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Predict the temperature distribution in gas-to-gas heat pipe heat exchanger

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Abstract

A theoretical model has been developed to investigate the thermal performance of a continuous finned circular tubing of an air-to-air thermosyphon-based heat pipe heat exchanger. The model has been used to determine the heat transfer capacity, which expresses the thermal performance of heat pipe heat exchanger. The model predicts the temperature distribution in the flow direction for both evaporator and condenser sections and also the saturation temperature of the heat pipes. The approach used for the present study considers row-by-row heat-transfer in evaporator and condenser sections of the heat pipe heat exchanger.

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Abbreviations

A :

Heat-transfer area [m2]

C c :

Flow-stream capacity rate of cold-side fluid [dimensionless]

C e :

Flow-stream rapacity rate of hot-side fired [dimensionless]

C L :

Heat pipe working fluid capacity rate [W/K]

C p :

Specific heat at constant pressure [J kg−1 K−1]

Csf :

Constant

D :

Tube diameter [m]

G :

Exchanger flow-stream mass velocity [kg m−2 s−1]

g :

Acceleration due to gravity [m s−2]

g c :

Proportionality factor m Newton’s second law [kgm/Ns2] heat-transfer

h :

Heat-transfer coefficient [Wm−2 K−1]

h ci :

Internal condenser heat-transfer coefficient [Wm−2 K−1]

h fg :

Latent heat of vaporization [J kg−1]

k :

Thermal conductivity [Wm−1 K−1]

k l :

Liquid thermal conductivity [Wm−1 K−1]

k m :

Wick thermal conductivity [Wm−1 K−1]

l :

Length [m]

l f :

Fin length [m]

m :

Mass flow rate [kg s−1]

N f :

Number of fins per meter [dimensionless]

n :

Number of row in direction of flow [dimensionless]

N :

TU number of heat-transfer units of an exchanger (UA/Cmin) [dimensionless]

Nu :

Nusselt number [dimensionless]

Pr :

Prandtl number \( \mu C_{p} /k \) [dimensionless]

Q :

Heat in [W]

R :

Thermal resistance [m2 KW−1]

Re :

Reynolds number [dimensionless]

St :

Stanton number (h/GCp) [dimensionless]

T :

Temperature [K or °C]

T s :

Temperature [K or °C]

t :

Thickness [m]

U :

Overall heat-transfer coefficient [W m−2 K−1]

β:

Defined as \( ( {1 + k_{m} /k_{l} } )/( {1 - k_{m} /k_{l} } ) \)

\( \varepsilon \) :

In Eq. 12 is defined as fractional void of the wick [dimensionless]

\( \varepsilon \) :

Exchanger effectiveness

\( \varepsilon_{e} \) :

Single row effectiveness m the evaporator sections [dimensionless]

\( \varepsilon_{c} \) :

Single row effectiveness m the condenser sections [dimensionless]

\( \varepsilon_{o} \) :

Overall effectiveness [dimensionless]

\( \eta_{o} \) :

Total surface temperature effectiveness [dimensionless]

\( \eta_{f} \) :

Fin temperature effectiveness [dimensionless]

\( \mu \) :

Viscosity coefficient [N s m−2]

\( \rho \) :

Density [kg m−3]

\( \sigma \) :

Surface tension [N m−l]

c :

Condenser

e :

Evaporator

f :

Fin

i :

Inside

l :

Liquid

o :

Outside, overall

v :

Vapor

w :

Wick

s :

Saturated temperature [deg. C]

References

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Authors and Affiliations

  1. Iranian Research Organization for Science and Technology, Department of Advanced Materials and Renewable Energy, Tehran, Iran

    E. Azad

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  1. E. Azad
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Correspondence to E. Azad.

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Azad, E. Predict the temperature distribution in gas-to-gas heat pipe heat exchanger. Heat Mass Transfer 48, 1177–1181 (2012). https://doi.org/10.1007/s00231-011-0960-z

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  • DOI: https://doi.org/10.1007/s00231-011-0960-z

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