Michaela Aufderheide
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Prof. Aufderheide has been working for more than 30 years in the field of cell-based alternative methods with a focus on inhalation toxicology, which studies the effect of airborne substances on the epithelial cells of the respiratory tract. For this research, she has developed special equipment together with colleagues: the patented CULTEX RFS module, which makes it possible to treat the cultivated cells with these active substances directly. Increasing pollution of the environment and workplaces demands new testing methods to predict the level of risk presented by such substances. The high sensitivity of biological testing systems requires a stable and precise technological set-up to test of such atmospheres where, in addition to the CULTEX technology, mass flow controllers are of vital importance in adjusting and controlling the aerosol flows over the cells.

The e-cigarette

The history of humankind is characterised by its receptiveness to stimulants. Since the beginning of time, these substances have included intoxicants such as alcohol, as well as smoking. Although we are all aware of the health risks, 'most people only give up their vices when they cause them discomfort' (William Somerset Maugham).

This adage is particularly true of smoking. It is widely known that excessive smoking increases the risk of cardiovascular diseases and lung cancer, yet we still yield to the temptation of the 'nicotine fix'. Epidemiological studies have repeatedly shown the harmful effects of this addictive pleasure, but attempts to quit smoking often fail, despite the certain knowledge that every cigarette can be one too many.

In response, the cigarette industry is propagating the e-cigarette as an alternative. Combustion of tobacco releases thousands of harmful substances that are of course inhaled by smokers as well. In contrast, the e-cigarette lets you inhale a vapour that does not contain any products which present a risk to your health; at least, it is claimed. This 'vapour' is created from an aromatic liquid (main ingredients include propylene glycol, glycerine, ethanol, various flavourings and nicotine, as required) using a vaporiser.

Accordingly, the electronic cigarette is marketed by the cigarette industry as a 'healthier' alternative to traditional cigarettes or a means to help people quit smoking. A lot of money is being invested to prove scientifically that e-cigarette products are less harmful than tobacco products. This statement is essentially true. However, it does not really answer the question about the effects of the 'vapour'. Epidemiological studies, such as those for cigarette smoking, are not available and no one can therefore rule out that excessive or long-term consumption could cause harm to users’ health.

Figure 1: A. CULTEX®RFS Compact with 6 transwell positions that are exposed separately to the test atmosphere. B. The test atmosphere is sucked centrally via the mass flow controllers into the module in a controlled manner, distributed radially to the cell culture vessels and drawn continually across the cells. Image description

In vitro studies

So how can I now approach this question? The only remaining option is to carry out in vitro studies. To do so, we use living cell cultures as an alternative to animal experiments.

Inhaled active substances first reach the epithelial tissues lining the lungs. These tissues are made up of a multitude of cells that serve to defend against or inactivate the inhaled substances based on their special functions. We find mucus-producing cells here whose secretions 'capture' harmful substances, as well as cilia-bearing cells that can transport the mucus away. Other cells have a detoxifying effect, while we have sufficient replacement cells in an intact body which can replace the function of damaged or dead cells. In the field of cell-based research, we can make these human cell populations available for research (see Figure 2A). These cells are cultivated in so-called transwells on microporous membranes, where they are fed nutrients from the underside of the membrane while the apical (outer) part of the culture can react with the surrounding atmosphere.

Figure 2: Cross-section of cell culture insert membranes with HE (Hematoxylin and Eosin) stained immortalized NHBE cells (CL-1548). After 21 days of cultivation at the air-liquid interface, the cells were exposed repeatedly (daily for five days and after a recovery phase of two days again on three subsequent days, maximum exposure cycle: 8 smoke exposure repetitions) to clean air (CA), mainstream cigarette smoke (CS; 4x K3R4F cigarettes per run according to ISO 3308, University of Kentucky, Lexington, KY, USA) and e-liquid vapor (EC) without nicotine (Tennessee Cured, Johnsons Creek, Hartland, WI, USA). K3R4F cigarettes were smoked by a smoking robot and operated as follows: 24 puffs with a volume of 35 mL in 2 s, a blowout time of 7 s and an inter-puff interval of 10s. The electronic cigarette type InSmoke Reevo Mini (InSmoke Shop, Switzerland) was handled in a comparable manner: 50 puffs (volume 35 mL, puff duration 2 seconds, low-out time of 7 seconds) with an inter-puff interval of 10 s.

