Date on Master's Thesis/Doctoral Dissertation


Document Type

Master's Thesis

Degree Name



Mechanical Engineering

Degree Program

Mechanical Engineering, MS

Committee Chair

Brehob, Ellen

Committee Co-Chair (if applicable)

Park, Sam

Committee Member

Kelecy, Andrea

Committee Member

Bae, Kihwan

Author's Keywords

pressure drop; low flow; U-bend; evaporation; refrigerator; orientation


This study was conducted to evaluate three currently popular two-phase pressure drop models for extremely low velocity refrigerant flow through smooth circular evaporators in household refrigeration systems. Experimental data was taken at mass fluxes under 70 kg/m2s for two refrigerants, R134A and R600A, internal diameters of aluminum evaporators ranging from 0.186 to 0.317 inches, U-bend internal radii ranging from 0.342 to 0.750 inches in horizontal and vertical orientations of evaporators. The geometry of the samples closely resembled a commonly used serpentine shape with multiple U-bends experiencing both, up- and down-flow of the refrigerant. Two empirical models, Müller-Steinhagen & Heck (1986) and Grönnerud (1979), as well as one phenomenological model, Silva Lima & Thome (2012), were compared to experimental data and all performed very well for horizontally oriented samples. However, in vertical orientation only 60.6 %, 63.3 % and 75.8 % data fell within ± 30 % accuracy band for Grönnerud, Silva Lima & Thome and Müller-Steinhagen & Heck correlations, respectively. The predicted values showed what steps could be taken to improve the performance of all models, which could be accomplished with future work.