**ABSTRACT**

The heat transfer and pressure drop analysis of conical coil heat exchanger with various tube diameters, fluid flow rates, and cone angles is presented in this paper. Fifteen coils of cone angles 180° (horizontal spiral), 135°, 90°, 45°, and 0° (vertical helical) are fabricated and analysed with, same average coil diameter, and tube length, with three different tube diameters. The experimentation is carried out with hot and cold water of flow rate 10 to 100 L per hour (Reynolds range 500 to 5000), and 30 to 90 L per hour, respectively. The temperatures and pressure drop across the heat exchanger are recorded at different mass flow rates of cold and hot fluid. The various parameters: heat transfer coefficient, Nusselt number, effectiveness, and friction factor, are estimated using the temperature, mass flow rate, and pressure drop across the heat exchanger. The analysis indicates that, Nusselt number and friction factor are function of flow rate, tube diameter, cone angle, and curvature ratio. Increase in tube side flow rate increases Nusselt number, whereas it reduces with increase in shell side flow rate. Increase in cone angle and tube diameter, reduces Nusselt number. The effects of cone angle, tube diameter, and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.

**KEYWORDS**

PAPER SUBMITTED: 2014-08-02

PAPER REVISED: 2014-11-28

PAPER ACCEPTED: 2014-11-28

PUBLISHED ONLINE: 2014-12-14

**THERMAL SCIENCE** YEAR

**2016**, VOLUME

**20**, ISSUE

**Issue 6**, PAGES [2087 - 2099]

- Naphon, P., and Wongwises, S., A review of flow and heat transfer characteristics in curved tubes, Renewable Sustainable Energy, Rev 10 (2006) pp 463-490.
- James R. Lines, Helically Coiled Heat Exchangers offers advantages, Bulletin HHE-30, Graham Manufacturing Co.
- Acharya, N., Sen, M., and H. C., Chang, Analysis of heat transfer enhancement in coiled-tube heat exchangers, International Journal of Heat and Mass Transfer, Vol. 44 (2001) pp. 3189-3199.
- Prabhanjan, D.G., Raghavan, G.S.V., and Rennie, T.J., Comparison of heat transfer rates between a straight tube heat exchanger and a helically coiled heat exchanger, International Communication of Heat and Mass Transfer, Vol. 29 (2002) 2, pp 185-191.
- Dravid, A. N., Smith., K. A., Merrill, E.A., and Brian, P.L.T., Effect of secondary fluid motion on laminar flow heat transfer in helically coiled tubes, AIChE Journal, Vol. 17 (1971) 5, pp. 1114-1122.
- Naphon, Paisarn, Jamnean Suwagrai, Effect of curvature ratios on the heat transfer and flow developments in the horizontal spirally coiled tubes, International Journal of Heat and Mass Transfer, Vol. 50 (2007), pp. 444-451
- H., Shokouhmand, M.R., Salimpour, M.A., Akhavan-Behabadi, Experimental investigation of shell and coiled tube heat exchangers using Wilson plots, International communications of Heat and Mass Transfer, 35 (2008) 84-92, 2008
- J.S. Jayakumar, S.M. Mahajani, J.C. Mandal, Kannan N. Iyer, P.K. Vijayan, CFD analysis of single-phase flows inside helically coiled tubes, Computers and Chemical Engineering, 34 (2010) pp. 430-446.
- Salimpour, M.R., Heat transfer coefficients of shell and coiled tube heat exchangers, Experimental Thermal and Fluid Science, Vol. 33, (2009) pp. 203-207.
- Paisarn Naphon, Somchai Wangwies, A experimental study on in-tube convective heat transfer coefficient in spiral coil heat exchanger, International Communications in Heat and Mass Transfer, Vol. 29 (2002) 6, pp. 797-809.
- C.E., Kalb, J.D., Seader, Fully developed viscous-flow heat transfer in curved circular tubes with uniform wall temperature, AIChE Journal, 20 (1971) pp. 340-346.
- R.C., Xin, M.A., Ebadian, The effects of Prandtl numbers on local and average convective heat transfer characteristics in helical pipes, Journal of Heat Transfer, 119, (1997) pp. 463-473.
- Y., Cengiz, B. Yasar, P., Dursun, Heat transfer and pressure drops in a heat exchanger with a helical pipe containing inside springs, Energy Conversion and Management, 38 (1997) pp. 619-624.
- N. Jamshidi, M. Farhadi, D.D. Ganji, K. Sedighi, Experimental analysis of heat transfer enhancement in shell and helical tube heat exchangers, Applied Thermal Engineering, 51 (2013), pp. 644-652.
- Xing Lu, Xueping Du, Min Zeng, Sen Zhang, Qiuwang Wang, Shell-side thermal-hydraulic performances of multilayer spiral-bound heat exchangers under different wall thermal boundary conditions, Applied Thermal Engineering, 70 (2014) pp 1216-1227.
- F. P., Incropera, D.P., Dewitt, Fundamentals of Heat and Mass Transfer, fourth ed., Wiley, New York, 1996.
- P. Bharadwaj, A.D. Khondge, A.W. Date, Heat transfer and pressure drop in a spirally grooved tube with twisted tape insert, International Journal of Heat and Mass Transfer, 52 (2009) pp. 1938-1944.
- H.W., Coleman, W.G., Steele, Experimental and Uncertainty Analysis for Engineers, Wiley, New York, 1989.
- ANSI/ASME, Measurement uncertainty, PTC 19, pp. 1-1985, 1986.
- N. Kannadasan, K. Ramanathan, S. Suresh, Comparison of heat transfer and pressure drop in horizontal and vertical helically coiled heat exchanger with CuO / water based nano fluids, Experimental Thermal and Fluid Science, 42 (2012), pp 64-70.
- N. Ghorbani, et al., An experimental study of thermal performance of shell-and-coil heat exchangers, International Communications in Heat and Mass Transfer (2010) doi:10.1016/j.icheatmasstransfer.2010.02.001
- N. Ghorbani , H. Taherian , M. Gorji , H. Mirgolbabaei , Experimental study of mixed convection heat transfer in vertical helically coiled heat exchanger, Experimental Thermal and Fluid Science, 34 (2010) pp. 900-905.
- N. Jamshidi, M. Farhadi*, D.D. Ganji, K. Sedighi, Experimental analysis of heat transfer enhancement in shell and helical tube heat exchangers, Applied Thermal Engineering, 51 (2013) pp. 644-652.
- H. Ito, Friction factors for turbulent flow in curved pipes, Transactions of ASME, Journal of Basic Engineering, 81(1959) pp. 123-132.
- P.S. Srinivsan, S.S. Nandapurkar, F. Holland, A friction factors for coils, Transactions of the Institution of Chemical Engineers, 48 (1970) pp. 156-161.