Natural convection heat transfer on the outer surface of inclined cylinders

An experimental investigation of natural convection heat transfer was conducted on inclined cylinders for Rayleigh numbers of 1.69×108–5.07×1010, and for angles of inclination of 0°–90°. A copper electroplating system was employed to simulate heat transfer in a mass transfer system, based on the analogy between heat and mass transfer. The measured mass transfer coefficients were highest for horizontal cylinders, gradually decreased with increasing inclination angle, and were lowest for vertical cylinders. The results showed trends similar to the existing heat transfer correlations for inclined cylinders, and were in good agreement with results for vertical and horizontal cylinders. This study expended the studies to turbulent heat transfer correlations were derived for inclined cylinders in either laminar or turbulent flow. Copper plating patterns on the cylinders enabled visualization of the local heat transfer and fluid flow. Distinct lines denoting flow separation were observed, with were dependent on the inclination angle.

► Reliable natural convection HT correlations for inclined cylinders are proposed for laminar and turbulent.
► Test results show similar trends with other studies on inclined cylinders.
► This study only agrees with the existing vertical and horizontal correlations.
► By using a short analogous electroplating system, Ra of order 10 was achieved.
► Copper plating patterns revealed the vertical flow separation and local heat transfer.