9.69. The heat flow from a fuel rod to the coolant proceeds through several resistances in series, the last of which is associated with the heat- transfer coefficient at the cladding-coolant interface. This resistance can vary over a wide range, depending on flow conditions and other param­eters, and so it is an important consideration both in the initial reactor design and in the analysis of the consequences of various accident possi­bilities. For example, an increase in resistance, corresponding to a decrease in the heat-transfer coefficient, would result in an increase in the temper­ature difference between the cladding and the bulk of the coolant if the heat flux were to remain constant. If the coolant temperature is not to change, the net result would be an increase in the temperature at the outer surface of the cladding, and ultimately in the temperature of the fuel, as can be seen from equation (9.21) et seq. Thus, an examination of the considerations that affect the convection heat transfer is important in re­actor design.