1. Pressure drop prediction models o Garimella et al. (2005) o Considered parameters o Single-phase pressure gradients o Martinelli parameter o Surface tension parameter o Fluid and geometric properties Heat and Mass Transfer Laboratory 1

2. Pressure drop prediction models o Garimella et al. (2005) Heat and Mass Transfer Laboratory 2 Void fraction is calculated using the Baroczy (1965) correlation: Liquid and vapor Re values are given by:

3. Pressure drop prediction models o Garimella et al. (2005) Heat and Mass Transfer Laboratory 3 Liquid and vapor friction factors: Therefore, the single-phase pressure gradients are given and the Martinelli parameter is calculated:

4. Pressure drop prediction models o Garimella et al. (2005) Heat and Mass Transfer Laboratory 4 Liquid superficial velocity is given by: This velocity is used to evaluate the surface tension parameter:

5. Pressure drop prediction models o Garimella et al. (2005) Heat and Mass Transfer Laboratory 5 Interfacial friction factor: Laminar region: Turbulent region (Blasius):

6. Pressure drop prediction models o Garimella et al. (2005) Heat and Mass Transfer Laboratory 6 The pressure gradient is determined as follows:

7. Heat transfer prediction models o Bandhauer et al. (2005) o Considered parameters o Pressure drop o Dimensionless film thickness o Turbulent dimensionless temperature o Pr o Fluid and geometric properties o Range / applicability o 0.4 < D < 4.9 mm o R134a o 150 < G < 750 kg/m 2 s Heat and Mass Transfer Laboratory 7

8. Heat transfer prediction models o Bandhauer et al. (2005) Heat and Mass Transfer Laboratory 8 Interfacial shear stress: Friction velocity is now calculated:

9. Heat transfer prediction models o Bandhauer et al. (2005) Heat and Mass Transfer Laboratory 9 Film thickness is directly calculated from void fraction: This thickness is used to obtain the dimensionless film thickness:

10. Heat transfer prediction models o Bandhauer et al. (2005) Heat and Mass Transfer Laboratory 10 Turbulent dimensionless temperature is given by: Therefore, the heat transfer coefficient is: