Local Condensation Curve from Dropwise to Glacial Region on Large Vertical Surface
Abstract
The existence of several regimes of condensation heat transfer is well known. Regimes are given academic names as dropwise, transition, film and glacial condensation along the condensation curve showing the relationship between heat flux and surface subcooling. In case of comparatively large vertical surface, the lower part on the gravitational direction is affected by condensate from the upper part, and will be covered by water stream like a rivulet. It has no longer an existence as dropwise condition, and it is absolutely impossible that heat transfer problems under constant temperature or constant heat flux take place. The reason is why as follows, heat transfer of film condensation is some orders of magnitude less than dropwise condensation, and various regimes exist together simultaneously. In the present paper we shall try to observe the coexisting appearance of regimes in steam condensation at atmospheric pressure and make researches in the local condensation curve from top to bottom on the same surface, that is divided into eight parts in the rear side. The main results are shown as follows
(1) Enhancement of heat transfer by wiping of drops appears toward somewhat lower position from top. (2) Frazil ice is observed in the supercooled liquid film flowing down on glacial condensation. (3) The regime of glacial condensation describes a thermal hysteresis loop.- Publication:
-
Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers
- Pub Date:
- 2011
- Bibcode:
- 2011TRACE..11..383H
- Keywords:
-
- Steam;
- Atmospheric pressure;
- Dropwise condensation;
- Transition condensation;
- Film condensation;
- Glacial condensation;
- Frazil ice