In this study, steady-state three-dimensional turbulent forced convection flow and heat transfer characteristics in a circular pipe with baffles attached inside pipe have been numerically investigated under constant wall heat flux boundary condition. Numerical study has been carried out for Reynolds number Re of 3000-50,000, Prandtl number Pr of 0.71, baffle distances s/D of 1, 2, and 3, and baffle angle a of 30o-150o. Ansys Fluent 12.0.1 software has been used to solve the flow field. It is observed that circular pipe having baffles has a higher Nusselt number and friction factor compared to the smooth circular pipe without baffles. Maximum Nusselt number and friction factor are obtained for the baffle angle of 90o. Nusselt number increases while baffle distance increases in the range of studied; however, friction factor decreases. Periodically fully developed conditions are obtained after a certain module. Thermal performance factor increases with increasing baffle distance in the rage of studied but decreases with increasing Reynolds number; maximum thermal performance factor is obtained for the baffle angle of 150?. Results show that baffle distance, baffle angle, and Reynolds number play important role on both flow and heat transfer characteristics. The accuracy of the results obtained in this study is verified by comparing the results with those available in the literature for smooth circular pipes. All the numerical results are correlated within accuracy of ?10 and ?15% for average Nusselt number and Darcy friction factor, respectively.

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The objective of this study is to investigate the effect of bio-heat transfer from large blood vessels on freezing region size of tumorous liver tissue using cryo-freezing method. Bio-heat transfer, one of the cancer treatment method, in tumorous tissue has been investigated experimentally using cryo-freezing method for vessels. Investigated parameters are the blood mass flow rate, the diameter of vessel, the number of vessel, and the location of tumorous tissue. Study is carried out for nine different blood mass flow rates varying from 10 g/min to 1200 g/ min. Tissues without blood vessel, with single, double and branched vessels are used for the experimental study. Vessels with inner diameter of 2.4, 3.2 and 4.0 mm are used. Liver of beef is employed as a tissue. Refrigerant is the nitrogen protoxide gas. Results show that the number of vessel, the diameter of vessel, the location of tumorous tissue, and the blood mass flow rate affect the freezing region size. Freezing region size decreases with increasing in diameter of vessel, number of vessel and blood mass flow rate. The large blood vessel located near the tumorous tissue affects the freezing time to destroy the tumor. The desired freezing region obtained in tumorous tissue with vessel develops later than the tumorous tissue without vessel. Results indicate that a tumorous tissue about 23 mm may be destroyed in a short time using cryo-freezing method when nitrogen protoxide gas is used as refrigerant gas.