Natural Convection Heat Transfer of Water Within a Horizontal Cylindrical Annulus With Density Inversion Effects

1983 ◽  
Vol 105 (1) ◽  
pp. 117-123 ◽  
Author(s):  
P. Vasseur ◽  
L. Robillard ◽  
B. Chandra Shekar
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Cold Water ◽  
Freezing Point ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Density Inversion ◽  
Cylindrical Annulus

The effect of density inversion on steady natural convection heat transfer of cold water, between two horizontal concentric cylinders of gap width, L, is studied numerically. Water near its freezing point is characterized by a density maximum at 4°C. Numerical solutions are obtained for cylinders with nonlinear Rayleigh numbers RA ranging from 2 × 103 to 7.6 × 104, a radius ratio 1.75 ≤ ra ≤ 2.6 and an inversion parameter γ, relating the temperature for maximum density with the cavity wall temperatures, between −2 and 2. The results obtained are presented graphically in the form of streamline and isotherm contour plots. The heat transfer characteristics, velocity profiles, and local and overall Nusselt numbers are studied. The results of the present study were found qualitatively valid when compared with an experimental investigation carried out in the past.

Natural Convection Heat Transfer of Cold Water Within an Eccentric Horizontal Cylindrical Annulus

1988 ◽  
Vol 110 (4a) ◽  
pp. 894-900 ◽  
Author(s):  
C. J. Ho ◽  
Y. H. Lin
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Cold Water ◽  
Convection Heat Transfer ◽  
Orientation Angle ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Density Inversion ◽  
Cylindrical Annulus ◽  
Isothermal Cylinders

Natural convection heat transfer of cold water, encompassing a density inversion, within an eccentric horizontal annulus made of two isothermal cylinders, is numerically studied via a finite difference method. Numerical results have been obtained for an annular radius ratio 2.6 with Rayleigh number ranging from 103 to 106, the inversion parameter being 0.0 to 1.0, the eccentricity varying from 0 to 0.8, and the orientation angle of the inner cylinder between 0 and π. Results indicate that the flow patterns and heat transfer characteristics are strongly influenced by the combined effect induced by the density inversion of water and the position of the inner cylinder of the annulus. For the cases considered in the present study, a minimum in heat transfer arises with the inversion parameter between 0.4 and 0.5 depending primarily on the position of the inner cylinder.

Numerical study of surface radiation and combined natural convection heat transfer in a solar cavity receiver

2017 ◽  
Vol 27 (10) ◽  
pp. 2385-2399 ◽  
Author(s):  
Kamel Milani Shirvan ◽  
Mojtaba Mamourian ◽  
Soroush Mirzakhanlari ◽  
A.B. Rahimi ◽  
R. Ellahi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Numerical Solutions ◽  
Convection Heat Transfer ◽  
Surface Radiation ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Surface Emissivity ◽  
Content Type

Purpose The purpose of this paper is to present the numerical solutions of surface radiation and combined natural convection heat transfer in a solar cavity receiver. The paper aims to discuss sundry issues that take place in the said model. Design/methodology/approach The numerical solutions are developed by means of second-order upwind scheme using the SIMPLE algorithm. Findings The effects of physical factors such as Rayleigh number (104 ≤ Ra ≤ 106), inclination angels of insulated walls (0º ≤ θ ≤ 10º) and the wall surface emissivity (0 ≤ ε ≤ 1) on natural convection-surface radiation heat transfer rate are analyzed. Impact of sundry parameters on flow quantities are discussed and displayed via graphs and tables. Stream lines and isothermal lines have also been drawn in the region of cavity. The numerical results reveal that increasing the Rayleigh number, wall surface emissivity and inclination angels of insulated walls in an open cavity enhances the mean total Nusselt number. The variations of the surface radiation and natural convection heat transfer mean Nusselt numbers are very small to the inclination angle of θ, while a significant change is noted for the case of Rayleigh number and emissivity. Originality/value To the best of authors’ knowledge, this model is reported for the first time.

Experimental Study on Natural Convection Heat Transfer With Density Inversion of Water Between Two Horizontal Concentric Cylinders

1975 ◽  
Vol 97 (4) ◽  
pp. 556-561 ◽  
Author(s):  
N. Seki ◽  
S. Fukusako ◽  
M. Nakaoka
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Nusselt Number ◽  
Natural Convection ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat ◽  
Density Inversion ◽  
Concentric Cylinders

An experimental investigation concerning the effect of density inversion on steady natural convection heat transfer of water between two horizontal concentric cylinders with diameter ratio ranging from 1.18 to 6.39 is carried out. Water, as a testing fluid, has the maximum density at 4°C. Temperature of the inner cylinder is maintained at 0°C, while temperatures of the outer cylinder are varied from 1 to 15°C, with Grashof number ranging from 3.2 × 101 to 2.7 × 105. Photographs and qualitative description of the flow patterns, temperature profiles, local and average Nusselt number are presented. From the present experimental investigation, it is demonstrated that the effect of density inversion is unexpectedly large and the average Nusselt number is a peculiar function of temperature difference between outer and inner cylinder, unlike the previous results on common fluids without density inversion.

Pseudosteady-State Natural Convection Inside Spheres

1975 ◽  
Vol 97 (1) ◽  
pp. 54-59 ◽  
Author(s):  
M. Y. Chow ◽  
R. G. Akins
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Driving Force ◽  
Numerical Solutions ◽  
Convection Heat Transfer ◽  
Flow Patterns ◽  
Natural Convection Heat Transfer ◽  
Constant Flow ◽  
Convection Heat ◽  
Rayleigh Numbers

Natural convection heat transfer to water contained within five different sized spheres was studied. Pseudosteady-state was maintained by keeping the driving force for convection constant, i.e., the temperature outside the sphere was increased steadily so that the temperature difference between the outside and the center remained constant. Flow visualization was used to determine flow patterns within the spheres. Laminar flow was found to exist below Rayleigh numbers of about 107. The flow patterns along with the position of the circulation centers are presented and compared with recent numerical solutions. The overall heat transfer in the laminar region was fitted by least squares and the following correlation obtained: Nu=0.80Ra0.30

Sign in / Sign up

Export Citation Format

Share Document