Results 1 - 2 of 2
Results 1 - 2 of 2. Search took: 0.014 seconds
|Sort by: date | relevance|
[en] Highlights: • Measurements of local evaporation heat transfer and pressure drop. • Experiments are conducted respecting the geothermal facilities application. • The new correlation are proposed for local evaporation heat transfer. • Two-phase flow structures for tested refrigerant mass fluxes are investigated. • The proposed correlation well predicts the experimental data of local pressure drop. - Abstract: Improving the energy efficiency of thermal machines is a key point which ensures a strong advancement in solving problems related to energy consumption and environmental protection. Our study concerns an energy characterization and optimization of geothermal heat pumps heat exchangers for industrial and residential applications. As part of this study, experimental analysis of the boiling of the R134a is carried out in a smooth horizontal tube external diameter 7.94 mm and 1 m of length. The refrigerant Reynolds number ranges from 4200 to 9820. This paper presents a detailed description of the experimental device, instrumentation of the test section and analysis of results. The influence of refrigerant inlet Reynolds number on the dry-out phenomenon is determined, and flow map is presented. Based on the experimental data, correlations are proposed to predict the heat transfer coefficient and frictional pressure drop.
[en] This paper presents an analytical model for a thermosyphon loop developed for cooling air inside a telecommunication cabinet. The proposed model is based on the combination of thermal and hydraulic management of two-phase flow in the loop. Experimental tests on a closed thermosyphon loop are conducted with different working fluids that could be used for electronic cooling. Correlations for condensation and evaporation heat transfer in the thermosyphon loop are proposed. They are used in the model to calculate condenser and evaporator thermal resistances in order to predict the cabinet operating temperature, the loop's mass flow rate and pressure drops. Furthermore, various figures of merit proposed in the previous works are evaluated in order to be used for selection of the best loop's working fluid. The comparative studies show that the present model well predicts the experimental data. The mean deviation between the predictions of the theoretical model with the measurements for operating temperature is about 6%. Besides, the model is used to define an optimal liquid and vapor lines diameters and the effect of the ambient temperature on the fluid's mass flow rate and pressure drop. - Highlights: • Modeling of thermosyphon loop for cooling telecommunication cabinet. • The cooling system operates with zero electrical consumption. • The new correlations are proposed for condensation and evaporation heat transfer. • FOM equation is defined for selecting the best working fluid. • The proposed model well predicts the experimental data and operating temperature