Experimental study of critical heat flux in flow boiling under subatmospheric pressure in a vertical square channel

• Published in: International journal of heat and mass transfer 2019-03, Vol.130, p.514-522
• Main Authors: Colgan, Nathan, Bottini, Joseph L., Martínez-Cuenca, Raúl, Brooks, Caleb S.
• Format: Article
• Language: English
• Subjects: Cooling; Critical heat flux; Departure from nucleate boiling; Flow boiling; Heat flux; Heat transfer; Nucleate boiling; Subatmospheric pressure; Wall temperature
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2018.10.082

•Low CHF values are observed in flow boiling of water under subatmospheric pressure.•New data of CHF is obtained across flow rates, subcooling and pressure conditions.•Performance of existing models is shown to vary significantly.•A new model is developed and shown to capture the range of condition considered. Critical Heat Flux (CHF) is the maximal limit of heat flux in two-phase nucleate boiling heat transfer; therefore, an understanding of CHF under a wide range of conditions is important for safe system operation. In this work, CHF experiments are conducted over a range of subatmospheric system pressures in a vertical square channel that is heated on one side. The experimental conditions cover a pressure range of 20 kPa to 108 kPa, a mass flux range of 45–190 kg/m2-s, and an inlet subcooling range of 0–14 K. Heat flux is gradually increased until an excursion of the wall temperature occurs, indicating CHF. For the experimental conditions considered, CHF increases with rising system pressure, mass flux, and inlet subcooling, although the effects of mass flux and inlet subcooling are weak. A new correlation for CHF is developed and found to predict the data with an average error of ±15.6%.