Chemical Peels - What You Need To Know About Chemical Peels
Chemical peels, also known as chemexfoliation or derma-peeling, are a technique used to improve the appearance of the skin. In this treatment, a chemical solution is applied to the skin, which causes it to eventually peel off. The new, regenerated skin is usually smoother and less wrinkled than the old skin.
Question 1, What Conditions Do a Chemical Peel Treat?
Chemical peels are performed on the face, neck or hands. Chemical peels can
be used to:
Question 2, How Are Chemical Peels Performed?
The skin is thoroughly cleansed with an agent(chemical peel) that removes excess oils while the eyes and hair are protected. One or more chemical solutions, such as glycolic acid, trichloroacetic acid, salicylic acid, lactic acid or carbolic acid (phenol), are applied to small areas on the skin. These Chemical Peel applications produce a controlled wound, enabling new, regenerated skin to appear.
Question 3, How do I prepare for a Chemical Peel?
Prior to the chemical peel, your Aesthetician may ask you to stop taking certain drugs and prepare your skin with topical preconditioning medications such as Retin-A, Renova, or glycolic acid. After the chemical peel, it’s important to use a broad-spectrum sunscreen every day.
The more clinical definition of a chemical peel is as follows: A chemical peel is a body treatment technique used to improve and smooth the texture of the facial skin using a chemical solution that causes the skin to blister and eventually peel off. The regenerated skin is usually smoother and less wrinkled than the old skin. Thus the term chemical peel is derived. Some types of chemical peels can be purchased and administered without a medical license, however people are advised to seek professional help from a
dermatologist on a specific type of chemical peel before a procedure is performed.
Chemical Industry - An Overview
Chemical Industry is one of the fastest growing Industries globally. Demand in different segments of chemical Industry like pharmaceuticals, Inorganic Chemicals, Organic Chemicals, Fine and specialties, Bulk Drugs, Agrochemicals, and Paints and Dyes are also increasing rapidly. Industry players are following state of the art techniques and extensive research and development policies to fulfill this increasing demand for chemical.
Chemical Industry and India
India was importing chemicals during early 1990s, but now India has become a net exporter of chemicals because of implementation of several large scale petrochemical plants, and tremendous growth of exports in sectors like bulk drugs and pharmaceuticals, pesticides, and dyes and intermediates.
Currently India is a strong player in chemicals export. Following are some facts related to Chemical Industry in India (Analysis based on Year 2005):
- 13% of total export
- 13% of total industrial output and 7% of GDP
- 10%-12% growth rate annually
- 2% of global chemical industry
- Indian pharmaceuticals industry ranks 4th in volume and 13th in terms of value in world
- 2nd largest producer of agrochemicals in Asia
Factors Affecting Indian Chemical Industry
There are few factors resulting growth of Indian Chemical Industry. Some important factors are as following:
- Friendly Government Policies: In recent years government policies have become more and more industry friendly, following the similar global industry friendly trend. Government is eager to provide land and basic infrastructure for new industry establishments, because industries are powerful elements in contributing rapid growth of development.
- Increasing Demand: There is increase in demand of chemicals globally, be it pharmaceutical, agrochemicals, adhesives, fertilizers, or other chemicals. So industry players are trying to increase their current production to match increasing demand.
- Technology factors: The change in technology is also a factor in development of chemical industry. Newer machinery, better technology, and research are major cause behind growth rate of this industry.
- Involvement of major players: Involvement of major industry players in chemical industry, as well as acquisition of overseas companies by Indian Giants led strong worldwide reputation of Indian chemical manufacturers.
- Presence of raw materials: India is rich in minerals and other raw materials required in production of chemicals that decreases input capital required and increases overall revenues of manufacturers.
In coming years industry is going to grow with more than current growth rate. In 2005 its contribution to GDP was 7%, which increased to 13% in year 2007. Domestic demand is also increasing so we don’t need to look for exports always. Past few years witnessed tremendous growth and we can expect similar trends in future too.
