A compound passive Heat Transfer Enhancement (HTE) method that utilizes the co-swirls tripped by the endwall angled ribs and the skewed sinusoidal sidewall waves is newly devised with cooling applications to gas turbine blades. Fitted with present HTE measure, the thermally transient heat transfer properties of a square twin-pass sharp-bend channel of AR (Aspect Ratio) = 1 are detected at Reynolds number (Re) of 7500,10000,12500,15000 and 20000. Prior to initiating the thermal boundary layer at each tested Re, the hydrodynamic boundary layer of the coolant flow is fully developed. A series of successive full-field endwall Nusselt number (Nu) distributions during which the thermal boundary layer is developing are detected using the infrared thermography technique at high frame rate of 60 FPS (Frame per Second). A set of full-field, sectioned and regionally averaged Nusselt number data is selected to illustrate the thermally transient heat transfer performances of present test channel. Transient periods for thermal boundary layer developments at all the tested Re are determined with the corresponding ranges of Nu variations evaluated. As an index to highlight the HTE benefit achieved by present HTE measure, the steady state area-averaged endwall Nusselt numbers (Nua¯) is compared against the Dittus-Boelter Nu∞ references with the Nu¯A/Nu∞ correlation developed to assist relevant engineering applications. Pressure drop coefficients (f) measured at steady states are normalized by the Balssius equation levels (f∞) to highlight the pressure drop penalties for acquiring the HTE benefits with Thermal Performance Factors [TPF=(Nu¯a/Nu∞)/(f/f∞)1/3] evaluated.
|Number of pages||17|
|Journal||Journal of Taiwan Society of Naval Architects and Marine Engineers|
|Publication status||Published - 2014 Nov 1|
All Science Journal Classification (ASJC) codes
- Ocean Engineering
- Mechanical Engineering