Comprehensive Experimental Investigation of Flow Boiling Performance in a Single Microchannel Utilizing Silver and Multi-Walled Carbon Nanotube Hybrid Nanofluids

Abstract

This study investigates the occurrence of flow boiling in a microchannel with a uniform cross-sectional area. The primary emphasis is placed on the attributes and qualities of deionized water when it is subjected to temperatures lower than its boiling point. The experiments utilized deionized water as the working fluid in a rectangular microchannel with a consistent cross-sectional shape. The experiments were conducted at an input temperature of 80°C, with a mass flux of 200 kg/m²s and a heat flux ranging from 1.735 to 625.1 kW/m². The increase in wall superheat is exactly proportional to the increase in heat flow, indicating that the onset of nucleate boiling (ONB) occurs at a far lower point in nanofluid channels compared to bare channels. The observed rise in heat transfer coefficient (HTC) at a mass flow rate of 200 kg/m²s suggests that nanofluids in microchannels demonstrate a similar pattern to microchannels without nanoparticles. The average heat transfer coefficient (HTC) for microchannels filled with nanofluids containing silver (Ag), multi-walled carbon nanotubes (MWCNTS), and a combination of Ag and MWCNTS (in a 1:1 ratio) is enhanced by 9%, 14.5%, and 18.01%, respectively, compared to the microchannel without any additives.

The pressure drop decreases significantly as the wall heat flux increases due to the reduced viscosity of the liquid. However, the phenomenon of pressure decrease experiences a change throughout the boiling process. The pressure reduction in microchannels containing nanofluids has a similar trend to that of the microchannel without any additives, where an increase in heat flow corresponds to an increase in pressure drop. The pressure drop for Ag, MWCNTS, and the Ag plus MWCNTS mixture is respectively 3.3%, 4.4%, and 10.4% higher compared to the bare channel. This study provides valuable insights into the behavior of deionized water and nanofluids in microchannels under various heat conditions.