Laminar developing flow (DF) and heat transfer between a series of conducting parallel plates (substrate) with surface mounted heat generating blocks were numerically studied with consideration given to flow of air (Pr = 0.7). These channels resemble cooling passages of electronic equipment. A single channel subjected to a repeated condition in the transverse direction was isolated as a computational domain. The governing equations were solved by a finite volume technique. The results of the DF problem were compared with the corresponding periodically fully developed flow (PDF) problem results and used to establish entry length. Thermal entry length decreased with an increase in substrate conductivity. Thermal performance of channels was characterized in terms of thermal resistance per unit length of the channel. To separate the effects of self heating and upstream heating for each module, thermal resistance based on the channel inlet temperature (R(o)) and module inlet bulk temperature (R(m)) was defined. These thermal resistances were correlated with the independent parameters such as the Reynolds number (Re), substrate thickness (t/w), block height (h/w), block spacing (s/w), channel height (d/w), and thermal conductivity ratio of the solid to fluid (K-s/K-f). The thermal resistance was found to decrease with an increase in Reynolds number, block spacing and substrate conductivity. The thermal resistance increased with an increase in the area of bypass flow (1 - h/d), substrate thickness (t/w) and block height (h/w).