The mathematical formulation of a heat transfer flow problem was developed assuming a laminar velocity distribution in both inner and annular channels with ignoring axial conduction, and the analytical solution was obtained using an orthogonal expansion technique in terms of power series. Qualitative agreement was achieved between the analytical solutions and the experimental results. Comparisons made between the results from the double-pass concentric circular heat exchanger and those in a single-pass device (open conduit) are presented graphically. A considerable improvement in heat transfer is obtainable by employing double-pass devices instead of single-pass.