Heat Transfer in a Supersonic Parallel Diffuser

1965 ◽  
Vol 7 (1) ◽  
pp. 1-7 ◽  
Author(s):  
P. J. Baker
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Cross Section ◽  
Static Pressure ◽  
Positive Pressure ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Flows ◽  
Pressure Distributions ◽  
The Mean

This paper presents the results of heat transfer measurements taken on a two-dimensional supersonic parallel diffuser. The wall static pressure distributions and the corresponding heat transfer coefficients and fluxes have been measured for a range of initial total pressures. The effects of varying the area of the diffuser cross-section for the same upstream generating nozzle have also been studied. Mach number profiles measured at sections along the diffuser show that in the presence of shock waves and a positive pressure gradient the flow is very much underdeveloped. In general, the mean level of heat transfer is found to be much greater than that predicted by conventional empirical equations for subsonic pipe flows with zero pressure gradient. Further, on comparison between normal and oblique shock diffusion the former is found to give the higher level of heat transfer.

Heat Transfer From the Heated Convex Wall of a Return Bend With Rectangular Cross Section

1983 ◽  
Vol 105 (1) ◽  
pp. 64-69 ◽  
Author(s):  
N. Seki ◽  
S. Fukusako ◽  
M. Yoneta
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convex Wall ◽  
The Mean

An experimental investigation has been performed to clarify the turbulent heat transfer characteristics along the heated convex wall of a return bend which has a rectangular cross section with large aspect ratio for various heights of the duct. The experiments are carried out under the condition that the convex wall is heated at constant heat flux while the concave wall is insulated. Water is used as the working fluid with duct heights of 15, 40, 60 and 80 mm, Reynolds numbers of 8 × 103 to 8 × 104, and Prandtl numbers ranging from 6.5 to 8.5. The mean and the local heat transfer coefficients are always smaller than those for the straight parallel plates and straight ducts. Both the local and the mean heat transfer coefficients decrease as the duct height increases. Near the outlet region of the return bend the local heat transfer coefficient increases in the flow direction as the height decreases. Behavior is just the opposite at the inlet. Correlation equations for the mean and the local Nusselt numbers are determined in the range of parameters covered.

scholarly journals Heat transfer and skin-friction in channel with flow behind a cylinder

2021 ◽  
Vol 2088 (1) ◽  
pp. 012055
Author(s):  
N A Kiselev ◽  
A G Zditovets ◽  
Yu A Vinogradov
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Static Pressure ◽  
Thermal Imager ◽  
Transfer Coefficients ◽  
Reynolds Analogy ◽  
Friction Coefficients ◽  
Heat Transfer Coefficients ◽  
Smooth Model ◽  
Transfer Method

Abstract The paper presents the results of an experimental study of the parameters of the boundary layer, distribution of static pressure, heat transfer and friction coefficients of smooth surface located in the wake behind the cylinder in the channel. Cylinders of various diameters were placed in a slotted channel with a height of 30 mm on its axis. In all experiments, the flow velocity at the inlet was 50 m/s. The cylinder was made unheated. The friction coefficients of the smooth model were determined both from the velocity profile in the boundary layer and by direct weighing of the model on a one-component strain-gage balance. The local values of the heat transfer coefficients were determined by transient heat-transfer method using a thermal imager. The values of the heat transfer and friction coefficients in the wake behind the cylinder, referred to the values on the smooth wall in the undisturbed flow, varied in the range 1.15–1.65 and 1.3–1.75, respectively. The value of the Reynolds analogy factor for all cylinder diameters turned out to be less than unity.

The Calculation of Heat Transfer Coefficients from Skin Friction Coefficients in the Compressible Laminar Boundary Layer on an Aerofoil

1968 ◽  
Vol 19 (3) ◽  
pp. 243-253 ◽  
Author(s):  
R. E. Luxton
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Gradient ◽  
Skin Friction ◽  
Laminar Boundary Layer ◽  
Strong Dependence ◽  
Transfer Coefficients ◽  
Friction Coefficients ◽  
Heat Transfer Coefficients ◽  
Similar Solutions

SummaryIn this note a relation is established between the correlation parameters obtained by Cohen and Reshotko from similar solutions of the compressible laminar boundary layer, and the Pohlhausen-type pressure gradient parameter used in the approximate methods devised by Luxton and Young. A simple graphical procedure is presented to allow heat transfer coefficients to be obtained from known skin friction coefficients in the presence of a pressure gradient. In view of the restrictions of the similar solutions it cannot be claimeda priorithat the method gives accurate results. It does, however, reflect the strong dependence of the heat-transfer skin-friction relation on the pressure gradient and, by reference to calculated results published previously, it is suggested that the method may give adequate accuracy under quite severe conditions.