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Mass Flow Controller – the guardians of cell exposure

Over a number of years, we have developed efficient cell exposure systems: the CULTEX®RFS module, which allows for a direct, stable and reproducible exposure of lung cells at the air-liquid interface ([ALI); see Figure 1A). Their stability in particular guarantees significant results, due to the aerophysically adjusted design of the CULTEX®RFS module on the one hand and the use of the computer-guided mass flow controller on the other (Bronkhorst IQ+FLOW series and EL-FLOW Select series), the control and design of which have been adapted to cell-based exposure. The flow control ensures a precise and reproducible atmosphere for the exposure of the cells to the test gases. It is primarily the robustness of the experimental design which delivers results that allow us to draw conclusions about the effect of the respective test atmospheres. In this case, the various cells were exposed in an unpressurised atmosphere to the e-cigarette vapour (50 puffs per run) and compared with normal cigarette smoke (24 puffs per run); the cells were exposed to the respective doses for 8 days. A control was provided in the form of cells exposed to clean air.

The remarkable results are summarised in Figure 2. Comparing histological preparations of cells treated with smoke and e-cigarette vapour to the clean air control confirms the expectation that cigarette smoke causes a clear reduction in mucus production as well as the number and occurrence of cilia. A comparable – albeit less pronounced – effect could also be observed for the e-liquid aerosol after this treatment period, however. Compared with the cells exposed to clean air, we observed a significant effect that certainly should give us pause for thought. The statement that the 'vapour is less harmful than smoke' must not be confused with the conclusion that the vapour is not harmful at all. In the future, this problem will have to be addressed in order to tackle long-term harm through preventive means.

Products used in this research are IQ+FLOW mass flow controller and EL-FLOW Select thermal mass flow controller.

Kevin van Dijk
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For most people the classic summer treat is ice cream. Around 7 billion gallons of ice cream and other related frozen desserts are produced every year worldwide, with production peaking (as you might expect) in the summer months, according to the International Dairy Foods Association. Yet, the moment you consume an ice cream, you will probably not wonder how this delicacy is being made. To get that perfect ice cream, a mass flow controller is often used.

What does ice cream have to do with mass flow meters?

Ice cream contains many different ingredients, such as fat, sugar, milk solids, an emulsifying agent, flavouring and sometimes colouring agents. But there is one main ingredient that you may not have thought about, probably because you can’t see it—air. Ice cream is made by freezing and simultaneously blending air into the ingredients. So why is air so important?

If you have ever had a bowl of ice cream melt, and then refroze it and tried to eat it later, it probably did not taste very good. Moreover, if you leave a carton of ice cream out in the hot sun and let it melt, the volume of the ice cream would simply go down. Air makes up anywhere from 30% to 50% of the total volume of ice cream, therefore, aeration in the production process is crucial.

The amount of air in ice cream (often called overrun) affects the taste, texture and appearance of the finished product. Higher aeration will produce a tastier and smoother ice cream. A side effect of adding air to ice cream is that it tends to melt more quickly . Thus, for attaining an optimal structure of the ice cream, it is important to have a stable inlet air flow in the production process with a constant cream/air ratio. This can be achieved by using a mass flow controller.

