Investigation of the Effects of Flow Swirl on Heat Transfer Inside a Cylindrical Cavity

1991 ◽  
Vol 113 (2) ◽  
pp. 348-354 ◽  
Author(s):  
A. Salce ◽  
T. W. Simon
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cylindrical Cavity ◽  
Flow Direction ◽  
Axial Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Sensitive ◽  
Transfer Coefficients ◽  
Cavity Bottom

Experiments were conducted to determine local heat transfer coefficients on the inside surfaces of a cylindrical cavity that is cooled by a swirling air flow. Temperature-sensitive liquid crystals were used as temperature sensors. Five blowing (cooling) modes were tested: three with swirl numbers of 0.36, 0.84, and 1.73; a fourth with no swirl (axial flow), and a fifth that was similar to the fourth but had the flow direction reversed. Flow visualization and static pressure measurements were performed to improve understanding of the situation. The smoke-wire technique was successfully used to picture the flow patterns. Plots of local Nusselt number along the cavity surfaces were obtained for the five blowing modes and for three different Reynolds numbers. The swirling cases had similar flow fields with higher heat transfer rates near the cavity top and lower rates near the cavity bottom (the opposite of the nonswirling cases). A tornadolike structure on the cavity bottom was observed in the swirling cases. This structure became stronger and more violent as the degree of swirl and the Reynolds number were increased. The Nusselt number curves for the two nonswirling cases were of similar shape, although the flow direction was reversed.

Experimental Investigation of the Effect of Synthetic Jets in Minichannels With Subcooled Boiling Flow

2013 ◽  
Author(s):  
David M. Sykes ◽  
Andrew L. Carpenter ◽  
Gregory S. Cole
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Heat Transfer ◽  
Local Heat ◽  
High Heat ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Augmentation

Microchannels and minichannels have been shown to have many potential applications for cooling high-heat-flux electronics over the past 3 decades. Synthetic jets can enhance minichannel performance by adding net momentum flux into a stream without adding mass flux. These jets are produced because of different flow patterns that emerge during the induction and expulsion stroke of a diaphragm, and when incorporated into minichannels can disrupt boundary layers and impinge on the far wall, leading to high heat transfer coefficients. Many researchers have examined the effects of synthetic jets in microchannels and minichannels with single-phase flows. The use of synthetic jets has been shown to augment local heat transfer coefficients by 2–3 times the value of steady flow conditions. In this investigation, local heat transfer coefficients and pressure loss in various operating regimes were experimentally measured. Experiments were conducted with a minichannel array containing embedded thermocouples to directly measure local wall temperatures. The experimental range extends from transitional to turbulent flows. Local wall temperature measurements indicate that increases of heat transfer coefficient of over 20% can occur directly below the synthetic jet with low exit qualities. In this study, the heat transfer augmentation by using synthetic jets was dictated by the momentum ratio of the synthetic jet to the bulk fluid flow. As local quality was increased, the heat transfer augmentation dropped from 23% to 10%. Surface tension variations had a large effect on the Nusselt number, while variations in inertial forces had a small effect on Nusselt number in this operating region.

Enhanced Heat Transfer in a Flat Rectangular Duct With Streamwise-Periodic Disturbances at One Principal Wall

1983 ◽  
Vol 105 (4) ◽  
pp. 851-861 ◽  
Author(s):  
E. M. Sparrow ◽  
W. Q. Tao
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Rectangular Duct ◽  
Transfer Coefficients ◽  
Local Maxima ◽  
Periodic Disturbances ◽  
Pressure Distributions ◽  
Friction Factors

Experiments were performed in a flat rectangular duct to determine the heat transfer and pressure drop response to periodic, rod-type disturbance elements situated adjacent to one principal wall and oriented transverse to the flow direction. In a portion of the experiments, heat transfer occurred only at the rodded wall, while in the remainder, heat was transferred at both principal walls of the duct. Highly detailed axial distributions of the local heat transfer coefficient were obtained. These distributions revealed the rapid establishment of a periodic (i.e., cyclic) fully developed regime as well as recurring local maxima and minima. Cycle-average, fully developed heat transfer coefficients were evaluated and were found to be much larger than those for a smooth-walled duct. Linear pressure distributions were measured between periodically positioned stations in the fully developed region, and the corresponding friction factors were several times greater than the smooth-duct values. The heat transfer and friction data were very well correlated using parameters that take account of the effective surface roughness associated with the disturbance rods.