Fluid Flow and Heat Transfer in Microchannels With Rectangular Cross Section

2003 ◽  
Author(s):  
Jung-Yeul Jung ◽  
Ho-Young Kwak
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Convective Heat Transfer Coefficients ◽  
Factor Constant

Forced convective heat transfer coefficients and friction factor for flow of water and FC-72 in microchannels with a rectangular cross section were measured. An integrated microsystem consisting of five microchannels on one side and a localized heater and seven polysilicon temperature sensors along the selected channels on the other side was fabricated by using a double side polished silicon wafer. For the microchannels tested, the friction factor constant C = f ReDh obtained are values between 35.7 and 81.9, which are close to the theoretical value of 57.0. The measured Nusselt number in the laminar regime tested could be correlated by a correlation, Nu = A ReDh1.37 Pr1/3 where A is the value between 0.000 454 and 0.000 646.

Heat Transfer and Surface Renewal Dynamics in Gas-Fluidized Beds

1994 ◽  
Vol 116 (4) ◽  
pp. 929-937 ◽  
Author(s):  
D. V. Pence ◽  
D. E. Beasley ◽  
R. S. Figliola
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Transfer Rate ◽  
Angular Position ◽  
Heat Transfer Surface ◽  
Transfer Coefficients ◽  
Emulsion Phase ◽  
Heat Transfer Coefficients ◽  
The Mean ◽  
Transient And Steady State

Local instantaneous heat transfer between a submerged horizontal cylinder and a gas-fluidized bed operating in the bubble-flow regime was measured and the resulting signals analyzed. Unique to this investigation is the division of particle convective heat transfer into transient and steady-state contact dynamics through analysis of instantaneous heat transfer signals. Transient particle convection results from stationary particles in contact with the heat transfer surface and yields a heat transfer rate that decays exponentially in time. Steady-state particle convection results from active particle mixing at the heat transfer surface and results in a relatively constant heat transfer rate during emulsion phase contact. The average time of contact for each phase is assessed in this study. Signals were acquired using a constant-temperature platinum film heat flux sensor. Instantaneous heat transfer signals were obtained for various particle sizes by varying the angular position of the heat transfer probe and the fluidization velocity. Individual occurrences of emulsion phase heat transfer that are steady-state in nature are characterized by contact times significantly higher than both the mean transient and mean emulsion phase contact times under the same operating conditions. Transient and steady-state contact times are found to vary with angular position, particle size, and fluidizing velocity. Due to the extremely short transient contact times observed under these fluidization conditions, mean transient heat transfer coefficients are approximately equal to the mean steady-state heat transfer coefficients.

Pressure Drop and Heat Transfer in a Duct With Triangular Cross Section

1960 ◽  
Vol 82 (2) ◽  
pp. 125-136 ◽  
Author(s):  
E. R. G. Eckert ◽  
T. F. Irvine
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Cross Section ◽  
Flow Region ◽  
Isosceles Triangle ◽  
Transfer Coefficients ◽  
Round Tube ◽  
Number Range ◽  
Heat Transfer Coefficients ◽  
Friction Factors

Friction factors have been measured for a duct whose cross section has the shape of an isosceles triangle with a side ratio 5 to 1 in the fully developed flow region for laminar, transitional, and turbulent conditions. In addition, local and average heat-transfer coefficients and the temperature field in the duct wall have been determined for the condition of constant heat generation per unit volume of the duct walls. Friction factors in laminar flow agreed well with analytical predictions. In the turbulent flow range they were by 20 per cent lower than values calculated from relations for a round tube with the use of the “hydraulic diameter.” Heat-transfer coefficients averaged over the circumference of the duct were only half as large as values calculated from round tube relations in the Reynolds number range from 4300 to 24,000. The measurements also revealed that thermal starting lengths were in excess of 100 diameters. In round tubes a length of 10 to 20 diameters has been found sufficient to develop the temperature field.

