A Simple Model to Identify Dryout Location: Validation and Computational Fluid Dynamics Predictions

Abstract

Prediction of dryout location is essential to identify reliable heat flux margins for the safe operation of different thermal systems. The present study proposes a simple model to predict the dryout type critical heat flux location in a circular tube and an annulus. Based on the flow topology, the annular flow boiling regime is demarcated into two zones viz., vapor flow in the core region and liquid film flow in the annular gap between the vapor core and the wall surface. An expression is derived for the dryout location which is purely a function of operating conditions and fluid properties. The dryout location and quality predictions of the present model are found to be in very good agreement and within 10% error margin against the experimental data for tube and annulus geometries. The present study is extended to investigate the effect of eccentricity on the dryout location and the inner wall temperature. It is observed that the eccentricity results in early occurrence of dryout in the narrow gap region of an eccentric annulus. Furthermore, the predictions from the present model are compared with the look-up table data, subchannel analysis and computational fluid dynamics simulation predictions.

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Notes on contributors

Harish Pothukuchi

Harish Pothukuchi obtained his masters and Ph.D. from the Indian Institute of Technology Madras, India. He specializes in multiphase flows and in particular, thermal hydraulics of rod bundles. He has computationally investigated the prediction of critical heat flux in annular geometries and rod bundles. He worked at RWTH Aachen on an exchange fellowship for a period of six months. He was awarded IIT Madras Institute Research award for the year 2018. During 2015, at the Indo-UK workshop at IGCAR Kalpakkam, he received the best poster award. He is currently working as Assistant Professor in the Department of Mechanical Engineering, IIT Jammu.

Prasad Patnaik B. S. V.

B. S. V. Prasad Patnaik received his Ph.D. from the Indian Institute of Technology Madras in 1998. During 1998-99, he was a post-doctoral fellow at UBC, Canada. He taught at the National University of Singapore during 1999-2006, before moving back to IIT Madras. He is currently working as Professor in the Department of Applied Mechanics at IIT Madras, Chennai. He specializes in CFD. His research interests include fluid structure interaction, nuclear thermal systems and bio-fluid mechanics. He is currently the Secretary for the Indian Society for Heat and Mass Transfer (ISHMT), with its Head Quarters in IIT Madras, Chennai.

Bhamidi V. S. S. S. Prasad

Bhamidi V. S. S. S. Prasad received his Ph.D. from Indian Institute of Technology Kharagpur, in 1986. He worked as Lecturer and Assistant Professor at IIT Kharagpur, prior to joining IIT Madras as Associate Professor in 1995. He is currently working as Professor in the Department of Mechanical Engineering, IIT Madras. He was a Visiting Research Scientist and Visiting Professor at University of Michigan, Dearborn, USA and Technical University of Nova Scotia, Halifax, Canada, respectively, during 1991-93. His research interest includes fluid flow and heat transfer pertaining to turbomachinery, CFD, fluidized bed technology and heat flux measurements. He mainly works on gas turbine blade cooling. He holds one patent on heat flux measurement. He has edited 8 conference proceedings. He is a life member of several professional Societies and currently President of both FMFP and FPSI (Madras Chapter).