In different kinds of applications like aging processes, validation testing and/or in research on plant growth, often a specified flow of moist air is needed to achieve specific ambient conditions in a test chamber. Nowadays, we have multiple solutions for these kinds of applications, one of them with the help of controlled evaporation and mixing systems. Let me explain what the benefits are of these systems in comparison with the more conventional bubbler systems.
How does a Bubbler System work?
Small concentrations of moist air can be created using a bubbler system. This conventional method requires optimal pressure and temperature control of the bubbler system. A complete bubbler level measurement system therefore consists of a source of compressed air, an air flow restrictor, sensing tube, and pressure controller. The latter converts the back pressure to provide output to a controller, which calculates the liquid level. The quality of the moist air fully depends on the theoretical calculation of the degree of saturation of the air flowing through the liquid and the accuracy of pressure and temperature control. With this conventional approach it is difficult to achieve a specific air moisture content.
Figure 1. Set-up Conventional Bubbler System
Bronkhorst evaporation systems
In addition to this approach, Bronkhorst developed a CEM-system, based on Controlled Evaporation and Mixing, which can be used for moist air applications. This CEM-system is an innovative vapor delivery solution, based on a liquid flow controller (LIQUI-FLOW or mini CORI-FLOW), a gas flow controller and a temperature controlled mixing and evaporating device.
Compared to the more conventional bubbler system, a CEM-system offers a more direct approach. The method is very straightforward, and theoretically any concentration can be made in a matter of seconds with high accuracy and repeatability. Moreover, it’s possible to adjust a relative humidity between 5 and 95 percent.
Figure 2. Set-up Bronkhorst CEM System
The moisture content is accurately controlled by the liquid flow controller and the amount of air flow can be adjusted by the gas flow controller. On top of the CEM a mixing valve allows for a correct atomization of water in the air flow. Because of the relatively low pressure ratio of the water mist in the air flow, the water can be evaporated at a low temperature in the spiralized heater tube at the outlet of the mixing valve.
The set-up of a CEM-system basically consists of:
- A Mass Flow Controller for gases for measurement and control of the carrier gas flow (e.g. EL-FLOW Select series).
- Mass Flow Meter for Liquids for measurement of the liquid source flow (e.g. LIQUI-FLOW series, mini CORI-FLOW series).
- Temperature controlled mixing and evaporating device (CEM) for control of the liquid source flow and mixing the liquid with the carrier gas flow resulting in total evaporation; complete with the Temperature Controlled Heat-Exchanger to add heat to the mixture; Basic Bronkhorst CEM-systems are available as a complete solution, including control electronics, offering total flexibility in realizing a vaporizing solution in virtually any situation.
Do you want to learn more about CEM technology? Visit the Bronkhorst Vapour Flow Control section on our website and read all about our different products and applications in vapour control.
Why Generating Vapour is easier, quicker and more accurate
Generating vapour is a perfect example of how technology development in one area can benefit multiple industries, as can be read in our blog ‘A new trend in vapour generation’. By combining the accuracy and digital performance of modern mass flow metering and control technology, alongside temperature control, you can control the properties of vapour as never before.
Vapour production has always been a necessary, yet complex and expensive process. There have been multiple methods employed to achieve the dispersion of liquid into a gas phase. The variety of methods used is a reflection of the bespoke approach taken by many to compensate for the lack of awareness of a commercially viable solution.
Some of the examples that we have come across;
What is the end goal?
There are many industries that need, or would benefit from vapour generation to achieve their end goal, we have been talking to biomedical researches, technical fabric manufacturers, glass coating companies, catalysis research & development, graphene research & development and bulk food packaging machine manufacturers.
As always there are a few common themes amongst each of the people that we speak to. In application development the drive is always to increase or decrease something, it could be: cost, waste, yield or raw materials. Almost anything associated with an application will either have an increase or decrease requirement.
How do we achieve the goal of increase and decrease?
Multiple factors can be improved by installing a Bronkhorst® Controlled Evaporating Mixing system (CEM) or Vapour Delivery Module (VDM) in your installation, these include:
- Speed of response to process changes
- Reduced raw materials costs
- Accurate temperature control
- Quick turnaround on substrate
- Choice of Parts per Million, Parts Per Billion, Mole or concentration output conditions.
