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Wärme - und Stoffübertragung

, Volume 17, Issue 1, pp 59–64 | Cite as

A note on an improvement of heat transfer of tube banks

  • S. Aiba
  • T. Ota
  • H. Tsuchida
Article
  • 78 Downloads

Abstract

An experimental investigation has been conducted for exploring a possibility to improve the heat transfer of tube banks of in-line arrangement, in which the first cylinder was roughened with pyramids. Measured were the heat transfer characteristics of the first cylinder for several cylinder spacings. It is found that there exists the critical Reynolds numberRe c , beyond which the heat transfer rate increases drastically by about 30 to 50% as compared with that for the smooth cylinder, though the increasing rate is small for the case of very narrow spacing such asC y /d×C x /d =1.2×1.2. In the region ofRe>Re c , the separation point shifts downstream to θ=120° to 130° from the forward stagnation point, and it results in the decrease of the form drag.

Keywords

Heat Transfer Experimental Investigation Pyramid Transfer Rate Apply Physic 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

cD

pressure drag coefficient=\(\int\limits_0^\pi {C_p \cos \theta d\theta } \)

Cp

pressure coefficient=\(\left( {P - P_f } \right)/\tfrac{1}{2}\varrho U_\infty ^2 \)

Cx,Cy

longitudinal and transversal spacing between cylinders' centers

d

cylinder diameter

h

relative roughness=(k/d)×103

k

roughness height

N

longitudinal row number

Nu

Nusselt number=α d/λ

P

static pressure

Re

Reynolds number=U t d/v

Red

Reynolds number=Ud/v

T

temperature

U

upstream uniform flow velocity

Ut

mean velocity at minimum clearance=U C y /(C y -d)

α

heat transfer coefficient

θ

circumferential angle from forward stagnation point

λ, ν, ϱ

thermal conductivity, kinematic viscosity and density of air at upstream uniform flow temperature

Subscript

c

critical

f

forward stagnation point

m

mean

w

wall

upstream uniform flow

max

maximum

min

minimum

θ

local value atθ

Eine Notiz zur Verbesserung der Wärmeübertragung an Rohrbündeln

Zusammenfassung

Es werden experimentelle Untersuchungen mitgeteilt, die das Ziel hatten, die Wärmeübertragung an fluchtenden Rohrbündeln dadurch zu verbessern, daß die erste Reihe pyramidenförmige Rauhigkeitselemente erhielt. Gemessen wurde die Wärmeübertragung der ersten Reihe, für verschiedene Rohrabstände. Man fand eine kritische Reynolds-ZahlRe c , oberhalb derer die Wärmeübertragung drastisch um 30% bis 50% anstieg, verglichen mit dem glatten Zylinder, wenn auch der Anstieg im Bereich sehr kleiner Abstände, so wieC y /d×C x /d=1,2×1,2, gering blieb. FürRe>Re c wandert der Ablösepunkt stromab zu Zentriwinkeln von 120° bis 130°, gemessen vom vorderen Staupunkt, wobei der Formwiderstand abnahm.

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References

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Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • S. Aiba
    • 1
  • T. Ota
    • 2
  • H. Tsuchida
    • 1
  1. 1.Department of Mechanical EngineeringAkita Technical CollegeAkitaJapan
  2. 2.Department of Mechanical and Production EngineeringAkita UniversityAkitaJapan

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