Bronkhorst CEM W-300B - Manual (Page 7)

BRONKHORST HIGH-TECH B.V.
Mix
Liquid Gas
C
ONTROLLED
VAPORATOR
E
M IXER
Control valve assembly
Purge connector
Liquid-gas mixing
device
Liquid Gas
Heat exchanger
Process
1 Introduction
1.1 General
The Bronkhorst HIGH-TECH B.V. series CEM system is a unique
system to realise Mass Flow Control of vapour & mixtures,
containing up to 1200 g/h vapour. A complete system is a
combination of a mixing valve, a heating device, a liquid meter with
control function and a mass flow controller for the carrier gas. The
liquid flow through the liquid meter is controlled by the mixing valve.
A complete system also incorporates a readout/control unit,
including power supply for operation of the CEM system
devices.
1.2 Principle of operation
The abbreviation "CEM" stands for:
"C" the control of a flow of gas mixture, gas, liquid or liquid/gas mixture
"E" the evaporation of a flow of liquid/gas mixture by means of a temperature controlled heating device
"M" the mixing of a gas and a liquid (vapour).
At room temperature the liquid, for instance water or TEOS, is drawn from a container with an inert gas
blanket, or membrane, and measured by a liquid mass flow meter type µ-FLOW* or LIQUI-FLOW ® *. The
required flow rate is controlled to the setpoint value by a control valve that forms an integral part of the CEM
system.
A carrier gas, controlled by a MFC* is used to stimulate the evaporation process as a mixing component, and
furthermore to transport the vapour.
The process is highly repeatable and efficient.
Subsequent total evaporation of the liquid is achieved in the CEM.
* For operation of these devices consult the appropriate instruction manuals.
1.3 CEM set-up
The CEM system is built up around 3 different parts; a control
valve, a mixing device and a heat exchanger in which heat is added
to the mixture of fluids for evaporation and furthermore to prevent
condensation. The temperature of the heat exchanger is controlled
by a temperature controller which is part of the readout and control
unit.
9.17.042 page 7