Showing papers on "Subcooling published in 1993"
TL;DR: In this paper, the authors investigated the single-phase forced-flow convection and boiling characteristics of subcooled liquid flowing through microchannels with a cross-section of 0.6 × 0.7 mm, machined on the stainless steel plate 2 mm thick.
322 citations
ENEA1
TL;DR: In this article, the critical heat flux (CHF) in subcooled flow boiling in short tubes was investigated and the effects due to variation of thermal hydraulic parameters (velocity, subcooling, pressure) on the heat transfer were presented together with a comparison of the experimental data with existing correlations and theoretical models.
112 citations
102 citations
TL;DR: In this article, a model to predict the mass flow rate has been developed and has been successfully validated, taking into account the persistence of some metastable liquid in the crack and the special flow pattern which appears in such particular geometry.
90 citations
TL;DR: In this article, a quasi-one-dimensional, five-equation, homogeneous, nonequilibrium model has been developed and utilized on a microcomputer to calculate the behavior of flowing, initially subcooled, flashing water systems.
85 citations
TL;DR: In this article, the melting of n- octadecane that is discretely heated at a constant rate from one side of an enclosure with inside dimensions of 100 mm × 60 mm × 50 mm was investigated experimentally.
70 citations
TL;DR: In this article, the authors investigated geysering in twin parallel channels in both natural and forced circulations under various conditions of heat input, inlet subcooling and non-heated riser length from the upper end of the heated section to the outlet plenum.
67 citations
TL;DR: In this article, the authors investigated the fundamentals of thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs in order to understand their driving mechanisms and to examine the methods preventing their occurrence with an aim of establishing a rational startup procedure and reactor configuration, and it was made clear that the in-phase natural circulation oscillation was induced in parallel channels by hydrostatic head fluctuation in a long vertical non-heated channel such as steam separators and a divided chimney.
Abstract: The authors have been investigating the fundamentals of thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs in order to understand their driving mechanisms and to examine the methods preventing their occurrence with an aim of establishing a rational start-up procedure and reactor configuration In this paper, ‘Natural Circulation Oscillation’ was investigated experimentally under various conditions of heat input, inlet subcooling and non-heated riser length to reveal the driving mechanism and its feature As a result, it was made clear that the in-phase natural circulation oscillation was induced in parallel channels by hydrostatic head fluctuation in a long vertical non-heated channel such as steam separators and a divided chimney in natural circulation BWRs due to alternate flow of vapor and liquid therein while the vapor generation rate is insufficient
62 citations
TL;DR: In this article, steady state, subcooled, low flow, critical heat flux (CHF) experiments simulating natural convection boiling are performed in a thin rectangular vertical channel.
62 citations
TL;DR: In this article, an investigation was carried out to identify the important parameters affecting critical heat flux (CHF) in rectangular channels, focusing on the effects of flow direction, channel inlet subcooling from 1 to 213 K, the channel outlet condition extending from sub-74 K to quality of 0-1.0, pressure of 0.1 to 4 MPa, water mass flux of [minus]25,800 to +6250 kg/m[sup 2]s, and channel configuration.
Abstract: In this study, an investigation was carried out to identify the important parameters affecting critical heat flux (CHF) in rectangular channels, focusing on the effects of flow direction, channel inlet subcooling from 1 to 213 K, the channel outlet condition extending from subcooling of 0-74 K to quality of 0-1.0, pressure of 0.1 to 4 MPa, water mass flux of [minus]25,800 to +6250 kg/m[sup 2]s, and channel configuration. In particular, the effect of the outlet subcooling in upflow and downflow on the CHF was quantitatively investigated. As a result of this study, a new CHF scheme covering downflow, countercurrent flow, and upflow was established in the rectangular channels within the ranges of parameters investigated in this study. 17 refs., 10 figs., 1 tab.
60 citations
TL;DR: In this paper, the parameters influencing heat balance conditions in a suspension crystallizer were studied to determine the conditions at which optimal crystal growth could be attained in skim milk, and the results suggest that large crystals can be grown in reasonably short times in batch crystallizers when the heat balance condition is maintained at high levels.
ENEA1
TL;DR: In this article, an overview of recent achievements obtained in water sub-cooled flow boiling CHF under operating conditions of interest to the thermal hydraulic design of fusion reactors is presented.
