Effects of Contact Charging on Spray Impingement Heat Transfer Performance and Spray Behavior

Kreitzer, Paul J.; Kuhlman, John M.; Mehra, Deepak; Gray, Donald D.; Yerkes, Kirk L.

doi:10.2514/6.2007-4269

Cited by 4 publications

(3 citation statements)

References 44 publications

(56 reference statements)

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“…The results of Puterbaugh et al [14,15] suggested that the amount of dissolved air in FC-72 has an insignificant effect on CHF. Kreitzer et al [16][17][18] investigated body force effects on spray cooling by applying a high voltage coulombic, electrostatic, force to the spray cone, demonstrating small changes in heat transfer performance under specific conditions. Additionally, Glaspell [19] applied a Kelvin force, a magnetic field, to the spray, achieving results that provided a maximum heat transfer improvement of 5.2% at a 6 [kV] electrode voltage.…”

Section: List Of Tablesmentioning

confidence: 99%

Effect of Variable Gravity on the Cooling Performance of a 16-Nozzle Spray Array

Elston

Yerkes

Thomas

et al. 2009

47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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It was found that the cooling performance was enhanced in micro-gravity over terrestrial and elevated gravity. In addition, a sudden degradation in performance was found at high mass flow rates in micro-gravity, possibly due to liquid buildup on the surface between the nozzle impact zones. A high degree of subcooling was found to be beneficial, but the dissolved air content had little effect on the heat transfer performance either in micro-gravity or elevated gravity. Also, an improved liquid-vapor separator concept was implemented to enable flow stability during the micro-gravity portions of the flight. Multiple liquid-vapor separator concepts were tested during micro-gravity flights until a final design was settled on. The final separator design went through more rigorous evaluation to compare performance at multiple fill levels, each with a higher percentage of vapor space within the reservoir. It was found that, using the final reservoir design, stable flow operation was achieved in micro-gravity for mass flow ratesṁ = 14, 17.5 and 21 [g/s].iv

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Section: List Of Tablesmentioning

confidence: 99%

Effect of Variable Gravity on the Cooling Performance of a 16-Nozzle Spray Array

Elston

Yerkes

Thomas

et al. 2009

47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…The atomization effect was infinitely close to the pure gasification diffusion. Kreitzer et al [ 24 ] demonstrated that conical electrodes were used to generate spray to reduce heat transfer and improve the cooling system. When the charging voltage exceeded 15 kV, a great change in the spray flow pattern was observed.…”

Section: Introductionmentioning

confidence: 99%

Atomization Characteristics of Hydrogen Peroxide Solutions in Electrostatic Field

Sheng

2022

Micromachines

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Hydrogen peroxide (H2O2) can be considered as a sterilant or a green propellant. For a common use in industrial application, spray is an effective method to form fine H2O2 droplets. In this paper, electrostatic atomization based on the configuration of needle ring electrodes is proposed to produce H2O2 spray by minimizing its effective surface tension. The breakup performances of H2O2 ligaments can be improved by increasing the electric field intensity, reducing the nozzle size, and adjusting suitable volume flow rate. The smallest average diameter of breakup droplets for 35 wt. % concentration H2O2 solution reached 92.8 μm under optimum operation conditions. The H2O2 concentration significantly influenced the breakup performance owing to the concentration effect on comprehensive physical properties such as density, surface tension, viscosity, and permittivity. The average diameters of breakup droplets decreased with decreasing H2O2 concentration. At 8 wt. % concentration, the average breakup droplet diameter was reduced to 67.4 μm. Finally, electrostatic atomization mechanism of H2O2 solution was analyzed by calculating dimensionless parameters of Re, We, and Oh numbers with the combination of the operation conditions and physical properties for in-depth understanding the breakup behaviors. The calculation showed that the minimum average diameter of breakup droplets was obtained at 8 wt. % concentration at the investigated range of H2O2 concentration, which kept in agreement with the experimental results.

