Showing papers on "Subcooling published in 1970"

Model of critical heat flux in subcooled flow boiling

Abstract: Sponsored by the Solid State Sciences Division, Air Force Office of Scientific Research (OAR) Sponsored by Air Force

Role of the surface in the measurement of the Leidenfrost temperature

Abstract: Surface roughness and contamination, drop volume and liquid subcooling effects on Leidenfrost temperature

Two stage refrigeration plant having a plurality of first stage refrigeration systems

Abstract: This is a two stage refrigeration plant consisting of a plurality of first stage change of phase refrigeration systems and one or more second stage liquid coolant circulation systems interconnected by heat exchange systems. One heat exchange system transfers heat from the brine or other liquid coolant circulating through one or more of the liquid coolant chilling elements in the second stage to the refrigerant in one or more of the evaporators of the first stage to thereby chill the liquid coolant and cool the associated space cooling elements. Another heat exchange system transfers heat from the hot refrigerant gas flowing between the compressor and condenser in one or more of the first stage refrigeration systems to the brine or other liquid in one or more of the second stage liquid coolant circulation systems to heat the liquid and thereby permit defrosting of the associated space cooling elements. One or more of the first stage refrigeration systems may be operated selectively at their most efficient capacity to satisfy the cooling requirements of one or more of the second stage liquid coolant circulation systems.

Effect of Uniform Suction on Laminar Film Condensation on a Porous Vertical Wall

Abstract: The problem of film condensation on a porous wall has been solved by a boundary layer treatment. A dimensionless suction velocity parameter β, which is proportional to the uniform suction velocity vw and 1/4 th the power of longitudinal coordinate (x1/4 ), is defined to characterize the process. The results are restricted to small values of β, as the solutions are given by power series expansion in β. The effects of uniform suction on heat transfer, condensation rate, film thickness, and velocity and temperature profiles are demonstrated through various examples. In general, uniform suction causes a substantial increase of heat transfer and condensation rate, especially at low subcooling and at high Prandtl numbers. The problem involves three governing parameters: subcooling, Prandtl number, and suction velocity. Comparison with the previous work of Jain and Bankoff is discussed.

Forced convection boiling near inception in zero-gravity

Abstract: Forced-convection boiling at low heat flux and flow velocities in zero gravity for slightly subcooled distilled water

Superheating steam generator

Abstract: Described herein is a shell and tube vapor generator in which vaporizable liquid is evaporated and superheated within the same vessel. Downflow and upflow passages are provided for conducting the vaporizable liquid in heat exchange relation with the heating medium that is conducted through the tubes. The downflow passages into which subcooled feedwater is introduced are defined by a plurality of mutually spaced conduits disposed between the shell wall and the tube bundle. The arrangement permits the shell wall to be wetted by liquid at substantially saturated temperature throughout the evaporation region of the chamber thus to reduce the stresses within the tube material caused by thermal loading.

Acoustical investigation of nucleate boiling

Abstract: An experiment to determine frequency responses from boiling under varying conditions was performed. A pressure sensitive hydro­ phone picked up pressure pulses from collapsing bubbles, and a wave analyzer separated the signal into its frequency components. Three different parameters were investigated for the purpose of determining their effect on the frequency response of the system. The effect of heater geometry was studied, using 0.036 inch and 0.018 inch diameter nichrome wire and flat stainless steel foil. The effect of varying the heat flux on the 0.036 inch diameter wire was examined, keeping the system subcooling constant. Finally, the effect of varying the subcooling of the surrounding liquid was investigated for the flat foil and the 0.036 inch wire. A model of bubble collapse frequency response was developed that predicted a resonance shape for the response which was centered on a characteristic frequency and which related the resonance width and the time constant associated with bubble collapse. The experimental results agreed with the predicted shape, and the trends in the measured parameters, time constant and characteristic frequency, were consistent with predictions from heat transfer considerations and with previous results reported in the . ■> . ■ literature.

Boiler inlet plug insert with heat dams

Abstract: A device for eliminating the thermal instability of a liquid in forced feed convection boilers in which subcooled liquids which are introduced at the inlet have a tendency to superheat and flash into vapor to produce liquid slugs which are discharged at the outlet with the dry or superheated vapor. The invention is a rod-or sleeve-type insert located in the heating coils which produces liquid flow damping and controls the liquid superheating, and incorporates a nucleation device or devices disposed axially along the direction of liquid flow and introduces heat dams at the nucleation sites created by vapor from the heated site to prevent the liquid being heated from entering the nucleation site and flashing into vapor.

Correlation Of The Second Virial Coefficient In TheModel Of Steam Bubble Collapse

Abstract: In many previous mathematical models of steam bubble collapse a perfect gas in the bubble was taken into consideration. It might lead to substantial mistakes, for example, wrong calculation of heat capacity Cy of vapour. A new mathematical model of steam bubble collapse in subcooled liquid has been proposed. It uses the equation of state for a real gas and the PitzerAbbott correlation for calculating the second virial coefficient B It takes also into account the ratio of vapour to liquid and a change in temperature of liquid during the process. The results of our own experimental and calculated data have been compared with those obtained by other authors. The model has been applied to investigation of the influence of various parameters, namely: subcooling of the liquid, bubble diameter and vapour to liquid ratio, on the bubble collapse time

Experimental effects of pressure, subcooling, and diameter on thin wire film boiling

Abstract: Pressure, subcooling and diameter effects on liquid nitrogen film boiling on thin horizontal wires, using high speed movies