In order to promote the engineering application of petal-shaped fuel rods in water-cooled reactors,it is necessary to understand the subcooled flow boiling characteristics of coolant in the sub-channels of petal-shaped fuel rod bundles.The Euler model and wall boiling model were applied to numerically simulate the subcooled flow boiling under the coupling effect of 3×3 petal-shaped fuel rods and coolant.Using the simulation results,the distribution of parameters such as void fraction,wall temperature and transverse flow velocity in different sub-channels,as well as the effects of uniform heating mode and axial cosine heating mode on flow and heat transfer were explored.The research results indicate that subcooled boiling occurs first on corner fuel rods,and with the increase of heating power,the position unevenness of onset of nucleate boilding(ONB)of subcooled boiling of the corner,edge and center fuel rods decreases.Under the same heating conditions,the wall superheat at ONB on the corner fuel rod is the largest,followed by the edge fuel rod and the center fuel rod is the smallest.The surface heat flux at the inner concave arc of the fuel rod is greater than that at the outer convex arc.Under the condition of constant total heating,cosine heating reduces the non-uniformity of wall temperature compared with uniform heating.
Small-scale nuclear reactorPetal-shaped fuel rodSubcooled flow boilingOnset of nucleate boiling(ONB)
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