How does the Bronkhorst® Controlled Evaporating Mixing sytem (CEM) or Vapour Delivery Module (VDM) system achieve these things?
Vapour is generated through the addition of a liquid into a gaseous stream, usually under temperature. We add control to each of the inputs, thereby acquiring control of the output. If we take the first example from the list at the beginning of this blog, Dew-point generation, then we can see;
- Evaporation of the fluid can cause concentration changes in vapour
- Differences in back pressure created by changing fluid levels
- Flow rate changes with fluid level resulting in changing process conditions
- Variations in thermostat accuracy can add temperature variations to the fluid
- High energy consumption from heating a fluid bed
By removing those sources of variation from the input, combining liquid flow control with a Coriolis mass flow meter (MFM) and gas flow control with thermal bypass mass flow controller (MFC) with a temperature controlled flow path you can predict the conditions of the resultant vapour more accurately. Once an output has been achieved with a known input combination, it can be replicated repeatably.
For example, in the picture below we know that the input conditions entered will achieve the desired process conditions, that level of control is not available in the other process.
With direct control of the liquid and gas flows into a temperature controlled flow path it is easy to change the input conditions and predict consistent process conditions. The Coriolis liquid mass flow meter and thermal bypass gas flow controller are directly linked to a 3-way mixing valve on top of a temperature controlled flow path. By passing the liquid and gas through the valve orifice the combined flow is aerosolized before being heated and this ensures complete vaporisation of the liquid in the gas stream.
Taking this a stage further, if you have a specific composition in mind then check out our online free to use database called Fluidat, go to www.fluidat.com register and you can check out yourself what is possible.
Looking at the 6 old ways and 1 new, the innovation and thought that has gone into the original and still used old methods of vapour generation is clear.
However the beauty of society is that we can learn from one another, another technology is available.
Smaller, faster, smarter - three keywords that summarise the trends in the high-tech machine building industry well. This holds for various industries:
- Complex machines in the semiconductor industry, that manufacture integrated circuits or 'chips' for devices like tablets, smartphones and notebooks.
- Machines in the solar industry, that manufacture solar panels to convert sunlight into electrical energy as a decentral replacement of traditional power plants.
- Analytical equipment within and outside chemical laboratories, that analyses or diagnoses the chemical composition or other physical properties of samples taken from a process flow.
- Machines in food and beverage industry where several nutritional compounds or flavourings are added, mixed and processed to obtain the desired food.
Measurement and control of gas and liquid flows
The common part where Bronkhorst and machine builders operate is that part of the machine where gas and liquid flows have to be measured or controlled. Machines for chips or solar panel manufacturing make use of chemical vapour deposition steps for coating application or diffusion doping, where organometallic vapours have to be generated and supplied to (silicon) supports onto which a solid deposition has to take place.
Read more in our blog about the solar energy future in which one of our project leaders shares his experience with Boron and Phosphor doping for solar panels.
In analytical devices such as various chromatography equipment (e.g. GC or HPLC) and mass spectrometers (MS), very low gas or liquid flows carry the to-be-analysed chemical compounds along with them.
In his blog ‘A closer ion them’ our analytical industry specialist shares his ideas about mass spectrometry and mass flow control.
In food machines, liquid additives such as colours, aromas and flavours have to be supplied accurately, to control the exact food composition.
For dosing flavours to your sweets the ultrasonic waves technology could be a solution. Read about it in our previous blog ‘Ultrasonic waves technology’.
Miniaturisation of high-tech machines
The miniaturisation trend is observed in many places. Small components need fewer quantities of raw materials, in production as well as in (chemicals) use. Customers of high-tech machines would like to have their equipment as compact as possible. Machines have to be smaller in size, as floor area is expensive, especially in cleanrooms - the 'natural' habitat of machines that manufacture solar panels and chips.
Compactness is also needed for online on-site analysis and monitoring - so outside the lab. Under those conditions, test equipment is preferably handy-sized. One would like to know on-site and in real-time what is going on - in order to react proactively instead of reactively, and to reduce the time to bring measuring samples to the lab. It is part of the online quality control: as a safeguard, but also to save on raw materials.
Removing the housings of standard products, and putting the components on a manifold gives a desired saving of space. Placing the input and output lines and connections on positions that are suitable for the customer often leads to a unique and compact solution. Compact devices with a combination of several analyses on a small surface area increase speed and reduce costs.
