Numerical Study of Heated Tube Arrays in the Laminar Free Convection Heat Transfer

Abstract

Laminar free convection heat transfer from a heated cylinder and tube arrays is studied numerically to obtain the local and average Nusselt numbers. To verify the numerical simulations, the Nusselt numbers for a single cylinder were compared to other authors for the Rayleigh numbers of 103 and 104. Furthermore, the vertically arranged heated tube arrays 4 × 1 and 4 × 2 with the tube ratio spacing SV/D = 2 were considered, and obtained average Nusselt numbers were compared to the existing correlating equations. A good agreement of the average Nusselt numbers for the single cylinder and the bottom tube of the 4 × 1 tube array is proved. On the other hand, the bottom tubes of the 4 × 2 tube array affect each other, and the Nusselt numbers have a different course compared to the single cylinder. The temperature fields for the tube array 4 × 4 in basic, concave, and convex configurations are studied, and new correlating equations were determined. The simulations were done for the Rayleigh numbers in the range of 1.3 × 104 to 3.7 × 104 with a tube ratio spacing S/D of 2, 2.5, and 3. On the basis of the results, the average Nusselt numbers increase with the Rayleigh numbers and tube spacing increasing. The average Nusselt number and total heat flux density for the convex configuration increase compared to the base one; on the other hand, the average Nusselt number decreases for the concave one. The results are applicable to the tube heaters constructional design in order to heat the ambient air effectively.

Impact of grooved cylinder on heat transfer by natural convection in cylindrical geometry

“…Furthermore, several research works have proved that the number of heated cylinders and their positions in the cavity have an important effect on the convective heat transfer rate. 18–24 Corcione 18 studied natural convection heat transfer from a vertical array of isothermal cylinders. The author found that the bottom cylinder exchanges the same amount of heat of single cylinder.…”

“…Brodnianská and Kotšmíd 22 studied the convective heat transfer from a tube array of 4 × 4 cylinders in basic, concave and convex configurations. The highest heat transfer rate was found at the convex configuration.…”

Experimental performance comparison between circular and elliptical tubes in evaporative condensers

“…Recently, Brodnianská and Kotšmíd [22] have studied numerically the heat transfer from a heated cylinder and tube arrays to obtain the local and average Nusselt numbers. The heated tubes have been arranged in arrays 4 × 1 and 4 × 2 with the tube ratio spacing SV/D = 2.…”

Numerical Simulation of Convective-Radiative Heat Transfer

“…This Special Issue consists of thirteen articles dedicated to convective stagnation point flows [1,2], non-Newtonian fluid heat transfer [3,4], fin efficiency [5], bubbly flow and heat transfer [6,7], cooling of heated elements [8,9], phase change materials application [10], vortex heat transfer enhancement [11], flow and heat transfer in engineering systems [12,13]. Moreover, numerical analysis in these mentioned papers [1][2][3][4][5][6][7][8][9][10][11][12][13] has been performed using MATLAB software [1][2][3]6,13], ANSYS software [5,9,12,13], COMSOL software [10] and using developed in-house computational codes [4,7,8,11].…”

“…The performed analysis has demonstrated that the total energy transport can be augmented by growth of the surface emissivity. Brodnianska and Kotsmıd [9] have examined numerically laminar natural convection of air from the heated horizontal tubes in a two-dimensional space. Using the ANSYS Fluent software, authors have obtained new correlating equations for the average Nusselt number illustrating a growth of the average Nusselt number with Rayleigh number and general tube ratio spacing.…”