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RESEARCH PAPERS

J. Heat Transfer. 1961;83(3):233-242. doi:10.1115/1.3682247.

A study is reported of the influence of system acceleration (1 to 21 g) on pool boiling heat transfer using distilled water at approximately atmospheric pressure. The acceleration of the system is such that the resulting force field is normal to the heating surface, thereby increasing the buoyant forces acting on the vapor bubbles. Heat-flux rate is varied from approximately 5000 Btu/hr-sq ft (nonboiling) to 100,000 Btu/hr-sq ft. Data are presented for the influence of subcooling with the boiling system under acceleration at the lower values of heat flux. A preliminary analysis is presented for a theoretical description of the process of boiling under the influence of high acceleration, including the simultaneous effect of natural convection.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):243-251. doi:10.1115/1.3682248.

A pool boiling apparatus was mounted on a counterweighted platform which could be dropped a distance of nine feet. By varying the size of the counterweight, the effective gravity field on the equipment was adjusted between zero and unity. A study of boiling burnout in water indicated that a variation in the critical heat flux according to the one quarter power of gravity was reasonable. A consideration of the transient burnout process was necessary in order to properly interpret the data. A photographic study of nucleate boiling showed how the velocity of freely rising vapor bubbles decreased as gravity was reduced. The bubble diameters at the time of breakoff from the heated surface were found to vary inversely as gravity to the 1/3.5 power. Motion pictures were taken to illustrate both nucleate and film boiling in the low gravity range.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):254-260. doi:10.1115/1.3682252.

An investigation of the surface-temperature variation during nucleate pool boiling at atmospheric pressure was conducted. The effect of surface temperature, heat flux, and heating-surface material was investigated. The temperature variation of the surface was found by a specially fabricated thermocouple placed in contact with it. The average maximum temperature variation may be found from the following equation:

ΔTavg max = c[q(f/α)1/2]−αqΔTsur−satk
The exponent a is a function of surface roughness. The rate of heat flow was denoted by q in Btu/sq ft-hr, α the thermal diffusivity in sq ft/hr, f the frequency of variations in cphr, k the thermal conductivity in Btu/ft-hr-deg F, and ΔTsur−sat the temperature difference between the heating surface and the saturation temperature of water. The coefficient c and exponent a were determined experimentally for various heating-surface materials and surface finishes.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):261-273. doi:10.1115/1.3682253.

Natural and forced-circulation test data for a closed-loop system are presented and analyzed. The data were obtained at pressures of 800, 1200, 1600, and 2000 psia from the natural-circulation loop at the Bettis Laboratory, using single rectangular channel test sections (0.100 in. × 1.0 in. × 27.0 in. long, 0.200 in. × 1.0 in. × 27.0 in. long, and 0.250 in. × 1.0 in. × 27.0 in. long). Heat fluxes ranged from 50,000 Btu/hr-sq ft to burnout with inlet subcoolings of 20, 70, and 100 deg F. The results showed that single and two-phase pressure drop, burnout heat flux, and riser density measured under natural-circulation operation are no different from those measured with forced circulation at the same thermal and fluid flow conditions. For the loop studied, it was shown that natural-circulation-loop flow rates can be predicted to within 10 per cent for both single and two-phase flow. Some data for slip ratios at liquid velocities less than 1/2 fps and for two-phase exit losses were obtained. Flow fluctuations were noted during some of the natural-circulation runs; these occurred before burnout heat flux was reached. In some instances these fluctuations were severe enough to cause a premature burnout.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):274-279. doi:10.1115/1.3682256.

Forced convection heat transfer is considered for laminar flow across a flat plate whose surface temperature varies with time. The case analyzed first is that of a step change in surface temperature, and series solutions are obtained which apply for both small and large time. These series results are used to construct an approximate solution which describes the entire time-history of the nonsteady heat-transfer process, and it is found that the results agree closely with an envelope composed of pure transient conduction and steady-state convection solutions. The analysis is then generalized to include any prescribed variation of surface temperature with time.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):281-291. doi:10.1115/1.3682259.

Experimental results are presented for film cooling of an adiabatic plate downstream of one to ten slots (Part 1) and two to twenty rows of discrete punched louvers (Part 2) in a subsonic turbulent flow under zero pressure gradient. The adiabatic wall temperatures downstreams of the last equivalent slot were measured and correlated in terms of the flow parameters, equivalent slot number and slot spacing, and distances downstreams of the last equivalent slot.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):293-305. doi:10.1115/1.3682263.

