International Journal of Engineering Research and General Science Volume 2, Issue 3, April-May 2014 ISSN 2091-2730 66 www.ijergs.org Fabrication and Analysis of Tube-In-Tube Helical Coil Heat Exchanger Mrunal P.Kshirsagar 1 , Trupti J. Kansara 1 , Swapnil M. Aher 1 1 Research Scholar, Sinhgad Institute of Technology , sswapnilaher@gmail.com,9881925601 ABSTRACT – Conventional heat exchangers are large in size and heat transfer rate is also less and in conventional heat exchanger dead zone is produce which reduces the heat transfer rate and to create turbulence in conventional heat exchanger some external means is required and the fluid in conventional heat exchanger is not in continuous motion with each other. Tube in tube helical coil heat exchanger provides a compact shape with its geometry offering more fluid contact and eliminating the dead zone, increasing the turbulence and hence the heat transfer rate. An experimental setup is fabricated for the estimation of the heat transfer characteristics. A wire is wounded in the core to increase the turbulence in turn increases the heat transfer rate. The paper deals with the pitch variation of the internal wounded wire and its result on the heat transfer rate. The Reynolds number and Dean number in the annulus was compared to the numerical data. The experimental result was compared with the analytical result which confirmed the validation. This heat exchanger finds its application mostly in food industries and waste heat recovery. Keywords—Tube-in-tube helical coil, Nusselt number, wire wound, Reynold number, Dean number, dead zone, efficiency . 1. INTRODUCTION Several studies have indicated that helically coiled tubes are superior to straight tubes when employed in heat transfer applications. The centrifugal force due to the curvature of the tube results in the development of secondary flows (flows perpendicular to the axial direction) which assist in mixing the fluid and enhance the heat transfer. In straight tube heat exchangers there is little mixing in the laminar flow regime, thus the application of curved tubes in laminar flow heat exchange processes can be highly beneficial. These situations can arise in the food processing industry for the heating and cooling of either highly viscous liquid food, such as pastes or purees, or for products that are sensitive to high shear stresses. Another advantage to using helical coils over straight tubes is that the residence time spread is reduced, allowing helical coils to be used to reduce axial dispersion in tubular reactors. The first attempt has been made by Dean to describe mathematically the flow in a coiled tube. A first approximation of the steady motion of incompressible fluid flowing through a coiled pipe with a circular cross-section is considered in his analysis. It was observed that the reduction in the rate of flow due to curvature depends on a single variable, K, which is equal to 2(Re)2r/R, for low velocities and small r/R ratio. It was then continued for the study of Dean for the laminar flow of fluids with different viscosities through curved pipes with different curvature ratios (δ). The result shows that the onset of turbulence did not depend on the value of the Re or the De. It was concluded that the flow in curved pipes is more stable than flow in straight pipes. It was also studied the resistance to flow as a function of De and Re. There was no difference in flow resistance compared to a straight pipe for values of De less than 14.6. Figure 1.1: Diagram of helical coil