The process of whipping ice cream into shape

To guarantee the right consistency and structure which ensures a full flavoured ice cream, the cream must contain the correct proportion and composition of air bubbles. Hence, aeration mixer manufacturers use a mass flow controller to dose an exact amount of air into the cooled mixer. Such a mass flow controller will ensure a continuous air delivery, proportional to the cream flow . The mass flow controller must be capable of maintaining its performance regardless of any possible back pressure variation. Occasionally, a check valve is mounted downstream of the mass flow controller. If inlet pressure drops, such valve will avoid ice back stream into the instrument. A pressure meter is also used with the purpose of monitoring the inlet pressure.

flowschemeofwhippingicecreamprocess

The SEM (Scanning Electron Microscope) picture below shows the ice cream microstructure. Air bubbles are a critical ingredient. Experts claim its optimal size, distribution and quantity are one of the secrets for having a creamy texture recipe. Hence, according to meet such demands, Bronkhorst has provided efficient solutions for enhancing continuous aeration processes.

Ice cream structure

So, the next time you head to the ice cream parlor with your friends, be sure to keep in mind the importance of Bronkhorst when it comes to that delicious refreshment.

EL-FLOW select

  • Watch the video about the EL-FLOW Select to learn more about the thermal mass flow instrument which can help you create ice cream.

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Graham Todd
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When you install a mass flow meter or mass flow controller it is important that you get the best performance from the moment you install and turn it on. To help you, I have listed a few simple things you can check focusing on thermal mass flow meters and controllers for gases.

1) Mounting position of flow meter

The mounting position is important. For flow meters the preferred position is horizontal, and at high pressures ( > 10 bar for by-pass instruments) all meters should be mounted in this position. Avoid installation in close proximity to mechanic vibration and heat sources.

2) Avoid interruptions

Avoid abrupt angles – or any objects in the flow path which can cause turbulence - directly on inlet and outlet of your flow instrument, especially for high flow rates. We recommend at least 10x the pipe diameter as the distance between the angle and the inlet of the flow instrument. If you are interested in why the choice of piping is important for thermal mass flow meters, please read our previous blog for more tips.

3) Name plate (serial number label)

Read the instrument’s name plate before installation and check the electrical connection, flow range, media to be measured, inlet and outlet pressure, operating temperature, ATEX classification (when applicable), as well as input and output signals. Also check the sealing material for compatibility with the process gas.

4) Electrostatic discharge (ESD)

The flow instrument contains electronic components which are sensitive to electrostatic discharges (ESD) – a sudden flow of electricity between two electrically charged objects caused by contact. Contact with electronically charged persons or objects could possibly endanger these components or even result in their failure.

5) Pressure

Do not apply pressure until electrical connections are made. When applying pressure to the system, take care to avoid pressure shocks and increase pressure gradually.

6) Check the piping

Ensure that the piping of the system is clean (before installing the instrument). For absolute cleanliness always install filters to ensure a moisture and oil-free gas stream. It is recommended to install an in-line filter upstream of the mass flow meter or controller, and if back flow can occur, a downstream filter or check valve is recommended too.

7) In line installing

Install the mass flow meter or controller in the line and tighten the fittings according to the instructions of the supplier of the fittings.

8) Piping diameter

Avoid small diameter piping on high flow rates, because the inlet jet flow will affect the accuracy and may cause too high pressure drops over the piping and adaptors. Choosing the right piping diameter is also of importance to minimize the effect of turbulence as much as possible. Our previous blog describes the effect of turbulent flow and what to do about this.

9) Leak testing

Always check your system for leaks, before applying fluid pressure. Especially if toxic, explosive or other dangerous fluids are used.

10) Power up

Apply power to the flow meter or controller and allow for approx. 30 minutes to warm-up and stabilize. This may be done with or without fluid pressure, applied to the system.

I hope that this list is of use. Please feel free to use it as a reference for the next time you need to install a mass flow meter or controller. If you have further questions or if you think I have left anything out then please let me know. At Bronkhorst, we are happy to learn from your experience.

Check the frequently asked questions (FAQs) on our website.

Or download the manual or quick installation guide of the flow instrument.