TL;DR: A pool boiling experiment on a sounding rocket (TR-IA 1st Flight) was conducted with a transparent glass heater and an interferometer under a relatively low heat flux.
TL;DR: In this paper, a heat transfer model and correlation of natural-convection film-boiling heat transfer with interfacial wave motion under subcooled conditions was presented. But the model was not applied to the case of saturated film boiling.
TL;DR: In this article, the hypervapotron was used to enhance the critical heat flux (CHF) in sub-cooled flow boiling (already characterized by high values of CHF) using water flowing in a horizontal annular test section designed for visualization.
TL;DR: In this article, the critical subcooling temperature for secondary nucleation of ice in aqueous sugar solutions and fluid dairy products was determined using two experimental techniques and the method of observation, type of solution and its concentration were found to affect critical sub cooling temperature.
TL;DR: In this article, the authors developed a mathematical model for the performance prediction of air-cooled condensers, which considers the heat exchanger as formed by three distinct zones: de-superheater, condenser and subcooler.
Abstract: The present paper deals with the development of a mathematical model for the performance prediction of air-cooled condensers. The model considers the heat exchanger as formed by three distinct zones: de-superheater, condenser and subcooler. To make the model as generally applicable as possible, each piece of straight tube, between two return bends, is treated as a separate heat exchanger. The coil can thus be formed by any particular composition of straihgt tubes, enabling the overall effectiveness of each zone to be determined, with the use of correlations available in the literature. Zone-ending (starting of condensation or subcooling half-way along a tube) is also considered, with appropriate modelling. The energy balances over each zone, for both air and refrigerant streams, together with the effectiveness equations, form a set of non-linear equations, which are solved numerically. Despite its simplicity the method produces results comparable with those produced by more sophisticated local analyses. In the present paper six coil configurations are studied. Predicted results are compared with existing experimental data, with generally good agreement. A few possible applications of the method are also presented.
TL;DR: In this paper, the effects of flow orientation on critical flux (CHF) were investigated on a series of nine in-line simulated microelectronic chips in Fluorinert FC-72.
Abstract: The effects of flow orientation on critical flux (CHF) were investigated on a series of nine in-line simulated microelectronic chips in Fluorinert FC-72. The chips were subjected to coolant in upflow, downflow, or horizontal flow with the chips on the top or bottom walls of the channel with respect to gravity. Changes in angle of orientation affected CHF for velocities below 200 cm/s, with some chips reaching CHF at heat fluxes below the pool boiling and flooding-induced CHF values. Increased subcooling was found to dampen this adverse effect of orientation slighltly
TL;DR: In this paper, a two-dimensional two-phase non-equilibrium model is presented to predict the void fraction distribution, flow and temperature fields for turbulent subcooled flow boiling at elevated pressures in heated vertical ducts (pipes and channels).
TL;DR: In this paper, a single water droplet impinging upon a hot solid surface has been investigated experimentally, and the instantaneous radius of the spreading droplet was measured by an electrical resistance probe.
Patent•
04 Mar 1993TL;DR: In this article, an improved subcooling system for non-azeotropic working fluid leaving a condenser in a multi-compartment system passes the fluid leaving the condenser through a conduit within the tube of a fin-tube evaporator.
Abstract: An improved subcooling system for nonazeotropic working fluid leaving a condenser in a multi-compartment system passes the fluid leaving the condenser in heat exchange relationship with fluid evaporating within the evaporator (102). The heat exchange relationship can be effected by an internal subcooler (106) in which the fluid leaving the condenser is directed through a conduit (106) within the tube of a fin-tube evaporator (102), the conduit (106) being of smaller dimension than the tube of the evaporator (102).
TL;DR: In this paper, the authors correlated pressure drop data from experiments on subcooled flow boiling of refrigerant R12 and R134a with the Jakob number and the ratio of heated and wetted perimeter of the flow channel.
TL;DR: In this article, the results of an experimental investigation of condensation within thin inclined porous coatings were presented, which consisted of a condensate region overlaying a thin, metallic, and permeable coating which was adhered to an isothermal copper block.
