Publikacje

Abstract:

The investigations aimed at experimentally examining the nucleate boiling incipience and development in minichannels. These phenomena are connected with local changes in the two-phase flow. The investigations were conducted while increasing and decreasing the heat flux delivered to an asymmetrically heated minichannel. The refrigerants R-11, R-123 and FC-72 were used. The liquid crystal thermography was employed to identify the two-dimensional heating foil temperature. The image acquisition system, including a fast digital camera, was used to identify flow structures and void fraction. The outcome of the analysis of experimental data was presented in the form of boiling curves and local heat transfer coefficient dependency on the distance from the minichannel. The content of the liquid and vapor phases, depending on local heat fluxes and the heating surface temperature, was also examined. The impact of selected thermal and flow parameters such as heat flux, inlet pressure, flow velocity, hydraulic diameter, local void fraction and vapor quality on the local boiling heat transfer coefficients and boiling incipience was identified and discussed. Finally, dimensionless correlations were developed to compute heat transfer coefficient for developed nucleate boiling and boiling incipience in a minichannel.

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Flow boiling in minichannels