How It Works
The CAIR™ System consists of two different subsystems, the Cabin Humidification system and the Zonal Drying system. The Cabin Humidification system increases the relative humidity to a pleasant and comfortable level in the passenger cabin. It can be designed to increase the humidity in parts of the cabin or the complete cabin as a specific humidifier can be installed in each cabin zone air-condition supply duct.
The Zonal Drying™ system reduces the fuselage skin condensation to a level where it is no risk of dripping water, preventing accumulation of excess water in the insulation blankets (reduction of weight), reduce the risk for electrical failure and also reduce internal corrosion. The system distributes dry air with a very low dew point close to the insulation blankets evenly over the whole length of the crown area and thereby prevents humid air to reach the cold fuselage structures.
The CAIR™ System includes the following main equipment and components:
- Zonal Dryer(s)
- Control Unit(s)
- Control Panel(s)
- Structural attachments
- Replacement ECS ducts for interface to aircraft ECS system
- Water Supply System, incl. water supply
- Water Drainage System
- Zonal Dryer Piccolo Ducting System
- Electrical System
The CTT Cabin Humidifier is based on the evaporative cooling principal. The humidifier works according to the method of evaporation from free water surface i.e. on the same principle as in nature where water evaporates from lakes and streams.
The Humidification System is designed to add humidity to the aircraft ventilation system using water from the aircraft potable water supply. This is achieved by the application of water to a pad within the Humidifier, in line with the Environmental Control System (ECS). The Cabin Humidifiers are controlled by a CAIRTM Control Unit (CCU) that can communicate via CAN bus directly with the aircraft system or with a Cabin Management System. The CCU also communicates with the Zonal Drying system for ON/OFF function Humidifier enable and failure indication.
A part of each cabin humidifier water system is automatically drained after each operation to ensure no build-up of any bacteria. The complete humidifier water system is disinfected and drained according to the aircraft manufacture procedure.
One Humidifier is integrated in the air condition supply duct to the cabin zone that shall be humidified. The Humidifier is attached to the fuselage structure via specific attachment brackets and directly connected to the aircraft air-condition ducting.
The humidifier is installed downstream of the trim air valve and upstream of the air-condition cabin temperature sensor, which ensures that the cabin temperature level is stable during the Humidification process. Each humidifier is supplied with fresh water from the potable water system. The Humidifiers are normally connected to the aircraft drain mast system and have also an overflow drain to the bilge area.
CTT Zonal Dryer
The ZD is a cylinder formed dehumidifier. The ZD is of parallel flow absorption type where the active part is a glass fibre honeycomb rotor, which is impregnated with silica gel. Other components in the ZD are a mixed flow, 11400 rpm, four pole fan designed for continuous operation, electrical heater, a geared rotor drive motor and thermistor, thermal sensor and switches for overheat protection and monitoring. The airflow from the fan at the inlet side of the unit is divided into two separate airstreams. About 80 % of the total airflow is passing directly through the rotor.
The air humidity is absorbed by the rotor silica gel, resulting in a dry (low water content) air stream, which is then leaving the ZD through the dry air outlet. The other 20 % of the airflow, the regeneration air, is routed through the electrical heater, heated to ~ 110°C, before it passes through the rotor. The warm air will absorb the humidity in the rotor and then leave the ZD through the regeneration air outlet.
The rotor is slowly driven by an electrical AC-motor over a belt drive. This ensures that the rotor is regenerated continuously by the warm airflow, keeping the rotor absorption capacity at a high level.