Experimental investigation of heat transfer of R134a in pool boiling on stainless steel and aluminum tubes

Original
  • 17 Downloads

Abstract

Due to high energy demand required for chemical processes, refrigeration and process industries the increase of efficiency and performance of thermal systems especially evaporators is indispensable. One of the possibilities to meet this purpose are investigations in enhancement of the heat transfer in nucleate boiling where high heat fluxes at low superheat are transferred. In the present work, the heat transfer in pool boiling is investigated with pure R134a over wide ranges of reduced pressures and heat fluxes. The heating materials of the test tubes are aluminum and stainless steel. The influence of the thermal conductivity on the heat transfer coefficients is analysed by the surface roughness of sandblasted surfaces. The heat transfer coefficient increases with increasing thermal conductivity, surface roughness and reduced pressures. The experimental results show a small degradation of the heat transfer coefficients between the two heating materials aluminum and stainless steel. In correlation with the VDI Heat Atlas, the experimental results are matching well with the predictions but do not accurately consider the stainless steel material reference properties.

Keywords

Nucleate boiling Thermal conductivity Heat flux Evaporators 

Nomenclature

A

Surface [m2]

b

Effusivity [Ws0.5/m2K]

c

Heat capacity [J/kgK]

d

Diameter [m]

FWM

Influence of the properties of the wall material

FWM, VDI

Influence of the properties of the wall material by VDI Heat-Atlas

Gr

Grashof number

L

Tube length [m]

Lh

Heated tube length [m]

n

Slope of regression lines

Nu

Nusselt number

Pr

Prandtl number

Pa

Mean roughness [μm]

Pa, 0

Reference mean roughness [μm]

p*

Reduced pressure

pc

Critical pressure

\( \dot{\mathrm{q}} \)

Heat flux [W/m2]

\( \dot{\mathrm{Q}} \)

Heat flow [W]

Greek symbols

α

Heat transfer coefficient [W/m2K]

\( {\upalpha}_{{\mathrm{P}}_{\mathrm{a},0}} \)

Heat transfer coefficient for the reference mean roughness [W/m2K]

∆α/α

Overall uncertainty [%]

∆T

Temperature difference [K]

Tm

Average temperature difference [K]

ρ

Density [kg/m3]

φ

Circumferential angle [°]

λ

Thermal conductivity [W/mK]

ϑS

Saturation temperature [°C]

ϑc

Critical temperature [°C]

ϑW

Wall temperature [°C]

Notes

References

  1. 1.
    Kaupmann P, Gorenflo D, Luke A (2001) Pool boiling heat transfer on horizontal steel tubes with different diameters. Multiph Sci Technol 12(2):14–26Google Scholar
  2. 2.
    Luke A, Kruck O (2008) Heat transfer measurement of R134a and propane boiling at evaporator tubes with plain and enhanced finned surfaces. Proc 12th Int Refrig and A.C. Conf, PurdueGoogle Scholar
  3. 3.
    Mertz R, Groll M (1997) Pool boiling with propane from enhanced tubes. 4th World Conference on Experimental Heat Transfer. Fluid Mechanics and Thermodynamics, BrusselsGoogle Scholar
  4. 4.
    Barthau G, Hahne E (2004) Experimental study of nucleate pool boiling of R134a on a stainless steel tube. Int J Heat Fluid Flow 25(2):305–312CrossRefGoogle Scholar
  5. 5.
    Stelute E, Saiz Jabardo JM, da Silva EF (2006) Roughness effects over nucleate boiling heat transfer of refrigerant R134a on cylindrical surfaces. Proceedings of the 13th International Heat Transfer Conference, Sydney, AustraliaGoogle Scholar
  6. 6.
    Müller BCF, Skusa S, Luke A (2013) Microstructure analysis and heat transfer measurements on a drawn steel tube. Proc. 13th UK Heat Transfer Conference, UKHTC2013, Imperial College LondonGoogle Scholar
  7. 7.
    Siebert M (1987) Untersuchung zum Einfluss des Wandmaterials und des Rohrdurchmessers auf den Wärmeübergang von horizontalen Rohren an siedende Flüssigkeiten. PhD-Thesis, KarlsruheGoogle Scholar
  8. 8.
    Braun R (1992) Wärmeübergang beim Blasensieden an der Außenseite von geschmirgelten und sandgestrahlten Rohren aus Kupfer, Messing und Edelstahl. PhD-Thesis, KarlsruheGoogle Scholar
  9. 9.
    Gorenflo D (2006) Behältersieden. VDI-Wärmeatlas, 10. überarbeitete Auflage, chapt. Hab, Springer-VerlagGoogle Scholar
  10. 10.
    Gorenflo D, Goetz J (1982) Proposal of a standard apparatus for the measurement of pool boiling heat transfer. Heat Mass Transf 16(2):69–78Google Scholar
  11. 11.
    Luke A, Bujok P (2013) Influence of fin geometry on heat transfer in boiling pure refrigerants and their mixtures. Proc. 4th IIR Conf. on Thermophysical Properties and Transfer Processes of Refrigerants, DelftGoogle Scholar
  12. 12.
    Luke A (2004) Active and Potential Bubble Nucleation Sites on Different Structured Heated Surfaces. Chem Eng Res Des 82:462–470CrossRefGoogle Scholar
  13. 13.
    Kotthoff S, Gorenflo D (2009) Heat transfer and bubble formation on horizontal copper tubes with different diameters and roughness structures. Heat Mass Transf 45:893–908CrossRefGoogle Scholar
  14. 14.
    Müller BCF, Luke A (2013) Zum Einfluss von Oberflächenstrukturen auf den Wärmeübergang beim Sieden. DKV-Tagungsbericht 40Google Scholar
  15. 15.
    Baehr HD (1995) Thermodynamische Eigenschaften umweltverträglicher Kältemittel, Zustandsgleichungen und Tafeln für Ammoniak, R22, R134a, R152a und R123. Springer-Verlag, BerlinGoogle Scholar
  16. 16.
    Kruck O (2009) Blasensieden von Propan und R134a an glatten und strukturierten Stahlrohren. PhD-Thesis, HannoverGoogle Scholar
  17. 17.
    Magrini U, Nannei E (1975) On the Influence of the Thickness and Thermal Properties of Heating Walls on the Heat Transfer Coefficients in Nucleate Pool Boiling. J Heat Transf 97:173–178CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Institute of Technical ThermodynamicsUniversity of KasselKasselGermany

Personalised recommendations