Humidity

Humidification is used for a variety of applications; to name a couple are:

Chemical Vapour Deposition (CVD)

Coatings such as Chemical Vapour Deposition (CVD) where a layer can be applied to surfaces.

Propagation of seeds

An interesting area of research requires the propagation of seeds and the growth of plants, the humidified atmosphere can reproduce clients around the globe allowing knowledge on the best areas to grow certain crops, it also gives valuable knowledge on greenhouse conditions for optimum yield of plant productions.

How humidified atmosphere is achieved by controlled flow rates

A gas and a liquid are accurately controlled for a specific flow rate, these are then mixed, heated and the result is a homogenous flow from the outlet. The humidified atmosphere allows for deposition on to the surface allowing very thin layers to be produced, the layers can be altered by changing compositions of the gas and liquid and over time a multi layered surface can be produced. The initial mixing can be achieved with more than one gas or one liquid with multiple Alicat Mass Flow Controllers. The reason for this is to change the surface properties or simply the appearance. Where the liquid content needs to be very small then a dilution stage can be added by adding a secondary gas stream. This can also be heated to match the heated humidification to eliminate rapid cooling of the humidified gas and thus constating out back into gas and liquid.

Trace heating can be applied where the outlet of the humidified gas is not being sent (typically to a chambre) directly to the point of use.

White paper reference for furtther reading on the Alicat website: Thin Film Deposition

Which products from our range would we suggest?

• Gases: The Alicat MC controller and MCS controller can be incorporated to provide accurate flow control of the gas, the 10,000 turn down can help in minimising the number of additional MFC’s needed when used at various flow rates. The MC and MCS Series also have built in Gas selection where up to 130 gases are pre-loaded in the MCS on board memory.
• Liquids: The Liquid can be accurately delivered to the stream with the Alicat CODA Controller, the CODA is the premium Coriolis Controller suited to low flow control of the liquid. Alicat have developed several valves that work with the Coriolis Meter to create a Flow Controller. Depending on flow rate and pressure Alicat have a solution to meet most demanding needs for high accuracy and reliable delivery of liquid to the vaporiser.

Evaporator system

The Vaporiser consists of a heating chambre with control for temperature up to 200 Deg C. The chambre and heating are manufacturers for the specific flow requirements.

To complete the system there are extra functionality with a Humidity sensor on the outlet, this can purely report the humidity or be incorporated into the system to control the heating, gas flow or liquid flow to ensure the correct humidity is produced. Finally, the humidified gas stream may be at a higher temperature than needed thus a cooling bath with careful consideration to condensation can be used to achieve a specific outlet flow temperature.

You can read more about evaporation systems here.

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