Natural Convection Heat Transfer From a Horizontal Cylinder Between Vertical Confining Adiabatic Walls

Abstract

This paper reports an experimental study of natural convection heat transfer from a horizontal isothermal cylinder between vertical adiabatic walls. Some of the industrial applications of this problem are cooling and casing design of electronic equipment, nuclear reactor safety, and heat extraction from solar thermal storage devices. Heat transfer from 3.81 cm and 2.54 cm diameter cylinders was determined by measuring the electric power supplied to the heater, which was placed inside the cylinders, and correcting for radiation and end losses. Average Nusselt numbers were determined for a Rayleigh number range of 2 × 103 to 3 × 105 and wall spacing to cylinder diameter ratios of 1.5, 2, 3, 4, 6, 8, 10, 12, and ∞. It was found that the confinement of a heated horizontal cylinder by adiabatic walls enhances the heat transfer from the cylinder continuously. This effect is more pronounced at low Rayleigh numbers. A maximum relative enhancement of 45 percent was obtained over the range of experimental conditions studied. Schlieren and flow visualization studies were conducted at selected values of Rayleigh number and wall spacing to cylinder diameter ratios to further explain the heat transfer characteristics and the associated flow physics of the present problem.

An experimental investigation on the effect of a perforated fin on free convection heat transfer from a confined horizontal cylinder

“…This enhancement occurred at minimum wall spacing equal to 1.5 times the cylinder diameter. Similar results were obtained by Karim et al [4], who investigated the natural convection from a horizontal isothermal cylinder confined between vertical adiabatic walls situated at the midheight of walls. The height of walls and the wall spacing varied from 32 to 48 cylinder diameters and from 1.5 times the cylinder diameter to infinity, respectively.…”

Optimum natural convection from square cylinder in vertical channel

“…In Marsters (1975), the enhancement of average Nusselt number for a single isothermal cylinder between two aluminum walls in comparison with the case of free space positioning was observed even for quite large wall spacing. Enhancements up to 40% and 45% were reported for a single isothermal cylinder confined with two adiabatic walls by Sparrow and Pfeil (1984) and Karim et al, 1986), respectively. The enhancement was found to be accentuated as the internal wall spacing was decreased and as the channel height was increased.…”

Natural convection heat transfer from two horizontal cylinders at high Rayleigh numbers

“…The test tank is made of Plexiglas, 1200 mm  1200 mm  2000 mm W/L/H, which is sufficiently large to emulate an array of unconfined cylinders, see Grafsrønningen et al [14] and Karim et al [16]. The PIV setup consisted of a b/w 14bit PCO.4000 in conjunction with a Quantel Twins BSL220 with an output energy of $220 mJ per pulse.…”