Imperial College London

Emeritus ProfessorGeoffreyHewitt

Faculty of EngineeringDepartment of Chemical Engineering

Emeritus Professor



+44 (0)20 7594 5562g.hewitt




Mrs Sarah Payne +44 (0)20 7594 5567




507aACE ExtensionSouth Kensington Campus






BibTex format

author = {Ahmad, M and Chandraker, DK and Hewitt, GF and Vijayan, PK and Walker, SP},
doi = {10.1016/j.nucengdes.2012.09.004},
journal = {Nuclear Engineering and Design},
pages = {280--290},
title = {Phenomenological modeling of critical heat flux: The GRAMP code and its validation},
url = {},
volume = {254},
year = {2013}

RIS format (EndNote, RefMan)

AB - Reliable knowledge of the critical heat flux is vital for the design of light water reactors, for both safety and optimization. The use of wholly empirical correlations, or equivalently “Look Up Tables”, can be very effective, but is generally less so in more complex cases, and in particular cases where the heat flux is axially non-uniform. Phenomenological models are in principle more able to take into account of a wider range of conditions, with a less comprehensive coverage of experimental measurements. These models themselves are in part based upon empirical correlations, albeit of the more fundamental individual phenomena occurring, rather than the aggregate behaviour, and as such they too require experimental validation. In this paper we present the basis of a general-purpose phenomenological code, GRAMP, and then use two independent ‘direct’ sets of measurement, from BARC in India and from Harwell in the United Kingdom, and the large dataset embodied in the Look Up Tables, to perform a validation exercise on it. Very good agreement between predictions and experimental measurements is observed, adding to the confidence with which the phenomenological model can be used. Remaining important uncertainties in the phenomenological modeling of CHF, namely the importance of the initial entrained fraction on entry to annular flow, and the influence of the heat flux on entrainment rate, are identified and partially quantified.
AU - Ahmad,M
AU - Chandraker,DK
AU - Hewitt,GF
AU - Vijayan,PK
AU - Walker,SP
DO - 10.1016/j.nucengdes.2012.09.004
EP - 290
PY - 2013///
SP - 280
TI - Phenomenological modeling of critical heat flux: The GRAMP code and its validation
T2 - Nuclear Engineering and Design
UR -
UR -
VL - 254
ER -