Pool boiling performance of oxide nanofluid on a downward-facing heating surface

Kerntechnik ◽  
2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhibo Zhang ◽  
Huai-En Hsieh ◽  
Yuan Gao ◽  
Shiqi Wang ◽  
Jia Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Roughness ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Heating Surface ◽  
Nano Particles

Abstract In this study, the pool boiling performance of oxide nanofluid was investigated, the heating surface is a 5 × 30 mm stainless steel heating surface. Three kinds of nanofluids were selected to explore their critical heat flux (CHF) and heat transfer coefficient (HTC), which were TiO2, SiO2, Al2O3. We observed that these nanofluids enhanced CHF compared to R·O water, and Al2O3 case has the most significant enhancement (up to 66.7%), furthermore, the HTC was also enhanced. The number of bubbles in nanofluid case was relatively less than that in R·O water case, but the bubbles were much larger. The heating surface was characterized and it was found that there were nano-particles deposited, and surface roughness decreased. The wettability also decreased with the increase in CHF.

Effect of Particle Morphology on Pool Boiling From Surfaces Coated With Sintered Particles

2015 ◽  
Author(s):  
Suchismita Sarangi ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Particle Morphology ◽  
Wall Superheat

Immersion cooling strategies often employ surface enhancements to improve the pool boiling heat transfer performance. Sintered particle/powder coatings with different constituent particle sizes and total layer thicknesses have been commonly used on smooth surfaces to reduce the wall superheat and increase the critical heat flux during pool boiling. However, the role of the particle morphology on pool boiling has not been explicitly investigated. Since the morphology of the particles affects the pore shape, permeability, surface roughness, effective conductivity and diffusivity of the sintered coating, it will impact the heat transfer coefficient and critical heat flux during boiling. In this study, pool boiling of FC-72 is experimentally investigated using copper surfaces coated with a layer of sintered copper particles of irregular, dendritic and spherical morphologies. In order to isolate the effect of particle morphology, particles with the same effective diameter (90–106 μm) are sintered under controlled conditions that yield the same porosity (∼60%) and coating thickness (∼6 particle diameters) for all samples tested. The effects of particle morphology on the incipient wall superheat, nucleate boiling heat transfer coefficient, and critical heat flux are analyzed. The morphology of the pore structure in the coating formed by sintering is observed with SEM images; bubble nucleation and departure characteristics affecting the heat transfer performance of the coatings are qualitatively assessed with the aid of high-speed flow visualizations to corroborate the trends observed in the boiling curves. The irregular particles are observed to show the highest heat transfer coefficient, followed by dendritic and then spherical particles. The critical heat flux is found to be independent of the particle morphology.

High Speed Imaging of Bubble Interface Motion in a Tapered Microgap

2020 ◽  
Author(s):  
Aranya Chauhan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
High Speed ◽  
Pool Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
Interface Motion

Abstract The current industrial trend requires development of efficient heat dissipation systems. A tapered microgap on the heater surface provides an efficient pool boiling heat transfer technique in dissipating large heat fluxes. This study is focused on capturing the high-speed images of bubble nucleation, growth and expansion processes. The interface velocities are estimated by tracking the interface of the growing bubble. The insight into interface motion will help in estimating the magnitude of the expanding force and predicting the pressure recovery effect during two-phase flow in the gap. The expansion force helps in establishing high flow rates resulting in high heat transfer coefficient (HTC) and critical heat flux (CHF) values. The effect of design parameters such as taper angle and height of the microgap on the bubble growth patterns are evaluated. The results show that the bubbles are nucleated and are then confined in the narrow gap. The tapered configuration propels the leading bubble interface in the flow direction and eventually the entire bubble in that direction. The bubble motion causes liquid to enter from the narrow region of the microgap. This effect, combined with the pressure recovery resulting from the two-phase flow in the expanding section of the microgap provides a bubble pumping mechanism. This configuration results in improving both the critical heat flux and heat transfer coefficient during pool boiling.

scholarly journals A comprehensive review on pool boiling heat transfer using nanofluids

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 3209-3237 ◽  
Author(s):  
Asif Khan ◽  
Hafiz Ali
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Research Work ◽  
Research Area ◽  
The Status

Nanofluids are suspensions of nanoparticles with small concentration spread in base fluids such as water, oil and ethylene glycol. Nanofluid boiling is an important research area which provides many chances to explore new frontiers but also poses great challenges. Over the last decade, various studies have been carried out on pool boiling of nanofluids for the enhancement of critical heat flux which is otherwise limited by the use of base fluids. Several efforts have been made in the literature on nanofluid boiling, however, data on the boiling heat transfer coefficient and the critical heat flux have been unpredictable. Current study is a review of the status of research work on effects of nanofluids on heat transfer coefficient and critical heat flux. An emphasis is put in a review form on the recent progresses in nanofluid heat transfer coefficient and critical heat flux of pool boiling. This study also focuses on advancements in nanofluids, their properties and various parameters affecting boiling critical heat flux and heat transfer coefficient. At the end correlations used by different researchers to find out the critical heat flux and heat transfer coefficient are listed.

Heat Flux Controlled Pool Boiling of Zirconia–Water and Silver–Water Nanofluids on a Flat Plate: A Coupled Map Lattice Simulation

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Sayan Sadhu ◽  
P. S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Roughness ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Pool Boiling ◽  
Coupled Map Lattice ◽  
Nanoparticle Concentration ◽  
Cml Model

In the present work, the characteristic atmospheric saturated heat flux controlled pool boiling curves for zirconia–water and silver–water nanofluids have been reproduced by the coupled map lattice (CML) method using a two-dimensional (2D) boiling field model. The heater is a long horizontal flat plate of thickness 0.44 mm. The pool height is 0.7 mm. The stirring action of the bubbles is modeled by increasing the fluid thermal diffusivity by an enhancement factor. The thermal conduction in the plate is also incorporated into the model. The basic advantage of CML is that individual bubbles are not tracked, and yet the effects of bubbles are reflected qualitatively in the final solution. In the simulation of atmospheric saturated pool boiling of water minimum cavity diameter taken is 0.8 μm based on which a random distribution of cavity sizes has been specified. In the boiling of ZrO2–water nanofluid there is a deposition of nanoparticles in the cavities on the heated surface resulting in reduction of surface roughness. This feature is taken care of by proportionate decrease in minimum cavity diameter. The CML model predicts decrease in heat transfer coefficient and increase in critical heat flux (CHF) with increase in zirconia nanoparticle concentration. In the case of Ag–water nanofluid no such deposition of nanoparticles has been reported; rather surface oxidation occurs which increases the surface roughness. This is simulated by proportionately increasing the minimum cavity diameter with weight fractions of nanoparticles. The present CML model predicts increase in the heat transfer coefficient and decrease in CHF with increase in silver nanoparticle concentration. Thus, the CML results for the boiling of the aforesaid two nanofluids match qualitatively with the published experimental works.

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