scholarly journals Investigating the Economical Performance of Four Suggested Designs for the Heat Exchangers

2020 ◽  
Vol 38 (4) ◽  
pp. 863-870
Author(s):  
Khaled M.K. Pasha ◽  
Mohamed Mahmoud El-Fawal
Keyword(s):  
Reynolds Number ◽  
Cross Section ◽  
Spiral Pattern ◽  
Pressure Loss Coefficient ◽  
A Value ◽  
Cross Section Area ◽  
Section Area ◽  
Rectangular Pattern ◽  
Air Passage ◽  
Spiral Type

It is required to investigate the economy of the performance of four suggested heat exchanger designs. The economy criteria are expressed by the ratio of the Nusselt number, Nu, and the pressure loss coefficient, ΔP∗. The four patterns are; rectangular, zigzag, spiral, and narrow-spiral. The air passages of each one of the four types have the same cross-section area and air passage length. Also, the inlet air temperature and flow rate for both; the air and water are the same in the four types. The narrow-spiral pattern has an equal passage thickness for both air and water. Reynolds number, Re, of values; 2535, 7606, 12677, 17748, 20284, 22819, 25355, (based on the hydraulic diameter of the cross-section) are investigated. For validation, the rectangular pattern type was checked experimentally, and the results were close to those of the prediction. For all values of the Reynolds number, the suggested narrow-spiral pattern exhibited the highest values of Nu/ΔP∗. At the Reynolds number of 25355, the ratio, Nu/ΔP∗ could achieve a value of about 15.74 for the narrow-spiral type. For each suggested pattern, (Nu/ΔP∗) and Re are correlated in a suitable formula.

An Experimental Study of Heat Transfer and Pressure Drop on the Bend Surface of a U-Duct

2010 ◽  
Author(s):  
Tareq Salameh ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Cross Section ◽  
Outer Wall ◽  
Cross Section Area ◽  
Section Area ◽  
The Cross

This work concerns an experimental study of pressure drop and heat transfer for turbulent flow inside a U-duct. Such duct geometries can be found in many engineering applications where cooling air extracts heat from hot internal walls of the duct, e.g., passage cooling inside gas turbine blades. Both friction factors and convective heat transfer coefficients were measured inside a U-duct for three different cases, namely (a) the smooth straight part, (b) the smooth bend (turn) part, and (c) a rough (ribbed) bend (turn) part. The details of the duct geometry were as follows: the cross section area of the straight part was 50×50 mm2, the inside length of the bend part 240 mm, the cross section area of the rib was 5×5 mm2 and the rib height-to-hydraulic diameter ratio, e/Dh, was 0.1. The Reynolds number was varied from 8,000 to 20,000. The test rig has been built in such a way that various experimental setups can be handled as the bend (turn) part of the U-duct can easily be removed and the rib configuration can be changed. Both the U-duct and the rib were made from plexiglass material to allow optical access for measuring the surface temperature by using a high-resolution measurement technique based on narrow band thermochromic liquid crystals (TLC R35C5W) and a CCD camera placed facing the bend (turn) part of the U-duct. The calibration of the TLC is based on the hue-based color decomposition system using an in-house designed calibration box. The rib was placed transversely to the direction of the main flow at the outer wall of the bend (turn) part where the wall was heated by an electrical heater. The friction factor ratio and the heat transfer enhancement ratio for case (c) at a Reynolds number of 20,000 were 48.75 and 2.66, respectively. It is found that the presence of the rib increases the heat transfer coefficient on the outer wall of the bend part (tip of side U-duct). The uncertainties were 3% and 6% for the Nusselt number and friction factor, respectively.

Thermoacoustic Shape Optimization of a Subsonic Nozzle

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Alexis Giauque ◽  
Maxime Huet ◽  
Franck Clero ◽  
Sébastien Ducruix ◽  
Franck Richecoeur
Keyword(s):  
Acoustic Emission ◽  
Cross Section ◽  
Source Term ◽  
Combustion Noise ◽  
Noise Emission ◽  
Cross Section Area ◽  
Section Area ◽  
The Cross ◽  
Nozzle Flows ◽  
Subsonic Nozzle

