A Parametric Study of Boiling Heat Transfer in a Horizontal Tube Bundle

1988 ◽  
Vol 110 (4a) ◽  
pp. 976-981 ◽  
Author(s):  
M. K. Jensen ◽  
J.-T. Hsu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Tube Bundle ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Boiling heat transfer outside of a section of a uniformly heated horizontal tube bundle in an upward crossflow was investigated using R-113 as the working fluid. The inline tube bundle had five columns and 27 rows with a pitch-to-diameter ratio of 1.3. Heat transfer coefficients obtained from the 14 instrumented tubes are reported for a range of fluid and flow conditions; slightly subcooled liquid inlet conditions were used. At most heat fluxes there was no significant variation in the local heat transfer coefficients throughout the tube bundle. However, at low heat fluxes and mass velocities, the heat transfer coefficient increased at positions higher in the tube bundle. As pressure and mass velocity increased so did the heat transfer coefficients. For the local heat transfer coefficient, a Chen-type correlation is compared to the data; the data tend to be overpredicted by about 20 percent. Reasons for the overprediction are suggested.

Experimental Study of Flow Boiling Heat Transfer in Mini-Tube

2005 ◽  
Author(s):  
Lihong Wang ◽  
Min Chen ◽  
Manfred Groll
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer

Flow boiling heat transfer characteristics of R134a were experimentally investigated in a horizontal stainless steel mini-tube. The inner diameter of the test tube is 1.3 mm and the tube wall thickness is 0.1 mm. Local heat transfer coefficients are obtained over a range of vapor qualities up to 0.8, mass fluxes from 310 to 860 kg/m2s, heat fluxes from 21 to 50 kW/m2, and saturation pressures from 6.5 to 7.5 bar. The mass flux, heat flux, saturation pressure, and vapor quality dependences of heat transfer coefficients are demonstrated. Based on an available model in recent literature potential heat transfer mechanisms are also analyzed.

Local Heat Transfer Coefficients for Horizontal Tube Arrays in High-Temperature Large-Particle Fluidized Beds: An Experimental Study

1986 ◽  
Vol 108 (4) ◽  
pp. 907-912 ◽  
Author(s):  
A. Goshayeshi ◽  
J. R. Welty ◽  
R. L. Adams ◽  
N. Alavizadeh
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
High Temperature ◽  
Tube Bundle ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Packed Bed ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

An experimental study is described in which time-averaged local heat transfer coefficients were obtained for arrays of horizontal tubes immersed in a hot fluidized bed. Bed temperatures up to 1005 K were achieved. Bed particle sizes of 2.14 mm and 3.23 mm nominal diameter were employed. An array of nine tubes arranged in three horizontal rows was used. The 50.8 mm (2 in.) diameter tubes were arranged in an equilateral triangular configuration with 15.24 cm (6 in.) spacing between centers. The center tube in each of the three rows in the array was instrumented providing data for local heat flux and surface temperature at intervals of 30 deg from the bottom to the top—a total of seven sets of values for each of the center tubes. The three sets of data are representative of the heat transfer behavior of tubes at the bottom, top, and in the interior of a typical array. Data were also obtained for a single horizontal tube to compare with the results of tube bundle performance. Superficial velocities of high-temperature air ranged from the packed-bed condition through approximately twice the minimum fluidization level. Comparisons with results for a single tube in a bubbling bed indicate only slight effects on local heat transfer resulting from the presence of adjacent tubes. Tubes in the bottom, top, and interior rows also exhibited different heat transfer performance.

Heat Transfer Enhancement by Turbulent Impinging Jets

2000 ◽  
Author(s):  
M. Kumagai ◽  
R. S. Amano ◽  
M. K. Jensen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract A numerical and experimental investigation on cooling of a solid surface was performed by studying the behavior of an impinging jet onto a fixed flat target. The local heat transfer coefficient distributions on a plate with a constant heat flux were computationally investigated with a normally impinging axisymmetric jet for nozzle diameter of 4.6mm at H/d = 4 and 10, with the Reynolds numbers of 10,000 and 40,000. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation k-ε turbulence model. The finite-volume differencing scheme was used to solve the thermal and flow fields. The predicted heat transfer coefficients were compared with experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients for short nozzle-to-plate distance (H/d = 4). The differences between H/d = 4 and 10 due to the correlation among heat transfer coefficient, kinetic energy and pressure were investigated for the impingement region. Predictions by the present model show good agreement with the experimental data.

Local Heat Transfer Coefficient of Flow Boiling in Microchannels With Artificial Reentrant Cavities

2007 ◽  
Author(s):  
Chih-Jung Kuo ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Bubble Generation ◽  
Parallel Microchannels

Flow boiling in parallel microchannels with structured reentrant cavities was experimental studied. Flow patterns, boiling inceptions and heat transfer coefficients were obtained and studied for G = 83 kg/m2-s to G = 303 kg/m2-s and heat fluxes up to 643 W/cm2. The heat transfer coefficient-mass velocity and quality relations had been analyzed to identify boiling mechanism. Comparisons of the performance of the enhanced and plain-wall microchannels had also been made. The microchannels with reentrant cavities were shown to promote nucleation of bubbles and to support significantly better reproducibility and uniformity of bubble generation.

