During a loss of coolant accident (LOCA), in a nuclear-pressurized water reactor, fuel assemblies can be damaged and water is injected to cool down the core. In this hypothetical situation, a dispersed flow of steam and droplets occurs downstream of the quenching front. This two-phase flow propagates through the assemblies which can be deformed due to the swelling of the fuel rods' cladding causing blocked sub-channels. This complex flow plays an important role in the initial cooling of fuel rods that are not yet immersed into water. However, blocked sub-channels cooling is degraded because of the preferential steam flow towards less blocked regions. In previous work, we presented a mechanistic model implemented in the NECTAR code, which calculates heat and mass transfer phenomena as well as droplets dynamics in a polydispersed flow film boiling. NECTAR was validated with experimental measurements using three different geometries representing the cladding ballooning at a sub-channel scale. The French Institut de Radioprotection et de Sûreté Nucléaire (IRSN) has recently performed measurements of flow redistribution in a 7×7 fuel rods bundle with 4×4 ballooned rods under different geometric conditions (blockage ratio, length, and coplanarity), as well as different flow rates, showing that the blockage ratio is the predominant factor in the amount of deviated flow. In this article, we analyze the influence of the steam deviation on the heat transfer in a blocked subchannel, with different blockage ratios (61% and 90%) and lengths (100 mm and 300 mm) for representative LOCA conditions. The internal heat dissipation is evaluated and the contributions of the different involved mechanisms are analyzed.