scholarly journals NATURAL CONVECTION IN A HORIZONTAL WATER LAYER WITH MAXIMUM DENSITY AT 4°C

2021 ◽  
Vol 24 (1) ◽  
pp. 1-18
Author(s):  
M. Sugawara ◽  
M. Tago
Keyword(s):  
Natural Convection ◽  
Water Layer ◽  
Maximum Density

Natural Convection in a Horizontal Layer of Water Cooled From Above to Near Freezing

1975 ◽  
Vol 97 (1) ◽  
pp. 47-53 ◽  
Author(s):  
R. E. Forbes ◽  
J. W. Cooper
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Natural Convection ◽  
Hydrodynamic Instability ◽  
Convective Heat Transfer Coefficient ◽  
Free Water ◽  
Ambient Air ◽  
Maximum Density ◽  
Surface Boundary ◽  
Initial Water

Natural convection in horizontal layers of water cooled from above to near freezing was studied analytically. The water was confined laterally and underneath by rigid insulators, and the upper horizontal surface was subjected to: (1) a constant 0C temperature, rigid conducting boundary, and (2) a free, water to air convection boundary condition, in which the convective heat transfer coefficient was held constant at values of 5.68 W/m2 · K and 284 W/m2 · K (1.0 and 50.0 Btu/hr ft2F) and the temperature of the ambient air was maintained at 0C. The ratios of the width to the depth of the rectangular water layers under consideration were W/D = 1, 3, and 6. Initially the water is assumed to be at a uniform temperature of either 4C or 8C, and then the upper surface boundary condition was suddenly applied. It was observed in all cases for which the initial water temperature was 4C, that the water remained stagnant and became thermally stratified. Heat transfer application of either of the surface boundary conditions to water initially at 8C produced large convective eddies extending from the bottom to the top of the layer of water. As the liquid layer cooled further, two distinct horizontal regions appeared, the 4C isothermal line separating the two. This produces a region of hydrodynamic instability in the fluid since the maximum density fluid (4C) is physically located above the less dense fluid in the lower portion of the cavity. The large eddies which appeared initially were confined to the hydrodynamically unstable region bounded by the 4C isotherm and the bottom of the cavity. The action of viscous shearing forces upon the stable water above the 4C isotherm produced a second “layer” of eddies. An alternating direction implicit finite difference method was used to solve the coupled system of partial differential equations. The paper presents transient isotherms and streamlines and a discussion of the effect of maximum density on the flow patterns.

An Experimental Study of Natural Convection in an Inclined Rectangular Cavity Filled With Water at Its Density Extremum

1984 ◽  
Vol 106 (1) ◽  
pp. 109-115 ◽  
Author(s):  
H. Inaba ◽  
T. Fukuda
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Water Layer ◽  
Flow Patterns ◽  
Maximum Density ◽  
Rectangular Cavity ◽  
Density Inversion ◽  
Different Temperatures ◽  
Inclination Angles

An experimental investigation pertaining to the effect of the density inversion of water on steady natural convective flow patterns and heat transfer in an inclined rectangular cavity whose two opposing walls are kept at different temperatures is carried out. Water as a testing fluid has its maximum density at about 4 °C. The temperature of one wall is maintained at 0 °C, while that of the opposing hot wall is varied from 2 to 20 °C. Photographs of the flow patterns, temperature distribution in the water layer, and average Nusselt number are presented under various hot wall temperatures and inclination angles of the cavity. The present results could indicate that the density inversion of water has an influential effect on the natural convective heat transfer in the prescribed water layer. Moreover, the average Nusselt number is a peculiar function of the temperature difference between the cold and hot walls and inclination angle, unlike the previous results for common fluids without density inversion.

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