Heat transfer coefficient (HTC) was experimentally measured for saturated and subcooled pool boiling of binary mixtures of water and glycerin. Saturated boiling was studied for mixtures with water ...mass fractions
from
to
on horizontal flat nickel-plated surfaces at heat fluxes from 50 to
at atmospheric pressure. Subcooled boiling was investigated in the range of subcooling from 0 to
at heat fluxes of approximately 250, 450 and
. It was found that mixture effects have a significant impact on saturated boiling HTC even for mixtures with very low content of glycerin as significant drops of HTC were observed for subtle changes in composition for mixtures of high
. Measured HTC was successfully correlated with the combination of Yagov (1999) and Inoue and Monde (2009) correlations with a mean relative error of
. A simple empirical HTC correlation is also proposed. For subcooled boiling, developed subcooled boiling regime was reached for all investigated heat fluxes. For this regime, correlations, which were able to predict HTC for saturated boiling, were employed to predict subcooled boiling HTCs for all investigated concentrations, heat fluxes and subcoolings. Effect of subcooling and effect of liquid composition on total HTC were of the same importance for mixtures with higher water content. With the increase in concentration of glycerin in the mixture, decrease in total HTC with increasing subcooling became more significant.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The effect of rinsing immediately after plating on the surface oxidation and solder wettability of bright nickel-plated surfaces has been studied. Nickel plating was carried out in a Watts bath with ...brightener by an electroplating technique, and the nickel-plated specimens were immediately dipped and rinsed in deionized water. The dissolved oxygen content in the deionized water was controlled by several methods such as aeration, exposure to open air and deaeration with nitrogen. Water temperature was varied from 5 to 100°C. The oxide films on the rinsed surfaces were examined by ellipsometry (ELL), X-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction (RHEED). The thickest oxide film was observed near 80°C with rinsing within 5 minutes. The amount of dissolved oxygen did not significantly affect oxide film thickness below 80°C. The surface oxide film was composed mainly of Ni2O3, its structure being controlled by water temperature. Oxide structure changed from amorphous to crystalline at about 40°C. Both the thickness and structure of the oxide films were found to be important factors for controlling the solder wettability of bright nickel-plated surfaces, and amorphous structure played a particularly decisive role in improving solder wettability. Rinsing in water containing ethyl alcohol dramatically improved solder wettability.
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