Abstract
Flow boiling heat transfer characteristics of water and hydrocarbons in mini and microchannels are experimentally studied. Two different test section geometries are employed; a circular channel with a hydraulic diameter of 1,500 μm, and rectangular channels with height values of 300–700 μm and a width of 10 mm. In both facilities, the fluid flows upwards and the test sections, made of the nickel alloy Inconel 600, are directly electrically heated. Thus, evaporation takes place under the defined boundary condition of constant heat flux. Mass fluxes between 25 kg/m2 s and 350 kg/m2 s and heat fluxes from 20 kW/m2 to 350 kW/m2 at an inlet pressure of 0.3 MPa are examined. Infrared (IR) thermography is applied to scan the outer wall temperatures. These allow the identification of different boiling regions, boiling mechanisms, and the determination of the local heat transfer coefficients (HTC). Measurements are carried out in initial, saturated, and post-dryout boiling regions. The experimental results in the region of saturated boiling are compared with currently available correlations and with a physically founded model developed for convective boiling.
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Abbreviations
- A :
-
Projected area of the smooth phase boundary, m2
- A W :
-
Real area of the wavy phase boundary, m2
- b :
-
Laplace constant, \( b = {\sqrt {\sigma \mathord{\left/ {\vphantom {\sigma {{\left( {g{\left( {{\rho }\ifmmode{'}\else$'$\fi - {\rho }\ifmmode{''}\else$''$\fi} \right)}} \right)}}}} \right. \kern-\nulldelimiterspace} {{\left( {g{\left( {{\rho }\ifmmode{'}\else$'$\fi - {\rho }\ifmmode{''}\else$''$\fi} \right)}} \right)}}} }, \) m
- Bo :
-
Boiling number, \( Bo = {\ifmmode\expandafter\dot\else\expandafter\.\fi{q}} \mathord{\left/ {\vphantom {{\ifmmode\expandafter\dot\else\expandafter\.\fi{q}} {{\left( {\ifmmode\expandafter\dot\else\expandafter\.\fi{m} \cdot \Delta h_{v} } \right)}}}} \right. \kern-\nulldelimiterspace} {{\left( {\ifmmode\expandafter\dot\else\expandafter\.\fi{m} \cdot \Delta h_{v} } \right)}}, \) –
- C :
-
Parameter, Eq. 7
- Co :
-
Convection number, \( Co = {\left( {{\rho _{G} } \mathord{\left/ {\vphantom {{\rho _{G} } {\rho _{{\text{l}}} }}} \right. \kern-\nulldelimiterspace} {\rho _{{\text{l}}} }} \right)}^{{0.5}} {\left( {{{\left( {1 - \ifmmode\expandafter\dot\else\expandafter\.\fi{x}} \right)}} \mathord{\left/ {\vphantom {{{\left( {1 - \ifmmode\expandafter\dot\else\expandafter\.\fi{x}} \right)}} {\ifmmode\expandafter\dot\else\expandafter\.\fi{x}}}} \right. \kern-\nulldelimiterspace} {\ifmmode\expandafter\dot\else\expandafter\.\fi{x}}} \right)}^{{0.8}} , \) –
- D :
-
Diameter, m
- F fl :
-
Fluid–surface parameter recommended by Kandlikar and Balasubramanian (2003)
- g :
-
Acceleration due to gravity, m/s2
- H :
-
Height, m
- Δh v :
-
Latent heat of vaporization, J/kg
- L :
-
Length, m
- l ch :
-
Hydraulic diameter, m
- \( \ifmmode\expandafter\dot\else\expandafter\.\fi{m} \) :
-
Mass flux, kg/(m2 s)
- N b :
-
Boiling number, \( N_{b} = {\ifmmode\expandafter\dot\else\expandafter\.\fi{q}} \mathord{\left/ {\vphantom {{\ifmmode\expandafter\dot\else\expandafter\.\fi{q}} {\ifmmode\expandafter\dot\else\expandafter\.\fi{m}\Delta h_{{\text{v}}} }}} \right. \kern-\nulldelimiterspace} {\ifmmode\expandafter\dot\else\expandafter\.\fi{m}\Delta h_{{\text{v}}} }, \), –