Using Gradient Heat Flux Measurement to Experimentally Determine Local Heat Transfer Coefficient on Combustion Chamber Surface in a Diesel Engine

2019 ◽  
pp. 87-96
Author(s):  
V.B. Sapozhnikov ◽  
V.Yu. Mityakov ◽  
A.V. Mityakov ◽  
A.V. Vintsarevich ◽  
D.V. Gerasimov
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Combustion Chamber ◽  
Local Heat Transfer ◽  
Flux Measurement ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Engine Operation ◽  
Heat Transfer Coefficients

We used gradient thermometry to determine local heat transfer coefficients on the fire deck surface. We studied two modes of engine operation, that is, motored and fired. We show that the heat transfer coefficient distribution over the fire deck surface is inhomogeneous. Our investigation results may be used to validate existing models of heat transfer in a combustion chamber.

Distribution of local heat transfer coefficient values in the wall region of an agitated vessel

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Magdalena Cudak ◽  
Joanna Karcz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Measuring Point ◽  
Agitated Vessel ◽  
Heat Transfer Coefficients

AbstractExperimentally found local heat transfer coefficients are analyzed as a function of the measuring point on the heat transfer surface area of the agitated vessel wall and of the impeller eccentricity. Eccentric Rushton turbine and A 315 impeller are considered. Local heat transfer coefficients were measured by means of the computer-aided electrochemical method. The measurements were performed in an agitated vessel with inner diameter 0.3 m, filled with liquid up to the height equal to the vessel diameter. The experiments were carried out within the turbulent regime of the Newtonian liquid flow in the agitated vessel. The results were compared with the data obtained for the agitated vessel equipped with an eccentrically located axial flow propeller or an HE 3 impeller. Experimental studies show that the distributions of the heat transfer coefficient values depend on the impeller eccentricity, impeller type and the direction of the liquid circulation in the agitated vessel.

Pin-Fin Heat Transfer: Contribution of the Wall and the Pin to the Overall Heat Transfer

1992 ◽  
Author(s):  
A. M. Ai Dabagh ◽  
G. E. Andrews
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Duct Flow ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients

The differences in the heat transfer coefficient between the pin and the wall in pin-fin heat transfer was determined for three pin length to diameter ratios. A staggered pin-fin array was used with a 50% duct flow blockage by the pins. The axial pitch-to-pin diameter ratio, X/D, was 1.5 and the transverse pitch-to-diameter ratio, S/D, was 2.0. Three pin length-to-diameter ratios, T/D, of 0.7. 1.0 and 2.2 were investigated. The mean heat transfer coefficient results were very similar to previous work for similar geometries. The axial variation of heat transfer coefficient showed this to be fairly uniform with a small peak at the fourth row. Around each pin four measurements of the heat transfer coefficients were made with four on the fin surface at each end. Thus 12 local heat transfer coefficients were made per pin-fin. These showed that for all three geometries the wall or fin heat transfer was always greater by 15–35% than the pin for the same velocity and Re.

Local Heat Transfer Coefficients and Pressure Drop During Evaporation in a Smooth Horizontal Tube

2002 ◽  
Author(s):  
C. Aprea ◽  
A. Greco ◽  
G. P. Vanoli
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

R22 is the most widely employed HCFC working fluid in vapour compression plant. HCFCs must be replaced within 2020. Major problems arise with the substitution of the working fluids, related to the decrease in performance of the plant. Therefore, extremely accurate design procedures are needed. The relative sizing of each of the components of the plant is crucial for cycle performance. For this reason, the knowledge of the new fluids heat transfer characteristics in condensers and evaporators is required. The local heat transfer coefficients and pressure drop of pure R22 and of the azeotropic mixture R507 (R125-R143a 50%/50% in weight) have been measured during convective boiling. The test section is a smooth horizontal tube made of a with a 6 mm I.D. stainless steel tube, 6 m length, uniformly heated by Joule effect. The effects of heat flux, mass flux and evaporation pressure on the heat transfer coefficients are investigated. The evaporating pressure varies within the range 3 ÷10 bar, the refrigerant mass flux within the range 200 ÷ 1000 kg/m2s, the heat flux within 0 ÷ 44 kW/m2. A comparison have been carried out between the experimental data and those predicted by means of the most credited literature relationships.

Convective Heat Transfer of Alumina Nanofluids in a Microchannel

2010 ◽  
Author(s):  
Saeid Vafaei ◽  
Dongsheng Wen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Axial Distance ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

This work reports an experimental study of convective heat transfer of aqueous alumina nanofluids in a horizontal microchannel under laminar flow condition. The variation of local heat transfer coefficients, in both entrance and developed flow regime, is obtained as a function of axial distance. The heat transfer coefficient of nanofluids is found to be dependent upon not only nanoparticle concentration but also mass flow rate. Different to the behavior in conventional-sized channels, the major heat transfer coefficient enhancement is observed in fully developed region in microchannels. Discussions of the results suggest that the heterogeneous nature of nanoparticle flow should be considered.

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