Inverse Determination of the Local Heat Transfer Coefficients for Nucleate Boiling on a Horizontal Cylinder

2003 ◽  
Vol 125 (6) ◽  
pp. 1087-1095 ◽  
Author(s):  
H. Louahlia-Gualous ◽  
P. K. Panday ◽  
E. A. Artioukhine
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pool Boiling ◽  
Gradient Methods ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Nucleate Boiling ◽  
Nucleate Pool Boiling ◽  
Transfer Coefficients ◽  
Iterative Regularization

This article treats the local heat transfer for nucleate pool boiling around the cylinder using the inverse heat conduction analysis. The physical model considers a half section of a cylinder with unknown surface temperature and heat flux density. The iterative regularization and the conjugate gradient methods are used for solving the inverse analysis. The local Nusselt number profiles for nucleate pool boiling are presented and analyzed for different electric heat. The mean Nusselt number estimated by IHCP is closed with the measured values. The results of IHCP are compared to those of Cornewell and Houston (1994), Stephan and Abdelsalam (1980) and Memory et al. (1995). The influence of the error of the measured temperatures and the error in placement of the thermocouples are studied.

scholarly journals Analysis of Backward and Forward Effects on a Grooved Co-axial Heat Exchanger by Response Surface Methodology

2019 ◽  
Vol 111 ◽  
pp. 01092
Author(s):  
Şahin GÜNGÖR ◽  
Levent AYDIN ◽  
Umut CEYHAN ◽  
Büşra KAYA ◽  
Ziya Haktan KARADENİZ
Keyword(s):  
Heat Transfer ◽  
Response Surface Methodology ◽  
Response Surface ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heated Wall ◽  
Transfer Coefficients ◽  
Pipe Model ◽  
Energy Equations

In the literature, it is proved that grooved pipe models are thermally more efficient than the smooth pipe model. Different than the previous studies in which the groove dimensions are constant along the pipe, we study the effect of groove radius and the gap between adjacent grooves on the local heat transfer coefficients using computational fluid dynamics software. The grooved section consists of three sub-sections to see the effects of groove dimension in stream-wise flow direction. We vary the radius of circular grooves parametrically in each section to optimize the local groove radius throughout the pipe. We couple the fluid flow (1200<Re<24000) with energy equations, and the grooved sections are set as heated wall at constant temperature of 350 K. The optimal mesh has been selected by performing mesh independence study and finer mesh has been used in heated wall section. The radii of grooves are varied from 2 to 6 mm with an increment of 0.2 mm considering the manufacturability of the pipe, to do so we use the design of experiments (DOE). All DOE tools in ANSYS software are examined and compared with full factorial results. After DOE process, local heat transfer coefficient values of all groove parts are examined by response surface methodology (RSM).

Local Heat Transfer Coefficients Under an Axisymmetric, Single-Phase Liquid Jet

1991 ◽  
Vol 113 (1) ◽  
pp. 71-78 ◽  
Author(s):  
J. Stevens ◽  
B. W. Webb
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Single Phase ◽  
Radial Distance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Plate Spacing

The purpose of this investigation was to characterize local heat transfer coefficients for round, single-phase free liquid jets impinging normally against a flat uniform heat flux surface. The problem parameters investigated were jet Reynolds number Re, nozzle-to-plate spacing z, and jet diameter d. A region of near-constant Nusselt number was observed for the region bounded by 0≤r/d≤0.75, where r is the radial distance from the impingement point. The local Nusselt number profiles exhibited a sharp drop for r/d > 0.75, followed by an inflection and a slower decrease there-after. Increasing the nozzle-to-plate spacing generally decreased the heat transfer slightly. The local Nusselt number characteristics were found to be dependent on nozzle diameter. This was explained by the influence of the free-stream velocity gradient on local heat transfer, as predicted in the classical analysis of infinite jet stagnation flow and heat transfer. Correlations for local and average Nusselt numbers reveal an approximate Nusselt number dependence on Re1/3.

Ice Formation and Heat Transfer With Water Flow Around Isothermally Cooled Cylinders Arranged in a Line

1990 ◽  
Vol 112 (3) ◽  
pp. 707-713 ◽  
Author(s):  
T. Hirata ◽  
H. Matsui
Keyword(s):  
Heat Transfer ◽  
Cold Water ◽  
Flow Direction ◽  
Storage System ◽  
Local Heat Transfer ◽  
Energy Storage System ◽  
Correlation Equation ◽  
Local Heat ◽  
Ice Formation ◽  
Transfer Coefficients

The ice formation phenomenon and heat transfer around isothermally cooled cylinders that are lined up in the direction of flow in a crossflow of cold water were examined experimentally. Under the conditions of low Reynolds numbers and low cooling temperatures, the cylinders became linked by an ice layer. The amount of ice formed around the cylinders was much more than that for a single cylinder. A correlation equation was proposed for the amount of linked ice around the cooled cylinders. It was found that the local heat transfer coefficients on the linked ice surface showed an alternating decrease and increase in the flow direction. The mean value of the local Nusselt number showed the same characteristic as that on a flat plate in a turbulent flow. A dimensionless parameter that represents how efficiently the cylinders can work as a thermal energy storage system was introduced.

