Showing papers on "Subcooling published in 2004"
TL;DR: In this paper, critical heat flux (CHF) was measured for a water-cooled micro-channel heat sink containing 21 parallel 215 × 821 μm channels, and a new CHF correlation was proposed which showed excellent accuracy in predicting existing heat sink data.
353 citations
TL;DR: In this article, the authors investigated the effect of acoustic cavitation and fluid sub-cooling on heat transfer in a heated horizontal copper tube and found that the addition of copper nanoparticles did not change the dependence of heat transfer.
183 citations
TL;DR: In this paper, the authors measured heat transfer under nucleating bubbles using a microheater array with 100 μm resolution with low and high subcooled bulk liquid along with images from below and from the side.
177 citations
TL;DR: In this article, a multidimensional modeling of vertical upward subcooled boiling flow using a two-fluid approach and calculation of local two-phase flow parameters (void fraction and bubble size) was taken into account.
136 citations
TL;DR: In this article, both pure water and R-134a were served as a working medium sprayed from a single circular nozzle onto a Cu (oxygen free) metal of an electrically heated surface which was heated to an initial temperature with a range of wall superheat for steadystate nucleate boiling experiments using thermocouples for heat transfer measurements.
99 citations
TL;DR: In this paper, the authors investigated direct contact condensation heat transfer occurring around a stable steam plume in subcooled water and determined the heat transfer coefficients at the steam-water interface using three different models, that is, the interfacial transport model due to the turbulent intensity, the surface renewal model, and the shear stress model.
93 citations
TL;DR: In this paper, a high-speed digital video camera was applied to record the dynamics of the subcooled boiling process, and the experimental data obtained from this study can be used in modeling the bubble departure frequency, bubble lift-off diameter, bubble growth rate and bubble velocity after bubble liftoff.
80 citations
TL;DR: In this paper, a heat transfer model was developed in order to explain the phenomena observed in nucleate pool boiling, and the results indicated that Marangoni convection associated with the bubbles formed by the air dissolved in the water which emerged from solution when the water was heated sufficiently, significantly influenced the heat transfer rate in subcooled nucleate pools boiling.
79 citations
TL;DR: In this paper, population balance equations combined with a three-dimensional two-fluid model are employed to predict bubbly flows with the presence of heat and mass transfer processes, and a comparison of model predictions with local measurements near the test channel exit is made for the radial distribution of the bubble Sauter diameter, void fraction, interfacial area concentration and gas and liquid velocities covering a range of different mass and heat fluxes and inlet subcooling temperatures.
77 citations
TL;DR: In this article, the performance of a I-type sparger in view of pressure oscillation and thermal mixing in a pool was investigated, and the effect of the hole pattern on the pressure load was relatively smaller than that of P/D.
TL;DR: In this paper, a high-speed video recording of pool boiling of environmentally acceptable surfactant solutions on a horizontal tube was used to investigate the kinetics of boiling (bubble nucleation, growth and departure).
TL;DR: In this article, two models of heat transfer through the heating foil and the isolating glass into the boiling liquid were proposed and discussed: one-and two-dimensional heat conduction problems were used with application of the least square and Trefftz computational techniques.
01 Nov 2004
TL;DR: In this article, the double-sensor conductivity probe method was used for measuring local void fraction, interfacial area concentration, and interfacial velocity in an internally heated annulus.
Abstract: Local measurements of flow parameters were performed for vertical upward subcooled boiling flows in an internally heated annulus. The annulus channel consisted of an inner heater rod with a diameter of 19.1 mm and an outer round pipe with an inner diameter of 38.1 mm, and the hydraulic equivalent diameter was 19.1 mm. The double-sensor conductivity probe method was used for measuring local void fraction, interfacial area concentration, and interfacial velocity. A total of 11 data were acquired consisting of four inlet liquid velocities, 0.500, 0.664, 0.987 and1.22 m/s and two inlet liquid temperatures, 95.0 and 98.0 degrees Celsius. The constitutive equations for distribution parameter and drift velocity in the drift-flux model, and the semi-theoretical correlation for Sauter mean diameter, namely, interfacial area concentration, which were proposed previously, were validated by local flow parameters obtained in the experiment.