Read more about miniaturization in flow control in our blog The trend towards miniaturization in flow solutions. The latest technology is MEMS (micro electro mechanical system) technology, a micro-Coriolis mass flow sensor. Read about this new development of our R&D department.
Customized measurement systems
To stay ahead of competition, and to cope with fast evolving technological demands, the time-to-market is getting shorter and shorter. This asks for a new and flexible approach, where machine builders increasingly need to subcontract parts of their machine in a smart and efficient way.
Such a subcontractor is fully responsible for his part of the machine, and he takes away the worries of the machine builder in the field where he is 'king' - by supplying a total solution, preferably a compact unit. This 'subsystem' is a reliable combination of components that works as a whole, contrary to components that operate independently of each other. Moreover, the subsystem requires no more than one I/O connection.
The scrum methodology - known from software development - is ideal for this approach, in order to guide the process in a flexible way, using multidisciplinary teams that co-operate in short runs to anticipate evolving conditions and product demands.
'Smarter' deals with the process to manufacture such a machine - as mentioned above - but also with the way the machine itself is being managed. Of course, each subsystem needs to be compatible with the rest of the machine, but it also needs to be well integrated - for example to be suitably controlled by the main control system of the machine. Preferably it should work instantly, tested and 'plug & perform' delivered to the machine builder.
Bronkhorst flow solutions
For machine builders all over the world who are searching for simplification and integration of their gas, liquid or vapour flow processes, Bronkhorst can help in developing and supplying customised flow solutions.
Watch our video about Bronkhorst Customized Flow Solutions and the Co-creating Process
New Year's marks a time not only for resolutions, but also reflection. We are very delighted that our blogs have been received so well! This past year there were again many interesting stories to tell, how could it be otherwise given the industries in which we operate. I would like to share our top 5 best-read blogs of 2017 with you.
1) The importance of mass flow measurement and the relevance of Coriolis technology
Why is Mass Flow Measurement important within process industries and what are the strengths of Coriolis Flow Meters and Controllers? Given the number of readers of this blog, this is a frequently asked question.
2) A typical day at Bronkhorst’s flow meter Calibration Centre
We followed Mandy Westhoff, one of our Calibration Centre operators at our headquarters in Ruurlo, during her daily routines to get a realistic view on the activities of the Calibration Centre. A unique moment for readers to gain more insight about this challenging and important work!
3) How to measure low flow rates of liquids using ultrasonic waves?
In June 2017 we were proud to launch our ultrasonic flow meter, the ES-FLOW™, for measuring and controlling liquid volume flows. In collaboration with TNO (Netherlands organization for applied scientific research) we were ably to develop this instrument using Ultrasonic Wave Technology. More in-depth information on this subject can been found in this blog post.
4) Bronkhorst, its share of a clean – solar – energy future
Sustainability and clean energy remains a hot topic. CO2 reduction is one of the major trends worldwide in the energy market. The global focus on CO2 reductions matches perfectly within the Bronkhorst principles regarding respect for nature and environment.
5) How low can you go?
Well, this recent blog of Marcel Katerberg is not very low on our rankings. If you are keen to learn more about how to handle ultra low flow, then you definitely should read this blog.
Furthermore, I would like to thank our guest bloggers of this year, who were so generous spending their time in crafting an interesting blog contribution.
Frank Nijsen (Quirem Medical), Bram de la Combé (Green Team Twente), Maarten Nijland (Veco B.V.), Jeremy Lowe and Ian Brown (Anglian Water Services), Jens Rother (Rubolab GmbH), and Kees Jalink (NKI – Netherlands Cancer Institute)
I am confident that you will enjoy reading these blog posts - if you haven't read them already. But for now, I wish you on behalf of our whole team great health, happiness and success in the coming year.
Today I would like to share an application story with you using mass flow meters in an application at Umicore in Suzhou (China).
Umicore is one of the world’s leading producers of catalysts used in automotive emission systems. The company develops and manufactures high performing catalysts for, among other things, gasoline and diesel engines to transform pollutants into harmless gases, resulting in cleaner air.
Umicore’s production location in Suzhou ‘Umicore Technical Materials’ is using Bronkhorst Mass Flow Controllers and Vapour Systems for research and testing of automotive emission catalyst materials. Newly developed catalytically active materials of Umicore consist of oxides and precious metals, such as platinum and palladium, incorporated into a porous structure which allows intimate contact with the exhaust gas.
