1987 Max Jakob Memorial Award Lecture: Dynamics and Stability of Thin Heated Liquid Films

1990 ◽  
Vol 112 (3) ◽  
pp. 538-546 ◽  
Author(s):  
S. G. Bankoff
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Liquid Films ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Molecular Forces ◽  
Memorial Award ◽  
Film Heat Transfer

This review covers the dynamics and tendency toward rupture of thin evaporating liquid films on a heated surface. Very large heat transfer coefficients can be obtained. The applications include various boiling heat transfer and film cooling devices. A relatively new area for study is heat transfer through ultrathin films, which are less than 100 nm in thickness, and hence subject to van der Waals and other long-range molecular forces. Some recent work employing lubrication theory to obtain an evolution equation for the growth of a surface wave is described. Earlier phenomenological work is briefly discussed, as well as the connection between forced-convection subcooled nucleate boiling and thin-film heat transfer.

Fully Developed Nucleate Boiling in Narrow Vertical Channels

2004 ◽  
Vol 127 (8) ◽  
pp. 941-944 ◽  
Author(s):  
M. S. Lakshminarasimhan ◽  
Q. Lu ◽  
Y. Chin ◽  
D. K. Hollingsworth ◽  
Larry C. Witte
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Mass Flux ◽  
Flow Boiling ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Vertical Flow ◽  
Transfer Coefficients ◽  
Liquid Crystal Thermography ◽  
Heat Transfer Coefficients

Experiments were performed to investigate nucleate flow boiling and incipience in a vertical flow channel, 20mmwide×357mmlong, with one wall heated uniformly and others approximately adiabatic. Three channel spacings, 2, 1 and 0.5mm, were investigated. Initially subcooled R-11 flowed upward through the channel; the mass flux varied from 60to4586kg∕(m2s), and the inlet pressure ranged up to 0.20MPa. Liquid crystal thermography was used to measure distributions of surface temperature from which the heat transfer coefficients on the heated surface were calculated. Fully developed saturated nucleate boiling was correlated well by a modification of Kandlikar’s technique.

The Effects of Nucleate Boiling Versus Film Boiling on Heat Transfer in Power Boiler Tubes

1962 ◽  
Vol 84 (4) ◽  
pp. 365-371 ◽  
Author(s):  
H. S. Swenson ◽  
J. R. Carver ◽  
G. Szoeke
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Inside Surface ◽  
Film Boiling ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Steam Quality ◽  
Heat Transfer Coefficients

In large, subcritical pressure, once-through power boilers heat is transferred to steam and water mixtures ranging in steam quality from zero per cent at the bottom of the furnace to 100 per cent at the top. In order to provide design information for this type of boiler, heat-transfer coefficients for forced convection film boiling were determined for water at 3000 psia flowing upward in a vertical stainless-steel tube, AISI Type 304, having an inside diameter of 0.408 inches and a heated length of 6 feet. Heat fluxes ranged between 90,000 and 180,000 Btu/hr-sq ft and were obtained by electrical resistance heating of the tube. The operation of the experimental equipment was controlled so that nucleate boiling, transition boiling, and stable film boiling occurred simultaneously in different zones of the tube. The film boiling data were correlated with a modified form of the equation Nu = a a(Re)m(Pr)n using steam properties evaluated at inside surface temperature. Results of a second series of heat-transfer tests with tubes having a helical rib on the inside surface showed that nucleate boiling could be maintained to much higher steam qualities with that type of tube than with a smooth-bore tube.

Heat Transfer Coefficients and Film Cooling Effectiveness on the Squealer Tip of a Gas Turbine Blade

2003 ◽  
Vol 125 (4) ◽  
pp. 648-657 ◽  
Author(s):  
Jae Su Kwak ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Rotor Blade ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio

Experimental investigations were performed to measure the detailed heat transfer coefficients and film cooling effectiveness on the squealer tip of a gas turbine blade in a five-bladed linear cascade. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of the GE-E3 aircraft gas turbine engine rotor blade. The test blade had a squealer (recessed) tip with a 4.22% recess. The blade model was equipped with a single row of film cooling holes on the pressure side near the tip region and the tip surface along the camber line. Hue detection based transient liquid crystals technique was used to measure heat transfer coefficients and film cooling effectiveness. All measurements were done for the three tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span at the two blowing ratios of 1.0 and 2.0. The Reynolds number based on cascade exit velocity and axial chord length was 1.1×106 and the total turning angle of the blade was 97.9 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach numbers were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9.7%. Results showed that the overall heat transfer coefficients increased with increasing tip gap clearance, but decreased with increasing blowing ratio. However, the overall film cooling effectiveness increased with increasing blowing ratio. Results also showed that the overall film cooling effectiveness increased but heat transfer coefficients decreased for the squealer tip when compared to the plane tip at the same tip gap clearance and blowing ratio conditions.

