scholarly journals Natural Convection Heat Transfer from Heated Horizontal Cylinders with Thermal Stratification and Circular Flow in Enclosure.

1998 ◽  
Vol 64 (623) ◽  
pp. 2294-2302
Author(s):  
Shinji KUBO ◽  
Norio AKINO ◽  
Amane TANAKA ◽  
Toshiyuki KAMEOKA ◽  
Yuuki OKADA
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Thermal Stratification ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Circular Flow ◽  
Horizontal Cylinders

Natural Convection From Horizontal Helicoidal Pipes

2000 ◽  
Author(s):  
Hamed Al-Ahmadi ◽  
Ahmad Fakheri
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Characteristic Length ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Coil Diameter ◽  
Horizontal Cylinders ◽  
High Degree ◽  
Rayleigh Numbers

Abstract Natural convection heat transfer from a horizontal helicoidal pipe is experimentally investigated for different coil-pitches. A modified characteristic length incorporating the tube diameter, the coil diameter, and the coil spacing, is proposed as the relevant scale for defining Nusselt and Rayleigh numbers. Using the proposed characteristic length, it is shown that the Nusselt number for horizontal helicoidal pipes can be determined using the available Nusselt versus Rayleigh number correlation for straight horizontal cylinders with high degree of accuracy over the range of the experimental data.

An Experimental Apparatus to Investigate Natural Convection Heat Transfer From a Vertical Array of Isothermal Horizontal Cylinders

2010 ◽  
Author(s):  
S¸evket O¨zgu¨r Atayılmaz ◽  
Hakan Demir ◽  
O¨zden Ag˘ra ◽  
I˙smail Teke
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Vertical Array ◽  
Transfer Rates ◽  
Surface Temperatures ◽  
Experimental Apparatus ◽  
Horizontal Cylinders

Steady natural convection heat transfer from vertical array of equally-spaced isothermal horizontal cylinders has been investigated experimentally and numerically. Experimental study was carried out at different ambient temperatures in a conditioned room which can be maintained at a stable required value and inside a sufficiently designed test cabin. The ambient and cylinders’ surface temperatures varied 20°C to 30°C and 30°C to 60°C respectively. The experimental apparatus was designed to adjust different operating parameters such as number of cylinders, cylinders’ surface temperatures, distance between the cylinders and environmental temperature. Each cylinder surface temperature can be accurately adjusted to the desired temperature by means of specially designed measurement and control system. Copper test cylinders have length of 1 m and outer diameter of 4.8 mm. The uncertainty analysis method proposed by Kline and McClintock was used and explained elaborately. Detailed information and algorithm of numerical method are given to ease the understanding of the numerical part of the study. The problem was solved numerically by means of a CFD program in 2D. Average Nusselt numbers are given based on the experimental data for single and each two horizontal cylinders. Heat transfer rates obtained from experimental and numerical studies for upper and lower cylinders were compared with each other. The deviation of experimental and numerical heat transfer rates are in a good agreement and stay in the range ± 20%. It is seen that heat transfer from the lower cylinder is close to the single cylinder case. However, higher temperature of the passing air reduces the heat transfer from the upper cylinder for S/D = 2.

Natural Convection Heat Transfer From a Short or Long, Solid or Hollow Horizontal Cylinder Suspended in Air or Placed on Ground

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Swastik Acharya ◽  
Sukanta K Dash
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Hollow Cylinder ◽  
Convection Heat Transfer ◽  
Horizontal Cylinder ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Solid Cylinder ◽  
D 20 ◽  
Horizontal Cylinders

Numerical simulations have been conducted to study natural convection heat transfer from solid or hollow cylinders in the laminar range of Ra spanning from 104 to 108 for L/D in the range of 0.05≤(L/D)≤20. Interesting flow structures around the thin hollow cylinder have been observed for small and large L/D. It has been found that the average Nu for solid or hollow horizontal cylinders in air is marginally higher than when they are on ground for the entire range of L/D and Ra limited up to 107. Up to a Ra of 107 Nu for a solid cylinder in air is higher than that of Nu for a hollow cylinder in air but when Ra exceeds 107 Nu for a hollow cylinder is marginally higher than that of the solid cylinder until an L/D of 0.2. When, L/D rises beyond 0.2 the situation reveres causing Nu for a solid cylinder to be again higher than that of the hollow cylinder when suspended in air. A solid cylinder on ground has higher Nu compared to that of a hollow cylinder on ground up to a Ra of 106. However, for higher Ra of 108 a hollow cylinder on ground has higher Nu compared to that of a solid cylinder on ground until an L/D of 5 and after that the situation reverses again.

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