Investigation of near-critical heat transfer in rectangular microchannels with single wall heating using infrared thermography

Abstract

This paper characterizes the thermal-hydraulic behavior of carbon dioxide near the critical point in rectangular microchannels with uniform heating limited to a single wall of the flow channel. Experiments were conducted in a horizontal, bottom heated channel with a hydraulic diameter of 923 µm and an aspect ratio (AR=WchHch) of 3.33. Experimental variables included the mass flux (430≤G≤800 kg m−2 s−1), heat flux (5.7≤q″≤14.12 W cm−2), inlet temperatures (31≤Tin≤32.9 ∘C), and a reduced pressure (PR) of 1.04. To limit the heating to a single wall of the flow channel, a novel test section was designed and built using Inconel-718, Torlon 4203, and stainless steel. Infrared thermography was used to obtain local heat transfer data. Existing supercritical heat transfer correlations, developed for uniform wall heating conditions, did not accurately predict the heat transfer for single wall heating boundary conditions.