Chemical Peel Basics
Chemical peels can help reduce the appearance of facial folds, wrinkles, and “crow’s feet” by removing damaged outer layers of skin. Because there are different chemicals available for exfoliation, your individual needs will determine the type and specific formula for your peel. Peels of various formulas can be used for purposes ranging from the basic smoothing of dry skin to correcting sun blotches and removing pre-cancerous growths.
How It’s Done
After the face is thoroughly washed to remove any excess oil, the chemical solution is painted on. The peeling agent is left on the skin for several minutes. All patents experience a stinging sensation, the severity of which is determined by the type of peel used. A fan is set up and pointed toward the patients to help alleviate some of the discomfort.
For the deeper, more intense peels, a mild sedative can be administered, but in general, and especially for mild and superficial peels, no special preparations are necessary. Peels usually last 15 minutes or less except for the most intense type which can last 1 - 2 hours.
Technology
There are three different categories of chemical peels. Increasing in strength and epidermis penetration, they are alphahydroxy acids (AHAs), trichloracetic acid (TCA), and carbolic acid (phenol). When choosing a peel consider the following:
AHAs
- Mildest peel
- Corrects minor problems like rough or dry skin and sun damage
- Is sometimes used to pre-treat skin before TCA peel
- More than one treatment may be necessary
TCA
- Smoothes wrinkles, removes blemishes, and corrects pigmentation problem
- No anesthesia is necessary, but mild sedatives are often used
- Requires pre-treatment with Retin-A or AHA
- Works well on dark skin tones
- Results are less dramatic and shorter in duration than with phenol peels
- Formula can be adjusted for desired results
- Must avoid sun exposure for several months following peel
Phenol
- Correct blotches, smoothes coarse wrinkles, and removes pre-cancerous growths
- Not recommended for darker skin tones
- Full recovery may take several months
Recovery / Post Op Expectations
The type of peel that a patient undergoes will determine the recovery process, however, after any peel it is necessary to limit sun exposure and wear sunscreen with a high SPF when outside. AHA peels can offer a quick recovery with little or no time away from work and normal activity, but most patients experience some redness, irritation, or flaking as the skin adjusts to the treatment.
After phenol and TCA peels a crust or scab will form over the treated areas, and will remain for a few days according to the physicians instructions. With TCA peels patients experience some swelling an irritation and should subside enough within 7 - 10 days to allow patients to return to normal activity. With phenol peels, swelling is usually severe and skin takes on a red hue that gradually fades to pink. Return to work after phenol peels can take 2 weeks or more.
Complications
Complications with AHA peels are minimal and include irritation, excess flaking and soreness, which can be treated with medication. Complications for TCA and phenol peels include scarring, cold sores, fever blisters, and change in skin color. Some patients with phenol peels develop a lighter skin tone in treated areas and may need to wear make up to disguise lines of demarcation.
Am I a Candidate?
Chemical peels are used mainly for cosmetic reasons. Patients with a history of herpes, taking birth control pills, or with a predisposition to brownish discoloration of the face may be at a greater risk for postoperative complications.
Cost
The national average of surgeon fees for chemical peels was $607 in 2003 according to the American Society of Plastic Surgeons (ASPS), but can range as high as $6,000 for full phenol peels.
Home Chemistry Supplies List
In addition to gathering chemicals for a home chemistry kit, be sure to collect a few everyday materials, too.
- measuring cup
A glass measuring cup is useful for many activities. - measuring cups/spoons
Don’t worry. You can still use them for baking and other cooking. Just be sure you have a way to measure both liquids and solids. - coffee filters
Coffee filters make great covers for projects that require evaporation, but not dust and bugs. They make nice pH paper and chromatography paper, plus they are good for their designed purpose, filtering. - clear glass jars
Most of the time, you can use dishes from the kitchen for projects, but sometimes you’ll want a clear container you can throw away when a project is completed. - string
String is used for growing crystals.
What Is the Difference Between an Ionic and Covalent Chemical Bond?
