Heat Transfer and Friction in Rectangular Channels With Ribbed or Ribbed-Grooved Walls

1994 ◽  
Vol 116 (1) ◽  
pp. 58-65 ◽  
Author(s):  
Y. M. Zhang ◽  
W. Z. Gu ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulence Intensity ◽  
Transfer Coefficients ◽  
Flow Measurements ◽  
Number Range ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Rectangular Channels ◽  
Rib Roughened

The effect of compound turbulators on friction factors and heat transfer coefficients in rectangular channels with two opposite ribbed-grooved walls was determined for a Reynolds number range of 10,000 to 50,000. The channel width-to-height ratio was 10. The fully developed heat transfer coefficients and friction factors on the ribbed-grooved and smooth side walls of each test channel were measured for six rib-groove spacings (p/e = 8, 10, 15, 20, 25, and 30). The fully developed friction and heat transfer in similar aspect ratio rectangular channels with two opposite ribbed walls with two rib spacings (p/e = 8.5 and 11.5) was also measured for comparison. The results show that the heat transfer performance of the rib-groove roughened duct is much better than the rib roughened duct. The rib-groove roughened wall enhances the heat transfer 3.4 times and pays 6 times the pressure drop penalty, whereas the rib roughened wall, with similar rib height and rib spacing, enhances the heat transfer 2.4 times and pays about the same pressure drop penalty. Semi-empirical friction and heat transfer correlations were obtained. Flow measurements show that the roughened ducts have flatter velocity profiles than the smooth duct and rib-groove roughened duct produces higher turbulence intensity than the rib roughened duct. The flatter velocity profile and higher turbulence intensity are responsible for producing higher heat transfer.

Experimental Study and Genetic-Algorithm-Based Correlation on Shell-Side Heat Transfer and Flow Performance of Three Different Types of Shell-and-Tube Heat Exchangers

2006 ◽  
Vol 129 (9) ◽  
pp. 1277-1285 ◽  
Author(s):  
Qiu-wang Wang ◽  
Gong-nan Xie ◽  
Bo-tao Peng ◽  
Min Zeng
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Shell Side ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Shell And Tube

The heat transfer and pressure drop of three types of shell-and-tube heat exchangers, one with conventional segmental baffles and the other two with continuous helical baffles, were experimentally measured with water flowing in the tube side and oil flowing in the shell side. The genetic algorithm has been used to determine the coefficients of correlations. It is shown that under the identical mass flow, a heat exchanger with continuous helical baffles offers higher heat transfer coefficients and pressure drop than that of a heat exchanger with segmental baffles, while the shell structure of the side-in-side-out model offers better performance than that of the middle-in-middle-out model. The predicted heat transfer rates and friction factors by means of the genetic algorithm provide a closer fit to experimental data than those determined by regression analysis. The predicted corrections of heat transfer and flow performance in the shell sides may be used in engineering applications and comprehensive study. It is recommended that the genetic algorithm can be used to handle more complicated problems and to obtain the optimal correlations.

Turbulent Convective Heat Transfer in Forced Cooled Underground Electric Transmission Systems

1985 ◽  
Vol 107 (2) ◽  
pp. 327-333 ◽  
Author(s):  
R. Ghetzler ◽  
J. C. Chato ◽  
J. M. Crowley
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Scale Model ◽  
Transfer Coefficients ◽  
Transmission Systems ◽  
Number Range ◽  
Heat Transfer Coefficients ◽  
Electric Transmission ◽  
Friction Factors ◽  
High Reynolds

Heat transfer and friction factors were experimentally determined in a scale model of high-voltage, pipe-type underground transmission systems for Reynolds numbers to 8000. Dielectric insulating oil (Sun No. 4) with a Prandtl number of 120 was utilized for the coolant. Two ratios of cable to enclosure pipe diameters, corresponding to standard and oversize enclosure pipes, were examined for the three-cable system. Helical wire wrap was included to simulate protective skid wires around the cables. Three configurations of cable positioning were considered—open triangular, close triangular, and cradled. A method of generalizing the heat transfer coefficients was developed and tested for rough pipe cables based on extensions of previous work in the literature. The generalized correlation, without correction factors, was found to be applicable only in two cases with appropriate flow pattens and geometries. Heat transfer to the pipe wall could be correlated by standard methods in the high Reynolds number range.

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.

scholarly journals Heat Transfer Enhancement inside Rectangular Channel by Means of Vortex Generated by Perforated Concave Rectangular Winglets

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 43
Author(s):  
Syaiful ◽  
Monica Pranita Hendraswari ◽  
M.S.K. Tony S.U. ◽  
Maria F. Soetanto
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Rectangular Channel ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Enhance Heat Transfer ◽  
Number Range ◽  
Heat Transfer Coefficients ◽  
Study Results

Passive methods using vortex generators (VGs) to enhance heat transfer have been a concern of researchers in recent decades. This study is intended to investigate the strength of the vortex generated by VGs by trying to reduce the pressure drop in the flow. The present work also takes into account the influence of the vortex intensity on the improvement of heat transfer, which can be indicated by the low value of the synergy angle. Experiments were carried out in the current investigation to validate the results of the numerical simulations in the Reynolds number range of 3102 to 16,132. The study results indicate that the observed heat transfer coefficients from the experimental and simulation results have a similar tendency with relatively small errors. A reduction in pressure drop is observed with the use of perforated concave rectangular winglets (PCRWs) against the nonperforated ones although there was a slight decrease in heat transfer improvements.