A detailed study of the heat transfer for tangential air injection through a single slot into a turbulent boundary layer on a flat plate is presented; the results apply to a specific slot size, one injection rate, and a fixed free-stream velocity. Boundary-layer velocity and temperature profiles for a number of positions downstream from the point of injection are presented as well as plate-temperature distribution and heat-transfer data for adiabatic and constant heat input-wall boundary conditions.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):307-318. doi:10.1115/1.3682268.
Abstract
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):321-336. doi:10.1115/1.3682271.

This paper investigates the dynamic response of a heat exchanger having a sinusoidally time-dependent rate of internal heat generation. Results for both the transient-periodic and the steady-periodic, or frequency response, are given. These results include the response of the wall and fluid temperatures and the wall-fluid temperature difference. A phenomena of resonance in the amplitude ratio and phase shift is disclosed. Analytical results are obtained through the use of the Laplace transform technique. Experimental results are presented which compare favorably with the theoretical analysis. Heat exchangers to which these results apply include the heterogeneous nuclear reactor.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):339-349. doi:10.1115/1.3682276.
Abstract
Topics: Cooling towers
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):351-356. doi:10.1115/1.3682280.

Taylor-Helmholtz Hydrodynamic Instability and its significance with regard to film boiling heat transfer from a horizontal surface is discussed. It is shown that near the minimum film-boiling heat flux, the bubble spacing and growth rate is determined by Taylor Instability neglecting the effect of fluid depth and viscosity. Utilizing a simplified geometrical model, an analytical expression for the heat-transfer coefficient near the minimum in film pool boiling from a horizontal surface was derived. Combining this equation with the available correlation for the minimum heat flux yields an analytical equation for the temperature difference at the minimum, which defines the location of the minimum point. The above equations agree with the available experimental measurements made on n-pentane and carbon tetrachloride within ±10 per cent.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):359-362. doi:10.1115/1.3682285.

By using the integral method, the task of solving the complicated two-phase boundary-layer differential equations in laminar-film condensation has been reduced to the simple work of solving an algebraic equation. It was shown analytically that the parameter [(ρμ)L /(ρμ)v ]1/2 can be removed from the film-condensation problem and hence only two parameters, cp ΔT/hfg and Pr, are involved. The calculated results in heat transfer and condensate flow rates agree very well with the results from the exact solution of the boundary-layer equations. With [(ρμ)v /(ρμ)L ]1/2 remaining as a parameter, it is believed that the present method can be used to solve the analogous two-phase boundary-layer problem in laminar film boiling.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):363-369. doi:10.1115/1.3682286.

This paper contains a mathematical analysis of three modes of oscillation of a simple two-phase flow, natural-circulation system, together with qualitative results of experiments with a small-scale loop model.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):370-375. doi:10.1115/1.3682287.

An analysis has been made to determine the heat transfer and friction characteristics in forced-convection film boiling on a flat plate. It is shown that the resulting two-phase flow problem can be formulated exactly within the framework of laminar boundary-layer theory. Solutions covering the parameter range of practical interest have been obtained by a combination analytical-numerical method. Heat-transfer and skin-friction results are presented both graphically and as simple, closed form analytical expressions. Relative to the case of pure liquid flow, the skin friction is substantially reduced due to film boiling. The heat transfer is found to increase as (ΔT)1/2 , a much smaller dependence than in other convection phenomena.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Heat Transfer. 1961;83(3):377-379. doi:10.1115/1.3682292.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):382-383. doi:10.1115/1.3682294.

A practical method is presented for obtaining a meaningful estimate of the truncation error associated with fully finite-difference forms of the heat-conduction equation. The analysis is applied in this instance to the Liebmann analog equations. It may also be used with other manual and analog methods of computation, where the error due to mesh size is relatively large. An example is given deriving error estimates for a case of one-dimensional heat flow.

Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):384-385. doi:10.1115/1.3682295.
Abstract
Topics: Ducts , Pressure drop
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):385-386. doi:10.1115/1.3682296.
Abstract
Topics: Heat exchangers
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):386-387. doi:10.1115/1.3682297.
Abstract
Topics: Cylinders
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):387-389. doi:10.1115/1.3682298.
Abstract
Commentary by Dr. Valentin Fuster
J. Heat Transfer. 1961;83(3):389-390. doi:10.1115/1.3682299.
Abstract
Commentary by Dr. Valentin Fuster

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