This study is concerned with the heat transfer characteristics in the entrance region of an annulus with varying cross-section by using liquid crystal technique. The surface temperatures were experimentally obtained by observing liquid crystal colors and a video recording was provided the time and location of the color play on the surfaces. Prediction of the heat transfer coefficient have been made by solving the energy balance equation. Experiments were carried out in three annulus for the various inlet and the same outlet diameter ratios. Measurements were made in Reynolds numbers ranging from 14000 to 45000 based on the average inlet velocity and hydraulic diameter. The variation of the local and mean heat transfer coefficients have been obtained dependence on Reynolds number and geometric parameters.