Experimental investigation of boiling heat transfer hystersis on metal fibrous porous coverings

• Autorzy: Poniewski M. , Wójcik T.
• Języki publikacji: EN

Abstrakty

EN

Knowledge of thermal characteristics of capillary-porous structures is indispensable for designing and constructing of heat exchangers based on the concept of a heat pipe. The paper presents the results of experimental research in boiling on heating surfaces covered with copper fibrous porous layers that provide a filling for heat pipes. The results of the research pertain to the structures with randam pore size distribution. The research was carried out for pool boiling of distilled water, ethanol and freon-113 for layers with porosity of 40, 70 and 85%. A significant enhancement of heat transfer in comparison to a smooth surface was noted. The heat transfer coefficient and the maximum heat flux depend on the structural parameters of the covering.The boiling curve was determined by increasing and decreasing the heat flux, which for certain sets of structural parameters of the coverings and the physical properties of liquid induce heat transfer hysteresis. Two different types of hysteresis were observed. For For a relatively thick coberings, the hysteresis is characterized by a decrease of the heat transfer coefficient after the flux is reduced (appering after the maximum flux is reached). The second type of hysteresis is characterized by an increase of the heat transfer coefficient when the flux is lowered to below its maximum value. The physical basis of the phenomenon of hysteresis was presented in consideraration of new factors characterizing the mechanism of boiling on a porous covering (intralayer crisis, gradual pore activation, delayed activation of cells within the structure). For the zones of the boiling curve without hysteresis, the experimental results were developed in a form of a correlation for the Nusselt number.

Słowa kluczowe

EN

heat transfer; hystersis; porous coverings

• Wydawca: Wydawnictwo Instytutu Maszyn Przepływowych PAN ; Komitet Termodynamiki i Spalania PAN
• Czasopismo: Archives of Thermodynamics
• Rocznik: 1999
• Tom: Vol. 20, no 1/2
• Strony: 93--118
• Opis fizyczny: Rys., wykr., tab.,Bibliogr. 11 poz.,

Twórcy

autor

Poniewski M.

autor

Wójcik T.

• Inżynier, mechanika stosowana, termodynamika