TL;DR: In this article, an experimental study was performed to characterize the boiling heat transfer of impinging circular submerged jets on simulated microelectronic chips with a nominal area of 5 mm × 5 mm.
Abstract: An experimental study was performed to characterize the boiling heat transfer of impinging circular submerged jets on simulated microelectronic chips with a nominal area of 5 mm × 5 mm. The heat transfer modes included natural convection, partially developed nucleate boiling, fully developed nucleate boiling and critical heat flux. The study included the effects of jet parameters and fluid subcooling on the nucleate boiling. The results showed that the nucleate boiling data varied only with fluid subcooling regardless of jet parameters and that both the pool and impingement nucleate boiling curves at the same subcooling condition were well correlated. The high heat flux portions of the boiling curves with jet exit velocities greater than 10 m/s were corrected for the elevated saturation temperature. A new expression was developed with an interpolation method to construct the partially developed nucleate boiling curve.
TL;DR: In this paper, a digital photographic study of subcooled flow boiling with R-134a was performed in a vertical rectangular channel heated from one side to observe near-wall structures.
TL;DR: In this paper, the authors used control circuitry to maintain an isothermal boundary condition on the heater surface while the power dissipated by the heater was measured, and obtained steady state boiling data in low-g and high-g.
TL;DR: In this paper, the authors present results for FC72 and FC87 saturated and subcooled nucleate pool boiling, at atmospheric pressure, on a downward facing surface and in confined spaces between a heated copper disk (diameter 12 mm and thickness 2 mm) and an unheated surface, for distances varying between 0.2 and 13 mm.
TL;DR: In this paper, an advanced four-bed mass recovery adsorption refrigeration cycle driven by low temperature heat source is proposed. And the performance of the proposed cycle is evaluated by the mathematical model at equilibrium condition.
TL;DR: In this paper, the double-sensor conductivity probe method was used for measuring local void fraction, interfacial area concentration, and interfacial velocity in an internally heated annulus.
TL;DR: In this paper, the authors present experimental results of observation of liquid-solid contact and bubble behaviors around the critical heat flux of saturated and subcooled pool boiling on a plate of single crystal sapphire.
TL;DR: In this paper, full cone circular sprays were used to cool a circular surface of diameter 80mm with an initial temperature about 250/70°C for pure water/R-134a, respectively.
TL;DR: An experimental investigation was carried out for predicting the critical heat flux (CHF) of steady boiling for a round subcooled water jet impingement on the flat stagnation zone as discussed by the authors.
Abstract: An experimental investigation was carried out for predicting the critical heat flux (CHF) of steady boiling for a round subcooled water jet impingement on the flat stagnation zone. The experimental data were measured in a steady nucleate boiling state. Three main influencing parameters, i.e., subcooling, impact velocity and jet nozzle size were widely changed and their effects on the critical heat flux were systemically studied. An empirical correlation was obtained using the experimental data over a wide experimental range for predicting the critical heat flux of steady boiling for a round subcooled crater jet impingement on the flat stagnation zone
TL;DR: In this article, the authors measured local heat transfer coefficients during flow boiling of water at atmospheric pressure in a vertical channel of rectangular cross-section 2 mm by 1 mm for ranges of mass flux 57-211 kg/m2
TL;DR: In this paper, experimental results of the gas-hydrate R141b cool-storage process are used to study the performance of a new type gashydrate cool storage system, and the relations among the cooling rate of the cool storage medium, the degree of subcooling of crystallization, the formation rate of gashydrates, the cold energy stored and the volumetric flow rate in the crystallizer are provided.