Influence of Surface Heating Condition on Local Heat Transfer in Enclosed Corotating Disks With Axial Throughflow

1993 ◽  
Author(s):  
S. Y. Kim ◽  
J. C. Han ◽  
G. L. Morrison ◽  
E. Elovic
Keyword(s):  
Heat Transfer ◽  
Axial Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Outer Radius ◽  
Surface Heating ◽  
Heating Condition ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Rotating Cavity

Local heat transfer in a rotating cavity with axial throughflow was experimentally investigated. The rotating cavity was bounded by two plane disks and a cylindrical rim (shroud). The ratio of the rim span to the disk outer radius was 0.4 and the ratio of the disk inner radius to outer radius was 0.25. This study investigated the effects of axial coolant flow rate, rotation speed, and disk surface heating condition on the local heat transfer coefficient distributions inside the cavity. Three cavity surface heating conditions were tested: case 1 - upstream and downstream disks with radially increasing temperature but colder than rim; case 2 - upstream and downstream disks at uniform temperature but colder than rim; and case 3 - upstream and downstream disks and rim at uniform temperature. Tests were systematically performed for the axial flow Reynolds numbers between 2500 and 25,000, the rotational Reynolds numbers between 0 and 5.11 × 105, and the rotational Grashof numbers between 5 × 106 and 1.3 × 1010, respectively. The results show that the local heat transfer coefficients for the non-rotating cavity increase with increasing axial flow Reynolds number. However, the local heat transfer coefficients initially decrease and then increase with increasing rotational Reynolds number. In general, the heat transfer coefficients on the rim for case 2 surface heating condition are higher than those for case 1 and case 3 whereas the heat transfer coefficients on the upstream and downstream disks for case 3 surface heating condition are higher than those for case 1 and case 2.

Heat Transfer Enhancement of Reactor Utilizing Taylor-Poiseuille Flow

2014 ◽  
Author(s):  
Li Ye ◽  
Huajun Peng ◽  
Bo Zhou ◽  
Mo Yang ◽  
Zheng Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Regime ◽  
Poiseuille Flow ◽  
Axial Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Taylor Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Numerical studies have been conducted to determine the heat transfer performances in a Taylor-Poiseuille flow regime. The flow is confined between two different heated, concentric cylinders. The inner cylinder is allowed to rotate while the outer one remains fixed, an axial flow is added. The influences of rotation Taylor number and axial Reynolds number on heat transfer coefficients are investigated. Results show that temperature in the flow regime presents a remarkable sinusoidal periodicity as the result of the axial arrangement of Taylor vortices, so does the local heat transfer coefficients. Heat transfer efficiency gets strengthened with increasing Taylor number, while damped with increasing Reynolds number. The accuracy of the simulation is validated by compared to the existing linear stability analysis.

Local Heat Transfer Coefficients for Condensation in Stratified Countercurrent Steam-Water Flows

1983 ◽  
Vol 105 (4) ◽  
pp. 706-712 ◽  
Author(s):  
H. J. Kim ◽  
S. G. Bankoff
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Flow Rates ◽  
Heat Transfer Coefficients ◽  
Flow Parameters ◽  
Eddy Transport

A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel inclined 33 deg to the horizontal. The variables in this experiment were the inlet water and steam flow rates, and the inlet water temperature. Condensation heat transfer coefficients were determined as functions of local steam and water flow rates, and the degree of subcooling. Correlations are given for the local Nusselt number for the smooth and for the rough interface regimes, and also for the dimensionless wave amplitude. A turbulence-centered model is also developed. It is shown that better agreement with the data can be obtained if the characteristic scales in the turbulent Nusselt number and Reynolds numbers are related to measured interfacial parameters rather than the bulk flow parameters. The important effect of interfacial shear, missing in previous eddy-transport models, is thus implicitly included.

Heat Transfer Coefficients in an Orthogonally Rotating Duct With Turbulators

1995 ◽  
Vol 117 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Ying-Jong Hong
Keyword(s):  
Heat Transfer ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Coolant Temperature ◽  
Transfer Coefficients ◽  
Base Surface ◽  
Square Duct ◽  
Number Range ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the influence of rotation on local heat transfer coefficient for the turbulent flow in a short square duct (L/DH = 15) with a pair of opposite rib-roughened walls. The ribs are configured in an in-line arrangement with an attack angle of 90 deg to the main flow. The coolant used was air with the flow direction in the radially outward direction. The Reynolds numbers ranged from 5000 to 25,000; the rib pitch-to-height ratio was 5; and the rib height-to-hydraulic diameter ratio was kept at a value of 0.20. The rotation number range was 0 to 0.5. Local Nusselt number variations along the duct were determined over the trailing and leading surfaces. In addition, local heat transfer measurements on all sides of a typical rib as well as on a typical exposed base surface between two consecutive ribs in a fully developed region were conducted at various rotational speeds. It is shown that the Coriolis acceleration tends to improve the heat transfer due to the presence of strong secondary flow. Centripetal buoyancy is shown to influence the heat transfer response with heat transfer being suppressed on both leading and trailing surfaces as the wall-to-coolant temperature difference is increased with other controlling parameters hold constant. Results are also compared with previous investigations. It was found that the results agree very well with those reported by other works in this field.

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