Experimental investigation of heat transfer on three pass a channel

Gas turbines are one of the most important equipments which are used in aircrafts and helicopters. High temperature gases (1150-1350°C) are needed to improve the thermal effiency and output power of gas turbines These temperatures are above the allowed limit of material temperature on gas turbine blades. Therefore gas turbines should be cooled so they don't cause any trouble and break down. Especially high temperatures occur on the first stage blades which require special cooling geometries, designs and cooling techniques. These techniques are internal cooling, rip turbulated cooling and airfoil film cooling techniques and impingement jet cooling. Approximetly %20 of the produced air in gas turbines compressor are used as a coolant air. The coolant taken is sent for distribution firstly to the channels, then to the airfoil and then to the trailing edge for cooling. Detailed information on gas turbines and cooling technique are in section 3. In this study we investigated the change of the heat transfer coefficient on the surface with the TLC method on a blade model with 3 pass channel. Section 4 describes the details about the experimental model, it is seen that the Reynolds number effects, speed distribution in the channel and heat transfer coefficient distribution differs as a result of the geometry of the parts' transition. In the experimental studies, comparision of circular and square-hole transition parts of 20m3/h, 30m3/h flow experiments show that although the channel with three passings has been found to have a more homogenous heat relay, the square hole used for the part of the transition with three passing channels has access to the higher heat occurring compared to the circular - hole transition piece. In the 40 m3/h and 50 m3/h value experiments the circular-hole transition piece used had the higher heat transfer coefficient in the channel and a more homogeneous distribution of the heat transfer was observed. Experiment results and comparisons of the obtained data from these results are detailed in section 5.