eng Ansari Education and Research Society Journal of Ultra Scientist of Physical Sciences April 2008 20 1 81 86 jusps-B 1363 article D. Subramanyam (prasannadsm@yahoo.com) 1 K. Ravindranath (mch_kr@svuniversity.in 2 K. Mallikarjuna Rao (kmr_svuce@yahoo.com) 3 Research Scholar, Deptt. of Mechanical Engineering, S.V. University College of Engineering- Tirupati - 517 502 A.P. (INDIA) Professor, Dept. of Mechanical Engineering S.V. University College of Engineering- Tirupati - 517 502 A.P. (INDIA) Associate Professor, Deptt. of Civil Engineering. S.V. University College of Engineering- Tirupati - 517 502 A.P. (INDIA) <p style="text-align: justify;">An experimental study of natural convection heat transfer in vertical annular cylinders embedded with porous medium at constant wall temperature has been undertaken. Three stainless steel (301SS) test sections of different aspect ratios were employed. Nusselt number is found to increase with increasing Radius ratio and Rayleigh number and decrease with increasing aspect ratio. Regression models were developed to predict Nusselt number in terms of aspect ratio, radius ratio and Rayleigh number.</p> https://ultraphysicalsciences.org/paper/1363/ Experimental study aspect ratio Rayleigh number natural convection vertical circular cylinder