High-Pressure Pool-Boiling Heat Transfer Enhancement Mechanism on Sintered-Particle Wick Surface

Smreeti Dahariya,Gisuk Hwang,Munonyedi K Egbo,Amy Rachel Betz,Nill Patel

doi:10.3389/fmech.2019.00071

Smreeti Dahariya, Gisuk Hwang + Show 3 more

Open Access

https://doi.org/10.3389/fmech.2019.00071

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Abstract

We experimentally study high-pressure pool-boiling heat transfer enhancement using a copper sintered-particle wick structure in water. The wicks are fabricated using the multi-step sintering process using 200 μm sintered copper powder. Thermophysical properties of water change at elevated pressure, therefore changing the bubble dynamics. For the monolayer wick, the Critical Heat Flux (CHF) 179.63 W/cm2, 182.42 W/cm2, and 198.16 W/cm2 are found at 0, 103.4, and 206.8 kPa, respectively. The maximum CHF is found at 206.8 kPa with the wick superheat of 9.89 K. A 110% enhancement is found in the CHF for 206.8 kPa, compared to 0 kPa. While we observe the CHF is 1.8 times higher as compared to the plain copper surface at 0 kPa. The maximum heat transfer coefficient, 252.46 W/cm2 K is found at heat flux 100 W/cm2 for 206.8 kPa. The high-pressure boiling result for the monolayer wick shows that the heat transfer coefficient is enhanced by 100% compared to 0 kPa. We suggest the reasons of enhancements in the pool-boiling performance are primarily due to high rate of bubble generation, high bubble release frequency and reduced thermal-hydraulic length modulation, and enhanced thermal conductivity due to the sintered wick layer. Our analysis suggests that the Rayleigh-critical wavelength decreases by 4.67 % with varying pressure, which may cause the bubble pinning between the gaps of sintered particles preventing bubble coalescence. Similarly, the dominant role of pressure over the wicking layer is also analyzed and found that the critical flow length, λu reduces by three orders of magnitude with 200 μm particles. We suggest that the porous wick layer provides a capillary-assist to liquid flow effect, and delays the surface dry out. The surface modification and the pressure amplify the boiling heat transfer performance. All these reasons may contribute to the CHF, and HTC enhancement in the wicking layer at high pressure.

Highlights

There is a need to improve advanced thermal management systems reliability and prevent premature failure in space applications, including efficient electricity production, water desalination, smart buildings, and food production
We suggest the reasons for enhancement of the pool-boiling performance is primarily due to high rate of bubble generation, high bubble release frequency, and reduced thermal-hydraulic length modulation, and enhanced thermal conductivity due to the sintered wick layer
The real technical challenges lie in the reduced heat transfer performance, i.e., Heat Transfer Coefficient (HTC), and limited Critical Heat Flux (CHF)

Summary

Introduction

There is a need to improve advanced thermal management systems reliability and prevent premature failure in space applications, including efficient electricity production, water desalination, smart buildings, and food production. Due to the excessive generation of heat in electronic devices, twophase liquid-vapor phase-change heat transfer has been received considerable interest in electronics cooling to transfer a large amount of heat in a small thermal resistance. Nucleate poolboiling is a simple, efficient, and reliable cooling approach. The real technical challenges lie in the reduced heat transfer performance, i.e., Heat Transfer Coefficient (HTC), and limited Critical Heat Flux (CHF). Zuber initially developed the theory for the Critical Heat Flux using hydrodynamic instability model for an infinite plain surface (Zuber, 1959).

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