Modeling of the vaporization front on a heater surface

Aktershev, S. P.; Ovchinnikov, V. V.

doi:10.1134/s1810232811010073

Cited by 15 publications

(6 citation statements)

References 9 publications

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“…When the molecules of the liquid collide, they transfer energy to each other based on how they collide. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas [27]. The internal energy of water molecules increases because of the increase in injected water temperature, and the heat conduction between the ambient air and the liquid water molecules increases when the CVV temperature increases.…”

Section: Resultsmentioning

confidence: 99%

Effects of Vessel and Water Temperatures on Direct Injection in Internal Combustion Rankine Cycle Engines

Kang

Zhang

et al. 2018

Automot. Innov.

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This study focused on the effects of vessel and water temperatures on direct injection in internal combustion Rankine cycle engines through experimental and numerical methods. First, a study was carried out with schlieren photography using a high-speed camera for simultaneous liquid-gas diagnoses. Water was directly injected into a constant-volume vessel that provided stable boundaries. We wrote a MATLAB program to calculate spray tip penetration and cone angle from the images. For the further extension of boundary conditions, a numerical model was established and calibrated in AVL-FIRE for the thorough analysis of injection characteristics. Both experimental and numerical results indicated that injection and vessel temperatures have different effects on spray tip penetration. An increase in injected water temperature leads to shorter spray tip penetration, while the spray tip penetration increases with increasing vessel temperature. However, increased injection and vessel temperatures can both decrease the spray cone angle. Moreover, the simulation results also suggested that heat conduction is a main factor in boosting evaporation under top dead center conditions. When the internal energy of water parcels surges, these parcels evaporate immediately. These results are helpful and crucial for internal combustion engines equipped with direct water injection technology.

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Section: Resultsmentioning

confidence: 99%

Effects of Vessel and Water Temperatures on Direct Injection in Internal Combustion Rankine Cycle Engines

Kang

Zhang

et al. 2018

Automot. Innov.

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“…When a step-wise increase in power is experienced by a heating element, a direct transition to film boiling may occur, bypassing entirely the nucleate boiling regime, which is sometimes referred to as the third heat-transfer crisis [16][17][18][19][20]. Then, the nucleating bubbles on the heater surface rapidly spread, resulting in formation and propagation of vaporization fronts that merge and fully encase it.…”

Section: Introductionmentioning

confidence: 99%

“…Then, the nucleating bubbles on the heater surface rapidly spread, resulting in formation and propagation of vaporization fronts that merge and fully encase it. A number of works reported that vaporization fronts propagate with a constant velocity [18,19,[21][22][23][24]. These works employed water (the latent heat of evaporation L = 2260 kJ/kg) [21,25], refrigerants (L = 246.7 kJ/kg for refrigerant FC-C318 Freon) [22,26], acetone (L = 515 kJ/kg) [16,27], ethanol (L = 844 kJ/kg) [20,27], alkali metals (for potassium L = 2023 kJ/kg, and for cesium L = 497 kJ/kg) [20,28], npentane (L = 356 kJ/kg), [23,29], etc.…”

Section: Introductionmentioning

confidence: 99%

“…[17,24,30]. The assumption of a constant velocity of vaporization fronts was embedded as a cornerstone in a number of theories of the inception of this phenomenon [18,19,21,22]. It should be emphasized that all the liquids employed in such experiments so far, possess relatively high latent heats of evaporation, and accordingly, the heaters were subjected to a relatively high power supply to trigger vaporization fronts.…”

Section: Introductionmentioning

confidence: 99%

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Exponential vaporization fronts and critical heat flux in pool boiling

Staszel

Yarin

2018

International Communications in Heat and Mass Transfer

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Here we study the inception and propagation of vaporization fronts and transition to the critical heat flux (CHF) and film-boiling regime triggered by a steep, almost instantaneous increase in the heat release from a strip heater submerged in Novec 7300 liquid. The propagation path of the resulting vaporization front along the strip heater is measured and shown to be exponentially increasing in time, in distinction from the previous reports in literature claiming that the increase is only linear. Since the previous experiments employed such liquids as water, refrigerants, acetone, ethanol, and alkali metals, which possess relatively high latent heat of evaporation and thus require a relatively high power to be supplied, the heater burnout at the inception of the CHF and film boiling was too fast to allow for longer-time observations. Accordingly, the previous works observed only an extremely short-time asymptotics of the propagation process, which means the short-time expansion of the exponential function, which is linear. On the other hand, in the experiments with Novec 7300 liquid, the heater burnout is delayed due to a much lower latent heat of evaporation, thus allowing for a much longer observation of the propagation path, which appears to be exponentially increasing in time. The experiments were preceded by our theoretical prediction of such a behavior, and this theory is also described in the present work. Due to the fact that this theory has been corroborated by the experimental data, the theory yields an adequate explanation and description of the CHF trigger and film boiling inception.

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“…Evaporation front is a complex nonequilibrium phenomenon which includes interrelated hydrodynamic and heat transfer processes at the interface, and also needs consideration of the arising hydrodynamic front instability, structure formation, evaporation, and thermocapillary effects. There are a few papers dedicated to model description of a self-sustained evaporation front [1][2][3]. But none of these models can describe front behaviour within a wide range of experimental parameters.…”

Section: Introductionmentioning

confidence: 99%

Study on dynamics and structure of evaporation front in ethanol depending on pressure and subcooling

Moiseev

Жуков

2017

MATEC Web Conf.

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Abstract. This paper is dedicated to study of self-sustained evaporation front in subcooled ethanol at stepwise heat generation. The data on evaporation front velocity and microstructure at different subcoolings and pressure are presented. Experiments show that development of the evaporation front drastically depends on studied parameters. At low pressures initial vapour bubbles grow without losing interface stability and initiation of evaporation fronts doesn't occur. At higher pressures the fronts propagate along the heater, and its structure depends on temperature.

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Modeling of the vaporization front on a heater surface

Cited by 15 publications

References 9 publications

Effects of Vessel and Water Temperatures on Direct Injection in Internal Combustion Rankine Cycle Engines

Effects of Vessel and Water Temperatures on Direct Injection in Internal Combustion Rankine Cycle Engines

Exponential vaporization fronts and critical heat flux in pool boiling

Study on dynamics and structure of evaporation front in ethanol depending on pressure and subcooling

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