Study of Entropy Generation in Heat Exchanger Tube With Multiple V Cuts in Perforated Twisted Tape Insert

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Bipin Kumar ◽  
Anil Kumar Patil ◽  
Siddharth Jain ◽  
Manoj Kumar
Keyword(s):  
Entropy Generation ◽  
Circular Tube ◽  
Operating Conditions ◽  
Entropy Generation Rate ◽  
Twisted Tape ◽  
Heat Exchanger Tube ◽  
Number Range ◽  
Entropy Generation Number ◽  
Twist Ratio ◽  
Exchanger Tube

The present work deals with the study of entropy generation in circular tube fitted with perforated twisted tape (PTT) insert with multiple V cuts. Experimental data pertaining to heat transfer and frictional losses are collected for solid twisted tape (STT), PTT, double V cut PTT, and PTT with multiple V cuts by varying the twist ratio in the range of 2–6 for the Reynolds number range of 2000–25,000. The entropy generation rate of heated tube with insert is found to be less than the smooth tube in most of the cases under similar operating conditions. The minimum value of entropy generation number corresponds to the PTT having twist ratio of 3.

Effects of Manufacturing Tolerances on Regenerative Exchanger Number of Transfer Units and Entropy Generation

2005 ◽  
Vol 128 (3) ◽  
pp. 585-598 ◽  
Author(s):  
Wei Shang ◽  
Robert W. Besant
Keyword(s):  
Entropy Generation ◽  
Flow Channel ◽  
Operating Conditions ◽  
Channel Diameter ◽  
Pressure Drops ◽  
Entropy Generation Number ◽  
Compact Heat Exchangers ◽  
Prime Concern ◽  
Manufacturing Tolerances ◽  
The Impact

A prime concern with the design of ultra-compact heat exchangers is the impact on performance of flow channel variations due to flow channel hydraulic diameter variations caused by manufacturing tolerances. This paper uses analytical methods to show that as the standard deviation in flow channel sizes, caused by manufacturing tolerances in a rotary regenerative exchanger, is increased compared to the average flow channel diameter the effective number of transfer units decreases. Depending on the operating conditions, the entropy generation number either increases or decreases with increasing flow channel size variations. These findings extend previous findings that showed that flow channel variations cause lower pressure drops and effectiveness.

Second-Law Analysis on Wavy Plate Fin-and-Tube Heat Exchangers

1998 ◽  
Vol 120 (3) ◽  
pp. 797-800 ◽  
Author(s):  
W. W. Lin ◽  
D. J. Lee
Keyword(s):  
Entropy Generation ◽  
Operating Conditions ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Second Law ◽  
Spanwise Direction ◽  
Minimum Entropy ◽  
Tube Heat Exchanger ◽  
Second Law Analysis ◽  
Minimum Entropy Generation

Second-law analysis on the herringbone wavy plate fin-and-tube heat exchanger was conducted on the basis of correlations of Nusselt number and friction factor proposed by Kim et al. (1997), from which the entropy generation rate was evaluated. Optimum Reynolds number and minimum entropy generation rate were found over different operating conditions. At a fixed heat duty, the in-line layout with a large tube spacing along streamwise direction was recommended. Furthermore, within the valid range of Kim et al.’s correlation, effects of the fin spacing and the tube spacing along spanwise direction on the second-law performance are insignificant.

Effect of thermal asymmetries on the entropy generation analysis of a variable viscosity Couette–Poiseuille flow

2017 ◽  
Vol 231 (5) ◽  
pp. 1011-1024 ◽  
Author(s):  
Pranab K Mondal ◽  
Harshad Gaikwad ◽  
Pranab Kumar Kundu ◽  
Somchai Wongwises
Keyword(s):  
Nusselt Number ◽  
Pressure Gradient ◽  
Entropy Generation ◽  
Variable Viscosity ◽  
Applied Pressure ◽  
Analytical Framework ◽  
Simultaneous Action ◽  
Entropy Generation Rate ◽  
Parallel Plates ◽  
Entropy Generation Number

The influence of viscous dissipation on forced convective heat transfer and entropy generation rate in the conduction limit for a variable-viscosity flow between asymmetrically heated parallel plates is studied in an analytical framework consistent with perturbation method. The study considers a flow of Newtonian fluid under the simultaneous action of an applied pressure gradient and an axial movement of the upper plate. The present study emphasizes on the effect of dissipative heat produced by the movable upper plate as well as viscous heating generated due to applied pressure gradient on the underlying thermo-hydrodynamic transport. A few non-dimensional parameters such as dimensionless upper plate velocity, degree of asymmetry parameter and Brinkman number have been defined and their influential role on the variation of temperature profile, the Nusselt number and entropy generation number has been discussed in detail. The study shows that the variation of Nusselt number exhibits an unbounded swing, which, in turn, leads to appearance of the point of singularities at some cases of asymmetrical plate heating. Finally, the source of appearance of point of singularities has been discussed in view of the energy balance, and from the second-law analysis of thermodynamics.

Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in SUS304-Circular Tubes With Various Twisted-Tape Inserts (Influence of Twist Ratio)

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Suguru Masuzaki
Keyword(s):  
Circular Tube ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Flow Boiling ◽  
Circular Tubes ◽  
Twisted Tapes ◽  
Subcooled Flow ◽  
Twist Ratio

The transient critical heat fluxes (transient CHFs) in SUS304-circular tubes with various twisted-tape inserts are systematically measured for mass velocities (G = 3988–13,620 kg/m2s), inlet liquid temperatures (Tin = 287.55–313.14 K), outlet pressures (Pout = 805.11–870.23 kPa) and exponentially increasing heat inputs (Q = Q0 exp(t/τ), exponential periods, τ, of 28.39 ms to 8.43 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-circular tube of inner diameter (d = 6 mm), heated length (L = 59.4 mm), effective length (Leff = 49.4 mm), L/d (=9.9), Leff/d (=8.23), and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted-tapes with twist ratios, y [H/d = (pitch of 180 deg rotation)/d], of 2.40 and 4.45 are used. The transient critical heat fluxes for SUS304-circular tubes with the twisted-tapes of y = 2.40 and 4.45 are compared with authors' transient CHF data for the empty SUS304-circular tube and a SUS304-circular tube with the twisted-tape of y = 3.37, and the values calculated by authors' transient CHF correlations for the empty circular tube and the circular tube with twisted-tape insert. The influences of heating rate, twist ratio and swirl velocity on the transient CHF are investigated into details and the widely and precisely predictable correlations of the transient CHF against inlet and outlet subcoolings for the circular tubes with various twisted-tape inserts are given based on the experimental data. The correlations can describe the transient CHFs for SUS304-circular tubes with various twisted-tapes of twist ratios (y = 2.40, 3.37, and 4.45) in the wide experimental ranges of exponential periods (τ = 28.39 ms to 8.43 s) and swirl velocities (usw = 5.04–20.72 m/s) obtained in this work within −26.19% to 14.03% difference. The mechanism of the subcooled flow boiling critical heat flux in a circular tube with twisted-tape insert is discussed.

Effect of Twin Delta-Winged Twisted-Tape on Thermal Performance of Heat Exchanger Tube

2013 ◽  
Vol 34 (15) ◽  
pp. 1278-1288 ◽  
Author(s):  
Smith Eiamsa-ard ◽  
Chayut Nuntadusit ◽  
Pongjet Promvonge
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Twisted Tape ◽  
Heat Exchanger Tube ◽  
Exchanger Tube

scholarly journals Inherent irreversibility impacts on thermal boundary layer flow over a mobile plate with convective surface boundary conditions

2019 ◽  
Vol 5 (2) ◽  
pp. 45
Author(s):  
Sajjad Haider ◽  
Adnan Saeed Butt ◽  
Asif Ali ◽  
Yun-Zhang Li ◽  
Tufail Hussain
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Temperature Profile ◽  
Entropy Generation ◽  
Free Stream ◽  
Entropy Generation Rate ◽  
Surface Boundary ◽  
Entropy Generation Number ◽  
Surface Boundary Conditions ◽  
Layer Flow

<p class="abstract"><strong>Background:</strong> The irreversibility impacts on flow and heat transfer processes can be quantified through entropy analysis. It is a significant tool which can be utilized to deduce about the energy losses. The current study investigates the inherent irreversibility impacts during a flow of boundary layer and heat transfer on a mobile plate.</p><p class="abstract"><strong>Methods:</strong> The flow is examined under thermal radiation and convective heat conditions. The fundamental governing equations of flow and heat phenomenon are transmuted into ordinary differential equations by employing similarity transmutations and shooting technique is utilized in order to solve the resultant equations. The temperature and velocity profiles are acquired to reckon Bejan and entropy generation number. Pertinent results are elucidated graphically for the movement of plate and flow in same and opposite directions.  </p><p class="abstract"><strong>Results:</strong> A decline in temperature profile is noted with rise in values of <em>Pr</em> in both cases when the movement of surface and free stream is in similar and converse directions. A decrease in temperature is observed for both cases with increase in <em>N<sub>R</sub></em> while with the rise in Biot number <em>a</em>, the temperature profile also increases. Entropy generation rate near the surface is high in case when surface and free stream are moving in opposite directions as compared to case when they move in same directions.</p><p class="abstract"><strong>Conclusions:</strong> It is observed that irreversibility impacts are more remarkable when the movement of fluid and plate is in opposite direction. Moreover, irreversibility impacts of heat transfer are prominent in free stream region.</p><p class="abstract"> </p><br /><em></em>

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