Investigation of impingement surface geometry effects on heat transfer in a laminar confined impinging slot jet

2017 ◽  
Vol 115 ◽  
pp. 347-353 ◽  
Author(s):  
Yeong Hwan Kim ◽  
Dae Hee Lee ◽  
Seung Ho Han
Keyword(s):  
Heat Transfer ◽  
Surface Geometry ◽  
Geometry Effects ◽  
Impingement Surface

Experimental Investigation of Heat Transfer From a Discretely Heated Protruding Pedestal to a Single Round Impinging Air Jet

2004 ◽  
Author(s):  
Amy S. Fleischer ◽  
Sharareh R. Nejad
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heated Surface ◽  
Operating Conditions ◽  
Surface Geometry ◽  
Stagnation Region ◽  
Exit Surface ◽  
Air Jet ◽  
Air Stream ◽  
Impingement Surface

An experimental investigation to understand the influence of the impingement surface geometry on the heat transfer from a discretely heated surface to a single round impinging jet is conducted. In this study, heat transfer at the stagnation region of a discretely heated pedestal protruding into an air stream is compared to the heat transfer on a discretely heated flat plate to determine the influence of impingement surface geometry on heat transfer for various Reynolds numbers, jet diameters and jet exit-surface spacings. The round jet issues from a tube of diameter 3.5 mm, 9.5 mm or 21 mm at jet exit-to-surface distances of 2–5 diameters with Re = 10,000–30,000. Under all operating conditions, the presence of a protruding pedestal is found to increase heat transfer.

Multi-Objective Optimization of a Microturbine Compact Recuperator

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Diego Micheli ◽  
Valentino Pediroda ◽  
Stefano Pieri
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Design Procedure ◽  
Domain Size ◽  
Multidisciplinary Optimization ◽  
Computational Domain ◽  
Surface Geometry ◽  
Multi Objective ◽  
Flux Boundary Conditions

An automatic approach for the multi-objective shape optimization of microgas turbine heat exchangers is presented. According to the concept of multidisciplinary optimization, the methodology integrates a CAD parametric model of the heat transfer surfaces, a three-dimensional meshing tool, and a CFD solver, all managed by a design optimization platform. The repetitive pattern of the surface geometry has been exploited to reduce the computational domain size, and the constant flux boundary conditions have been imposed to better suit the real operative conditions. A new approach that couples cold and warm fluids in a periodic unitary cell is introduced. The effectiveness of the numerical procedure was verified comparing the numerical results with available literature data. The optimization objectives are maximizing the heat transfer rate and minimizing both friction factor and heat transfer surface. The paper presents the results of the optimization of a 50kWMGT recuperator. The design procedure can be effectively extended and applied to any industrial heat exchanger application.

Comparison of Heat Transfer Characteristics of Radial Jet Reattachment Nozzle to In-Line Impinging Jet Nozzle

1998 ◽  
Vol 120 (2) ◽  
pp. 335-341 ◽  
Author(s):  
J. Seyed-Yagoobi ◽  
V. Narayanan ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Peak Pressure ◽  
Exit Angle ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Zero Degree ◽  
Jet Nozzle ◽  
Flow Power ◽  
Impingement Surface

The heat transfer characteristics of three submerged radial jet reattachment (RJR) nozzles with exit angles of +45, 0, and −10 deg are compared to the heat transfer characteristics of a conventional submerged in-line jet (ILJ) nozzle. The nozzles are compared at their favorable spacing from the impingement surface. The comparisons are based on two criteria: (1) identical fluid flow power, and (2) identical peak pressure exerted on the impingement surface. The local and area-averaged Nusselt numbers are presented. Experiments were conducted for two different flow power conditions. Comparison under identical flow power indicates that significant enhancements in local and comparable enhancements in area-averaged Nusselt numbers can be achieved with the RJR nozzles over the conventional ILJ nozzle while being able to control the net force exerted on the impingement surface. The comparison between the ILJ and RJR nozzles on the basis of the same peak pressure exerted on the impingement surface indicates that the zero degree exit angle RJR nozzle heat transfer characteristics are superior to the ILJ nozzle.

Heat Transfer Characteristics of a Radial Jet Reattachment Flame

1997 ◽  
Vol 119 (2) ◽  
pp. 258-264 ◽  
Author(s):  
J. W. Mohr ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Combustion Process ◽  
Local Heat ◽  
Operating Conditions ◽  
Recirculation Region ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

A Radial Jet Reattachment Combustion (RJRC) nozzle forces primary combustion air to exit radially from the combustion nozzle and to mix with gaseous fuel in a highly turbulent recirculation region generated between the combustion nozzle and impingement surface. High convective heat transfer properties and improved fuel/ air mixing characterize this external mixing combustor for use in impingement flame heating processes. To understand the heat transfer characteristics of this new innovative practical RJRC nozzle, statistical design and analysis of experiments was utilized. A regression model was developed which allowed for determination of the total heat transfer to the impingement surface as well as the NOx emission index over a wide variety of operating conditions. In addition, spatially resolved flame temperatures and impingement surface temperature and heat flux profiles enabled determination of the extent of the combustion process with regards to the impingement surface. Specifically, the relative sizes of the reaction envelope, high temperature reaction zone, and low temperature recirculation zone were all determined. At the impingement surface in the reattachment zone very high local heat flux values were measured. This study provides the first detailed local heat transfer characteristics for the RJRC nozzle.

Effects of Surface Geometry on Film Cooling Performance at Airfoil Trailing Edge

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Akira Murata ◽  
Satomi Nishida ◽  
Hiroshi Saito ◽  
Kaoru Iwamoto ◽  
Yoji Okita ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Surface Geometry ◽  
Enhanced Heat Transfer ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
The Heat Transfer Coefficient

Cooling at the trailing edge of a gas turbine airfoil is one of the most difficult problems because of its thin shape, high thermal load from both surfaces, hard-to-cool geometry of narrow passages, and at the same time demand for structural strength. In this study, the heat transfer coefficient and film cooling effectiveness on the pressure-side cutback surface was measured by a transient infrared thermography method. Four different cutback geometries were examined: two smooth cutback surfaces with constant-width and converging lands (base and diffuser cases) and two roughened cutback surfaces with transverse ribs and spherical dimples. The Reynolds number of the main flow defined by the mean velocity and two times the channel height was 20,000, and the blowing ratio was varied among 0.5, 1.0, 1.5, and 2.0. The experimental results clearly showed spatial variation of the heat transfer coefficient and the film cooling effectiveness on the cutback and land top surfaces. The cutback surface results clearly showed periodically enhanced heat transfer due to the periodical surface geometry of ribs and dimples. Generally, the increase of the blowing ratio increased both the heat transfer coefficient and the film cooling effectiveness. Within the present experimental range, the dimple surface was a favorable cutback-surface geometry because it gave the enhanced heat transfer without deterioration of the high film cooling effectiveness.

Sign in / Sign up

Export Citation Format

Share Document