An experimental investigation of inverted annular film boiling heat transfer has been performed for vertical up-flow in a round tube. The working fluid was R-134a and the flow conditions covered a pressure range of 640 to 2390 kPa (water equivalent range: 4000 to 14000 kPa) and a mass flux range of 500 to 4000 kgm-2s-1 (water equivalent range: 700 to 5700 kgm-2s-1 ). The inlet qualities of the tests ranged from -0.75 to -0.03. The hot-patch technique is used to obtain the subcooled film boiling measurements.
The parametric trends of the heat transfer coefficient with respect to mass flux, inlet quality, heat flux and pressure are examined and compared to reported parametric trends from the literature. The comparison shows agreement between observed effects of flow parameters with those reported by other researchers. The heat transfer vs. quality curve is divided into four different regions. It is shown that these regions are dependent on pressure, mass flux and local quality.
A two-fluid one-dimensional model has been developed to predict the wall temperature of an internally-heated tube during IAFB. The model is derived using basic conservation equations of mass, momentum and energy. To simplify the derivation of the constitutive heat transfer relations, flow between two parallel plates is assumed. The model features shear stress and interfacial relations that make it accurately predicts the parametric effects and heat transfer characteristics of IAFB over a wide range of flow conditions. The model predicts wall temperatures of R-134a-cooled tubes with an average error of -1.21% and an RMS error of 6.37%. This corresponds to average and RMS errors in predicted heat transfer coefficients of 1.33% and 10.07%, respectively. Using water data, the model predicts wall temperatures with an average error of -1.76% and an RMS error of 7.78% which corresponds to average and RMS errors in predicted heat transfer coefficients of 4.16% and 15.06%, respectively.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/29641 |
| Date | January 2007 |
| Creators | El Nakla, Meamer A |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 243 p. |
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