Experimental investigation of natural convection heat transfer in a helicaled coiled pipe

الملخص EN

The research presents an experimental investigation on the steady state natural convection heat transfer for helical coiled pipes with a vertical orientation.

Water is used as the working fluid for both the target fluid and the bath medium.

The heat transfer characteristics have been studied for three helical coils that having three curvature ratio (0.056, 0.0625, and 0.115) and three coil pitches (12.5, 25, and 37.5)mm with a volume flow rate of the target fluid ranges (10-25)L/min and two constant bath water temperatures (70 and 90)oC.

All the experiments were performed for Rayleigh number range (1.76*109 – 1.15*1012).

The experimental data have been used in SPSS software to predicted the empirical correlation of outside Nusselt number as a function of Rayleigh number by using height of the coil as a characteristic length then using this empirical relation in a computer program that have written in Fortran 90 to predict the outlet temperature and compared with the measured one.

The results show that the inner and outer heat transfer coefficients increase with increasing of curvature ratio (d/D) and the mass flow rate.

Also the results show that the difference between the measured and predicted outlet temperature equal to 1.5oC.