Hot spots in heat transfer

It is often important in engineering development work to identify regions in heat transfer equipment at which the convective heat transfer coefficient to a stream of coolant is abnormally low; such potential 'hot spots' limit the overall efficiency or performance of the heat transfer system. It is generally extremely laborious and difficult to detect all such regions by direct measurement; and the fluid flow patterns are often so complicated as to preclude a priori calculation of local heat transfer coefficients.