The effect of flow pattern on the heat transfer performance during the transportation of gas-Newtonian/non-Newtonian liquids two-phase flow in a horizontal microchannel

The objective of the present research is to investigate the impact of flow patterns on the heat transfer process of gas-Newtonian/non-Newtonian liquid two-phase flow in a horizontal microchannel. A square copper microchannel with a side length of 8 x 10-4 m was employed. Various working liquids were examined, including water, 0.2 %wt CMC (Carboxymethyl Cellulose) aqueous solutions, 0.4 %wt CMC, and 0.2 %wt XG (Xanthan Gum). Nitrogen was used as the working gas. The liquid apparent velocity, jL was varied in the range of 0.05-1.0 m/s, while the gas apparent velocity, jG ranged from 0.26 to 7.81 m/s. Some of DPTs (Differential Pressure Transducers) were used to measure the pressure drop. A constant heat flow of 12.08 kW/m2 was maintained, and the temperature of the channel's wall was monitored using a T-type thermocouple located on the copper channel as the heating section. Flow patterns were captured with a high-speed video camera. Results revealed four distinct flow patterns: BB (bubbly), SL (slug), SA (slug-annular), and CH (churn) flow. The coefficient of convective heat transfer in the CH flow exhibited the highest value in comparison with other observed flow patterns. However, the CH flow pattern also resulted in the highest-pressure gradient in both the upstream heating and heating sections. Furthermore, correlations proposed by Kawahara et al. (2011) and Rezkallah (1986) demonstrated good agreement with the present experimental data for pressure gradient and coefficient of convective heat transfer hTP, respectively. Despite this, the SL flow exhibited the best performance index for the heat transfer process in the present gas-non-Newtonian two-phase flow. Furthermore, the use of a nonNewtonian liquid in the present experimental study suggests its potential application as a cooling fluid.