Experimental investigation on the effect of pulsating flow on heat transfer and pressure drop in conical tubes

In order to boost the heat transfer rate in a conical coiled tube (CCT) using an active technique, a solenoid valve was placed ahead of the CCT and employed as a pulse generator in this research. Experimentally, the effect of pulsation on heat transfer and pressure drop in the CCT was investigated. Experiments were conducted for pulsating flow throughout a Womersley number (Wo) range of 30-48, which corresponds to a pulsating frequency of 4-10 Hz, a Dean number (De) of 1148-2983, and a coil torsion (lambda) of 0.02-0.052. Results revealed that pulsating flow yields larger Nu values than steady flow. A rise in heat transfer characteristics is achieved by decreasing both the pulse frequency and the coil torsion. A pulsating flow at 4 Hz (Wo = 30) was shown to promote heat transfer by the most of all the examined frequencies. The average Nu increases as De increases, although the friction factor often decreases as De increases. When the coil torsion is reduced from 0.052 to 0.02 while maintaining the same De and Wo, the average Nu and integral increase by 23% and 30%, respectively. A correlation for the average Nusselt number and friction factor was presented, taking frequency and coil torsion into account.