ISSN Online: 2377-424X
ISBN Print: 0-89116-299-2
International Heat Transfer Conference 7
MINIMUM FLOW-RATES AND REWETTING-RATES OF FALLING FILMS
摘要
In order to precalculate the minimum flow-rates
of isothermally falling films Hartley/Murgatroyd
and Hobler in 1964 proposed two models
known as the force criterion and the energy criterion.
The results indicate an extremely strong
influence of the contact angle. Own measurements
especially directed to the water contact angle
on industrial surfaces and a thermodynamic analysis
of the wetting behaviour of heterogeneous
surfaces reveal that the contact angle hysteresis
on these surfaces can be very large.
This means that to predict minimum flow-rates and rewetting-rates for falling films it has to be distinguished between the advancing and the receding contact angle. The receding contact angle has to be considered if a minimum flow-rate to prevent film rupture is to be calculated. The flow-rate however that rewets a dry surface is determined by the advancing contact angle.
This means that to predict minimum flow-rates and rewetting-rates for falling films it has to be distinguished between the advancing and the receding contact angle. The receding contact angle has to be considered if a minimum flow-rate to prevent film rupture is to be calculated. The flow-rate however that rewets a dry surface is determined by the advancing contact angle.