What catalyst materials does Umicore test?
Umicore in Suzhou uses various test benches in which newly developed catalytic materials are tested on performance (read: low output of toxic emissions). “Umicore develops new catalysts directly with top-tier automobile manufacturers in China. We are testing new formulations of materials and shapes of the catalysts on performance” explains Mr. Yang Jinliang.
How are the mass flow meters and controllers applied for identical testing and simulation?
The Bronkhorst mass flow meters and controllers are used to accurately deliver the right amount of several gases in a mixture that simulates the exhaust of an engine in different circumstances. “To really compare the performance of newly developed formulations, we have to be sure that the operational conditions of our tests are identical.” Mr. Yang explains that this requires the use of high performance mass flow controllers to accurately mix the simulated exhaust gas.
“We need flow control equipment which is reliable and has excellent repeatability during our simulation runs. Therefore Umicore developed the test equipment together with the Bronkhorst flow specialists.” Umicore runs various simulations. “We simulate exhaust gases of engines under various life cycle simulations and operating conditions. For example, the exhaust gas of the car is different if the engine is still cold or if the engine has a high number of revolutions.”
Test bench for ageing simulation
One special test bench of Umicore simulates the ageing of the catalyst materials. This has been achieved by heating the ambient temperature of the Catalyst up to 800° Celsius for a couple of hours up to 24 hours in a test run while adding the simulated exhaust gas. “Here the Bronkhorst instruments prove high stability under the harsh testing conditions,” says Mr. Yang.
Exhaust gas simulation recipe
In order to simulate engine exhaust gas, Umicore mixes multiple gases. In general the following reactions take place in the catalytic converter:
- Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
- Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
- Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O
To mix these gases, EL-FLOW Select digital mass flow controllers are being used. In order to maintain the gas mix under the same pressure, an EL-PRESS pressure controller instrument is used to control the pressure simultaneously with the flow.
Exhaust gases of engines also contain evaporated H2O. For this purpose the Bronkhorst ‘Controlled Evaporation Mixer’ (CEM) is used. All digital mass flow controllers, pressure controller and the CEM are connected with a computer that runs a software program to control the instruments.
In the ageing simulation test-bench of Umicore, high-temperature mass flow controllers of Bronkhorst are applied. The Bronkhorst EL-FLOW Select controllers have remote electronics to resist gas temperatures as high as 110° Celsius and still control the gases with high accuracy and excellentrepeatability.
How do you like the support of Bronkhorst products in China?
When asked about Bronkhorst support and service in China, Mr. Yang is very enthusiastic: “All Bronkhorst experts in China are very professional and have quick response. Especially during the start-up phase of our project, when we needed it most, my contacts were determined to support us. The system runs smoothly, but it’s comfortable to know that Bronkhorst is having one of its Global Service Offices in Shanghai if we need calibration or service.”
What is FLUIDAT?
FLUIDAT is Bronkhorst’s online calculation software. It allows our end users to make many theoretical calculations for their instruments and also have access to over 1800 different fluid properties and corresponding data.
Working with fluids and ever changing process conditions can provide many challenges, especially when trying to understand the behaviour of the given fluid depending on the actual pressure and temperature of the process. Along with understanding the behaviour of your particular fluid or fluid mixture making sure that you select an instrument that is able to operate effectively to the level you expect and that meets your application’s demands. In this case the initial selection of the correct instrument is fundamental, understanding what is possible for the future of your instrument can however be just as important.
This is where FLUIDAT can assist by allowing our end users to fully understand their instruments capability. If it’s working at different pressure conditions or using a completely different fluid for example, FLUIDAT can allow you to make an informed decision about whether or not the instrument is up for the task at hand. Of course, sometimes we have to accept that returning the instrument for recalibration is the only option but with FLUIDAT at your fingertips you have the ability to make an informed choice.
Traditionally, fluid data has been stored in technical handbooks and manuals with graphs and tables of data in a listed format demonstrating fluid properties along with their coefficients. However, this is a very inflexible format and does not allow immediate access to changing fluid behaviour (due to external factors) without making what can sometimes be complex calculations.
