Akışa dik yerleştirilmiş kare boşluklar içeren bir plakanın kanal içerisindeki akış ve ısı transferi karakteristiklerine etkisinin sayısal incelenmesi

Flow in channel is encountered frequently within the engineering system. Cooling of electronic devices, heat exchangers, many places where the fluid acts as cooling and heating ducts are exemplary flow within the channel. When fluid encounters an obstacle or wall, it is forced to stop due to the shear stress in the opposite direction in the fluid flow inside the chanell. It have importance that the type of flow is laminar or turbulent due to friction effects in these areas. Turbulent flow is an undesirable case because it creates unstable vortex motions. Sometimes, though flow is laminar turbulence can be seen after striking an obstacle. Although increase in friction is undesirable, friction on the walls will increase the heat transfer by generating some heat. The important matter is consideraton that when increasing the heat transfer controlled by placing obstacle in the vertical direction of flow, frictional resistance will also increase. Flow sometimes become irregular suddenly with the sudden increase in velocity due to the cross-sectional narrowing when passing through narrowing place like nozzle and ventury. To prevent this case, grill type obstacles are placed perpendicular direction to flow in various sections. Placed these obstacles allow the recovery again or earlier of flow becamed unstable. Sometimes using the opposite way to this event, flow is allowed to enter the earlier turbulence from laminar. All of these systems may be preferable to control the flow. In this study, flow effects within the channel with 9 squares gaps perpendicular direction to the flow was investigated. Square shaped spaces are positioned at the center of the channel. Study was performed in three dimensions.. Blockage rates (width / height) for square gaps are selected as 1. It was taken side length of each square gaps used as 4s, the distance between space and wall as s, wall thickness of the hollow portion as w = s/2, the channel width and height as D=16s, channel length as 200s, the distance from the channel inlet to square hollow section as 100s, fromsquare hollow section to channel output as 200s. Laminar has been studied for 1000 value of the Reynolds number. Surfaces where the gaps placed are in constant wall temperature of 50 ° C. Ansys Cfx software was used for modeling and solution process. 22747 node and 115742 elements were use in study. Convergence values are taken as 1.10-6 for continuity, x, y, z momentum and energy equation As a result of study, velocity, pressure and temperature values along obstacles were examined. These effects were observed as distinct especially at square hollow sections and following of them. Sudden narrowing at hollow portion and sudden expantion immediately afterwards have changed follow structure fairly quite) Slow flow recovery was observed due to the swirls and unstable flow. It has been observed that the effect of hollow portion on velocity, pressure and temperature values considerably reduced after 100-300 mm of hollow portions, When velocity values analyzed; 800 mm after the channel entry wall effects has led to the formation of fully developed velocity profile. L = 1000 mm is the centre of square gap. Here, the velocity profile has changed completely. Fluid has undergone sudden contraction in this region. Section has decreased and velocity has increased. Undergoing a sudden expansion of the fluid after the 2.5 mm distance from this area has delayed the recovery of flow after space. Maximum velocity has up to about 0.24 m/s from 0.19 m/s in this region. Flow has failure in recovery due to sudden expansion and formed swirl effects from gap output to 300 mm after. L = 1300 mm was obtained as critical length that the velocity profile starts recovering. It has seen that space effects reduced completely at 400 mm for pressure values and at 70 mm and after for temparature values.