A New Perspective on Heat Transfer Mechanisms and Sonic Limit in Pool Boiling

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Superheated Liquid ◽  
Heater Surface ◽  
Liquid Stream ◽  
Maximum Heat ◽  
Pool Boiling Heat Transfer ◽  
Maximum Heat Transfer ◽  
Secondary Evaporation

Pool boiling is postulated as a single-phase heat transfer process with nucleating bubbles providing a liquid pumping mechanism over the heater surface. This results in three fluid streams at the heater surface—outgoing vapor and liquid streams, and an incoming liquid stream. Heat transfer during periodic replacement of the liquid in the influence region around a nucleating bubble is well described by transient conduction (TC) and microconvection (MiC) mechanisms. Beyond this region, free convection (FC) or macroconvection (MaC) contributes to heating of the liquid. A bubble growing on the heater surface derives its latent heat from the surrounding superheated liquid and from the microlayer providing a direct heat conduction path. Secondary evaporation occurs in the bubbles rising in the bulk after departure, and at the free surface. This secondary evaporation does not directly contribute to the heat transfer at the heater surface but provides a means of dissipating liquid superheat. A sonic limit-based model is then presented for estimating the theoretical upper limit for pool boiling heat transfer by considering the three fluid streams to approach their respective sonic velocities. Maximum heat transfer rates are also estimated using this model with two realistic velocities of 1 and 5 m/s for the individual streams and are found to be in general agreement with available experimental results. It is postulated that small bubbles departing at high velocity along with high liquid stream velocities are beneficial for heat transfer. Based on these concepts, future research directions for enhancing pool boiling heat transfer are presented.

Numerical Investigation on Pool Boiling Over a Vertical Tube Coupled With In-Tube Condensation

2019 ◽  
Author(s):  
Shuai Ren ◽  
Wenzhong Zhou
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Boiling Heat Transfer ◽  
Power Plants ◽  
Pool Boiling ◽  
Heat Removal ◽  
Vertical Tube ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract Pool boiling and in-tube condensation phenomena have been investigated intensively during the past decades, due to the superior heat transfer capacity of the phase change process. In passive heat removal heat exchangers of nuclear power plants, the two phase-change phenomena usually occur simultaneously on both sides of the tube wall to achieve the maximum heat transfer efficiency. However, the studies on the effects of in-tube condensation on external pool boiling heat transfer are very limited, especially in numerical computation aspect. In the present study, the saturated pooling boiling over a vertical tube under the influences of in-tube steam condensation is investigated numerically. The Volume of Fluid (VOF) interface tracking method is employed based on the 2D axisymmetric Euler-Euler multiphase frame. The phase change model combining with a mathematical smoothing algorithm and a temporal relaxation procedure has been implemented into CFD platform by user defined functions (UDFs). The two-phase flow pattern and bubble behavior have been analyzed. The effects of inlet steam mass flow rate on boiling heat transfer are discussed.

Experimental Study of Subcooled Pool Boiling Heat Transfer on Metal Foam

2011 ◽  
Author(s):  
Juan Shi ◽  
Anthony M. Jacobi ◽  
Zhenqian Chen
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Boiling Heat Transfer ◽  
Metal Foam ◽  
Pool Boiling ◽  
Metal Foams ◽  
Working Fluid ◽  
Maximum Heat ◽  
Pool Boiling Heat Transfer

The present experimental study is focused on subcooled pool boiling heat transfer on aluminum metal foam at atmospheric pressure. Experiments are conducted with open-cell metal foam of different porosity and different thickness, using water as the working fluid. The surface superheat ranges up to 15 °C, with maximum heat flux of about 30 W/cm2. The thermal performance of pool boiling on metal foams is compared to that on a roughened copper surface of the same dimensions. The thickness and the geometry of metal foams significantly influence the pool boiling heat transfer coefficient. The effect of orientation on the thermal performance in metal foam is also studied. The surface temperature excursion at boiling incipience and small hysteresis is observed in the experiments. When the metal foam thickness is reduced, hysteresis becomes more significant.

Numerical Study of Pool Boiling Heat Transfer From Surface With Protrusions Using Lattice Boltzmann Method

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Kaushik Mondal ◽  
Anandaroop Bhattacharya
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Boiling Heat Transfer ◽  
Plane Surface ◽  
Pool Boiling ◽  
Geometrical Parameters ◽  
Maximum Heat ◽  
Pool Boiling Heat Transfer ◽  
Boltzmann Method

Abstract This paper reports our numerical studies on pool boiling heat transfer from a plane and with protruding surface using single component pseudo-potential phase change model of lattice Boltzmann method. The surface protrusions are assumed to be rectangular in shape with a given height and width. The surface protrusions are seen to promote nucleation of bubbles from the heated surface resulting in significantly higher heat transfer rates compared to the plane surface. Spatial and temporal averaged heat fluxes from all these protruding surfaces are found to be 3–4 times higher than that of a plane surface. The effects of the protrusion height, width, spacing, and associated geometrical parameters on surface heat flux have been investigated in order to arrive at an optimal design for maximum heat transfer.

Effects of Surface Orientation on the Pool Boiling Heat Transfer in Water/2-Propanol Mixtures

1999 ◽  
Vol 121 (1) ◽  
pp. 80-88 ◽  
Author(s):  
S. Ahmed ◽  
V. P. Carey
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Heat Flux ◽  
Binary Mixtures ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Bulk Liquid ◽  
Heater Surface ◽  
Pool Boiling Heat Transfer

To explore the role of Marangoni effects in the pool boiling heat transfer of binary mixtures, experiments have been conducted with water/2-propanol mixtures at three different concentrations under normal gravity with different orientations of the heater surface. The system pressure was subatmospheric (∼5.5 kPa) and the bulk liquid temperature was near the saturation temperature of the fluids tested. The molar concentrations of2-propanol tested were 0.015, 0.025, and 0.1. These concentrations of 2-propanol are selected because their strong variation of surface tension with concentration gives rise to high surface tension gradients near the heater surface during nucleate boiling. Boiling curves were obtained both for an upward-facing and a downward-facing heater surface. For each concentration of 2-propanol, the critical heat flux has been reached in both orientations of the heater surface. Models of pool boiling heat transfer and the critical heat flux condition for binary mixtures are tested to correlate the data. Comparison of boiling curves and CHF obtained at different orientations of the heater surface indicates that there is strong gravity independent mechanism of boiling heat transfer in these mixtures.

Nucleate Pool Boiling Heat Transfer in Microgravity

1998 ◽  
Vol 29 (1-3) ◽  
pp. 196-207
Author(s):  
Haruhiko Ohta ◽  
Koichi Inoue ◽  
Suguru Yoshida ◽  
Tomoji S. Morita
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Pool Boiling ◽  
Pool Boiling Heat Transfer

SOME PROBLEMES ON POOL BOILING HEAT TRANSFER

1970 ◽  
Author(s):  
V. I. Subbotin ◽  
D. N. Sorokin ◽  
A.A, Tsiganok
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Pool Boiling Heat Transfer
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