Knowing that these challenges were sometimes a hindrance to our end users, Bronkhorst released this on-line fluid management programme to support our customers in a way we never had before. This on-line programme allows immediate data and calculations relating to the behaviour of thousands of fluids under different working conditions.
One example of this is our Controlled Evaporation Mixing (CEM) vapour generation calculation tool. To calculate the output vapour to the process you need to calculate the combination and vaporisation properties of both a liquid and gas at differing temperatures and flow rates. Our CEM calculation tool can make this task easy, at just a click of a button.
The newly added interactive Vapour-Pressure line allows users to simply glide the cursor over the chosen fluid graph to establish the phase at the given temperature and pressure. Added value comes from the ability to create and save your own fluid mixtures, which alone can remove hours of calculations and research from a single project.
OK, so let’s have a look in more detail at some of the calculation tools available in FLUIDAT.
Gas Conversion Factor:
Here, the end user can choose a pure gas or create a gas mixture to find the conversion factor for a different gas to which an instrument can be sized on. As with most thermal mass flow controllers the output signal from the MFC is determined by which gas it has been calibrated for. With the gas conversion factor tool you simply choose the ‘Fluid from’ and ‘Fluid to’ to find out the conversion / correction factor. You can also select your exact model to improve the accuracy of the conversion. This function also allows you to add the specific pressure and temperature conditions you are converting from and to, for even more accuracy. The conversion factor can then be applied to the output measurement of the MFC to know the actual flow of the new gas.
Example of a gas conversion made in FLUIDAT:
Controlled Evaporation Mixing (CEM) Calculation Tool:
A CEM system can be an extremely versatile addition to any vapour generation requirement. FLUIDAT allows the end user to make various calculations to not only enable the correct CEM heater temperature setting , the flow rates required for both the liquid and gas instruments and the relative humidity of the generated vapour. It is also possible to back calculate the flow rates needed to achieve the required relative humidity of your vapour. All of the fluid data is stored within the FLUIDAT software, the heat capacity, thermal conductivity and heat of vaporisation to name a few. This data can also be accessed by the user under the ‘Fluid Properties’ calculation.
The possibilities of the CEM calculation tool are endless, from knowing the pressures needed to supply the liquid and gas MFCs to calculating the vapour temperature on the outlet, or knowing the flow of the vapour output and having the ability to choose between thousands of different fluids to make your calculations. This makes FLUIDAT a ‘must-have’ for any Bronkhorst customer using our CEM vapour delivery systems.
Example of a CEM calculation in FLUIDAT:
Pressure Drop Calculations:
For most applications it is important for the end user to understand the pressure drop across the instrument. It is not only important to understand the pressure loss across a device but sometimes it can also be critical to know the required pressure for the instrument to function correctly, especially when using control valves.
In FLUIDAT it is possible to calculate the pressure drop for both our gas instruments and our mini-Coriolis Series. Calculating the pressure drop using FLUIDAT is easy, all you need to do is select the correct pressure drop calculation tool. You have the choice of selecting our MASS-STREAM, EL-FLOW/IN-FLOW or Coriolis Instruments.
The calculation tool for the Coriolis Instruments is called ‘CoriCalc’ and for the other instruments are referred to as ‘Pressure Difference D-6300’ or ‘Pressure Difference LOW-dP-FLOW and EL-FLOW'. Once you have selected the correct tool and instrument type you can then select the fluid and flow rate and simply hit the calculate button. You can choose to readout the pressure drop in many different units from mbar to psi for example. For meters this is pretty straight forward, the pressure drop will be displayed across the sensor and fittings and yes, you can also choose the fitting size and type in many situations.
This calculation tool can also demonstrate the minimum required inlet pressure to flow the fluid you want at the required flow rate. Without the complication of the control valve calculating for meters is relatively straight forward. When making calculations involving both a meter and control valve (e.g. in a controller), it is important to make sure your calculation includes the correct selected orifice for your given controller, the easiest way to do this is using the inlet and outlet pressures to be used.
Example of a Pressure Drop Calculation in FLUIDAT:
FLUIDAT is an extremely useful and powerful tool for those using Bronkhorst instruments. It allows an end user access to additional information which can be used to not only enhance the potential of our instruments but also allows our customers to gain an advantage over competitors and gain an understanding of mass flow. The above examples are just a snippet of some of the tools available.
Please register at www.fluidat.com to take full advantage of this free online software.