A molecule or compound is made when two or more atoms form a chemical bond, linking them together. The two types of bonds are ionic bonds and covalent bonds. In an ionic bond, the atoms are bound together by the attraction between oppositely-charged ions. For example, sodium and chloride form an ionic bond, to make NaCl, or table salt. In a covalent bond, the atoms are bound by shared electrons. If the electron is shared equally between the atoms forming a covalent bond, then the bond is said to be nonpolar. Usually, an electron is more attracted to one atom than to another, forming a polar covalent bond. For example, the atoms in water, H2O, are held together by polar covalent bonds.
Progress and recent trends in biofuels
In this paper, the modern biomass-based transportation fuels such as fuels from Fischer–Tropsch synthesis, bioethanol, fatty acid (m)ethylester, biomethanol, and biohydrogen are briefly reviewed. Here, the term biofuel is referred to as liquid or gaseous fuels for the transport sector that are predominantly produced from biomass. There are several reasons for bio-fuels to be considered as relevant technologies by both developing and industrialized countries. They include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues related to the rural sector. The term modern biomass is generally used to describe the traditional biomass use through the efficient and clean combustion technologies and sustained supply of biomass resources, environmentally sound and competitive fuels, heat and electricity using modern conversion technologies. Modern biomass can be used for the generation of electricity and heat. Bioethanol and biodiesel as well as diesel produced from biomass by Fischer–Tropsch synthesis are the most modern biomass-based transportation fuels. Bio-ethanol is a petrol additive/substitute. It is possible that wood, straw and even household wastes may be economically converted to bio-ethanol. Bio-ethanol is derived from alcoholic fermentation of sucrose or simple sugars, which are produced from biomass by hydrolysis process. Currently crops generating starch, sugar or oil are the basis for transport fuel production. There has been renewed interest in the use of vegetable oils for making biodiesel due to its less polluting and renewable nature as against the conventional petroleum diesel fuel. Biodiesel is a renewable replacement to petroleum-based diesel. Biomass energy conversion facilities are important for obtaining bio-oil. Pyrolysis is the most important process among the thermal conversion processes of biomass. Brief summaries of the basic concepts involved in the thermochemical conversions of biomass fuels are presented. The percentage share of biomass was 62.1% of the total renewable energy sources in 1995. The reduction of greenhouse gases pollution is the main advantage of utilizing biomass energy.
Dietary Sources Of Iron And Folic Acid
Folic acid is a collective term for pteroylglutamic acids and their oligoglutamic acid conjugates. Folic acid deficiency results in macrocytic anemia due to impairment of erythrocyte synthesis and is associated with elevation of plasma homocysteine levels, a risk factor for cardiovascular disease, including coronary atherosclerosis, stroke, and thromboembolism.
While the dietary sources of folic acid are in abundance proper care should be taken while cooking. The more you burn the gas the less the nutrients so just try to steam the vegetables. One other way to save the folic acid content is through heating them with as little water as possible. Natural sources of folic acid include whole-grain breads and cereals, orange juice, kidney beans, yeast, liver, and dark green leafy vegetables such as broccoli, kale, and spinach. Folic acid and cobalamin (vitamin B12) serve as components of coenzymes in 1-carbon reactions such as the methylation of homocysteine to methionine. Other sources would include citrus fruits and juices, dried beans and peas, fortified breads, cereals, lentils, legumes, peanuts, whole grain products, beef, chicken, cabbage, Brussels sprouts, spring greens, kale, okra and fresh peas and the pulses are chickpeas, black-eyed beans, and lentils.
Iron is a metallic element that occurs in the heme of hemoglobin, myoglobin, transferrin, ferritin, and iron-containing porphyrins, and is an essential component of enzymes such as catalase, peroxidase, and the various cytochromes. Its salts are used medicinally.
