Effect of Thermal Properties on Heat Transfer in Cryopreservation and Cryosurgery

2002 ◽  
Author(s):  
Bumsoo Han ◽  
John C. Bischof
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Eutectic Phase ◽  
Temperature Dependent ◽  
Constant Property ◽  
Water Ice ◽  
Wide Range ◽  
Dependent Property ◽  
Temperature Dependent Properties ◽  
Property Changes

Biological materials in both cryopreservation and cryosurgery are composed of various chemicals and experience a wide range of temperature change. Therefore, their thermal properties including specific heat, latent heat (including water/ice and eutectic phase change) and thermal conductivity are expected to change significantly during freezing/thawing. The effects of thermal properties on heat transfer in cryopreservation/cryosurgery were studied experimentally and numerically. Thermal properties of various biological aqueous solutions were measured over a wide temperature range (−150~30°C). To estimate the effect of thermal property changes on the heat transfer, numerical simulations of both cryopreservation (cooled from outside) and cryosurgery (cooled from inside) geometries were performed with constant and temperature-dependent properties. The results show that the constant-property case significantly under-predicts the heat transfer over the temperature-dependent-property case regardless of the geometry.

A variable property heat transfer model for predicting soil temperature profiles during simulated wildland fire conditions

2008 ◽  
Vol 17 (2) ◽  
pp. 205 ◽  
Author(s):  
Ebenezer K. Enninful ◽  
David A. Torvi
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Wildland Fire ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Temperature Dependent ◽  
Heat Penetration ◽  
Experimental Values ◽  
Temperature Dependent Properties ◽  
Plant Shoots

A numerical model of heat transfer in dry soil was developed to predict temperatures and depth of lethal heat penetration during cone calorimeter tests used to simulate wildland fire exposures. The model was used to compare predictions made using constant and temperature-dependent thermal properties with experimental results for samples of dry sand exposed to heat fluxes of 25, 50 and 75 kW m–2. Depths of lethal heat penetration predicted using temperature-dependent properties were within 2 to 10% of the values determined using measured temperatures, while predictions made using constant properties were within 10 to 21% of the experimental values. In both cases, predictions made by the model were within the 1-cm accuracy with which the depth of seeds and plant shoots in the soil can be determined in practice. The model generally over-predicted the depth of lethal heat penetration in dry or moist soil when temperature-dependent properties were used, and over-predicted the depth of lethal heat penetration in soils with a moisture content of greater than 10% if constant thermal properties were used.

The effect of low temperature coating and annealing on structural and optical properties of CdSe/CdS core/shell QDs

2016 ◽  
Vol 55 (4) ◽  
Author(s):  
Maya Isarov ◽  
N. Grumbach ◽  
Georgy I. Maikov ◽  
Jenya Tilchin ◽  
Youngjin Jang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Interface Layer ◽  
Longitudinal Optical ◽  
Band Gap Energy ◽  
Longitudinal Optical Phonon ◽  
Core Shell ◽  
Temperature Dependent ◽  
Structural And Optical Properties ◽  
Wide Range ◽  
Temperature Dependent Properties

This paper presents the optical temperature dependent properties, over a wide range of temperatures from 4 to 300 K, of new CdSe/CdS core/shell colloidal quantum dots (QDs) with varying shell thickness coated and annealed at low temperature. It was demonstrated that low temperature coating and annealing processes enhanced the photoluminescence (PL) quantum yield accompanied by variation in the QDs structure, formation of an alloyed interface layer, suppression of the number of defects at the CdSe/CdS interface, band gap energy red-shift, narrowing of CdS longitudinal optical phonon band, and decrease of the PL inhomogeneous broadening parameter.

The Mass Transfer Analogy to Heat Transfer in Fluids With Temperature-Dependent Properties

1991 ◽  
Vol 113 (1) ◽  
pp. 27-33 ◽  
Author(s):  
J. N. Shadid ◽  
E. R. G. Eckert
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Transport Processes ◽  
Constant Property ◽  
Impingement Cooling ◽  
Fluid Properties ◽  
Temperature Dependent Properties ◽  
Isothermal Mass

The analogy between heat transfer in a single-component fluid and isothermal mass transfer of a two-component fluid without chemical reaction is presented. The analogy is well established and frequently used for fluids with constant properties. However, in various applications such as in the cooling of hot components in gas turbines, the temperature varies widely, causing significant fluid property variations. The present paper reviews the constant-property situation and considers in detail the conditions necessary to ensure similarity of the two transport processes with temperature and concentration-dependent fluid properties. An application of the variable property analogy to mass transfer in binary mixtures is presented along with specific recommendations for the CO2–air and Freon-air systems. It is demonstrated that the essential similarity conditions of the analogy are very well fulfilled for film cooling, total coverage film cooling, and impingement cooling when the heat (mass) flux into the wall in the transport process is zero. The heat/mass transfer analogy can, therefore, be used with confidence for these processes.

Thermally Symmetric Nonlinear Heat Transfer in Solids

1981 ◽  
Vol 103 (4) ◽  
pp. 745-752 ◽  
Author(s):  
M. Imber
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Analytical Solutions ◽  
Solution Method ◽  
Equivalent Linearization ◽  
Temperature Dependent ◽  
Numerical Examples ◽  
Nonlinear Heat Transfer ◽  
Composite Wall ◽  
Thermal Conductivities

Material thermal properties are temperature dependent, and this effect cannot be disregarded at elevated design temperatures. Based upon the principle of equivalent linearization, analytical solutions are developed for thermally symmetric planar solids. The solution method is, in turn, extended to a composite wall whose individual thermal conductivities are also temperature dependent. As a demonstration of the method’s accuracy several numerical examples are shown.

