Measurement of radiation heat transfer in supercritical carbon dioxide medium

•A first-of-its-kind measurement of radiation flux & emissivity of s-CO2 is presented.•s-CO2 acts as a participating medium: ignoring radiation may bring substantial errors.•Radiative heat transfer component was found to be significant in comparison to convection.•The current measurement confirms need for detailed spectroscopic studies for s-CO2. In this work, a novel experimental method for measurement of radiation emitted by supercritical carbon dioxide (s-CO2) at high pressure and high temperature is presented. Due to high pressure conditions, use of conventional spectroscopic methods to measure radiative properties of s-CO2 is challenging. In the present method, supercritical conditions are created in a shock tube by using carbon dioxide (CO2) as the driven gas. The radiative emission by s-CO2 is measured using a platinum based thin film sensor. The total emissivity for s-CO2 is estimated and the value compares favourably with that predicted theoretically using a standard method available in literature. It is estimated that the total emissivity value of supercritical conditions is nearly 0.2 for the conditions studied, implying that s-CO2 acts as a participating medium for radiation heat transfer. The outcome of this study will have significant impact on the design of heat transfer equipment such as solar thermal receivers and heat exchangers typically used in s-CO2 based closed Brayton cycle, for which participating medium radiation heat transfer has been neglected traditionally.