Showing papers on "Subcooling published in 1976"

A Comprehensive Model for Nucleate Pool Boiling Heat Transfer Including Microlayer Evaporation

Abstract: The results of an experimental investigation are presented in which dichloromethane (methylene chloride) boiling on a glass surface was studied using laser interferometry and high-speed photography. New data for active site density, frequency of bubble emission, and bubble departure radius were obtained in conjunction with measurements of the volume of microlayer evaporated from the film underlying the base of each bubble for various combinations of heat flux and subcooling. These results were used to support a model for predicting boiling heat flux incorporating microlayer evaporation, natural convection, and nucleate boiling mechanisms. Microlayer evaporation heat transfer is shown to represent a significant proportion of the total heat transfer for the range of heat flux and subcooling investigated.

An Experimental Investigation of the Thermally Induced Flow Oscillations in Two-Phase Systems

Abstract: An experimental study on the onset of thermally induced two-phase flow oscillations has been carried out in a uniformly heated boiling channel using Freon-113 as the operating fluid. The effects of inlet subcooling, system pressure, inlet and exit restrictions, and inlet velocity have been studied. The experimental data have been compared with the equilibrium as well as the nonequilibrium theory including the effect of subcooled boiling. It has been found that the effect of thermal nonequilibrium should be included in a theoretical model for accurate prediction of the onset and the frequency of thermally induced flow oscillations. A simplified stability criterion has also been presented and compared with the experimental data.

Secondary nucleation of ice in sugar solutions and fruit juices

Abstract: From thermal response measurements, ice nucleation rates in distilled water, sugar solutions, and fruit juices were determined for a stirred, batch-seeded crystallizer High resolution thermometry permitted use of initial sub-coolings between 001° and 02°K Nucleation increased with approximately the second power of subcooling Applications to freeze concentration are considered

Heat pump system with high efficiency reversible helical screw rotary compressor

Abstract: A helical screw rotary compressor is provided with oppositely oriented slide valves at the suction and discharge sides of the machine to control compressor capacity and balance the closed thread pressure at discharge with discharge line pressure in a main closed loop heat pump refrigeration system. The compressor may be bidirectional if the function of the slide valves is reversed. Additional slide valves carried by the compressor may be employed to vary the injection point of intermediate pressure refrigerant gas to a compressor closed thread and to control flow to and/or from closed threads and a secondary loop for subcooling the main loop refrigerant or for other functions.

Fractional condensation of an NG feed with two independent refrigeration cycles

Abstract: A process for the liquefaction of natural gas which employs a multi-component refrigerant system and a second independent refrigeration system. The process differs from the prior art processes in that the feed gas is cooled only by the independent refrigeration system until it has been freed of those components which could precipitate as solids at the low temperatures of the liquefaction process and thereafter is cooled by the multi-component refrigeration system. The multi-component refrigerant system is a self-contained cycle and does not reject heat to the independent refrigeration system, but directly to the ambient temperature surroundings.

Subcooled Decompression Analysis in PWR LOCA

Abstract: The thermo-hydraulic behavior of the coolant in the primary system of a nuclear reactor is important in the core heat transfer analysis during a hypothetical loss-of-coolant accident (LOCA). The heat transfer correlations are strongly dependent on local thermo-hydraulic conditions of the coolant. The present work allows to calculate such thermo-hydraulic behavior of the coolant during subcooled decompression in PWR LOCA by solving the mass, momentum, and energy conservation equations by the method of characteristics. Detailed studies were made on the transient coolant outflow at the pipe rupture and the effect of frictional loss and heat addition to the coolant on the decompression. Based on the studies, a digital computer code, DEPCO-MULTI, has been prepared and numerical results are compared with the ROSA (JAERI) and the LOFT (NRTS) semiscale test data with various coolant pressures, temperatures, pipe break sizes, and complexity of flow geometry. Good agreement is generally obtained.

Refrigeration system using enthalpy converting liquid turbines

Abstract: A refrigeration system in which refrigerant liquid is cooled by self-evaporation and is used for refrigerating in the liquid form, in which the self-evaporation is in stages, each having a vapor compressor, the expansion taking place in enthalpy converting liquid turbines instead of permitting partial vaporization through valves into vapor separators. The enthalpy converting liquid turbines are much more efficient than the adiabatic liquid expansion which is customarily used in refrigeration systems in which a cold liquid cooled by the expansion is evaporated to absorb heat and thus to provide cooling. There is much less irreversibility and hence increase in entropy is reduced, especially when removal of super heat from the compressed vapors in each stage is effected by quenching with a small portion of the refrigerant liquid. A good portion of this heat is recovered as mechanical energy in the enthalpy converting turbines. With ammonia as the refrigerant, improvements of efficiency of 15% and more are achieved. Other refrigerants may be used instead of ammonia and the choice of refrigerant used is based on the conditions of operation. The type of refrigeration system is normally used for fairly large scale refrigeration plants and is not suitable for home refrigerators.

Steam heater with helical coils - having greater flow area for condens. zone than desuperheating or condensate cooling

Abstract: Heater using steam as the heating medium consists of a shell enclosing a series of helical coils mounted around a central axis, the liquid to be heated flowing through teh coils The shell space into which the steam is passed is divided into several zones, one for taking the superheat out of the steam, one for the condensation and one for subcooling the condensate An annular baffle surrounds the upper section of the coils while there is an annular gap around the section where condensation occurs between the coils and the vessel wall In the lower subcooling section there is also a baffle For use with ht exchangers where fluids are being heated In the desuperheating zone the ht transfer is improved by a higher flow velocity over the coils The effectiveness is in part measured by the pressure drop Thus a pressure drop in this zone is of advantage In the condensation zone, the ht transfer mechanism is different and pressure drop is no advantage In the condensate sub-colling zone, ht transfer is again proportional to flow and a pressure drop is an advantage The heater described combines these features

Evaluation of Subcooled Water Thrust Forces

Abstract: Subcooled water thrust forces for use in pipe rupture analyses have been normalized with respect to an enthalpy normalization factor. This normalization is based on comparisons with thrust forces calculated using the Henry-Fauske model, and the answers are within +-3 percent in the range 300 to 2400 psia (21.1 to 168.7 kg/cm/sup 2/). The numerical evaluation makes it unnecessary for the user to rely on figures for the particular conditions desired or to program the Henry-Fauske method.