Experimental and Numerical Study on the Effects of the Relative Position of Film Hole and Orientation Ribs on the Film Cooling With Ribbed Cross-Flow Coolant Channel

2020 ◽  
Author(s):  
Bingran Li ◽  
Cunliang Liu ◽  
Lin Ye ◽  
Huiren Zhu ◽  
Fan Zhang
Keyword(s):  
Heat Transfer ◽  
Relative Position ◽  
Film Cooling ◽  
Numerical Study ◽  
Cross Flow ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Numerical Studies

Abstract To investigate the application of ribbed cross-flow coolant channels with film hole effusion and the effects of the internal cooling configuration on film cooling, experimental and numerical studies are conducted on the effect of the relative position of the film holes and different orientation ribs on the film cooling performance. Three cases of the relative position of the film holes and different orientation ribs (post-rib, centered, and pre-rib) in two ribbed cross-flow channels (135° and 45° orientation ribs) are investigated. The film cooling performances are measured under three blowing ratios by the transient liquid crystal measurement technique. A RANS simulation with the realizable k-ε turbulence model and enhanced wall treatment is performed. The results show that the cooling effectiveness and the downstream heat transfer coefficient for the 135° rib are basically the same in the three position cases, and the differences between the local effectiveness average values for the three are no more than 0.04. The differences between the heat transfer coefficients are no more than 0.1. The “pre-rib” and “centered” cases are studied for the 45° rib, and the position of the structures has little effect on the film cooling performance. In the different position cases, the outlet velocity distribution of the film holes, the jet pattern and the discharge coefficient are consistent with the variation in the cross flow. The related research previously published by the authors showed that the inclination of the ribs with respect to the holes affects the film cooling performance. This study reveals that the relative positions of the ribs and holes have little effect on the film cooling performance. This paper expands and improves the study of the effect of the internal cooling configuration on film cooling and makes a significant contribution to the design and industrial application of the internal cooling channel of a turbine blade.

scholarly journals The study of spray impact on the heated sapphire plate

2021 ◽  
Vol 2119 (1) ◽  
pp. 012172
Author(s):  
T G Gigola ◽  
V V Cheverda
Keyword(s):  
Heat Transfer ◽  
Sapphire Substrate ◽  
Substrate Surface ◽  
Heated Surface ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Liquid Spray ◽  
Sapphire Plate

Abstract The process of the liquid spray impact on the heated surface is studied experimentally using the IR-transparent sapphire plate method. The spatiotemporal distribution of the temperature field on the sapphire substrate surface during impacting spray is received. The obtained experimental data are an important step in a study of the local characteristics of heat transfer in the areas of the contact lines during liquid spray impact on the heated surface. Further, the local heat fluxes and heat transfer coefficients will be determined by solving the problem of thermal conductivity in the sapphire substrate.

Prediction of Heat Transfer Coefficients Under Sub-Cooled Boiling Conditions

2000 ◽  
Author(s):  
Edward V. McAssey ◽  
Jinfeng Wu ◽  
Thomas Dougherty ◽  
Bao Wen Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Sharp Increase ◽  
Nucleate Boiling ◽  
Prediction Methods ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract Data are presented for sub-cooled boiling of water in the range of two to four atmospheres. The results show that the sharp increase in heat transfer coefficient associated with nucleate boiling occurs at wall superheats of 20 °C to 30 °C. Comparisons between experimental and predicted heat transfer coefficients are also presented. The two prediction methods examined are the Chen correlation and the Kandlikar correlation.

