Design, fabrication and testing of hybrid micro nano surfaces for nucleate pool boiling heat transfer

S.A. khan
Hamad Bin Khalifa University,
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Keywords: nucleate pool boiling, concentrated photovoltaics, thermal management;,critical heat flux;,micro-nano scale surfaces, hybrid micro-nano coatings

Summary:

Nucleate pool boiling heat transfer (NBHT) offers a promising solution to this problem with the ability to effectively remove high heat flux from a confined place in small temperature differences (N. Sezer et al., 2019; Nurettin Sezer et al., 2019; Nurettin Sezer & Koc, 2018). The technique has been well known and applied in various applications in electronics, nuclear power plants, space crafts, and satellites, but has rarely been studied for thermal management of photovoltaics Surface and working fluid modification are main techniques used in literature for the enhancement of NBHT enhancement (Shoukat Alim Khan et al., 2019; Min et al., 2009). Both nano and micro-coating has widely been used in literature for the enhancement of nucleate pool boiling (Gilmore et al., 2018; Shoukat A Khan et al., 2018). Keeping in view the enhanced performance of both micro and nano scale, in literature, this study investigates the synergistic performance of hybrid micro-nano porous surfaces (HMNP) for nucleate pool boiling (NBHT). A new set of HMNP surfaces was prepared by two-step method of hot powder compaction of micro-particles followed by nanoparticles coating. Three different surfaces, i.e., plain (P), microporous (MP), and hybrid micro-nano porous (HMNP) were examined for NBHT performance with de-ionized (DI) water as working fluid. In HMNP surfaces three different concentration of nanoparticles 0.0001%, 0.001%, and 0.01% were used for coating. MP showed enhanced HTC and CHF performance, which was further improved by HMNP coating with the highest performance at 0.01% concentration. Compared to P surface, the maximum increase for CHF of MP and HMNP was 1.79 and 2.5 times while the maximum increase in HTC was 1.8 and 2.33 for MP and HMNP surfaces, respectively. For the lowest applied heat flux of 110 kW/m2, the maximum decrease in wall superheat for MP, and HMNP coating was 2.5°C and 3.7°C, respectively as compared to the P surface. The increase in CHF and HTC was observed to increase with an increase in the concentration of coated nanoparticles in HMNP surface. Bubble dynamics were observed by the high-speed camera and Scanning Electron Microscope (SEM) analysis, and contact angle analysis were performed for P, MP and HMNP surfaces.