Comparison of Flow and Heat Transfer Distributions in a Can Combustor for Radial and Axial Swirlers Under Cold Flow Conditions

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Andrew Carmack ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
Hee-Koo Moon ◽  
Ram Srinivasan
Keyword(s):  
Heat Transfer ◽  
Cross Sections ◽  
Reverse Flow ◽  
Rotational Velocity ◽  
Central Area ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Flow Core ◽  
Cold Flow ◽  
Field Geometry

A comparison study between axial and radial swirler performance in a gas turbine can combustor was conducted by investigating the correlation between combustor flow field geometry and convective heat transfer at cold flow conditions for Reynolds numbers of 50,000 and 80,000. Flow velocities were measured using particle image velocimetry (PIV) along the center axial plane and radial cross sections of the flow. It was observed that both swirlers produced a strong rotating flow with a reverse flow core. The axial swirler induced larger recirculation zones at both the backside wall and the central area as the flow exits the swirler, and created a much more uniform rotational velocity distribution. The radial swirler however, produced greater rotational velocity as well as a thicker and higher velocity reverse flow core. Wall heat transfer and temperature measurements were also taken. Peak heat transfer regions directly correspond to the location of the flow as it exits each swirler and impinges on the combustor liner wall.

Condensation of Steam on Finned Surfaces With Addition of a Surfactant

2005 ◽  
Author(s):  
Andrew T. Morrison ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Surface Energy ◽  
Reynolds Numbers ◽  
Film Condensation ◽  
Vapor Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Enhancement Of Heat Transfer ◽  
Flat Surfaces ◽  
Extended Surfaces

A fundamental knowledge of the parameters affecting film condensation is essential for the design of two phase heat exchangers. The current study examines the effect of extended surfaces and surface energy modifications and their interaction for condensation of steam in quiescent and vapor flow conditions. The enhancement of heat transfer for vertical, flat surfaces and two finned surfaces were compared for Reynolds numbers ranging from approximately 10 to 50. The addition of a nonionic surfactant, alcohol alkoxylate, to the system was evaluated for the same surfaces and vapor field conditions. Vapor flow of 0.25 m/s enhanced the heat transfer approximately 40%, while 0.5 m/s vapor velocity produced almost 100% increase in heat transfer. The addition of surfactant to the system produced small enhancement in heat transfer except in the case of condensate hold-up between the fins. In this case, the addition of surfactant increase the heat transfer an additional 25%, likely because the vapor flow and change of surface energy were sufficient to largely eliminate the hold-up of condensate between the fins.

Heat Transfer and Pressure Loss Measurements in a Turbulated High Aspect Ratio Channel With Large Reynolds Number Flows

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Shantanu Mhetras ◽  
Je-Chin Han ◽  
Michael Huth
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Steady State ◽  
Aspect Ratio ◽  
Compressible Flow ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Transfer Enhancement ◽  
High Reynolds ◽  
Wide Wall

Experiments to investigate heat transfer and pressure loss are performed in a rectangular channel with an aspect ratio of 6 at very high Reynolds numbers under compressible flow conditions. Reynolds numbers up to 1.3 × 106 are tested. The presence of a turbulated wall and the resultant heat transfer enhancement against a smooth surface is investigated. Three dimpled configurations including spherical and cylindrical dimples are studied on one wide wall of the channel. The presence of discrete ribs on the same wide wall is also investigated. A steady state heat transfer measurement method is used to obtain the heat transfer coefficients while pressure taps located at several streamwise locations in the channel walls are used to record the static pressures on the surface. Experiments are performed for a wide range of Reynolds numbers from the incompressible (Re = 100,000–500,000; Mach = 0.04–0.19) to compressible flow regimes (Re = 900,000–1,300,000, Mach = 0.35–0.5). Results for low Reynolds numbers are compared to existing heat transfer data available in open literature for similar configurations. Heat transfer enhancement is found to decrease at high Re with the discrete rib configurations providing the best enhancement but highest pressure losses. However, the small spherical dimples show the best thermal performance. Results can be used for the combustor liner back side cooling at high Reynolds number flow conditions. Local measurements using the steady state, hue-detection based liquid crystal technique are also performed in the fully developed region for case 1 with large spherical dimples. Good comparison is obtained between averaged local heat transfer coefficient measurements and from thermocouple measurements.

Fluid Flow and Heat Transfer Features at a Cross-Flow of Dimpled Tubes in a Confined Space

2003 ◽  
Author(s):  
G. V. Kovalenko ◽  
A. A. Khalatov
Keyword(s):  
Heat Transfer ◽  
Reverse Flow ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Smooth Tube ◽  
Confined Space ◽  
Transfer Enhancement ◽  
Flow And Heat Transfer ◽  
Heat Exchange Surface ◽  
Exchange Surface