Iron deficiency can result in anemia. Iron supplements form an important part of the diet in women during the pregnancy period. It is for a fact that the iron stores could be stabilized in the body easily by ingesting meat products than the vegetables, but still there are a lot number of iron resources than one could imagine in the vegan part too. Natural dietary sources of iron would include beef, meat, fish, poultry, liver, eggs, pork, red meat, and turkey. To see it in a vegetarian way it would be whole meal breads, apricots, kidney beans, and spinach. Other sources of iron would include fortified greens, tomato, potato, green and red chillies, fortified breads, cereals, beans, and legumes. The following have the much-needed iron extracts to fill the iron reserves in human body and they include shellfish, shrimp, clams, mussels, oysters, lean meats, beef, and liver, ready-to-eat cereals with added iron, turkey dark meat, sardines, cooked dry beans, pinto beans, peas, black-eyed peas, seaweed, dried fruits, pulses, wheat germ, bran, yeast, nuts, seeds, parsley, molasses, jaggery, and enriched and whole grain breads.
Coriolis Principle
To some of us the Coriolis Principle is an exact science, but to most of us it is still a black art. Well, imagine a fluid flowing (at velocity V) in a rotating elastic tube as shown below. The fluid will deflect the tube.
If the mass M is guided by Wall A (i.e. the tube), a Coriolis Force will be exerted on the wall as shown below.
CORIOLIS FORCE : Fc = -2 M V W
The tube walls guide the process fluid as it flows through the U-Tube pathway. With no fluid inside the tubes the Driver excites the tubes apart at a nominal 150Hz.
Now imagine fluid of Mass M flowing through and out of the RotaMASS tubes. As the fluid flows down the first half of the U-Tubes it will tend to deflect the tubes in towards each other. Conversely, when the fluid flows up the second half of the U-Tubes it will tend to deflect the tubes out away from each other. This Coriolis Twist action is shown above.
Turbine Flowmeters for Liquid Measurement
The basic construction of the turbine flowmeter incorporates a bladed turbine rotor installed in a flow tube. The rotor is suspended axially in the direction of flow through the tube. The turbine flowmeter is a transducer, which senses the momentum of the flowing stream. The bladed rotor rotates on its axis in proportion to the rate of the liquid flow through the tube.
TURBINE ROTATION
As the liquid product strikes the front edge of the rotor blades, a low-pressure area is produced between the upstream cone and the rotor hub.
The blades of the turbine rotor will tend to travel toward this low-pressure area as a result of this pressure differential across the blades. The pressure differential (or pressure drop) constitutes the energy expended to produce movement of the rotor. The initial tendency of the rotor is to travel downstream in the form of axial thrust. But since the rotor is restrained from excessive downstream movement, the only resulting movement is rotation.
Fluid flowing through the meter impacts an angular velocity to the turbine rotor blades, which is directly proportional to the linear velocity of the liquid. The degree of the angular velocity or number of revolutions per minute of the turbine rotor is determined by the angle of the rotor blades to the flowing stream of the approach velocity.
ROTOR BALANCE
With axial thrust forcing the turbine rotor downstream, the friction resulting from contact between the turbine rotor and the downstream cone would cause excessive wear if there were not some means of balancing the turbine rotor on its axis between the upstream and the downstream cone.
Bernoulli’s Principle states that when flow velocity decreases, the static pressure increases. Therefore, a high-pressure area exists at the downstream side of the turbine rotor exerting an upstream force on the rotor. As a result, the turbine rotor is hydraulically balanced on its axis.
SIGNAL OUTPUT
Electrical output is generated using the principle of reluctance. A pickup coil, wrapped around a permanent magnet, is installed on the exterior of the flow tube or the meter body immediately adjacent to the perimeter of the rotor (Figure 1). The magnet is the source of the magnetic flux field that cuts through the coil. Each blade of the turbine rotor passing in close proximity to the pickup coil causes a deflection in the existing magnetic field. This change in the reluctance of the magnetic circuit generates a voltage pulse within the pickup coil.
Each pulse generated represents a discrete amount of volumetric throughput. Dividing the total number of pulses generated by the specific amount of liquid product that passed through the turbine flowmeter determines the K-Factor. The K-Factor, expressed in pulses per unit volume, may be used with a factoring totalizer to provide an indication of volumetric throughput directly in engineering units. The totalizer continuously divides the incoming pulses by the K-Factor (or multiplies them with the inverse of the K-Factor) to provide factored totalization. The frequency of the pulse output, or number of pulses per unit time, is directly proportional to the rotational rate of the turbine rotor. Therefore, this frequency of the pulse output is proportional to the rate of the flow.
