scholarly journals Distribution of Heat Transfer Coefficients of an Impinging Two Dimensional Free Jet on an Oblique Flat Surface.

2000 ◽  
Vol 66 (650) ◽  
pp. 2669-2674 ◽  
Author(s):  
Hiroyuki SERIZAWA ◽  
Takehiko YANAGIDA ◽  
Taketo KUBOYAMA
Keyword(s):  
Heat Transfer ◽  
Flat Surface ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Free Jet ◽  
Heat Transfer Coefficients

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.

Heat Transfer Characteristics of Impinging Two-Dimensional Air Jets

1966 ◽  
Vol 88 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Robert Gardon ◽  
J. Cahit Akfirat
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Air Jets

Local as well as average heat transfer coefficients between an isothermal flat plate and impinging two-dimensional jets were measured for both single jets and arrays of jets. For a large and technologically important range of variables the results have been correlated in relatively simple terms, and their application to design is briefly considered.

scholarly journals Two-dimensional heat transfer coefficients with simultaneous flow visualisations during two-phase flow boiling in a PDMS microchannel

2018 ◽  
Vol 130 ◽  
pp. 624-636 ◽  
Author(s):  
Sofia Korniliou ◽  
Coinneach Mackenzie-Dover ◽  
John R.E. Christy ◽  
Souad Harmand ◽  
Anthony J. Walton ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Pdms Microchannel

Convective Boiling Heat Transfer Enhancement by Microgrooves in Plate Evaporator

2011 ◽  
Author(s):  
Hirofumi Arima ◽  
Nobuhiko Matsuo ◽  
Keita Shigyou ◽  
Akio Okamoto ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Flat Surface ◽  
Saturation Pressure ◽  
Transfer Coefficients ◽  
Convective Boiling ◽  
Heat Transfer Coefficients ◽  
Boiling Heat Transfer Coefficient

In this experimental study, we investigate the enhancement of heat transfer in ammonia on a new plate evaporator whose surface is configured with microgrooves. The microgrooves have a depth of 30 μm and a width of 200 μm. The local boiling heat transfer coefficients were measured on the evaporator. To compare the heat transfer characteristics of the evaporator, the local boiling heat transfer coefficient on a flat surface and on two microgrooved surfaces—one vertical and one horizontal to the direction of the ammonia flow—were measured at different ranges of mass flux (2–7.5 kg/m2s), heat flux (10–20 kW/m2), and saturation pressure (0.7–0.9 MPa). The results show that the local boiling heat transfer coefficient of the horizontal and vertical microgrooved surfaces was larger than that of a flat surface. In particular, the horizontal microgrooved surface had the best heat transfer coefficient.

The Effect of Entrance Configuration on Local Heat-transfer Coefficients in Subsonic Diffusers

1972 ◽  
Vol 94 (4) ◽  
pp. 355-359 ◽  
Author(s):  
E. O. Stoffel ◽  
J. R. Welty
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Subsonic Diffuser

The effects of square and reentrant entrances on flow regimes (no “appreciable” separation, large transitory stall, and fully developed two-dimensional stall) and local heat-transfer coefficients were determined with air flowing through a symmetrical, plane-wall, two-dimensional subsonic diffuser with one of the diverging walls heated and maintained isothermal. Flow and heat-transfer studies were made for the following ranges: 2θ = 0 to 45 deg, L/W = 6 to 18, and Rextut = 4 × 104 to 3 × 105. Results indicated that 2θ, L/W, and entrance configuration greatly affected the flow regime and heat transfer. Equations relating Um′ to Ut, Ur to Ut, and equations of the type Nu = C Pr0.6Rex0.8 are presented. For the configurations tested, heat-transfer rates were greater for reentrant than for square entrances.

Two-Dimensional Study of Heat Transfer and Fluid Flow in a Natural Convection Loop

1982 ◽  
Vol 104 (3) ◽  
pp. 508-514 ◽  
Author(s):  
A. Mertol ◽  
R. Greif ◽  
Y. Zvirin
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
A Priori ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
One Dimensional ◽  
Heat Transfer Coefficients ◽  
First Time ◽  
Good Agreement

A study has been made of the heat transfer and fluid flow in a natural convection loop. Previous studies of these systems have utilized a one-dimensional approach which requires a priori specifications of the friction and the heat-transfer coefficients. The present work carries out a two-dimensional analysis for the first time. The results yield the friction and the heat-transfer coefficients and give their variation along the loop with the Graetz number as a parameter. Comparison is also made with experimental data for the heat flux and good agreement is obtained.