This paper provides the primary results of an experimental study into the fluid flow and heat transfer features at a cross-flow of a dimpled tube in a rectangular-shaped duct between two adjacent dimpled tubes. The cylindrical dimples were engraved on each tube surface both in the staggered and in-line mode; altogether nine dimpled tubes were tested in the range of the Reynolds number Re from 8,000 to 115,000. The first group (four samples) represents tubes structured with symmetrical dimples drilled in the radial direction, while the second group (five samples) is tubes with asymmetrical dimples. In the latter case each dimple was made in such a way that its axis is parallel to the tube diameter with a certain clearance between axes. For comparisons a row of smooth tubes of the same configuration was tested under identical fluid boundary conditions. Three factors primarily influencing heat transfer are under consideration in this paper: a) increase in a heat exchange surface due to a tube dimpling, b) variations in the flow pattern, c) interaction between boundary layer and main flow. Behind a smooth tube in confined space the reverse flow zone grows initially to Re = 37,000 however decreases at larger Reynolds numbers. Unlike this, behind a dimpled tube in confined space the reverse flow zone reduces at low Reynolds numbers to reach minimum magnitude at Re = 10,000–28,000, and increases afterwards to become approximately constant at Reynolds numbers over 45,000. It has been found, the reverse flow length depends on the Reynolds number, dimple parameters and configuration. The frequency spectrum of the dimpled tube is different from that occurring for a smooth tube. A few frequency ‘picks’ with corresponding the Strouhal numbers were registered including those typical to a single dimple on a flat plate. The heat transfer enhancement rates of around 45%–55% compared with a smooth tube in confined space were obtained depending on dimple parameters and flow regimes. Increase in the heat transfer enhancement rate for tubes with shallow dimples exceeds growth of heat exchange surface due to a dimpling. Increases in a pressure drop at the tube bundle caused by dimpling do not exceed 14%.

scholarly journals Rib Spacing effect on Heat Transfer and pressure loss in a Rectangular channel with semicircular ribs

2021 ◽  
Author(s):  
Mr. Prakash S. Patil ◽  
◽  
Dr. K. K. Dhande ◽  
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Spacing Effect ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Transfer Enhancement ◽  
Geometrical Features ◽  
Spacing Ratio ◽  
Result Show ◽  
Better Than

Ribs of various shapes are used for heat transfer enhancement but its performance is significantly depends on geometrical features and flow conditions. This study experimentally find out the influence of rib spacing, semicircular shape ribs with three rib spacing ratio (P/e) = 8, 10 and 12 are studied and located on lower wall of the rectangular channel. Reynolds numbers varied from 10000 to 29,000 and the blockage ratio of the channel (e/Dh) was 0.151.Result show that semicircular rib performed better than plain plate but found more friction. semicircular rib with rib spacing of 50 mm (P/e =10) shows highest thermal performance, enhanced avg. 39 % heat transfer than rib spacing of 40 and 60 mm (P/e=8 & 12). Friction losses observed highest in rib spacing ratio of 8,found average 10 % more friction compared to rib spacing ratio of 10 & 12. Semicircular rib with spacing ratio 8 shows least thermal performances compared to other configurations.

Numerical investigation of the effect of water/Al2O3 nanofluid on heat transfer in trapezoidal, sinusoidal and stepped microchannels

2019 ◽  
Vol 30 (5) ◽  
pp. 2439-2465 ◽  
Author(s):  
Vahid Jaferian ◽  
Davood Toghraie ◽  
Farzad Pourfattah ◽  
Omid Ali Akbari ◽  
Pouyan Talebizadehsardari
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Section ◽  
Cross Sections ◽  
Volume Fraction ◽  
Pure Water ◽  
Circular Cross Section ◽  
Reynolds Numbers ◽  
Two Phase ◽  
Content Type

Purpose The purpose of this study is three-dimensional flow and heat transfer investigation of water/Al2O3 nanofluid inside a microchannel with different cross-sections in two-phase mode. Design/methodology/approach The effect of microchannel walls geometry (trapezoidal, sinusoidal and stepped microchannels) on flow characteristics and also changing circular cross section to trapezoidal cross section in laminar flow at Reynolds numbers of 50, 100, 300 and 600 were investigated. In this study, two-phase water/Al2O3 nanofluid is simulated by the mixture model, and the effect of volume fraction of nanoparticles on performance evaluation criterion (PEC) is studied. The accuracy of obtained results was compared with the experimental and numerical results of other similar papers. Findings Results show that in flow at lower Reynolds numbers, sinusoidal walls create a pressure drop in pure water flow which improves heat transfer to obtain PEC < 1. However, in sinusoidal and stepped microchannel with higher Reynolds numbers, PEC > 1. Results showed that the stepped microchannel had higher pressure drop, better thermal performance and higher PEC than other microchannels. Originality/value Review of previous studies showed that existing papers have not compared and investigated nanofluid in a two-phase mode in inhomogeneous circular, stepped and sinusoidal cross and trapezoidal cross-sections by considering the effect of changing channel shape, which is the aim of the present paper.

scholarly journals Experimental Determination of Stator Endwall Heat Transfer

1989 ◽  
Author(s):  
Robert J. Boyle ◽  
Louis M. Russell
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Test Section ◽  
Electrical Power ◽  
Exhaust System ◽  
Ambient Air ◽  
Reynolds Numbers ◽  
Inlet Velocity ◽  
Turbine Vane

Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane passage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Results were obtained for Reynolds numbers based on inlet velocity and axial chord between 73,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heat transfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heat transfer. Endwall heat transfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heat transfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Sign in / Sign up

Export Citation Format

Share Document