Two-dimensional laminar heat transfer between a series of parallel plates with surface mounted block heat sources was numerically studied. These channels resemble cooling passages of electronic equipment. Consideration was given only to periodically fully developed flow (PDF) and heat transfer. The computational domain was subjected to periodic condition in the streamwise direction and repeated condition in the cross-stream direction (double cyclic). The governing equations were solved by a finite volume technique. Calculations were made for a wide range of independent parameters (Re, ks/kf, s/w, d/w, H/w, and t/H). Consideration was given only to airflow (Pr= O. 7). The friction factor was found to be a strong function of channel height and a weak function of block spacing. The thermal performance was studied in terms of the average Nusselt number and overall thermal resistance. For the most part, the thermal performance was independent of the Reynolds number, however, it deteriorated drastically for Re ≪ 500. The thermal resistance was found to decrease with an increase in substrate conductivity up to a particular value of ks/kf, and beyond this value thermal resistance dM not decrease further. This value of ks/kf is a function of geometric parameters and occurs between 1 and 10. Correlations in terms of independent parameters were developed for friction factor, average Nusselt number, and thermal resistance. © 1995 by ASME.