Bronkhorst Mass-Stream instruments, utilizing the CTA (Constant Temperature Anemometry) sensing technique, are extremely versatile and robust and have been used within many different sectors and industries.
The CTA sensor consists of two probes, the first being a heater and the second being a temperature sensor. A constant temperature difference is created between the probes, regardless of flow-rate. The actual mass flow rate is calculated by measuring the variable power required to maintain this constant temperature difference as the gas flows across the sensor.
Based on King’s Law, the greater the velocity of the gas across the probes, the greater the cooling effect, and in conjunction with a Wheatstone bridge, the power required to maintain a constant temperature difference across the probes can be represented by an increasing voltage signal.
The two probes of the sensor act as the legs of the Wheatstone bridge and as the heater probe is cooled by the fluid, the resistance of the probe is decreased and more energy is required to maintain the temperature difference.
The pressure loss over the Mass Stream instruments is almost comparable to a straight length pipe and is thus usually negligible. However, to ensure that the instruments less sensitive to upstream piping configurations, special mesh screens are used to condition the flow profile through the body of the instrument. These screens, along with the type of piping connections, are often the most significant cause of pressure loss through the Mass-Stream instruments.
Application examples of where the Mass-Stream instruments have been used can be seen as follows:
Breweries
-Oxygen injection into wort (liquid pre-cursor to beer)
Oxygen is an essential component for the growth and reproduction of the yeast that turns the sugars present in the wort into alcohol. Too much Oxygen could stimulate undesired bacterial growth which produce unpleasant aromas and flavours in the end product. Conversely, if there is not enough Oxygen in the wort, the yeast cell growth will be extremely limited as Oxygen is used in cell membrane synthesis. With limited yeast growth, the full fermentation of the sugars in the wort will be extended or not be complete which will also produce unwanted flavours and aromas.
The amount of Oxygen required is dependent on the strain of yeast used and the composition of the wort and as such will be varied for different recipes of beer.
-Carbon Dioxide injection
Commercial beer is often brewed “flat” with the Carbon Dioxide injected after fermentation has been completed and the beer has been pasteurised. This results a more uniform end product desired by most mass producers.
Carbonation gives the beer its head and the sparkling quality that is particularly expected in lagers and wheat beers.
The Mass-Stream product series is ideal for both of these applications in the brewing industry as it offers a rugged design and optional water proof (IP65) integrated display. The Mass-Stream series also feature counter and batch control functions to enable users to be assured that just the right amount of gas has been injected into the product.
Heat treatment and gas burner control
In burner control, and similar applications such as heat treatment and flame spraying, the amount gas needs to be both controlled and highly repeatable. This ensures that the correct flame size, shape and temperature are maintained irrespective of the pressure of the supply gas. This is particularly important as the supply pressure may vary depending on such variables as how full – or empty – is the gas bottle or how many points of use are being employed on a supply gas ring main.
-Thermal spraying (Plasma spraying in particular)
There are several different types of thermal spraying but, in general, the method involves spraying molten particles onto a prepared surface, whereby as the particles hit the surface they both flatten and cool to form a continuous, conformant coating. This coating can (depending on the coating) confer various enhancements to the surface of the material such as improved wear, corrosion resistance or creating a thermal barrier.
For plasma spraying the feed stock (coating), which is typically a wire, liquid or powder, is injected into a plasma flame thereby being melted into droplets and deposited at high velocity onto the material to be coated.
-Heat treatment
Heat treatment is a controlled process used to change the micro-structure of metals, alloys and sometimes plastics to impart certain desired properties onto that substrate. These properties could include surface hardness, temperature resistance, ductility and strength.
The work-piece to be heat treated can either be placed within an oven or furnace where the surrounding atmosphere is carefully temperature controlled, or it can be placed directly within the flame itself for a more targeted, limited area of heat treatment.
For oven or furnace applications, the emphasis lies within the stability and repeatability of the control such that reliable and predictable temperature change can be maintained.
For direct flame treatment it is essential that the size, shape and efficiency of the burner is maintained, both at optimal process temperature and at initial ignition. Each condition requires the accurate and repeatable supply of the combustion gas.
The Bronkhorst Mass-Stream instrument series provides an ideal solution for thermal spraying and heat treatment by providing:
- Single point solution with on-board PID control for meter and valve
- “Stay in position” valve in the event of a power interruption such that the furnace or flame remains constant and the process can continue
- Digital and analogue control signals, with an optional visual display, to suit a wide variety of customer specifications.
- Low power consumption for high combustion gas flow control.
In conclusion, a wide variety of industries, applications and processes can be served by the Bronkhorst Mass-Stream product series. Quality and user benefits are paramount. To request a demonstration of the product series, or to simply request further information, please contact :
Bronkhorst UK Ltd
1 Kings Court
Willie Snaith Road
Newmarket
Suffolk
CB8 7TG
Tel : 01223 833222
Email : sales@bronkhorst.co.uk