Numerical study on the effects of variable properties and nanoparticle diameter on nanofluid flow and heat transfer through micro-annulus

2017 ◽  
Vol 27 (8) ◽  
pp. 1851-1869 ◽  
Author(s):  
Morteza Heydari ◽  
Hossein Shokouhmand
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Numerical Study ◽  
Simple Algorithm ◽  
Variable Properties ◽  
Temperature Dependent ◽  
Constant Property ◽  
Content Type ◽  
Nanoparticle Diameter ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to evaluate differences between the results of constant property and variable property approaches in solving the problem of Al2O3-water nanofluid heat transfer in an annular microchannel. Also, the effect of nanoparticle diameter on flow and heat transfer characteristics is investigated. Design/methodology/approach Thermo-physical properties of the nanofluid including density, specific heat, viscosity and thermal conductivity are assumed to be temperature dependent. Governing equations are descritized using the finite volume method and solved by SIMPLE algorithm. Findings The results reveal that the constant property assumption is unable to predict the correct trend of variations along the microchannel for some of the characteristics, especially when the range of temperature change near the wall is considerable. In the fully developed region, constant property solution overestimates the values of shear stress near the walls of the microchannel. In addition, the values of Nusselt numbers are different for the two solutions. Furthermore, a decrease in wall’s shear stress has been observed as a result of increasing nanoparticle size. Originality/value This paper reflects that how the friction factor and heat transfer vary along the microchannel in temperature dependent modeling, which is not reflected in the results of constant property approach. To the best of the authors’ knowledge, there is no similar investigation of the effect of nanofluid variable properties with Pr=5 or in annular geometry.

Application of a Simplified Velocity Profile to the Prediction of Pipe-Flow Heat Transfer

1968 ◽  
Vol 90 (2) ◽  
pp. 191-198 ◽  
Author(s):  
R. D. Haberstroh ◽  
L. V. Baldwin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Velocity Profile ◽  
Pipe Flow ◽  
Energy Equation ◽  
Momentum Equation ◽  
Turbulent Pipe Flow ◽  
Transfer Coefficients ◽  
Constant Property ◽  
Wide Range

The temperature profiles and heat-transfer coefficients are predicted for fully developed turbulent pipe flow with constant wall heat flux for a wide range of Prandtl and Reynolds numbers. The basis for integrating the energy equation comes from a continuously differentiable velocity profile which fits the physical boundary conditions and is a rigorous (though not necessarily unique) solution of the Reynolds equations. This velocity profile is the semiempirical relation proposed by S. I. Pai, reference [12]. The assumptions are those of steady, incompressible, constant-property, fully developed, turbulent flow of Newtonian fluids in smooth, circular pipes with constant heat flux at the wall. The ratio of the turbulent thermal diffusivity to the turbulent momentum diffusivity is taken to be unity. The thermal quantities are obtained by numerical integration of the energy equation, and they are presented as curves and tables. A compact formula for the Nusselt number is given for a wide range of Reynolds and Prandtl numbers. The results degenerate identically to the case of laminar flow. The heat-transfer calculation requires neither adjustable factors nor data-fitting beyond the empirical constants in the momentum equation; thus this analysis constitutes a heat-transfer prediction to be tested against heat-transfer data.

Internal Laminar Heat Transfer With Gas-Property Variation

1971 ◽  
Vol 93 (4) ◽  
pp. 432-440 ◽  
Author(s):  
T. B. Swearingen ◽  
D. M. McEligot
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Bulk Temperature ◽  
Parallel Plates ◽  
Temperature Dependent ◽  
Property Variation ◽  
Constant Wall Heat Flux ◽  
Mixed Mean ◽  
Two Dimensional Flow ◽  
Temperature Dependent Properties

The results of a numerical investigation of internal laminar heat transfer to a gas with temperature-dependent properties are reported. In this investigation the authors obtained numerical solutions to the coupled partial differential equations of continuity, energy, momentum, and integral continuity describing the two-dimensional flow of perfect gas between heated parallel plates. A sequence of numerical solutions was obtained for the case of constant wall heat flux with a fully developed velocity profile at the start of the heated section and pure forced convection. The results may be summarized by Nu=Nuconst.prop.+0.024(Q+)0.3(Gzm)0.75f·Rem=24(Twall/Tbulk) where the subscript “m” refers to properties evaluated at the local mixed-mean (or bulk) temperature.

Effect of Temperature Dependent Properties on the Applicability of the Heat Conduction Equations for Rapid Heat Deposition Applications

2016 ◽  
Author(s):  
John G. Michopoulos ◽  
Andrew Birnbaum ◽  
Athanasios P. Iliopoulos
Keyword(s):  
Differential Equation ◽  
Thermal Properties ◽  
Heat Conduction ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Proper Form ◽  
Heat Deposition ◽  
Hyperbolic Form ◽  
Parabolic Form ◽  
Temperature Dependent Properties

Despite significant efforts examining the suitability of the proper form of the heat transfer partial differential equation (PDE) as a function of the time scale of interest (e.g. seconds, picoseconds, femtoseconds, etc.), very little work has been done to investigate the millisecond-microsecond regime. This paper examines the differences between the parabolic and one of the hyber-bolic forms of the heat conduction PDE that govern the thermal energy conservation on these intermediate timescales. Emphasis is given to the types of problems where relatively fast heat flux deposition is realized. Specifically, the classical parabolic form is contrasted against the lesser known Cattaneo-Vernotte hyperbolic form. A comparative study of the behavior of these forms over various pulsed conditions are applied at the center of a rectangular plate. Further emphasis is given to the variability of the solutions subject to constant or temperature-dependent thermal properties. Additionally, two materials, Al-6061 and refractory Nb1Zr, with widely varying thermal properties, were investigated.

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