Improved vapor flow solution via Controlled Evaporation & Mixing
One way to overcome the above hurdles is by making use of a CEM (Controlled Evaporation & Mixing) system for vapor delivery. In this vapor system, a gas mass flow controller (such as an EL-FLOW Select model) provides an accurately controlled carrier gas flow rate, whereas a liquid flow meter (such as a mini CORI-FLOW or LIQUI-FLOW) measures the flow of the liquid to be evaporated, for example drawn from a room temperature pressurized liquid vessel.
Subsequently a mixing control valve allows tiny droplets of the liquid flow to be injected into the carrier gas flow, which enters a heated, temperature-controlled mixing and evaporation chamber where the liquid fully evaporates, and a vapor/gas mixture is generated. A complete CEM system also contains a readout/control unit, including power supply, for operation of the CEM-system components.
A CEM system is a straightforward vapor delivery module that outperforms a bubbler in many ways. As the temperature distribution inside the evaporation chamber is much more controlled, the vapor supply - so the amount of vapor that is being carried along by the carrier gas - is much more accurate and reproducible. This results in a stable vapor delivery over time. Due to the gas and liquid flow instruments as components, the system is virtually temperature and pressure independent, and has a fast response time.