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Showing papers in "Journal of Heat Transfer-transactions of The Asme in 1972"


Journal ArticleDOI
TL;DR: Experimental thermal-conductivity data were obtained on the following in-vitro human organs: liver, kidney, heart, spleen, whole brain, brain gray matter, and brain white matter and three nondimensional groups for time, temperature, and blood flow emerge.
Abstract: A small needle-like probe has been developed for the determination of the thermal conductivity of either in-vitro or in-vivo tissue. This probe consists of a copper cylinder having a diameter of 1.5 mm and a length of 22.5 mm. Constantan and copper leads are attached to the center and top of the cylinder, respectively, and as a consequence the probe acts as a thermocouple. The distinguishing characteristic of this probe is that when it is suddenly embedded into a medium at a different temperature, the duration of its temperature–time response is such that it can be related to the thermal properties of the medium. This is accomplished by a match with an analytically determined response curve which accounts for metabolic heat generation, blood flow, and conductive effects. By nondimensionalizing the governing equations for the probe–tissue system, three nondimensional groups for time, temperature, and blood flow emerge. The results of a parametric study of these effects are presented in tabular form. Initially, the probe technique was used to determine the thermal conductivity of a 1 percent agar–water mixture and the results were within 5 percent of water. Subsequently, experimental thermal-conductivity data were obtained on the following in-vitro human organs: liver, kidney, heart, spleen, whole brain, brain gray matter, and brain white matter. In addition, density, specific-heat, and water-content measurements were also obtained on these organs. In-vivo conductivity data have recently been obtained for canine liver with and without blood flow. These data indicate that the in-vivo value without blood flow is approximately the same as the in-vitro value after the organ had been removed and refrigerated for 24 hr. Blood flow, if not considered, resulted in apparent conductivities which were 15 to 25 percent higher than that of the tissue.

136 citations




Journal ArticleDOI
TL;DR: In this paper, a gas-controlled heat pipe was used to predict heat and mass transfer along a heat pipe, leading to a predictive capability for heat transfer along the heat pipe.
Abstract: Axially conducting gas controlled heat pipes leading to predictive capability for heat and mass transfer along heat pipe

55 citations





Journal ArticleDOI
TL;DR: In this article, it was shown that the fractional deviations of Nu* from that of pure conduction are also small in the case of Pe < 1, whereas for all prac- tical purposes Nu* depends only on Fo (r < 0.5).
Abstract: +Tf we utilize the conduction-regime criterion for this case to be that of the previous, then the fractional deviations of Nu* from that of pure conduction are also small. Clearly then, the Nusselt numbers within this regime differ uniformly by two, and pjg. 8 of Professor Watts shows this to be the case. However, in view of the implicit dependence of the abscissa on Pe, this figure shows an explicit dependence on Pe, whereas for all prac­ tical purposes Nu* depends only on Fo (r < 0.5): Nu* = 2/\ArFo 4- 2 for Pe < 1 and Nu* = 2/VirFo for Pe » 1. In order to explain the aforementioned discrepancy, it is necesjgry to examine the nature of the physical processes involved and to explain the asymptotic solutions used in each of the limit­ ing oases. The Pe < 1 case, being conduction-dominated, exhibits nearly spherical isotherms around a sphere for the entire duration of the lieftt transfer, whereas for the Pe»l case this holds only during the initial stage, and with passage of time the isotherms are "carried away" from the sphere into the fluid in the direction of the fluid flow, exhibiting the maximum extent at steady state at

45 citations



Journal ArticleDOI
TL;DR: In this paper, a method of cooling turbine blades internally by continuous injection through an interior baffle is analyzed, which consists of a two-dimensional channel formed by a solid wall (blade surface) and a porous plate (injection source).
Abstract: A method of cooling turbine blades internally by continuous injection through an interior baffle is analyzed. The analytical model consists of a two-dimensional channel formed by a solid wall (blade surface) and a porous plate (injection source). Based on incompressible- and laminar-flow assumptions, the velocity and the temperature fields are determined. The Nusselt numbers for a power-law surface-temperature variation are obtained and expressed in terms of the Prandtl and the Reynolds numbers. A related problem of cooling the turbine disk is also solved.

42 citations




Journal ArticleDOI
TL;DR: In this paper, film boiling of a saturated liquid on a vertical surface is analyzed to determine the local heat-transfer rates as a function of height and heater-surface superheat.
Abstract: Film boiling of a saturated liquid on a vertical surface is analyzed to determine the local heat-transfer rates as a function of height and heater-surface superheat. Experiments show that the laminar-flow model is inadequate. A turbulent-vapor-flow model is used, and the influence of the interfacial oscillations is incorporated on a semiempirical basis. Measurements of local film boiling were obtained with a transient technique using saturated liquid nitrogen.



Journal ArticleDOI
TL;DR: In this article, a finite-difference method has been employed to solve the time-dependent coupled flow and energy equations in a rectangular two-dimensional enclosure representative of the longitudinal section of an industrial glass-melting furnace.
Abstract: Natural convection currents in a rectangular two-dimensional enclosure representative of the longitudinal section of an industrial glass-melting furnace have been established by both model experiments and numerical calculation. For the latter a finite-difference method has been employed to solve the time-dependent coupled flow and energy equations. The highly generalized mathematical model makes allowance for buoyancy, temperature-dependent viscosity, and diffusive radiation. Generalized boundary conditions are employed to permit specification of any combination of temperature, flux, or mixed thermal boundary conditions. Representative temperature and flow contour maps obtained from the calculations are shown to agree well with experimental results obtained with a 1/20 scale model in which glycerine was employed as the modeling fluid.








Journal ArticleDOI
TL;DR: In this paper, the spectral absorption coefficient of the glass was measured from 2000 to 2300 deg F, and two analyses were performed: one for a diffuse platinum-glass boundary and the other for a specular boundary.
Abstract: One-dimensional temperature profiles and heat fluxes within a slab of molten glass were measured experimentally. The glass slab was contained between two parallel platinum-lined ceramic plates. The plate temperatures were kept above 2000 deg F so that radiation heat flux was always equal to or larger than conduction. An optical method of temperature measurement was developed in which a helium–neon laser beam was directed along an isothermal path through the glass. The attenuation of the beam was a strong function of temperature and was used to evaluate the local temperatures within the glass slab. In order to perform a theoretical analysis the spectral absorption coefficient of the glass was measured from 2000 to 2300 deg F. Two analyses were performed: one for a diffuse platinum–glass boundary and the other for a specular boundary. The calculated temperatures agree with the measured values within 5 deg F throughout the slab, and the measured and predicted heat fluxes agree within 10 percent.