TL;DR: In this article, an efficient integral profile computational method is used to solve the problem of the solidification of highly subcooled droplets, including the effects of surface cooling by radiation and convection, interface crystallization kinetics and fully time-dependent heat conduction.
TL;DR: In this article, the performance characteristics of a convergent-divergent nozzle for flashing expansion of initially subcooled hot water were investigated and the results showed that the maximum nonequilibrium pressure drop at the throat decreased and the thrust coefficient increased by 10%.
Patent•
26 Mar 1993
TL;DR: In this paper, a method and apparatus for subcooling a liquid composed of a volatile fluid, for instance, a saturated liquid cryogen, in which two chambers are filled with the fluid and are each initially pressurized after filling so that the fluid is converted to a subcooled liquid.
Abstract: A method and apparatus for subcooling a liquid composed of a volatile fluid, for instance, a saturated liquid cryogen, in which two chambers are filled with the fluid and are each initially pressurized after filling so that the fluid is converted to a subcooled liquid. The pressurization of the two chambers is maintained as the subcooled liquid is delivered from each of the two chambers. The filling and the delivery of the two chambers is effected in accordance with a cycle in which one chamber is filled and initially pressurized just prior to the completion of the delivery from the other chamber to allow the continual delivery of the subcooled liquid.
Patent•
08 Dec 1993
TL;DR: In this paper, a heat exchanger for a refrigeration circuit for condensing gaseous refrigerant and incorporating an integral refrigerant subcooler is described, where the lower region of the receiver is automatically provided with liquified refrigerant from the condensing portion of the heat exchange.
Abstract: A heat exchanger for a refrigeration circuit for condensing gaseous refrigerant and incorporating an integral refrigerant subcooler. The heat exchanger utilizes an oversized header communicating with the heat exchanger coils of sufficient volume to serve as a reservoir for condensed refrigerant eliminating the need for a separate receiver receptacle. Refrigerant subcooling occurs at the lower region of the receiver whereby the subcooler is automatically provided with liquified refrigerant from the condensing portion of the heat exchanger.
TL;DR: In this article, the authors studied the effect of velocity and number of jets on the heat flux in jet impingement cooling using deionized distilled water. But the results showed no significant dependence on the number or velocity of jets for fixed flow rates.
Abstract: Experiments were performed to study the effect of nozzle rotation, flow rate, degrees of subcooling, number of jets, and velocity on the heat flux in jet impingement cooling using deionized distilled water. The heat flux is a strong function of the flow rate and degree of subcooling, attaining a maximum value of the order of 600 W/cm at the highest flow rates. The heat flux shows no significant dependency on velocity and number of jets for fixed flow rates. The rate of rotation shows no significant effect on the heat flux within the forced convective and early nucleate boiling region. At temperatures close to the critical heat flux the rotation retards the heat flux (compared with a stationary jet) diminishing it by 20%. Comparisons with published results are presented.
TL;DR: In this article, the effects of chip protrusion on the forced-convection boiling and critical heat flux (CHF) of a dielectric coolant (FC-72) were investigated.
Abstract: The effects of chip protrusion on the forced-convection boiling and critical heat flux (CHF) of a dielectric coolant (FC-72) were investigated. The multi-chip module used in the present study featured a linear array of nine, 10mm x 10 mm, simulated microelectronic chips which protruded 1 mm into a 20-mm wide side of a rectangular flow channel. Experiments were performed in vertical upflow with 5-mm and 2-mm channel gap thicknesses. For each configuration, the velocity and subcooling of the liquid were varied from 13 to 400 cm/s and 3 to 36° C, respectively. The nucleate boiling regime was not affected by changes in velocity and subcooling, and critical heat flux generally increased with increases in either velocity or subcooling. Higher single-phase heat transfer coefficients and higher CHF values were measured for the protruded chips compared to similar flush-mounted chips. However, adjusting the data for the increased surface area and the increased liquid velocity above the chip caused by the protruding chips yielded a closer agreement between the protruded and flush-mounted results. Even with the velocity and area adjustments, the most upstream protruded chip had higher single-phase heat transfer coefficients and CHF values for high velocity and/or highly-subcooled flow as compared the downstream protruded chips. The results show that, except for the most upstream chip, the performances of protruded chips are very similar to those of flush-mounted chips.