Heat Transfer Characteristics of Insulation Materials Available in Kuwait

1987 ◽  
Vol 11 (1) ◽  
pp. 53-57
Author(s):  
Adnan M. Waked
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Heat Flow ◽  
Heat Transfer Characteristics ◽  
Insulation Materials ◽  
Transfer Characteristics ◽  
High Thermal Diffusivity ◽  
Flow Through

Several insulation materials are being used in the construction of buildings in Kuwait. In this work the heat transfer characteristics of these insulation materials are being studied. It has been shown that the thermal diffusivity (α) of the insulation materials will significantly influence the characteristics of the heat flow through the material. The results show that materials with high thermal diffusivity, mainly materials with low densities, will have higher peak heat transfer loads than those of higher densities. Thus, the lower the value of (α) the better heat transfer characteristics the material will have.

Validation and Development of DNS Database for Low Prandtl Numbers in Rod Bundle

2019 ◽  
Author(s):  
Jonathan K. Lai ◽  
Elia Merzari ◽  
Yassin A. Hassan ◽  
Aleksandr Obabko
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Prandtl Number ◽  
Liquid Metals ◽  
Heat Transfer Characteristics ◽  
Reynolds Analogy ◽  
Transfer Characteristics ◽  
Rod Bundle ◽  
High Thermal Diffusivity ◽  
Prandtl Numbers

Abstract Difficulty in capturing heat transfer characteristics for liquid metals is commonplace because of their low molecular Prandtl number (Pr). Since these fluids have very high thermal diffusivity, the Reynolds analogy is not valid and creates modeling difficulties when assuming a turbulent Prandtl number (Prt) of near unity. Baseline problems have used direct numerical simulations (DNS) for the channel flow and backward facing step to aid in developing a correlation for Prt. More complex physics need to be considered, however, since correlation accuracy is limited. A tight lattice square rod bundle has been chosen for DNS benchmarking because of its presence of flow oscillations and coherent structures even with a relatively simple geometry. Calculations of the Kolmogorov length and time scales have been made to ensure that the spatial-temporal discretization is sufficient for DNS. In order to validate the results, Hooper and Wood’s 1984 experiment has been modeled with a pitch-to-diameter (P/D) ratio of 1.107. The present work aims at validating first- and second-order statistics for the velocity field, and then analyzing the heat transfer behavior at different molecular Pr. The effects of low Pr flow are presented to demonstrate how the normalized mean and fluctuating heat transfer characteristics vary with different thermal diffusivity. Progress and future work toward creating a full DNS database for liquid metals are discussed.

A Thermal Barrier With Adaptive Heat Transfer Characteristics

1994 ◽  
Vol 116 (2) ◽  
pp. 302-310 ◽  
Author(s):  
P. Furmanski ◽  
J. M. Floryan
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Volume Fraction ◽  
Large Temperature ◽  
Thermal Barrier ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Apparent Slip ◽  
Small Volume Fraction ◽  
Relative Thermal Conductivity

A thermal barrier with adaptive heat transfer characteristics for applications in zero gravity environments is considered. The barrier consists of a mixture of fluid with a small volume fraction of arbitrarily oriented, randomly distributed particles of ellipsoidal shape. Heat flux control is obtained by changing the orientation of the particles. Heat flow may be increased up to several hundred times by rotating the particles from being parallel to the walls to being transverse to the walls and by increasing their aspect ratio, volume fraction, and relative thermal conductivity. An increase in the size of the particles results in the appearance of wall effects, which may substantially reduce heat flow as compared to the case of an infinite medium. Very large temperature variation is found to occur near the walls where an apparent “slip” of temperature occurs for barriers whose thickness is large compared to the particle size.

Comparison of Heat Transfer in Solar Collectors With Heat-Pipe Versus Flow-Through Absorbers

1987 ◽  
Vol 109 (4) ◽  
pp. 253-258 ◽  
Author(s):  
J. R. Hull
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Solar Collector ◽  
Hot Water ◽  
Solar Collectors ◽  
Heat Transfer Characteristics ◽  
Absorption Chiller ◽  
Transfer Characteristics ◽  
Proper Design ◽  
Flow Through

Analysis of heat transfer in solar collectors with heat-pipe absorbers is compared to that for collectors with flow-through absorbers for systems that produce hot water or other heated fluids. In these applications the heat-pipe absorber suffers a heat transfer penalty compared with the flow-through absorber, but in many cases the penalty can be minimized by proper design at the heat-pipe condenser and system manifold. When the solar collector is used to drive an absorption chiller, the heat-pipe absorber has better heat transfer characteristics than the flow-through absorber.

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