scholarly journals Entropy analysis in spray cooling for dosing water injection

2022 ◽  
Vol 960 (1) ◽  
pp. 012004
Author(s):  
S.O.L. Lacour ◽  
M. Feidt
Keyword(s):  
Chemical Potential ◽  
Water Injection ◽  
Numerical Approach ◽  
Spray Cooling ◽  
Cooling Capacity ◽  
Air Cooling ◽  
Thermodynamic Quantities ◽  
Cooling Efficiency ◽  
Flow Conditions ◽  
Experimental Values

Abstract Spraying water in air improves air-cooling capacity, which then relies on the evaporation of water. Even for small drop sizes, literature reports that the evaporation remains limited inside the spray and below saturation limits. In this article, we describe the evolution of thermodynamic quantities in a mixture of air and evaporating liquid water. A complete and coherent formulation is used to express enthalpy, entropy and chemical potential. At constant enthalpy, we show that the chemical equilibrium corresponds to an intermediate state in which droplet evaporation is not complete and entropy is maximum under certain conditions. Results are compared with some experimental values measured in a wind tunnel downstream of a spray. The calculated values are consistent with observations. Cooling efficiency is discussed for the various parameters, which are the amount of water, air temperature and ambient humidity. Then, the numerical approach is inverted in order to forecast the amount of water needed to reach a target cooling temperature. This numerical approach is used to set water flow depending on inlet flow conditions and cooling objectives.

scholarly journals Gluodynamics and deconfinement phase transition under rotation from holography

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Xun Chen ◽  
Lin Zhang ◽  
Danning Li ◽  
Defu Hou ◽  
Mei Huang
Keyword(s):  
Phase Transition ◽  
Angular Velocity ◽  
Chemical Potential ◽  
Entropy Density ◽  
Thermodynamic Quantities ◽  
Strongly Coupled ◽  
Trace Anomaly ◽  
Holographic Qcd ◽  
Deconfinement Phase Transition ◽  
Small Chemical

Abstract We investigate rotating effect on deconfinement phase transition in an Einstein-Maxwell-Dilaton (EMD) model in bottom-up holographic QCD approach. By constructing a rotating black hole, which is supposed to be dual to rotating strongly coupled nuclear matter, we investigate the thermodynamic quantities, including entropy density, pressure, energy density, trace anomaly, sound speed and specific heat for both pure gluon system and two-flavor system under rotation. It is shown that those thermodynamic quantities would be enhanced by large angular velocity. Also, we extract the information of phase transition from those thermodynamic quantities, as well as the order parameter of deconfinement phase transition, i.e. the loop operators. It is shown that, in the T − ω plane, for two-flavor case with small chemical potential, the phase transition is always crossover. The transition temperature decreases slowly with angular velocity and chemical potential. For pure gluon system with zero chemical potential, the phase transition is always first order, while at finite chemical potential a critical end point (CEP) will present in the T − ω plane.

Rotor Air-Cooling Efficiency of Powerful Turbogenerator

2020 ◽  
pp. 1-1
Author(s):  
Nikolay Vladimirovich Korovkin ◽  
Dmitry Verkhovtsev ◽  
Stanislav Gulay
Keyword(s):  
Air Cooling ◽  
Cooling Efficiency

scholarly journals Application of Ultrasonic Atomization in a Combined Circulation System of Spray Evaporative Cooling and Air Cooling for Electric Machines

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1773
Author(s):  
Yu Wang ◽  
Lin Ruan
Keyword(s):  
Cooling System ◽  
Evaporative Cooling ◽  
Convection Heat Transfer ◽  
Cooling Capacity ◽  
Circulation System ◽  
Air Cooling ◽  
Test Model ◽  
Ultrasonic Atomization ◽  
System A ◽  
Air Circulation

A combined circulation system of spray evaporative cooling and air cooling (CCSSECAC) is a way to enhance the cooling performance of an air-cooled electric machine while maintaining its existing structure. Based on a traditional air-cooled machine, when the discrete evaporative cooling medium particles are scattered into the airflow, they will reach the heat source with the air circulation. The cooling capacity of the cooling system is enhanced simultaneously through the phase transition and convection heat transfer. Ultrasonic atomization is a simple way to produce tiny droplets and a good way to improve the performance of CCSSECAC. To verify the effectiveness of such a system, a principle test model was built and a multi-operational condition experiment was carried out as an exploratory study. The experimental results showed that the new cooling system was feasible for horizontal machines, and the stator coil temperature was significantly reduced compared with the air-cooled mode.

