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FEM application in phase change exchangers

Anwendung der Finite Elemente Methode bei Wärmetauschern mit Phasenwechsel

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Abstract

Application of FEM in the analysis of condenser and vaporizer has been illustrated taking into account property variation with temperature. Accurate shell side pressure drop in a condenser has been determined by the present method taking into account the gradual reduction in vapour flow due to condensation from inlet to outlet. As the present method analyses the exchanger in small elements, analysis of an evaporator working under the conditions of partial vapour blanketing is also possible.

Zusammenfassung

Die Verwendung der Finite Elemente Methode zur Berechnung von Kondensator und Verdampfer unter Berücksichtigung von temperaturabhängigen Stoffwerten ist hier dargestellt worden. Mit dem dargestellten Verfahren ist der genaue Druckverlust im Rohrraum eines Kondensators bestimmt worden, wobei die schrittweise Verminderung der Dampfströmung aufgrund der Kondensation von Ein-zu Auslaß mit berücksichtigt wurde. Mit der gegenwärtigen Methode, die einen Wärmeaustausch mittels kleiner Elemente berechnet, ist ebenso eine Auslegung eines Verdampfers mit einer partiellen Dampfabdeckung möglich.

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Abbreviations

A :

heat transfer area in an elment upto any section, m2

A c :

elemental heat transfer area, m2

B :

weightage

C :

UA/2

D e :

characteristic dimension, m

D s :

shell diameter, cm

F t :

temperature correction factor

f :

friction factor, m2/cm2

G :

mass velocity, kg/m2 sec

G″ :

W/LN 2/3

g :

acceleration of gravity, m/sec2

h :

condensing coefficient, W/m2°C

h 0 :

boiling coefficient, W/m2°C

k 1 :

thermal conductivity of condensate atT f , W/m°C

L :

length of tubes in the element, m

l :

distance of the fluid stream traverses in the element, m

LMTD :

log mean temperature difference, °C

N 1,N 2 :

shape functions

N t :

number of tubes effective for condensation

P :

pressure drop, N/cm2

P shell :

shell side vapour pressure drop, N/cm2

P tube :

tube side stream pressure drop, N/cm2

q :

heat flux in the element, W/m2

S :

specific gravity of vapour

T c :

tube side stream temperature, °C

T c2 :

tube side stream exit temperature, °C

T f :

(T w +T s )/2

T s :

saturation temperature, °C

T w :

mean wall temperature in an element, °C

T 1,T 2 :

temperatures at nodes 1 and 2, °C

U :

overall heat transfer coefficient, W/m2°C

W 1 :

tube side fluid thermal capacity rate, W/°C

W 2 :

vapour mass flow rate, kg/hr

W :

mass of vapour condensed in any element, kg/sec

μ f :

viscosity of condensate atT f , N sec/m2

σ f :

density of condensate atT f , kg/m3

References

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Authors and Affiliations

  1. Dept. of Mechanical Engineering, I.I.T, 600 036, Madras, India

    C. M. D. Moorthy, S. G. Ravikumaur & K. N. Seetharamu

Authors
  1. C. M. D. Moorthy
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  2. S. G. Ravikumaur
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  3. K. N. Seetharamu
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Moorthy, C.M.D., Ravikumaur, S.G. & Seetharamu, K.N. FEM application in phase change exchangers. Wärme - Und Stoffübertragung 26, 137–140 (1991). https://doi.org/10.1007/BF01590112

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  • DOI: https://doi.org/10.1007/BF01590112

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