Heat transfer and surface flow visualization around a 180 deg turn in a rectangular channel
- Univ. of Naples (Italy)
The efficiency of gas turbine engines strongly depends on the gas entry temperature, the higher the latter, the more efficient is the turbine thermal cycle. Present advanced gas turbines operate at gas entry temperatures much higher than metal creeping temperatures and therefore require intensive cooling of their blades especially in the early stages. The aim of the present study is to obtain detailed measurements of the convective heat transfer coefficient nearby a 180deg sharp turn in a rectangular channel, and to prove that the use of infrared thermography may be appropriate to experimentally study this type of problem. A rectangular two-pass channel, which is 40 mm high and 200 mm wide, is tested for two different geometries of the tip of the partition wall: a square tip and semicircular one. To perform surface flow visualization and heat transfer measurements, the heated-thin-foil technique is used and results in terms of temperature maps and Nusselt number Nu distributions are obtained. Nu is computed by means of the local bulk temperature which is evaluated by making a one-dimensional energy balance along the channel. Reynolds number, based on average inlet velocity and hydraulic diameter of the channel is varied between 1.6 {times} 10{sup 4} and 6.4 {times} 10{sup 4}. By moving in the streamwise direction, at the beginning of the heated zone a rapid increase of the wall temperature is found due to the development of the thermal boundary layer. Two well distinguishable separation zones are found, one at the first outer corner of the channel and the other attached to the partition wall and just downstream of its tip. The influence of the geometry of the latter seems to be limited mainly to the position of the onset of the second separation zone. A third weak recirculation zone seems to appear in the vicinity of the second outer corner at the highest tested Reynolds number.
- OSTI ID:
- 455409
- Report Number(s):
- CONF-951135-; ISBN 0-7918-1752-0; TRN: IM9716%%258
- Resource Relation:
- Conference: 1995 International mechanical engineering congress and exhibition, San Francisco, CA (United States), 12-17 Nov 1995; Other Information: PBD: 1995; Related Information: Is Part Of Heat transfer in turbulent flows -- 1995. HTD-Volume 318; Anand, N.K. [ed.] [Texas A and M Univ., College Station, TX (United States)]; Amano, R.S. [ed.] [Univ. of Wisconsin, Milwaukee, WI (United States)]; Armaly, B.F. [ed.] [Univ. of Missouri, Rolla, MO (United States)]; PB: 174 p.
- Country of Publication:
- United States
- Language:
- English
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