Introduction; General; Principle Of Operation; Cem Set-Up - BRONKHORST W-300B Instruction Manual

1 Introduction

1.1 General

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The Bronkhorst 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
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.
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BRONKHORST
Control valve assembly
Liquid-gas mixing
device
Gas
Liquid Liquid Gas
Mix
C
ONTROLLED
E
VAPORATOR
M
IXER
Heat exchanger
Process
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*. The
Purge connector
9.17.082