In this paper the double pipe helical coil is analysed under turbulent flow conditions for optimum heat exchanger properties. The parameters used for optimization are cross-sectional shape and taper angles. Optimization analysis is being carried out for finding best cross sectional shape of heat exchanger coils by using rectangular, square, triangular and circular crosssections. The tapered double pipe helical coil is then analysed for best heat transfer and pressure drop characteristics by varying the angle of taper. Finally, an optimum coil on the basis of all the analysis is selected. This optimized double pipe helical coil is compared with double pipe straight tube of equivalent cross-sectional area and length as that of unwounded length of double pipe helical coil.

Conclusions

Simulations are carried out for finding out optimum crosssectional shape for double pipe helical coil using 4 shapes which are circular, rectangular, triangular, and square. It was found that rectangular cross-section was having best heat transfer properties followed by triangular, square and circular. But pressure drop was highest for rectangular shape and least for circular shape. Various simulations are carried out for finding out how the taper angle on helical coil influences heat transfer and pressure drop properties. It was found that as the coil taper angle increases, the heat transfer rate increases considerably, while pressure drop also increases with taper angle. After carrying out various simulations for finding out optimum coil, it was found out that a rectangular crosssection coil (Fig. 12) with maximum possible taper angle can give best heat transfer characteristics. The extent of taper angle is limited by coil length increase which would demand more space, and also the pressure drop and pumping power. This rectangular cross-section coil with a fixed taper angle of 30 is used for comparison with double pipe straight tube. It was observed that heat transfer in the optimized helical coil was nearly twice more than that of straight tube. The friction factor was higher in the helical coil than straight tube which implies more pumping power requirement for helical coil.