Performance Analysis and Optimization of Eccentric Annular Disk Fins

1999 ◽  
Vol 121 (1) ◽  
pp. 128-135 ◽  
Author(s):  
B. Kundu ◽  
P. K. Das
Keyword(s):  
Heat Transfer ◽  
Heat Conduction Equation ◽  
Circular Tube ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Annular Disk ◽  
Heat Transfer Coefficients ◽  
Lagrange Multiplier Technique ◽  
Annular Fins ◽  
Space Restriction

In the first part of the paper, a semi-analytical method has been described for solving the two-dimensional heat conduction equation in an eccentric annular disk fin circumscribing a circular tube, subjected to convective cooling. Analysis has been done considering both convective and insulated conditions at the fin tip. The effects of surface and tip heat transfer coefficients and eccentricity on the performance of the fin have been studied. Comparative studies have also been made between the performance of concentric and eccentric fins with same radius ratio. Next, the optimum dimensions for eccentric annular fins have been determined using Lagrange multiplier technique. In the scheme, either the fin volume or the heat transfer duty can be taken as the constraint. Finally, it has been shown that when space restriction is imposed on one side of the tube, eccentric annular fins can be designed to have lesser volumes compared to concentric annular fins above a certain heat transfer duty.

scholarly journals Modeling of the Two-Dimensional Thawing of Logs in an Air Environment

2020 ◽  
Author(s):  
Nencho Deliiski ◽  
Ladislav Dzurenda ◽  
Natalia Tumbarkova
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Experimental Studies ◽  
Longitudinal Section ◽  
Nonstationary Temperature ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Finite Difference Method

A two-dimensional mathematical model has been created, solved, and verified for the transient nonlinear heat conduction in logs during their thawing in an air environment. For the numerical solution of the model, an explicit form of the finite-difference method in the computing medium of Visual FORTRAN Professional has been used. The chapter presents solutions of the model and its validation towards own experimental studies. During the validation of the model, the inverse task of the heat transfer has been solved for the determination of the logs’ heat transfer coefficients in radial and longitudinal directions. This task has been solved also in regard to the logs’ surface temperature, which depends on the mentioned coefficients. The results from the experimental and simulative investigation of 2D nonstationary temperature distribution in the longitudinal section of poplar logs with a diameter of 0.24 m, length of 0.48 m, and an initial temperature of approximately –30°C during their many hours thawing in an air environment at room temperature are presented, visualized, and analyzed.

Heat Transfer Coefficients Over a Flat Surface With Air and CO2 Injection Through Compound Angle Holes Using a Transient Liquid Crystal Image Method

1995 ◽  
Author(s):  
Srinath V. Ekkad ◽  
Dyrk Zapata ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Flat Surface ◽  
Density Ratio ◽  
Test Surface ◽  
Image Method ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Blowing Ratio ◽  
Compound Angle

This paper presents the detailed heat transfer coefficients over a flat surface with one row of injection holes inclined streamwise at 35° for three blowing ratios (M=0.5–2.0). Three compound angles of 0°, 45°, and 90° with air (D.R.=0.98) and CO2 (D.R.=1.46) as coolants were tested at an elevated free-stream turbulence condition (Tu≈8.5%). The experimental technique involves a liquid crystal coating on the test surface. Two related transient tests obtained detailed heat transfer coefficients and film effectiveness distributions. Heat transfer coefficients increase with increasing blowing ratio for a constant density ratio but decrease with increasing density ratio for a constant blowing ratio. Heat transfer coefficients increase for both coolants over the test surface as the compound angle increases from 0° to 90°. The detailed heat transfer coefficients obtained using the transient liquid crystal technique, particularly in the near hole region, will provide a better understanding of the film cooling process in gas turbine components.

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