TL;DR: In this paper, a high temperature sphere in Al2 O3 nanofluids was used to investigate the characteristics of film boiling and compared to those in pure water tests, which suggests that the presence of nanoparticles in liquid enhances vaporization process during the film boiling.
Abstract: Quenching experiments of a high temperature sphere in Al2 O3 nanofluids are conducted to investigate the characteristics of film boiling and compared to those in pure water tests. One stainless steel sphere of 10 mm in diameter at the initial temperatures of 1000∼1400 K was tested in the nanofluids of the volume concentrations from 5 to 20% and the degrees of subcooling from 20 to 80 K. The test results show that film boiling heat fluxes and heat transfer rates in nanofluids were lower than those in pure water. The differences of the film boiling heat transfer rates between pure water and nanofluids become larger when the liquid subcooling decreases. Those results suggest that the presence of nanoparticles in liquid enhances vaporization process during the film boiling. The effects of nanoparticle concentrations of more than 5 vol. % on film boiling appear to be insignificant. However, the minimum heat fluxes tend to decrease when the concentration increases. Direct quenching without film boiling was repeatedly observed when an unwashed sphere was employed for quenching tests in nanofluids. It suggests that nanoparticle deposition on the sphere surface prevents the sphere from forming film around the sphere, which consequently promotes the rapid quenching of the hot sphere.Copyright © 2004 by ASME
TL;DR: In this article, the boiling front location was determined from the temperature distribution of the heated wall obtained from liquid crystal thermography, and the impact of various factors on the boiling incipience in microchannels, such as pressure, the inlet liquid subcooling, and flow velocity, were investigated.
Abstract: In this paper, attempts were made to experimentally investigate the boiling incipience in a narrow rectangular vertical channel of 1 mm depth with an external 40 mm wide wall heated uniformly and others assumed quasiadiabatic. The “boiling front” location was determined from the temperature distribution of the heated wall obtained from liquid crystal thermography. Boiling incipience occurs when a considerable rise in the wall temperature above the saturation temperature takes place. Thus, boiling incipience is accompanied by “nucleation hysteresis.” The impact of various factors on the boiling incipience in microchannels, such as pressure, the inlet liquid subcooling, and flow velocity, were investigated.
TL;DR: In this paper, the effects of non-condensable gases and surface aging on boiling curves were considered, and the physical mechanism of boiling hysteresis was discussed in terms of irregular activation of vapor embryos within larger cavities.
Patent•
19 Apr 2004
TL;DR: In this paper, a method for evaluating operation of a compression cooling system includes the steps of: (a) in no particular order: measuring a first temperature of the refrigerant in a saturated state; and (b) calculating a difference between the first temperature and the second temperature to determine the extant amount of subcooling to which the fridge is subjected.
Abstract: A method for evaluating operation of a compression cooling system includes the steps of: (a) in no particular order: (1) measuring a first temperature of the refrigerant in a saturated state; and (2) measuring a second temperature of the refrigerant in a liquid state; and (b) calculating a difference between the first temperature and the second temperature to determine the extant amount of subcooling to which the refrigerant is subjected.
TL;DR: In this paper, the results obtained during an experimental study on film boiling on wires in the presence of an externally imposed electric field were reported, which showed that two different film boiling regimes, separated by an additional boiling transition, can exist.
Abstract: The paper reports the results obtained during an experimental study on film boiling on wires in the presence of an externally imposed electric field. The arrangement allowed achieving various combinations of pressure and subcooling independently of the environmental conditions. The test section was an electrically heated platinum wire with diameters of 0.1 and 0.2 mm. The working fluid was FC-72. The results showed that two different film boiling regimes, separated by an additional boiling transition, can exist in the presence of an electric field. The first regime, at low wire superheat, was strongly influenced by the electric field, showing a remarkable heat transfer enhancement with increasing voltage. The second regime, at higher superheat, was weakly dependent on the field strength and almost coincident with the zero field one. These results are analogous to the ones previously obtained using R113 as working fluid. The reasons for the occurrence of the transition were investigated. A simple model of ...