Heat Transfer Analysis of a Wedge Shaped Duct With Pin Fin and Pedestal Arrays: A Comparison Between Numerical and Experimental Results

Journal of Turbomachinery

2015

Pin fin arrays are employed as an effective means for heat transfer enhancement in the internal passages of a gas turbine blade, specifically in the blade's trailing edge. Various shapes of the pin itself have been used in such arrays. In this study, oblong pin fins are investigated whereby their long axis is perpendicular to the flow direction. Heat transfer measurements were taken at the pin midspan with unheated endwalls to isolate the pin heat transfer. Results show important differences in the heat transfer patterns between a pin in the first row and a pin in the third row. In the third row, wider spanwise spacing allows for two peaks in heat transfer over the pin surface. Additionally, closer streamwise spacing leads to consistently higher heat transfer for the same spanwise spacing. Due to the blunt orientation of the pins, the peak in heat transfer occurs off the stagnation point.

Section: Previous Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat Transfer Measurements of Oblong Pins

Kirsch

Journal of Turbomachinery

2015

“…Andreini et al [15] and Metzger et al [16] are the only studies in the public domain, to the authors' knowledge, that investigated oblong-shaped pin fins. Andreini et al simulated one row of oblong pin fins in a converging channel and noted the combinatorial effects of the horseshoe vortex formation, flow recirculation in the wake region, and mean flow acceleration due to the channel convergence.…”

Section: Previous Studiesmentioning

confidence: 99%

Comparison of Pin Surface Heat Transfer in Arrays of Oblong and Cylindrical Pin Fins

Kirsch

Ostanek

Volume 3A: Heat Transfer

2013

Pin fin arrays are most commonly used to promote convective cooling within the internal passages of gas turbine airfoils. Contributing to the heat transfer are the surfaces of the channel walls as well as the pin itself. Generally the pin fin cross-section is circular; however, certain applications benefit from using other shapes such as oblong pin fins. The current study focuses on characterizing the heat transfer distribution on the surface of oblong pin fins with a particular focus on pin spacing effects. Comparisons were made with circular cylindrical pin fins, where both oblong and circular cylindrical pins had a height-to-diameter ratio of unity, with both streamwise and spanwise spacing varying between two and three diameters. To determine the effect of relative pin placement, measurements were taken in the first of a single row and in the third row of a multi-row array. Results showed that area-averaged heat transfer on the pin surface was between 30 and 35 percent lower for oblong pins in comparison to cylindrical. While heat transfer on the circular cylindrical pin experienced one minimum prior to boundary layer separation, heat transfer on the oblong pin-fins experienced two minimums, where one is located before the boundary layer transitions to a turbulent boundary layer and the other prior to separation at the trailing edge.

Comparison of Pin Surface Heat Transfer in Arrays of Oblong and Cylindrical Pin Fins

Kirsch¹,

Ostanek²,

Journal of Turbomachinery

2013

Pin fin arrays are most commonly used to promote convective cooling within the internal passages of gas turbine airfoils. Contributing to the heat transfer are the surfaces of the channel walls as well as the pin itself. Generally the pin fin cross section is circular; how-ever, certain applications benefit from using other shapes such as oblong pin fins. The current study focuses on characterizing the heat transfer distribution on the surface of oblong pin fins with a particular focus on pin spacing effects. Comparisons were made with circular cylindrical pin fins, where both oblong and circular cylindrical pins had a height-to-diameter ratio of unity, with both streamwise and spanwise spacing varying between two and three diameters. To determine the effect of relative pin placement, meas-urements were taken in the first of a single row and in the third row of a multirow array. Results showed that area-averaged heat transfer on the pin surface was between 30 and 35 % lower for oblong pins in comparison to cylindrical. While heat transfer on the circular cylindrical pin experienced one minimum prior to boundary layer separation, heat transfer on the oblong pin fins experienced two minimums, where one is located before the boundary layer transitions to a turbulent boundary layer and the other prior to separation at the trailing edge. [DOI: 10.1115/1.4025213