QCT Condensation

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QCT How it Works: Condensation

The water in the bottom of the test chamber is heated to generate hot vapor.
The vapor mixes with air and fills the chamber, creating 100% relative humidity.
Because the test panels are the actual roof of the test chamber, the panels are cooled down by the room air on the outer sides.
The resulting temperature difference causes the vapor to condense on the underside of the panels. This condensate is distilled water, which is saturated with dissolved oxygen. A small amount of water vapor escapes through vapor diffusion channels on each side of the QCT unit. Air continually replaces the escaping water vapor, standardizing the proportions of the air mixture.

Condensation occurs first as microscopic droplets. They coalesce into larger and larger drops until they finally run off. Under constant conditions, this droplet cycle will repeat, providing an excess of condensate to the test surface. Constant condensation develops strong osmotic pressure across a coating, tending to pull pressure into the coating. Drying off the test specimen relieves this pressure. One hour of drying will remove most of the water from a 23-hour condensation cycle. These dry-off periods are representative of many service conditions. Transition back and forth from wet to dry is much more important than the length of dry-off time. When a material is dry, very little deterioration occurs. A drying time of one to two hours is usually enough for cyclic operation.

QUV Weathering	Florida Weathering	Q-Trac Sunlight Concentrator	Q-Panel Substrates
Q-Sun Light Stability	Arizona Weathering	Q-Rack Exposure Systems	Q-Fog Corrosion
Radiometer Calibrations	Accelerated Lab	Weathering ROI	QCT Condensation

QCT Snap Shot

The QCT tester accelerates outdoor moisture attack, because it supplies controlled amounts of “aggressive water” to the test surface under temperature-controlled, cyclic or constant conditions.

QCT Overview

QCT How it Works