Effect of pitch-to-diameter ratio on the natural convection heat transfer of two vertically aligned horizontal cylinders

Numerical investigation of the laminar natural convection heat transfer from two horizontally attached horizontal cylinders

“…It differs from those previous studies [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] that are restricted to the arrays of cylinders in free space, where the optimal spacing in the arrays must take the volumetric heat transfer into account, rather than simply maximize the value of Nusselt number for the upper cylinders or the whole arrays. Bejan et al [42] proposed a metric for measuring the heat transfer volumetric density to optimize the spacing of a staggered tube bank with the centers of any three consecutive cylinders forming equilateral triangles in a fixed volume.…”

“…In such background, the studies conducted on the effect of their interactions thus also have been a basic work for the heat transfer from cylinders cooling by natural convection over the past several decades. For the case of a pair of or more equal-diameter heated horizontal cylinders arranged in a vertical configuration, there are abundant results to be available [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. A detailed review of these previous literatures is presented by Shyam et al [39], who have numerically analyzed the laminar natural convection heat transfer from a pair of horizontal cylinders aligned vertically in power-law fluids, spanning the range of Grashof number from 10 to 10 4 , the Prandtl number ranging from 0.72 to 100, the center-to-center separation distances as 2 6 S=D 6 20, and the power-low index 0:3 6 n 6 1:5, where the values for n < 1 correspond to the shear-thinning fluids, n ¼ 1 represents the Newtonian behavior, whereas n > 1 is the shear-thickening fluids.…”

The influence of tip clearance and Prandtl number on turbulent forced convection heat transfer of rectangular fins

“…When compared with temperature measurement, this technique is attractive as it provides a simple, cheap, and accurate measurement method through measurement of the electric current [11,12]. This technique was developed by several researchers [13][14][15][16] and the methodology has been tested to various flow conditions such as forced, natural, and mixed convection [17][18][19][20][21][22][23] and now is well-established. Nusselt number would depend on all three numbers: Pr, Re and Ra.…”

Numerical Simulation of Unsteady Natural Convection from Heated Horizontal Circular Cylinders in a Square Enclosure

“…Their results showed that the fluid flow and heat transfer around the upper heated cylinder were strongly affected by the presence of the heated lower cylinder, because a plume rising from the heated lower cylinder interacted with the heated upper cylinder. Another experimental investigation on the natural convection heat transfer for two parallel horizontal cylinders was carried out by Chae and Chung [21]. They measured the mass transfer rate from the cylinders and obtained the heat transfer rate (Nusselt number) based on the analogy concept by changing various parameters including pitch-to-diameter ratios (P=D) (1.02-9.00), Prandtl numbers (2,014-8,334), and Rayleigh numbers (7.3 Â 10 7 to 4.5 Â 10 10 ).…”