The Formation and Runoff of Condensate on a Vertical Glass Surface
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Date
2014
Authors
Wright, John L.
Kansal, Vivek
Collins, Michael R.
Journal Title
Journal ISSN
Volume Title
Publisher
American Society of Heating, Refrigerating and Air-Conditioning Engineers
Abstract
An experimental study of condensate formation and runoff was performed by exposing a sheet of glass, cooled at its bottom edge, to an enclosure with a controlled environment. This arrangement mimics the indoor glass surface at the bottom edge of a window when the window is exposed to a cold, outdoor environment. The air in the enclosure was maintained
at a constant dry-bulb temperature (Tdb = 22.1°C [Tdb = 71.8°F]) and constant relative humidity (RH = 30%, 35%, 40%, 45%, or 50%) during individual experiments. It
was found that the time until initial runoff, tir, decreased with increasing RH, and tir was sensitive to RH at low RH, but insen-sitive to RH at high RH. At first, condensate runoff occurred near the bottom of the glass and left one to believe that the remaining condensate was at steady state. But over a 16-hour period, it was found that the condensate runoff front, in every case, progressed upward to include the entire condensate area. The speed of the condensate runoff front increased with RH, and was less sensitive to RH at low RH. Measurement results were used to produce a summary plot showing runoff front position as a function of glass surface temperature and RH.
This chart can be used to predict tir and runoff front progression at the bottom edge of any window if the surface temperature
profile is known.
Description
© 2014 ASHRAE (www.ashrae.org). Published in ASHRAE Transactions, Volume 120, Part 1. For personal use only.
Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
Keywords
Fenestration, Condensation, Runoff