Some Generalizations in Compressible Flow Characteristics

1973 ◽  
Vol 95 (2) ◽  
pp. 65-74
Author(s):  
R. P. Benedict
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Compressible Flow ◽  
Flow Characteristics ◽  
Loss Coefficient ◽  
All Solutions

Certain generalizations in compressible flow characteristics are first reviewed including specific solutions to flow with losses in the absence of heat transfer (i.e., Fanno flow), in terms of an empirical loss coefficient, Kf. The analysis is then extended to specific solutions to flow with heat transfer, with and without losses (i.e., isothermal and Rayleigh flows), in terms of an empirical heat transfer coefficient, Kq. All solutions are mapped on generalized plots which, in addition to their utility, exhibit a certain beauty of symmetry and continuity.

One Dimensional Model for Rotating Channels in the Turbine System: Part 2 — Formulation and Validation for Film Condensation

2013 ◽  
Author(s):  
Murali Krishnan R. ◽  
Zain Dweik ◽  
Deoras Prabhudharwadkar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Steam Turbine ◽  
Compressible Flow ◽  
Saturation Temperature ◽  
Film Condensation ◽  
Bulk Temperature ◽  
Dimensional Model ◽  
One Dimensional

This paper provides an extension of the previously described [1] formulation of a one-dimensional model for steady, compressible flow inside a channel, to the steam turbine application. The major challenge faced in the network simulation of the steam turbine secondary system is the prediction of the condensation that occurs during the engine start-up on the cold parts that are below the saturation temperature. Neglecting condensation effects may result in large errors in the engine temperatures since they are calculated based on the boundary conditions (heat transfer coefficient and bulk temperature) which depend on the solution of the network analysis. This paper provides a detailed formulation of a one-dimensional model for steady, compressible flow inside a channel which is based on the solution of two equations for a coupled system of mass, momentum and energy equations with wall condensation. The model also accounts for channel area variation, inclination with respect to the engine axis, rotation, wall friction and external heating. The formulation was first validated against existing 1D correlation for an idealized case. The wall condensation is modeled using the best-suited film condensation models for pressure and heat transfer coefficient available in the literature and has been validated against the experimental data with satisfactory predictions.

scholarly journals Estimation of Heat Transfer Coefficient and Flow Characteristics on Heat Transfer Tube in Sodium-Water Reaction

2011 ◽  
Vol 48 (3) ◽  
pp. 315-321 ◽  
Author(s):  
Toshinori MATSUMOTO ◽  
Takashi TAKATA ◽  
Akira YAMAGUCHI ◽  
Akikazu KURIHARA ◽  
Hiroyuki OHSHIMA
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Characteristics ◽  
Heat Transfer Tube ◽  
Transfer Tube

scholarly journals Modeling Film-Coolant Flow Characteristics at the Exit of Shower-Head Holes

2000 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Coolant Flow ◽  
The Heat Transfer Coefficient

Abstract The coolant flow characteristics at the hole exits of a film-cooled blade are derived from an earlier analysis where the hole pipes and coolant plenum were also discretized. The blade chosen is the VKI rotor with three staggered rows of shower-head holes. The present analysis applies these flow characteristics at the shower-head hole exits. A multi-block three-dimensional Navier-Stokes code with Wilcox’s k-ω model is used to compute the heat transfer coefficient on the film-cooled turbine blade. A reasonably good comparison with the experimental data as well as with the more complete earlier analysis where the hole pipes and coolant plenum were also gridded is obtained. If the 1/7th power law is assumed for the coolant flow characteristics at the hole exits, considerable differences in the heat transfer coefficient on the blade surface, specially in the leading-edge region, are observed even though the span-averaged values of h match well with the experimental data. This calls for span-resolved experimental data near film-cooling holes on a blade for better validation of the code.

scholarly journals The analysis of thermal and flow characteristics of the condensation of refrigerant zeotropic mixtures in minichannels

