Heat transfer coefficients in a two-dimensional serpentine channel with a series of right angle turns are measured in the turbulent flow regime using the naphthalene sublimation technique. The experimental results are compared with the numerical predictions in the periodically fully developed region. The local heat transfer coefficients are measured in the periodically fully developed region at Re = 18,460 and Re = 32,940. To examine the continuous variation of local heat transfer distributions, heat transfer coefficients are measured throughout the channel surfaces (from the entrance to the periodically fully developed region) at Re = 32,940. By analyzing the experimental results, it is found that a region where flow impinges reaches the periodically fully developed condition in a relatively short distance from the channel entrance compared to a region where flow recirculates. The thermal field in the channel investigated becomes periodically fully developed after three flow turns. The numerical prediction by the standard k-ε turbulence model underpredicts the average heat transfer coefficients by 15.0 to 17.4% in the periodically fully developed region.