| In the two-phase closed thermosyphon, the latent heat of fluids is utilized in the evaporation and condensation processes to transfer large amounts of heat over a small temperature difference. This work concentrates on the heat transfer within a tilted thermosyphon and its use in a heat pipe evacuated tube solar collector.;Including the shear term in the constitutive equations changes the predicted film thickness in the condenser by less than 1%, depending on location along the surface. This change causes a slight increase in the predicted heat transfer. Accounting for surface waves changes the heat transfer +10% to +50% in the Reynolds number range studied. The condenser results are combined with a simple trough model for the evaporator portion of the thermosyphon to give the effective heat transfer coefficient for the entire tube. Predicted performance of the condenser, the evaporator and the entire tube compare favorably with available data.;Also presented is a method to include these results in an existing model for heat pipe evacuated tube solar collectors.;Within the thermosyphon, an example is made of the laminar film condensation process, including the effects of film surface waves and interfacial shear due to the moving vapor. |
