Numerical analysis of heat transfer with forced convection in triangular channels

In this study, the forced convection of a hydrodynamically fully developed and thermally developing turbulent flow in horizontal equilateral triangular channels have been analysed numerically for the constant heat flux boundary condition. The air (Pr = 0,7) has been selected as the fluid. The material of the triangular channel consists of aluminium and inner surface of the wall is accepted as smooth. One edge of the channel is 76 mm long and its hydraulic diameter is 44 mm. The entrance section of the channel where no heating/cooling implemented is 700 mm and test section is 1050 mm long. In the study, air flow conditions have been created for the Reynolds numbers between 3000 and 10000. In addition, for the Reynolds numbers 3000 to 10000, the effects of the buffles which is put on the bottom surface of the equilateral triangular channel from entrance to the exit section, to thermal performance of the forced convection have been analysed. The width of the buffle is 12 mm and the hight of the buffle is changing with the values; 10,42 mm and 20,84 mm, (according to blokage to entrance surface area ratio %5 and %10 respectively). The design of the channel and flow condition is made on Gambit 2.4.6. modelling program and the thermal analysisis is carried out by Fluent 12.0.16. At the result of the study, fort the mean Nusselt number and mean Darcy friction factor equations in the form Nu = a x Reb and f = c x Red for the test section is obtained. The obtained results have been compared with experimental results of the literature. It is found out that the increase in the Reynolds numbers increases the thermal performance of the channels by increasing the Nusselt number and it also increasing the pressure drop. In the second section of the study it is also determined that as the buffle hight (blokage ratio) increases the thermal performance of the channel also increases. But, as the buffle size increases the pressure drop of the flow also increases and this requires high energy consumption to maintain the flow through channel. It was determined that the mean convection coefficient of the flow through channel without buffle for the Reynolds number 10000 is 16,71 W/m2K, for 5 % blokaged channel, 19,92 W/m2K and for 10 % blokaged channel as 22,53 W/m2K. In this case, the thermal performance of the triangular channel is enhanced around 19 % and 34 % by implementing 5 % and 10 % blokage respectively.Key Words:Triangular channels, turbulent flow, forced convection, nümerical heat transfer analysis