2016 ◽  
Vol 37 (2) ◽  
pp. 41-69 ◽  
Author(s):  
Tadeusz Bohdal ◽  
Katarzyna Widomska ◽  
Małgorzata Sikora
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Characteristics ◽  
Internal Diameter ◽  
Test Results ◽  
Experimental Heat ◽  
Experimental Heat Transfer ◽  
Calculation Results

Abstract The paper presents the results of experimental heat transfer and pressure drop during condensation of the single component refrigerant R134a and zeotropic mixtures R404A, R407C, and R410A in tube minichannels of internal diameter from the range 0.31-3.30 mm. The local values and the average of heat transfer coefficient and pressure drop in the whole range of the change in mass quality were measured. On the basis of the obtained test results there was illustrated the influence of the change of mass vapor quality, the mass flux density, and the inner diameter of channel on the studied parameters. These results were compared with the calculation results based on the relations postulated by other authors. The discrepancy range was ± 50%. On the basis of given test results own correlation was developed to calculate the heat transfer coefficient and pressure drop of tested refrigerants which presents the obtained results in a range of discrepancy of ±25%.

Wind Induced Heat Transfer Coefficient From Flat Horizontal Surfaces Exposed to Solar Radiation

2007 ◽  
Author(s):  
Subhash C. Mullick ◽  
Suresh Kumar ◽  
Basant K. Chourasia
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Heat Loss ◽  
Convective Heat ◽  
Solar Collector ◽  
Convective Heat Transfer Coefficient ◽  
Loss Coefficient ◽  
Operating Conditions

Upward heat losses have strong effect on the performance of flat plate solar collectors under different operating conditions. Suitable equations for estimation of top heat loss coefficient have already been proposed [1,2]. The top heat loss coefficient is a function of wind induced convective heat transfer coefficient in a flat plate solar collector. It is, therefore, important to choose appropriate values of this convective heat transfer coefficient for correct estimation of the top heat loss coefficient. Researchers [3–6] have suggested different wind speed based correlations for estimation of the wind induced convective heat transfer coefficient. These correlations give different values of wind heat transfer coefficient thus resulting in variation in values of the top heat loss coefficient of a solar collector under same operating conditions. In present study, an attempt has been made to measure and study the wind induced convective heat transfer coefficient from exposed flat horizontal surfaces in real wind. For this purpose, three unglazed test plates of similar construction and different sizes were employed. Experiments were conducted on the three test plates over rooftop of a building in built environment. From experimental data of the test plate, of size 925mm × 865mm × 2mm, a correlation between wind heat transfer coefficient and wind speed has been obtained by linear regression. The obtained correlation has also been compared with work of other researchers [3–6]. Results obtained from experimental data of the three test plates provide some interesting information about wind induced convective heat transfer coefficient.

scholarly journals Nonlinear peristaltic flow of Walter's B fluid in an asymmetric channel with heat transfer and chemical reactions

2014 ◽  
Vol 18 (4) ◽  
pp. 1095-1107 ◽  
Author(s):  
Ullah Mehmood ◽  
Norzieha Mustapha ◽  
Sharidan Shafie
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Concentration ◽  
Flow Characteristics ◽  
Wave Number ◽  
Asymmetric Channel ◽  
Regular Perturbation ◽  
Viscoelastic Parameter ◽  
Walter’S B Fluid

In this paper, effects of heat and mass transfer on peristaltic transport of Walter's B fluid in an asymmetric channel are investigated. The governing equations are solved using regular perturbation method by taking wave number as a small parameter. Expressions for the stream function, temperature distribution, heat transfer coefficient, and mass concentration are presented in explicit form. Solutions are analyzed graphically for different values of arising parameters such as viscoelastic parameter, Prandtl, Eckert, Soret, Schmidt and Reynolds number. It has been found that these parameters considerably affect the considered flow characteristics. Results show that with an increase in Eckert and Prandtl number temperature and heat transfer coefficient increase while mass concentration decreases. Further, Mass concentration also decreases with increasing Soret and Schmidt number.

scholarly journals An Experimental Study to Compare the Naphthalene Sublimation With the Liquid Crystal Technique in Compressible Flow

