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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1959

Experimental Investigation of Gas-Side Performance of a Compact Finned-Tube Heat Exchanger

Heat-transfer and pressure-drop data were obtained experimentally for the gas side of a liquid-metal to air, compact finned-tube heat exchanger. The heat exchanger was fabricated from 0.185-inch Inconel tubing in an inline array. The fins were made of 310 stainless-steel- clad copper with a total thickness of 0.010 inch, and the fin pitch was 15.3 fins per inch. The liquid used as the heating medium was sodium. The heat-exchanger inlet gas temperature was varied from 5100 to 1260 R by burning JP fuel for airflow rates of 0.4 to 10.5 pounds per second corresponding to an approximate Reynolds number range of 300 to 9000. The sodium inlet temperature was held at 1400 R with the exception of a few runs taken at 1700 and 1960 R. The maximum ratio of surface temperature to air bulk temperature was 1.45. Friction-factor data with heat transfer were best represented by a single line when the density and viscosity of Reynolds number were evaluated at the average film temperature. At the lower Reynolds numbers reported, the friction data with heat transfer plotted slightly above the friction data without heat transfer. The density of the friction factor was calculated at the average bulk temperature. Heat-transfer results of this investigation were correlated by evaluating the physical properties of air (specific heat, viscosity, and thermal conductivity) at the film temperature.

Gedeon, Louis↗
NASA NTRS1948

Generalized Charts for Determination of Pressure Drop of a High-speed Compressible Fluid in Heat-exchanger Passages I : Air Heated in Smooth Passages of Constant Area with Constant Wall Temperature

In the present paper an analysis is made of the compressible-flow variations occurring in heat-exchanger passages. The results of the analysis describe the flow and heating characteristics for which specific flow passages can be treated as segments of generalized flow systems. The graphical representation of the flow variations in the generalized flow systems can then be utilized as working charts to determine directly the pressure changes occurring in any specific flow passage. On the basis of these results, working charts are constructed to handle the case of air heated at constant wall temperature under turbulent-flow conditions. A method is given of incorporating the effect on the heat-exchanger flow process of high temperature differential between passage wall and fluid as based on recent NACA experimental data. Good agreement is obtained between the experimental and the chart pressure-drop values for passage-wall average temperatures as high as 1752 degrees R (experimental limit) and for flow Mach numbers ranging from 0.32 to 1.00 (choke) at the passage exit.

Valerino, Michael F↗
NASA NTRS1951

Temperature distribution in internally heated walls of heat exchangers composed of nonnuclear flow passages

In the walls of heat exchangers composed of noncircular passages, the temperature varies in the circumferential direction because of local variations of the heat-transfer coefficients. A prediction of the magnitude of this variation is necessary in order to determine the region of highest temperature and in order to determine the admissible operating temperatures. A method for the determination of these temperature distributions and of the heat-transfer characteristics of a special type of heat exchanger is developed. The heat exchanger is composed of polygonal flow passages and the passage walls are uniformly heated by internal heat sources. The coolant flow within the passages is assumed to be turbulent. The circumferential variation of the local heat-transfer coefficients is estimated from flow measurements made by Nikuradse, postulating similarity between velocity and temperature fields. Calculations of temperature distributions based on these heat-transfer coefficients are carried out and results for heat exchangers with triangular and rectangular passages are presented.

Eckert, E R G↗
NASA NTRS1956

Study of Ram-air Heat Exchangers for Reducing Turbine Cooling-air Temperature of a Supersonic Aircraft Turbojet Engine

The sizes and weights of the cores of heat exchangers were determined analytically for possible application for reducing turbine cooling-air temperatures of an engine designed for a Mach number of 2.5 and an altitude The sizes and weights of the cores of heat exchangers were determined analytically for possible application for reducing turbine cooling-air temperatures of an engine designed for a Mach number of 2.5 and an altitude of 70,000 feet. A compressor-bleed-air weight flow of 2.7 pounds per second was assumed for the coolant; ram air was considered as the other fluid. Pressure drops and inlet states of both fluids were prescribed, and ranges of compressor-bleed-air temperature reductions and of the ratio of compressor-bleed to ram-air weight flows were considered.

Diaguila, Anthony J↗
NASA NTRS1995

A Probabilistic Model of a Porous Heat Exchanger

This paper presents a probabilistic one-dimensional finite element model for heat transfer processes in porous heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional model of heat transfer phenomenon in superfluid flow through a porous media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.

O P Agrawal↗