- p :
-
Pressure, Pa
- \( \ifmmode\expandafter\dot\else\expandafter\.\fi{q} \) :
-
Heat flux, W/m2
- r :
-
Radial coordinate, m
- R :
-
R
adius, m
- T :
-
Temperature, K
- s :
-
Thickness of the channel wall, m
- W :
-
Width, m
- \( \ifmmode\expandafter\dot\else\expandafter\.\fi{x} \) :
-
Vapor quality, –
- \( \ifmmode\expandafter\tilde\else\expandafter\~\fi{x}_{1} \) :
-
Mole fraction of the more volatile component, –
- z :
-
Axial coordinate, m
- α :
-
Heat transfer coefficient, W/(m2 K)
- δ :
-
Film thickness, m
- ɛ :
-
Emissivity, –
- η :
-
Dynamic viscosity, Ns/m2
- λ :
-
Heat conductivity, W/(mK)
- ρ :
-
Density, kg/m3
- σ :
-
Surface tension, N/m
- B :
-
Reference value of α
- cb:
-
Convective boiling
- dry:
-
D
ryout
- eff:
-
Effective value
- in:
-
Inner
- ini:
-
Reference length in the initial region
- l:
-
Liquid
- nb:
-
Nucleate boiling
- out:
-
Outer
- S:
-
Saturated
- v:
-
Vapor
- W:
-
Wall
References
Hapke I, Boye H, Schmidt J (2000) Onset of nucleate boiling in minichannels. Int J Therm Sci 39:505–513
Hapke I, Boye H, Schmidt J (2002) Flow boiling of water and n-heptane in micro channels. Microscale Thermophys Eng 6:99–115
Kandlikar SG (2002) Two-phase flow patterns, pressure drop, and heat transfer during boiling in minichannel flow passages of compact evaporators. Heat Transfer Eng 23:5–23
Kandlikar SG, Balasubramanian P (2003) Extending the applicability of the flow boiling correlation to low Reynolds number flows in microchannels. In: Proceedings of the 1st ASME international conference on microchannels and minichannels, Rochester, New York, April 2003
Moriyama K, Inoue A (1992) The thermohydraulic characteristics of two-phase flow in extremely narrow channels. Heat Transfer Jpn Res 21(8):838–856
Niederkrüger M (1991) Strömungssieden von reinen Stoffen und binären zeotropen Gemischen im waagerechten Rohr bei mittleren und hohen Drücken. VDI, Fortschrittbericht Nr. 245, Reihe 3
Palm B (2000) Heat transfer in microchannels. In: Proceedings of the international conference on heat transfer and transport phenomena in microscale, Banff, Canada, October 2000, pp 54–65
Steiner D, Taborek J (1992) Flow boiling heat transfer in vertical tubes correlated by an asymptotic model. Heat Transfer Eng 3(2):43–69
Sumith B, Kaminaga F, Matsumura K (2003) Saturated flow boiling of water in a vertical small diameter tube. Exp Thermal Fluid Sci 27:789–801
VDI-Waermeatlas (2002) Chapter Hbb, 9 Auflage, Springer, Berlin Heidelberg New York
Wadekar VV (2002) Compact heat exchangers for phase change. Int J Heat Exchangers 3:169–200
Watel B, Thonon B (2001) A correlation for nucleate and convective flow boiling in a compact plate-fin heat-exchanger with perforated fins. Trends Heat Mass Momentum Transfer 7:81–103
Yan YY, Lin TF (1998) Evaporation heat transfer and pressure drop of refrigerant R-134a in a small pipe. Int J Heat Mass Transfer 41:4183–4194
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Díaz, M.C., Boye, H., Hapke, I. et al. Investigation of flow boiling in narrow channels by thermographic measurement of local wall temperatures. Microfluid Nanofluid 2, 1–11 (2006). https://doi.org/10.1007/s10404-004-0030-7
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DOI: https://doi.org/10.1007/s10404-004-0030-7