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Abstract
Fin-and-tube heat exchangers are often used as evaporators in HVAC&R systems. To increase the compactness, the tubes of these heat exchangers are folded up in a sequence of hairpin tubes. These hairpins consist of two straight tubes interconnected by a sharp U-bend. The working fluid will pass through one or multiple hairpin tubes while evaporating. The geometry of the bends and how the sequence of bends is built up influences the two-phase flow behaviour. In this work the evolution of the two-phase flow behaviour downstream of a sharp return bend is studied. This is done by measuring the capacitance of the flow on several locations downstream of the return bend. Due to the difference in dielectric constant between the phases, the measured capacitance will vary depending on the amount of each phase present between the electrodes. Previous work has already shown that the flow behaviour can be characterized based on the capacitance signal of the flow. The refrigerant used in this study is R134a, the mass flux was varied between 150 and 450 kg/m²s and the vapour quality varied between 0 and 1. It was observed that downstream of the return bend a significant effect on the flow regime was induced up to 10 tube diameters downstream of the bend.

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MLA
De Kerpel, Kathleen, Caro De Groof, Menno Dreesen, et al. “Two-phase Flow Behaviour in a Smooth Hairpin.” Eurotherm Seminar N°96 on Convective Heat Transfer Enhancement, Proceedings. Ed. JM Buchlin, W Bosschaerts, & S Harmand. Brussels, Belgium: von Karman Institute for Fluid Dynamics, 2013. Print.
APA
De Kerpel, K., De Groof, C., Dreesen, M., De Schampheleire, S., & De Paepe, M. (2013). Two-phase flow behaviour in a smooth hairpin. In J. Buchlin, W. Bosschaerts, & S. Harmand (Eds.), Eurotherm Seminar n°96 on Convective Heat Transfer Enhancement, Proceedings. Presented at the Eurotherm Seminar n°96 on Convective Heat Transfer Enhancement, Brussels, Belgium: von Karman Institute for Fluid Dynamics.
Chicago author-date
De Kerpel, Kathleen, Caro De Groof, Menno Dreesen, Sven De Schampheleire, and Michel De Paepe. 2013. “Two-phase Flow Behaviour in a Smooth Hairpin.” In Eurotherm Seminar N°96 on Convective Heat Transfer Enhancement, Proceedings, ed. JM Buchlin, W Bosschaerts, and S Harmand. Brussels, Belgium: von Karman Institute for Fluid Dynamics.
Chicago author-date (all authors)
De Kerpel, Kathleen, Caro De Groof, Menno Dreesen, Sven De Schampheleire, and Michel De Paepe. 2013. “Two-phase Flow Behaviour in a Smooth Hairpin.” In Eurotherm Seminar N°96 on Convective Heat Transfer Enhancement, Proceedings, ed. JM Buchlin, W Bosschaerts, and S Harmand. Brussels, Belgium: von Karman Institute for Fluid Dynamics.
Vancouver
1.
De Kerpel K, De Groof C, Dreesen M, De Schampheleire S, De Paepe M. Two-phase flow behaviour in a smooth hairpin. In: Buchlin J, Bosschaerts W, Harmand S, editors. Eurotherm Seminar n°96 on Convective Heat Transfer Enhancement, Proceedings. Brussels, Belgium: von Karman Institute for Fluid Dynamics; 2013.
IEEE
[1]
K. De Kerpel, C. De Groof, M. Dreesen, S. De Schampheleire, and M. De Paepe, “Two-phase flow behaviour in a smooth hairpin,” in Eurotherm Seminar n°96 on Convective Heat Transfer Enhancement, Proceedings, Brussels, Belgium, 2013.
@inproceedings{4143662,
  abstract     = {Fin-and-tube heat exchangers are often used as evaporators in HVAC&R systems. To increase the compactness, the tubes of these heat exchangers are folded up in a sequence of hairpin tubes. These hairpins consist of two straight tubes interconnected by a sharp U-bend. The working fluid will pass through one or multiple hairpin tubes while evaporating. The geometry of the bends and how the sequence of bends is built up influences the two-phase flow behaviour. In this work the evolution of the two-phase flow behaviour downstream of a sharp return bend is studied. This is done by measuring the capacitance of the flow on several locations downstream of the return bend. Due to the difference in dielectric constant between the phases, the measured capacitance will vary depending on the amount of each phase present between the electrodes. Previous work has already shown that the flow behaviour can be characterized based on the capacitance signal of the flow. The refrigerant used in this study is R134a, the mass flux was varied between 150 and 450 kg/m²s and the vapour quality varied between 0 and 1. It was observed that downstream of the return bend a significant effect on the flow regime was induced up to 10 tube diameters downstream of the bend.},
  articleno    = {7},
  author       = {De Kerpel, Kathleen and De Groof, Caro and Dreesen, Menno and De Schampheleire, Sven and De Paepe, Michel},
  booktitle    = {Eurotherm Seminar n°96 on Convective Heat Transfer Enhancement, Proceedings},
  editor       = {Buchlin, JM and Bosschaerts, W and Harmand, S},
  isbn         = {9782875160591},
  language     = {eng},
  location     = {Brussels, Belgium},
  pages        = {6},
  publisher    = {von Karman Institute for Fluid Dynamics},
  title        = {Two-phase flow behaviour in a smooth hairpin},
  year         = {2013},
}