Heat Transfer Associated With Air-Water Spray Cooling of Forgings From High Temperatures

2001 ◽  
Author(s):  
J. Ward ◽  
M. de Oliveira ◽  
D. R. Garwood ◽  
R. A. Wallis
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Gas Turbines ◽  
Spray Cooling ◽  
Solution Temperature ◽  
Air Cooling ◽  
Water Spray ◽  
Transfer Rates ◽  
Wide Range ◽  
Water Spray Cooling

Abstract The desired mechanical properties of the nickel-based or titanium forgings used in gas turbines for aircraft and power generation applications can be controlled by varying the rate of cooling from the so-called solution temperature during an initial heat treatment process. The use of dilute air-water spray cooling of these forgings is a technique which can provide heat transfer rates lying between those associated with conventional oil quenching or convective air-cooling. Air assisted atomisation can result in fine sprays over a wide range of water flow rates and it has a further advantage in that the air “sweeps” the surface and hence helps to prevent the build up of deleterious vapour films at high surface temperatures. The paper presents experimental data for the heat transfer rates associated with the use of these sprays to cool surfaces from temperatures of approximately 800°C. Many forgings contain surface recesses, which can lead to build up or “pooling” of the water so that the effect of variations in surface geometry is also reported. Periodic interruption of the water flow is a technique which can be employed to provide additional control of the heat transfer rate, particularly at temperatures below 500°C so that data is also presented for pulsed sprays.

Laminar Swirling Pipe Flow

1954 ◽  
Vol 21 (1) ◽  
pp. 1-7
Author(s):  
L. Talbot
Keyword(s):  
Swirling Flow ◽  
Nonlinear Effects ◽  
Critical Conditions ◽  
Flow Conditions ◽  
Rotationally Symmetric ◽  
Rate Of Decay ◽  
Linearized Theory ◽  
The Stability ◽  
Experimental Values ◽  
Rates Of Decay

Abstract The problem of the decay of a rotationally symmetric steady swirl superimposed on Poiseuille flow in a round pipe was investigated theoretically and experimentally. The object was to determine the degree to which the rate of decay of the swirl as predicted by a linearized theory agreed with measured rates of decay at flow conditions near the critical conditions for swirl instability. The solution to the linearized equation of motion for the swirl was obtained. Swirling flow was produced experimentally by rotating a section of the test pipe. Swirl velocities were determined from motion-picture studies of colored oil droplets introduced in the flow. The stability of the swirl was investigated through visualization of a dye filament, and a critical curve for swirl instability was determined experimentally relating the angular velocity of the rotating section to the Reynolds number. The theoretical and experimental values for the decay parameter were found to agree closely, even at conditions of flow near the critical conditions for instability. It was concluded that in the problem under consideration the nonlinear effects are not appreciable for stable decay of the swirl.

Capillary Pumped Loop Heat Spreader for Electronics Cooling

2001 ◽  
Author(s):  
Jaewon Chung ◽  
Costas P. Grigoropoulos ◽  
Ralph Greif
Keyword(s):  
Electronics Cooling ◽  
Cooling Capacity ◽  
Impinging Jets ◽  
Heat Sinks ◽  
Manufacturing Cost ◽  
Air Cooling ◽  
Capillary Pumped Loop ◽  
Heat Spreader ◽  
Vertical Orientation ◽  
Thermoelectric Coolers

Abstract As cooling requirements for electronic devices, e.g. computer processor units, power modules, etc. increase beyond the capabilities of air-cooling, interest has moved to several alternatives such as thermoelectric coolers, impinging jets and heat exchangers with phase change. Included among these, the capillary pumped loop is a very competitive cooling device, because of its performance reliability, no power requirements and low manufacturing cost. In this paper, a heat spreader employing capillary pumped loop principles was made of aluminum and copper and tested. The copper CPL heat spreader with heat sinks and fans on the condenser (86mm thick, 60mm wide, 181mm long) has demonstrated a cooling capacity of 640W at atmospheric pressure in the vertical orientation and maintains a difference between TIHE (temperature of the interface between heater and evaporator) and TAMB (ambient temperature) lower than 100°C.

