The non-invasive optical techniques of holographic interferometry and liquid crystal thermography have been applied to the study of heat transfer by forced convection from a rib-toughened channel. Two test sections were built in order to carry out separate experiments using the two optical methods. The investigated geometry consisted of a plane heated wall with square ribs attached at regular intervals. The rib pitch to height ratio was 7.2 for all experiments. Results obtained from both techniques, presented in terms of local Nusselt number distributions, were found to be in satisfactory agreement.