1995 ◽  
Author(s):  
M. Häring ◽  
A. Hoffs ◽  
A. Bolcs ◽  
B. Weigand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Mach Number ◽  
Transfer Coefficient ◽  
Compressible Flow ◽  
Test Facility ◽  
Number Range ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The naphthalene sublimation and the liquid crystal technique are two methods being used for measurements of the heat transfer coefficient on turbine airfoils. In this paper the results obtained with the two methods for the same compressible flow conditions are compared. The measurements were performed in a free jet test facility on a flat plate and a cylinder. The free stream Mach number ranged from M=0.4 to 0.8. The naphthalene sublimation technique was applied to obtain the local Nusselt number, based on the Sherwood number, applying a new analogy function (Häring, Weigand (1995)). These results were compared with measurements on the same test arrangement using the transient liquid crystal technique. A good agreement between the two measurement techniques and correlations was found for the entire Mach number range. An application of both techniques on a turbine airfoil confirmed this observation. The sublimation technique was also applied to measure the local heat transfer coefficient on a turbine vane at exit Mach numbers up to M=0.9 and exit Reynolds numbers up to Re=1.8e6. The experimental results were compared with the two dimensional boundary layer code TEXSTAN (Crawford, 1986).

Numerical Prediction of 45° Angled Ribs Effects on U-shaped Channels Heat Transfer and Flow under Multi Conditions

2020 ◽  
Vol 37 (1) ◽  
pp. 41-59 ◽  
Author(s):  
Longfei Wang ◽  
Songtao Wang ◽  
Xun Zhou ◽  
Fengbo Wen ◽  
Zhongqi Wang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Narrow Channel ◽  
Aspect Ratios ◽  
Cooling Air Flow

AbstractRibs effects on the heat transfer performance and cooling air flow characteristics in various aspect ratios (AR) U-shaped channels under different working conditions are numerically investigated. The ribs angle and channel orientation are 45° and 90°, respectively, and the aspect ratios are 1:2, 1:1, 2:1. The inlet Reynolds number changes from 1e4 to 4e4 and rotational speeds include 0, 550 rpm, 1,100 rpm. Local heat transfer coefficient, endwall surface heat transfer coefficient ratio and augmentation factor are the three primary criteria to measure channel heat transfer. Ribs increase the heat transfer area and improve heat transfer coefficient of ribbed surfaces significantly, especially in the 1st pass, while the endwall surface contributes more to channel heat transfer because of the larger area and relatively smaller heat transfer coefficient. The wide channel (AR =2:1) owns the better augmentation factor than the narrow channel (AR =1:2) and ribs heat transfer weight increases with an increase of the inlet Reynolds number. Rotating slightly reduces the ribs heat transfer weight in channel and the trailing surface in 1st pass is the main influence object of rotating.

Direct Experimental Measurements of Heat Transfer Coefficient Augmentation Due to Approach Flow Effects

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Flow Characteristics ◽  
Density Ratios ◽  
High Level

Film cooling can have a significant effect on the heat transfer coefficient (HTC) between the overflowing freestream gas and the underlying surface. This study investigated the influence of approach flow characteristics, including the boundary layer thickness and character (laminar and turbulent), as well as the approach flow Reynolds number, on the HTC. The figure of merit for this study was the HTC augmentation, that is, the ratio of HTCs for a cooled versus uncooled surface. A heated foil surface provided a known heat flux, allowing direct measurement of HTC and augmentation. The foil was placed both upstream and downstream of the film cooling holes, in order to generate an approaching thermal boundary layer, as representative of actual engine conditions. High-resolution IR thermography provided spatially resolved HTC augmentation data. An open-literature shaped-hole design was used, known as the 7-7-7 hole, in order to compare with existing results in the literature. A variety of blowing conditions were tested from M = 0.5 to 3.0. Two elevated density ratios of DR = 1.20 and DR = 1.80 were used. The results indicated that turbulent boundary layer thickness had a modest effect on HTC augmentation, whereas a very high level of augmentation was observed for a laminar approach boundary layer. The presence of upstream heating greatly increased the HTC augmentation in the near-hole region, although these effects died out by 10–15 diameters from the holes.

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