Evaporation Heat Transfer Characteristics on the Outside of Horizontal Smooth, Herringbone and Enhanced Surface 1EHT Tubes

2015 ◽  
Author(s):  
Jian-jun Sun ◽  
Jing-xiang Chen ◽  
David J. Kukulka ◽  
Kan Zhou ◽  
Wei Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Smooth Tube ◽  
External Diameter ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer ◽  
Enhanced Surface

An experiment investigation was performed using R410A in order to determine the single-phase and evaporation heat transfer coefficients on the outside of (i) a smooth tube; (ii) herringbone tube; and (iii) the newly developed Vipertex enhanced surface 1EHT tube; all with the same external diameter (12.7 mm). The nominal evaporation temperature is 279 K, with inlet and outlet qualities of 0.1 and 0.8. Mass fluxes ranged from 10 to 40 kg m−2s−1. Results suggest that the 1EHT tube has excellent heat transfer performance but a higher pressure drop when compared to a smooth tube. Evaporation heat transfer coefficient for the 1EHT is lower than the herringbone tube and the pressure drop is almost the same.

Experimental Study of Evaporation Heat Transfer Characteristics and Pressure Drops of R410A and R134a in a Multiport Mini-Channel

2009 ◽  
Author(s):  
Jatuporn Kaew-On ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer ◽  
R 134A

The evaporation heat transfer coefficients and pressure drops of R-410A and R-134a flowing through a horizontal-aluminium rectangular multiport mini-channel having a hydraulic diameter of 3.48 mm are experimentally investigated. The test runs are done at refrigerant mass fluxes ranging between 200 and 400 kg/m2s. The heat fluxes are between 5 and 14.25 kW/m2, and refrigerant saturation temperatures are between 10 and 30 °C. The effects of the refrigerant vapour quality, mass flux, saturation temperature and imposed heat flux on the measured heat transfer coefficient and pressure drop are investigated. The experimental data show that in the same conditions, the heat transfer coefficients of R-410A are about 20–50% higher than those of R-134a, whereas the pressure drops of R-410A are around 50–100% lower than those of R-134a. The new correlations for the evaporation heat transfer coefficient and pressure drop of R-410A and R-134a in a multiport mini-channel are proposed for practical applications.

Periodically Converging-Diverging Tubes and Their Turbulent Heat Transfer, Pressure Drop, Fluid Flow, and Enhancement Characteristics

1984 ◽  
Vol 106 (1) ◽  
pp. 55-63 ◽  
Author(s):  
P. Souza Mendes ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Surface Area ◽  
Equal Mass ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Friction Factors

A comprehensive experimental study was performed to determine entrance region and fully developed heat transfer coefficients, pressure distributions and friction factors, and patterns of fluid flow in periodically converging and diverging tubes. The investigated tubes consisted of a succession of alternately converging and diverging conical sections (i.e., modules) placed end to end. Systematic variations were made in the Reynolds number, the taper angle of the converging and diverging modules, and the module aspect ratio. Flow visualizations were performed using the oil-lampblack technique. A performance analysis comparing periodic tubes and conventional straight tubes was made using the experimentally determined heat transfer coefficients and friction factors as input. For equal mass flow rate and equal transfer surface area, there are large enhancements of the heat transfer coefficient for periodic tubes, with accompanying large pressure drops. For equal pumping power and equal transfer surface area, enhancements in the 30–60 percent range were encountered. These findings indicate that periodic converging-diverging tubes possess favorable enhancement characteristics.

Nucleate Pool Boiling Heat Transfer Coefficients of Distilled Water (H2O) and R-134a/Oil Mixtures From Rib-Roughened Surfaces

1997 ◽  
Vol 119 (1) ◽  
pp. 142-151 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Chun-Jen Weng
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Distilled Water ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Oil Mixtures ◽  
R 134A ◽  
Rib Roughened

Measurements of pool-boiling heat transfer coefficients in distilled water and R-134a/oil mixtures with up to 10 percent (by weight) miscible EMKARATE RL refrigeration lubricant oil are extensively studied for a smooth tube and four rib-roughened tubes (rib pitch 39.4 mm, rib height 4 mm, rib width 15 mm, number of rib element 8, rib angle 30 deg–90 deg). Boiling data of pure refrigerants and oil mixtures, as well as the influences of heat flux level on heat transfer coefficient, are presented and discussed. A correlation is developed for predicting the heat transfer coefficient for both pure refrigerants and refrigerant-oil mixtures. Moreover, boiling visualizations were made to broaden our fundamental understanding of the pool boiling heat transfer mechanism for rib roughened surfaces with pure refrigerants and refrigerant-oil mixtures.

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