Dr. Jens Rother
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Each industrial process starts on laboratory scale to define the important parameters efficiently. These parameters might be pressure, temperature, flow but also cost efficiency and standing times. The process with the highest yield is not automatically the most efficient one. For example in catalysis or exhaust/raw gas purification it is very important to find the economically best materials and parameters. From the laboratory beaker to bulk is the process which starts at a microscale and ends with a fully operating industrial process. In between often a pilot stage is included.

Biogas Purification Testing

In Pressure Swing Adsorption systems (PSA), adsorption processes are used for the purification of bio- or natural gas. Thereby, the preferred adsorption of CO2 by zeolites or carbon-based sorbents is used to generate highly pure methane. This methane can be used for heat and power generation, offering an alternative to fossil fuels. Particularly in case of pressure swing adsorption systems, new materials are continuously being developed and evaluated, promising optimized efficiency caused by better sorptive separation properties. Laboratory scale studies are of special interest as the potential of new materials as well as the associated economics of corresponding industrial processes can be assessed in advance.

Breakthrough Measurements on Laboratory Scale

The Rubolab GmbH has been a spin-off from Rubotherm GmbH, Germany and the Ruhr-University in Bochum, Germany. Rubolab offers a broad versified portfolio of different adsorption measurement instruments. As Managing Director of Rubolab, I developed the worldwide first manometric high pressure adsorption screening instrument in 2012. During the last years, dynamic adsorption measurement instruments, so called Breakthough Analyzers, have gained increasing importance. In this context, Rubolab offers costumized instruments for the evaluation of novel sorbents in smallest amounts (MiniBTC series).

High pressure resistant vessels are filled with the materials which have to be analyzed. Afterwards this adsorber bed is pressurized using defined gas flows. A corresponding flow sheet of the instrument is shown in the following figure.

Rubolab breakthrough analyzer

In the example above, the sorptive separation of CO2 and CH4 is investigated. In this case, CO2 is adsorbed by the material while the gas is flowing through the fixed bed. A high-purity methane stream is recovered at the top end of the adsorber column.

Three temperature sensors are positioned at different heights within the adsorber column. Due to the exothermic adsorption process, a temperature change within the adsorber bed can be detected, indicating the so-called Mass Transfer Zone (MTZ) going through the fixed bed. When this zone reaches the adsorber head, a corresponding breakthrough can be observed by using downstream gas analysis. Thereby the measured CO2 concentration in the product stream approaches the CO2 concentration of the feed stream. In larger industrial systems the adsorber should be regenerated at this time. This kind of experimental data provides information about adsorption capacities of the substances being investigated.

Mass Flow Controller and pressure regulation valves

For the highly accurate controlling of mass flows and downstream pressures these instruments are equipped with Bronkhorst mass flow controller and pressure regulation valves. In particular devices of the newest generation of mass flow controllers, the Bronkhorst EL-FLOW Prestige series, are used in corresponding laboratory instruments for high end accuracy and versatility. In other devices where the size is of high importance, the Bronkhorst IQ+FLOW series is used to take advantage of it’s very compact size and the possibility to set up small manifolds.

Mass Flow Controller of the EL-FLOW Prestige Series

EL-FLOW Prestige mass flow controllers and meters are highly versatile instruments with their onboard database for gases and mixtures. So it is easy to react on changing customer needs without the necessity to purchase another instrument, when the test gas changes. The Prestige guarantees highly accurate and reproducible gas flow due to an automatic temperature correction, newly designed sensor and valve technology.

el-flow prestige flow meter

Mass Flow Controller of the IQ+FLOW Series

The IQ+FLOW series consists of ultra compact mass flow meters, controllers and also pressure controllers, which are designed for analytical instruments with limited space. The integrated chip technology enables fast measurement and control down to smallest ammounts. 3-Channel devices designed for customer’s application are also available.

IQ+Flow flow meter

To get familiar with this mass flow controller series, please download the white paper for more in-depth information.

You will receive the white paper when you fill out your email in the form above.

Check our instruments used in this application: