Open Access

ARTICLE

Experimental Study on the Flow Boiling of R134a in Sintered Porous Microchannels

Shuo Wang^1,2,*, Huiming Wang^1,2, Ying Zhang^1,2, Zhiqiang Zhang^1,3, Li Jia^1,2
1 Beijing Key Laboratory of Flow and Heat Transfer of Phase Changing in Micro and Small Scale, Beijing, 100044, China
2 Institute of Thermal Engineering, School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing, 100044, China
3 Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce, Tianjin, 300134, China
* Corresponding Author: Shuo Wang. Email:
(This article belongs to the Special Issue: Advances in Microscale Fluid Flow, Heat Transfer, and Phase Change)

Frontiers in Heat and Mass Transfer https://doi.org/10.32604/fhmt.2025.073226

Received 13 September 2025; Accepted 21 October 2025; Published online 20 November 2025

Abstract

This experimental investigation was conducted on the flow boiling performance of refrigerant R134a in two types of parallel microchannels: sintered porous microchannels (PP-MCs) and smooth parallel microchannels (SP-MCs). The tests were performed under controlled conditions including an inlet subcooling of 5 ± 0.2°C, saturation temperature of 33°C, mass fluxes of 346 and 485 kg/m²·s, and a range of heat fluxes. Key findings reveal that the sintered porous microstructure significantly enhances bubble nucleation, reducing the wall superheat required for the onset of nucleate boiling (ONB) to only 0.13°C compared to 2.2°C in smooth channels. The porous structure also improves heat transfer coefficients at low and medium heat fluxes (<20–30 W/cm²) and low vapor quality (x < 0.2–0.4) due to augmented thin-film evaporation and intensified nucleate boiling. However, smooth microchannels exhibit superior performance under high heat flux and high vapor quality conditions, as the porous structure is prone to early dry-out and flow blockage. Notably, the porous microchannels demonstrate lower flow resistance and enhanced stability, with pressure drop fluctuations reduced by up to 46.4% in amplitude and 44.8% in standard deviation, attributed to improved capillary-assisted liquid replenishment and suppressed flow oscillations. The results underscore the potential of PP-MCs as a high-performance cooling solution for high-heat-flux applications.

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Keywords

Flow boiling; porous microchannels; heat transfer; pressure drop; flow instability; R134a; sintered surface

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