Heat Transfer Coefficient Measurements of Film-Cooling Holes With Expanded Exits

1998 ◽  
Author(s):  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Superposition Method ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Heat Transfer Coefficients ◽  
Film Cooling Holes ◽  
Injection Location

Detailed measurements of heat transfer coefficients in the nearfield of three different film-cooling holes are presented. The hole geometries investigated include a cylindrical hole and two holes with a diffuser shaped exit portion (i.e. a fan-shaped and a laidback fanshaped hole). They were tested over a range of blowing ratios M = 0.25…1.75 at an external crossflow Mach number of 0.6 and a coolant-to-mainflow density ratio of 1.85. Additionally, the effect of the internal coolant supply Mach number is addressed. Temperatures of the diabatic surface downstream of the injection location are measured by means of an infrared camera system. They are used as boundary conditions for a finite element analysis to determine surface heat fluxes and heat transfer coefficients. The superposition method is applied to evaluate the overall film-cooling performance of the hole geometries investigated. As compared to the cylindrical hole, both expanded holes show significantly lower heat transfer coefficients downstream of the injection location, particularly at high blowing ratios. The laidback fanshaped hole provides a better lateral spreading of the injected coolant than the fanshaped hole which leads to lower laterally averaged heat transfer coefficients. Coolant passage crossflow Mach number affects the flowfield of the jet being ejected from the hole and, therefore, has an important impact on film-cooling performance.

Heat transfer coefficients for quenching process simulation

2004 ◽  
Vol 120 ◽  
pp. 269-276
Author(s):  
M. Maniruzzaman ◽  
R. D. Sisson
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Process Simulation ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Quenching Process

Quenching heat treatment in a liquid medium is a very complex heat transfer process. Heat extraction from the part surface occurs through several different heat transfer mechanisms in distinct temperature ranges, namely, film boiling, partial film boiling (i.e. transition), nucleate boiling and convection. The maximum heat transfer occurs during the nucleate boiling stage. Experimental study shows that, the effective surface heat transfer coefficient varies more than two orders of magnitude with the temperature during the quenching. For quenching process simulation, accurate prediction of the time-temperature history and microstructure evolution within the part largely depends on the accuracy of the boundary condition supplied. The heat transfer coefficient is the most important boundary condition for process simulation. This study focuses on creating a database of heat transfer coefficients for various liquid quenchant-metallic alloy combinations through experimentation using three different quench probes. This database is a web-based tool for use in quench process simulation. It provides at-a-glance information for quick and easy analysis and sets the stage for a Decision Support System (DSS) and Data Mining for heat-treating process.

scholarly journals The Superposition Approach to Local Heat Transfer Coefficients in High Density Ratio Film Cooling Flows

1999 ◽  
Author(s):  
Michael Gritsch ◽  
Stefan Baldauf ◽  
Moritz Martiny ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Cooling Flows ◽  
Heat Transfer Coefficients ◽  
High Density Ratio ◽  
The Heat Transfer Coefficient

The present paper reports on the use of the superposition approach in high density ratio film cooling flows. It arises from the linearity and homogeneity of the simplified boundary layer differential equations. However, it is widely assumed that the linearity does not hold for variable property flows. Therefore, theoretical considerations and numerical calculations will demonstrate the linearity of the heat transfer coefficient with the dimensionless coolant temperature θ as long as identical flow conditions are applied. This makes it necessary to perform at least two experiments at different θ but with the coolant to main flow temperature ratio kept unchanged. A comprehensive set of experiments is presented to demonstrate the capability of the superposition approach for determining heat transfer coefficients for different film cooling geometries. These comprise coolant injection from two dimensional tangential slots, single holes, and rows of cylindrical holes. Particularly, two dimensional local distributions of the heat transfer coefficient will be addressed.

A Transient Calorimeter Technique for Determining Regional Heat Transfer Coefficients in the Three-Temperature Flowfield at a Turbine Airfoil Leading Edge

2005 ◽  
Author(s):  
Scott R. Nowlin ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Ralf Knoche ◽  
T. Robert Kingston
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Internal Flow ◽  
Leading Edge ◽  
Internal Surface ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Novel Method ◽  
Exposed Surface Area

In this paper, the authors develop a novel method of obtaining regionally-averaged heat transfer coefficients in flowfields characterized by three temperatures using the well-known transient calorimeter technique. The technique is used to determine heat transfer in aluminum models of idealized turbine blade leading edges cooled through internal surface impingement, film cooling feed passages, and external convective film cooling. The external surface is subject to a stagnating mainstream crossflow. Importantly, the contributions to heating from the external flow and cooling from the internal flow can be separately resolved solely by heating the internal flow. Results for a basic showerhead geometry and an advanced intersecting-passage cooling configuration are presented for a range of internal and external Reynolds numbers. The intersecting-passage model shows little improvement in heat transfer coefficient over the showerhead for the flow conditions tested; however, the total cooling carried out is improved by the increase in exposed surface area. The technique’s uncertainties are fully assessed.

Sign in / Sign up

Export Citation Format

Share Document