Modeling of work of plate water evaporation coolers of indirect operation principle

10.12737/2199 ◽  
2014 ◽  
Vol 3 (4) ◽  
pp. 160-166
Author(s):  
Шацкий ◽  
Vladimir Shatskiy ◽  
Гулевский ◽  
Vyacheslav Gulevskiy
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Boundary Conditions ◽  
Cross Section ◽  
Parabolic Type ◽  
Water Evaporation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Proposed Model ◽  
Complex Mathematical Model

More complex mathematical model is proposed which is a system of partial differential equations of elliptic and parabolic type with the corresponding initial and boundary conditions, which are not involved in the heat transfer coefficients, the deter-mination of the numerical values of which is very difficult. For its implementation diffe-rence analogue of the proposed model was built with Nx steps along the length of the channel, Ny steps along the section of channels, Ny / 2 +1 steps of the cross section of the plate. The presented model and the method of its implementation makes it possible to determine the temperature of the air flows along the length of coolers that offers a choice of the geometric parameters.

scholarly journals Boiling of a refrigerant of low GWP on the surface with copper microchannels

2018 ◽  
Vol 70 ◽  
pp. 02007
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Atmospheric Pressure ◽  
Rectangular Cross Section ◽  
Heating Surface ◽  
Heat Transfer Process ◽  
Geometrical Parameters ◽  
Variable Depth ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The boiling curves and heat transfer coefficients between the heating surface and fluid were investigated in the paper. Copper samples with horizontal microchannels of rectangular cross-section, variable depth and width were the objects of the study. The following geometrical parameters have been used: microchannel width 0.2; 0.3 and 0.4 mm, depth between 0.2 and 0.5 mm (change every 0.1 mm). Boiling refrigerant was Novec-649 (GWP = 1), and the experiment was performed at atmospheric pressure. Geometrical parameters impact, within a given range of heat flux 3 – 130 kW/m2, on the heat transfer process was determined.

A Method for the Determination of the Local Turbulent Friction Factor and Heat Transfer Coefficient in Generalized Geometries

1971 ◽  
Vol 93 (1) ◽  
pp. 61-68 ◽  
Author(s):  
E. Aranovitch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Transfer Coefficient ◽  
Cross Section ◽  
Arbitrary Cross Section ◽  
Transfer Coefficients ◽  
Turbulent Friction ◽  
Heat Transfer Coefficients

A method is presented for the determination of the distributions of velocity, local friction, and heat transfer coefficients in a forced axial turbulent flow with an arbitrary cross section. The method uses as basis the characteristics of the laminar flow. A comparison is made with some experimental results concerning different geometries.

scholarly journals Heat transfer and skin-friction in a nonequilibrium adverse pressure gradient

2021 ◽  
Vol 2039 (1) ◽  
pp. 012010
Author(s):  
N A Kiselev ◽  
Yu A Vinogradov ◽  
A G Zditovets
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Gradient Flow ◽  
Adverse Pressure Gradient ◽  
Opening Angle ◽  
Transfer Coefficients ◽  
Reynolds Analogy ◽  
Heat Transfer Coefficients ◽  
Gradient Parameter ◽  
Relative Friction

Abstract The paper presents the results of an experimental study of influence of a weak and moderate nonequilibrium adverse pressure gradient (APG) on the parameters of the dynamic and thermal boundary layers. The Reynolds number based on the momentum thickness at the beginning of the APG region was Re **=5500. The section of the channel with APG was a slotted channel with an opening angle of the upper wall of 0-14°. The values of the relative (referred to the parameters in a zero pressure gradient flow at the same Re **) friction and heat transfer coefficients, as well as the Reynolds analogy factor depending on the longitudinal pressure gradient, are obtained. The values of the relative friction coefficient decreased to cf/cf0 =0.7 and those of the heat transfer to St/St0=0.9. A maximum value of the Reynolds analogy factor (St/St0)/(cf/cf0 )=1.16 was reached for the pressure gradient parameter β=2.9. The ratio of the heat transfer and drag coefficients of the dimpled to smooth surfaces remained approximately constant regardless of the presence or magnitude of a adverse pressure gradient.

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