We offer the widest product range of low-flow mass flow meters on the market. Numerous styles of both standard and bespoke instruments can be offered for applications in laboratory, machinery, industry and hazardous areas.
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Bronkhorst instruments are used for numerous applications in many different markets. In this section you will find an overview of the main markets for our equipment, illustrated with some typical examples of applications.
Are you looking for technical documentation, are you interested to learn more about the measuring principles of Bronkhorst products, or you do want to get in contact with a Bronkhorst Service Engineer? This section will guide you to the relevant service & support topics.
Bronkhorst High-Tech BV the leaders in Mass Flow Meter / Mass Flow Controller technology for gases and liquids, Pressure Controllers and Evaporation Systems.
In our daily life, we are surrounded by vapors. They enter our nose, and we notice their presence in the form of a specific smell. Another profound example is water vapor as part of the air that surrounds us in our homes. Noticeable if the air encounters a colder surface, such as a window. The contained water vapor may condense on the windowpane and becomes visible and touchable as a liquid.
Also in industrial processes, vapors do have a useful role. Time to explain: what are vapors, where are they used, and how can they be delivered in a controlled way to these processes?
A vapor is very similar to a gas - which is a fundamental state of matter, just as solids and liquids are. Gases and vapors consist of separate molecules that move as free particles. However, there is an essential difference between a gas and a vapor. If a compound is a liquid at room temperature (around 20 °C) and normal pressure (1 atmosphere), then we call the ‘gaseous’ form of that compound a vapor. That is why we call the ‘gaseous’ form of water a vapor, whereas the gaseous form of oxygen is a gas, as oxygen is still a gas at ambient conditions.
When raising the temperature or lowering the pressure, a liquid can evaporate and convert into a vapor. On a molecular level, at any temperature at the liquid surface there are always molecules with enough velocity to leave the liquid. So, above a liquid there is always a vapor of the same liquid. Evaporation occurs at any temperature, and not just at the liquid’s boiling temperature. This boiling temperature is just a definition: it is a point at which the vapor pressure of the liquid equals the ambient pressure.
Playing with temperature and pressure are two ways to control the vapor pressure and because of that the amount of vapor or - in a dynamic situation - the vapor flow. A third way to control the vapor pressure - actually reducing it - is by diluting the vapor, for example by adding an inert gas such as nitrogen to the vapor.
There are circumstances in which you may want to add a vapor to a process in a controlled manner. For example, consider fuel cells - PEMFC – of which the electrolytes need to be in a hydrated state (humidified) to maintain a high conductivity and, hence, optimal performance. Read more about this in our customer story alternatively, you might want to supply accurate water vapor concentrations for the calibration and certification of humidity sensors, in order for these devices to display the correct humidity values.
Another type of vapor delivery is in the controlled supply of metalorganic vapors to a reactor. These vapor compounds act as precursors in a chemical vapor deposition reaction to deposit a thin layer on an object, for example to deposit semiconducting thin films. Accurate vapor supply is necessary here, to precisely control the layer growth - even on complex shaped objects - and to avoid spilling expensive metalorganic precursors.
A traditional way to deliver a vapor to a client’s process is by using a bubbler system. Here, a gas flow is bubbled through a heated vessel filled with a liquid compound. This carrier gas flow becomes entirely or partly saturated with the compound vapor, and this vapor flow is further guided by the carrier gas to the client’s process. Although this is quite a simple setup which can be used versatilely, there are a few drawbacks. Small changes in process conditions may give large variations in vapor flow, rendering it a relatively inaccurate delivery technique with a poor long-term stability. Since the vapor pressure largely relies on the vessel temperature, a slight change in temperature will result in a rather large deviation in vapor pressure and thus vapor flow. In addition, the total pressure and the carrier gas flow rate need to be stable to give a stable vapor flow. This vapor flow solution strongly relies on temperature and pressure.
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.
A vapor can be converted back into a liquid relatively easily by increasing the pressure or decreasing the temperature - something that will never work with a gas. One significant challenge in working with vapors is preventing condensation, as it can result in droplets that may disrupt or harm the ongoing process.
So, without altering the system pressure, keep the temperature beyond the CEM always higher than the temperature inside the CEM. Or alternatively, without changing the temperature, keep the pressure beyond the CEM always lower than the pressure inside the CEM.
Vapor delivery using CEM systems occurs typically in applications such as surface treatment, food & beverage industry, pharmaceutical applications and energy research.
Are you interested in our technologies and do you want to learn more about vapor flow measurement?
Bronkhorst High-Tech designs and manufactures innovative instruments and subsystems for low-flow measurement and control for use in laboratories, machinery and industry. Driven by a strong sense of sustainability and with many years of experience, we offer an extensive range of (mass) flow meters and controllers for gases and liquids, based on thermal, Coriolis and ultrasonic measuring principles. Our global sales and service network provides local support in more than 40 countries. Discover Bronkhorst®!