scholarly journals Experimental and Numerical Investigation of Self-Burial Mechanism of Pipeline with Spoiler under Steady Flow Conditions

2019 ◽  
Vol 7 (12) ◽  
pp. 456 ◽  
Author(s):  
Woo-Dong Lee ◽  
Hyo-Jae Jo ◽  
Han-Sol Kim ◽  
Min-Jun Kang ◽  
Kwang-Hyo Jung ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Steady Flow ◽  
Pressure Field ◽  
Dynamic Pressure ◽  
The Self ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Projected Area ◽  
Experimental Values ◽  
Subsea Pipelines

Herein, hydraulic model experiments and numerical simulations were performed to understand the self-burial mechanism of subsea pipelines with spoilers under steady flow conditions. First, scour characteristics and self-burial functions according to the spoiler length-to-pipe diameter ratio (S/D) were investigated through hydraulic experiments. Further, the Navier–Stokes solver was verified. The experimental values of the velocity at the bottom of the pipeline with a spoiler and the pressure on the sand foundation where the pipeline rested were represented with the degree of conformity. Scour characteristics of a sand foundation were investigated from the numerical analysis results of the velocity and vorticity surrounding the pipelines with spoilers. The compilation of results from the hydraulic experiment and numerical analysis showed that the projected area increased when a spoiler was attached to the subsea pipes. This consequently increased the velocity of fluid leaving the top and bottom of the pipe, and high vorticity was formed within and above the sand foundation. This aggravated scouring at the pipe base and increased the top and bottom asymmetry of the dynamic pressure field, which developed a downward force on the pipeline. These two primary effects acting simultaneously under steady flow conditions explained the self-burial of pipelines with a spoiler attachment.

scholarly journals Qualifying Combustion Turbines for Inlet Air Cooling Capacity Enhancement

1995 ◽  
Author(s):  
Brian J. Kitchen ◽  
Jerry A. Ebeling
Keyword(s):  
Pressure Ratio ◽  
Heat Rate ◽  
Cooling Capacity ◽  
Effectiveness Factor ◽  
Air Cooling ◽  
Cooling Effectiveness ◽  
Capacity Enhancement ◽  
Exhaust Temperature ◽  
Turbine Performance ◽  
Relative Potential

The relative potential of combustion turbines for capacity enhancement by inlet air cooling was examined. A new inlet air cooling effectiveness factor was developed for this purpose. It was found that combustion turbines vary significantly in terms of inlet air cooling effectiveness. Of the combustion turbines presented in this paper, the best-ranked combustion turbine had an effectiveness factor of 0.48 while the lowest-ranked turbine had a factor of 1.35. No strong correlation was found between the inlet air cooling effectiveness factor and the ISO turbine performance parameters of heat rate, pressure ratio, exhaust temperature, and the ratio of inlet air mass flow rate to power output.

Small-angle scattering from collections of interacting hard ellipsoids of revolution studied by Monte Carlo simulations and other methods of statistical thermodynamics

1999 ◽  
Vol 32 (5) ◽  
pp. 917-923 ◽  
Author(s):  
Bo Sjöberg
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Small Angle ◽  
Chemical Potential ◽  
Compressibility Factor ◽  
Particle Method ◽  
Spherical Particles ◽  
Angle Scattering ◽  
Approximation Formulas ◽  
Experimental Values

Computer simulations using Monte Carlo methods are used to investigate the effects of interparticle correlations on small-angle X-ray and neutron scattering from moderate or highly concentrated systems of ellipsoids of revolution. Both oblate and prolate ellipsoids, of varying eccentricities and concentrations, are considered. The advantage with Monte Carlo simulation is that completely general models, both regarding particle shapes and interaction potentials, can be considered. Equations are also given that relate the nonideal part of the chemical potential, βμni, with the scattering at zero angle,I(0), and the compressibility factor,z. The quantity βμnican be obtained during the Monte Carlo simulations by using Widom's test-particle method. For spherical particles, the simulations are compared with approximation formulas based on the Percus–Yevick equation. A method is also suggested for the calculation of both βμniandzfrom experimental values ofI(0) recorded as a function of concentration.

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