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“…The results of Puterbaugh et al [14] and Puterbaugh [15] suggested that the amount of dissolved air in FC-72 has an insignificant effect on CHF. Kreitzer and Kuhlman [16], Kreitzer [17] and Kreitzer et al [16][17][18] investigated body force effects on spray cooling by applying an electrostatic force to the spray cone, demonstrating small changes in heat transfer performance under specific conditions. Additionally, Glaspell [19] applied a magnetic field to the spray, achieving results that provided a maximum heat transfer improvement of 5.2% at a 6 kV electrode voltage.…”

Section: Introductionmentioning

confidence: 99%

Cooling Performance of a 16-Nozzle Array in Variable Gravity

Elston

Yerkes

Thomas

et al. 2009

Journal of Thermophysics and Heat Transfer

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The objective of this paper was to investigate the cooling performance of a 16-nozzle spray array using FC-72 as the working fluid in variable-gravity conditions. A flight-test experiment was modified to accommodate a 16-nozzle spray array, which was then tested in the parabolic flight trajectory environment of NASA's C-9 reduced-gravity aircraft. The 16-nozzle array was designed to cool a 25:4 25:4 mm 2 area on a thick-film resistive heater used to simulate an electronic component. Flight tests were conducted over the course of two flight weeks (each week consisting of four flights and each flight consisting of 40 to 60 parabolas). The mass flow rate through the 16-nozzle spray array ranged from 13:1 _ m 21:3 g=s. The heat flux at the thick-film resistor ranged from 2:9 q 00 25 W=cm 2 , the subcooling of the working fluid ranged from 1:6 T sc 18:4 C, the saturation temperature ranged from 37:4 T sat 47:2 C, and the absorbed air content in the working fluid was C 10:1, 14.3 and 16.8% by volume. The spray chamber pressure ranged from 42 P 78 kPa and the acceleration ranged from 0:02 a 2:02 g. Two-phase cooling was emphasized, but some single-phase data were also collected. A one-dimensional model was used to predict the heater surface temperature from the heat input and mean heater base temperature. It was found that the cooling performance was enhanced in microgravity over terrestrial and elevated gravity. In addition, a sudden degradation in performance was found at high mass flow rates in microgravity, possibly due to liquid buildup on the surface between the nozzle impact zones. A high degree of subcooling was found to be beneficial, but the dissolved air content had little effect on the heat transfer performance in either microgravity or elevated gravity. Nomenclature A = area, m 2 a = acceleration, m=s 2 C = percent of dissolved air content by volume, V air =V FC-72 V air 100 D = mean droplet diameter, m Fr = Froude number, v 2 =aD f = fraction of heat lost down the pedestal Ga = Galileo number, aD 3 2 = 2 G = nondimensional heat input, Q=2k r WT sat T 1 k = thermal conductivity, W=m K L = heater layer thickness, m _ m = mass flow rate, kg=s P = chamber pressure, kPa Q = heat rate, W q 00 = heat flux, W=m 2 T = temperature, K T = average temperature, K V = volume, m 3 v = droplet velocity, m=s W = heater width, m We = Weber number, v 2 D= T = temperature difference, K = viscosity, Pa s = density, kg=m 3 = surface tension, N=m, or standard deviation = nondimensional temperature, T T 1;surf =T sat T 1;surf Subscripts c = heater ceramic layer (substrate) g = heater glass layer (cover plate) in = nozzle inlet int = interface between phenolic base and bottom of heater r = heater resistive layer sat = saturated condition sc = subcooling surf = heater surface exposed to spray 1 = freestream condition

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Effects of Contact Charging on Spray Impingement Heat Transfer Performance and Spray Behavior

Cited by 4 publications

References 44 publications

Effect of Variable Gravity on the Cooling Performance of a 16-Nozzle Spray Array

Effect of Variable Gravity on the Cooling Performance of a 16-Nozzle Spray Array

Atomization Characteristics of Hydrogen Peroxide Solutions in Electrostatic Field

Cooling Performance of a 16-Nozzle Array in Variable Gravity

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