Indirect combustion noise originates from the acceleration of nonuniform temperature or high vorticity regions when convected through a nozzle or a turbine. In a recent contribution (Giauque et al., 2012, “Analytical Analysis of Indirect Combustion Noise in Subcritical Nozzles,” ASME J. Eng. Gas Turbies Power, 134(11), p. 111202) the authors have presented an analytical thermoacoustic model providing the indirect combustion noise generated by a subcritical nozzle when forced with entropy waves. This model explicitly takes into account the effect of the local changes in the cross-section area along the configuration of interest. In this article, the authors introduce this model into an optimization procedure in order to minimize or maximize the thermoacoustic noise emitted by arbitrarily shaped nozzles operating under subsonic conditions. Each component of the complete algorithm is described in detail. The evolution of the cross-section changes are introduced using Bezier's splines, which provide the necessary freedom to actually achieve arbitrary shapes. Bezier's polar coordinates constitute the parameters defining the geometry of a given individual nozzle. Starting from a population of nozzles of random shapes, it is shown that a specifically designed genetic optimization algorithm coupled with the analytical model converges at will toward a quieter or noisier population. As already described by Bloy (Bloy, 1979, “The Pressure Waves Produced by the Convection of Temperature Disturbances in High Subsonic Nozzle Flows,” J. Fluid Mech., 94(3), pp. 465–475), the results therefore confirm the significant dependence of the indirect combustion noise with respect to the shape of the nozzle, even when the operating regime is kept constant. It appears that the quietest nozzle profile evolves almost linearly along its converging and diverging sections, leading to a square evolution of the cross-section area. Providing insight into the underlying physical reason leading to the difference in the noise emission between two extreme individuals, the integral value of the source term of the equation describing the behavior of the acoustic pressure of the nozzle is considered. It is shown that its evolution with the frequency can be related to the global acoustic emission. Strong evidence suggest that the noise emission increases as the source term in the converging and diverging parts less compensate each other. The main result of this article is the definition and proposition of an acoustic emission factor, which can be used as a surrogate to the complex determination of the exact acoustic levels in the nozzle for the thermoacoustic shape optimization of nozzle flows. This acoustic emission factor, which is much faster to compute, only involves the knowledge of the evolution of the cross-section area and the inlet thermodynamic and velocity characteristics to be computed.

An Analytical Method of Analyzing the Heat Conduction for the Unequal Cross-Section Straight Fin

2013 ◽  
Vol 365-366 ◽  
pp. 1211-1216
Author(s):  
Fan Zhang ◽  
Peng Yun Song
Keyword(s):  
Heat Conduction ◽  
Cross Section ◽  
Analytical Method ◽  
Thermal Analyses ◽  
Cross Sectional ◽  
Cross Section Area ◽  
Section Area ◽  
Calculation Results ◽  
The Cross ◽  
Analytical Expressions

The cross-section area of straight fin is often considered to be equal in the thermal analyses of straight fin, but sometimes it is unequalin actual situation. Taking a straight fin with two unequal cross-sectional areas as an example,an analytical method of heat conduction for unequal section straight fin is presented. The analytical expressions of temperature field and heat dissipating capacity about the fin,which has a smaller cross-section area near the fin base and a larger one, is obtained respectively. The calculation results of the unequal cross-section are fully consistent with the equal area one, so the method is proved right. The results show that the larger the cross section areanear the base,the better is the heat transfer, and the temperature at the base with larger cross-section area is lower than that with smaller cross-section area when the amount of heat is fixed.

Rotational Temperature Measurement in Multicomponent Gases Using Raman Scattering Spectroscopy

1976 ◽  
Vol 30 (2) ◽  
pp. 179-183 ◽  
Author(s):  
R. S. Hickman ◽  
A. E. Kassem ◽  
L. H. Liang
Keyword(s):  
Temperature Field ◽  
Raman Scattering ◽  
Temperature Measurement ◽  
Cross Section ◽  
Room Temperature ◽  
Rotational Temperature ◽  
Raman Scattering Spectroscopy ◽  
Scattering Experiment ◽  
Cross Section Area ◽  
Section Area

The rotational temperature at pressures near 1 atm and at room temperature has been successfully measured using spectra obtained in an intracavity Raman scattering experiment. The accuracy of the method is sufficient to allow local temperature measurement of multicomponent gases with no disturbance in the temperature field. The advantage of the method lies in the fact that it does not require knowledge of the relative scattering cross-section area of the component gases.

scholarly journals Load bearing capacity of thin-walled rectangular and I-shaped steel sections of short both empty and concrete-filled columns

2021 ◽  
Vol 15 (58) ◽  
pp. 77-85
Author(s):  
Amor Bouaricha ◽  
Naoual Handel ◽  
Aziza Boutouta ◽  
Sarah Djouimaa
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Load Capacity ◽  
Cross Sectional ◽  
Short Columns ◽  
Cross Section Area ◽  
Section Area ◽  
Specimen Height ◽  
Steel Sections ◽  
Thin Walled

In this experimental work, strength results obtained on short columns subjected to concentric loads are presented. The specimens used in the tests have made of cold-rolled, thin-walled steel. Twenty short columns of the same cross-section area and wall thickness have been tested as follows: 8 empty and 12 filled with ordinary concrete. In the aim to determine the column section geometry with the highest resistance, three different types of cross-sections have been compared: rectangular, I-shaped unreinforced and, reinforced with 100 mm spaced transversal links. The parameters studied are the specimen height and the cross-sectional steel geometry. The registered experimental results have been compared to the ultimate loads intended by Eurocode 3 for empty columns and by Eurocode 4 for compound columns. These results showed that a concrete-filled composite column had improved strength compared to the empty case. Among the three cross-section types, it has been found that I-section reinforced is the most resistant than the other two sections. Moreover, the load capacity and mode of failure have been influenced by the height of the column. Also, it had noted that the experimental strengths of the tested columns don’t agree well with the EC3 and EC4 results.

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