By dividing the pulse rate by the K-Factor, the volumetric throughput per unit time of the rate of flow can be determined. Frequency counters or converters are commonly used to provide instantaneous flow rate indication. Plotting the electrical signal output versus flow rate provides the characteristics profile or calibration curves for the turbine flowmeter.
Electrical output is also generated using the principle of inductance. A pickup coil is installed on the exterior of the flow tube immediately adjacent to the perimeter of the turbine rotor. The magnetic source of the flux field in this type of output is either the rotor itself or small magnets installed in the rotor. In the case of the rotor, the material of construction would be nickel or some other easily magnetized flux field. The results are identical to that of the reluctance principal.
ACCURACY
The accuracy of a turbine flowmeter is derived from its output (electrical or mechanical) and is the measure of the deviation of an indicated measurement from the referenced standard. Turbine meter accuracy is dependent upon several items.
The accuracy must include the error associated with the calibration standard. In the USA, the National Institute of Standards and Technology represents the flow standard.
Linearity is the variation of the flowmeter K-factor from a nominal value of a point on a curve. Normally during calibration, a value is chosen which makes linearity fall in line with accuracy. Linearity may remain constant during meter life although the absolute accuracy level has changed.
Repeatability is the ability of a turbine flowmeter to reproduce its output indefinitely under constant operating conditions at any point over its specified operating range.
SPECIFIC GRAVITY
The specific gravity of a liquid is the ratio of its density to that of water at 4BC (39.2BF) and is dimensionless. While changes in specific gravity do not affect the average turbine meter K-factor value, the overall linear range of the flowmeter is changed (Figure 2). The linear range represents the minimum to the maximum flow rate within which the linearity of the flowmeter is specified.
As stated previously, the rotor rotates due to pressure differential across the rotor blades. Specific gravity is one of the factors affecting this pressure differential. As the specific gravity decreases, the pressure differential decreases. On a fluid with a low specific gravity and a low flow rate, the pressure differential across the blades is very low. This leaves almost no energy for turning the rotor. Consequently, the rotor cannot turn in proportion to the liquid throughput and the K-factor drops off.
Therefore, the angle of the rotor blades is changed to help compensate for the change to a lower specific gravity. This allows products with lower specific gravity’s to be measured accurately by the turbine flowmeter.
VISCOSITY
Viscosity if the measure of the liquid products resistance to flow. Kinematics viscosity is the ratio of the absolute viscosity to the specific gravity, usually expressed in centistokes (cs), where the resistance to flow is measured in square millimeters per second (mm2/s).
VISCOSITY EFFECTS ON RANGEABILITY
Viscosity has two different effects on the turbine flowmeter rotor. First of all, the profile causes boundary layer thickness to increase as viscosity increases for a fixed volume. This means that rotor-blade shape and length will be important in determining the K-factor since the flow around the blade tip region changes with respect to viscosity. This boundary layer thickness causes the turbine flowmeter to be non-linear. Supplying a shroud around the turbine rotor, with the shroud outer diameter slightly smaller than the inside diameter of the flow tube, increases the viscosity and creates a drag (resistance to rotation). This drag offsets the non-linear effect of the boundary layer.
The second effect of viscosity is one of viscous shear-force change on the rotor and increased viscous drag within the bearing. These effects act to slow the rotor while the profile effect acts to speed the rotor. The relative magnitude of all these forces changes the Reynolds number.
As previously indicated, some turbine flowmeter designs introduce a device or shroud that introduces viscous drag, which eliminates the hump that normally, occurs in the transition region.
While linearity is affected by viscosity, repeatability is not.
FLOW RANGE
The minimum flow rate of a turbine flowmeter becomes a factor of viscosity versus the degree of accuracy. As product viscosity increases, the minimum flow rate required to maintain a specific degree of accuracy increases. The maximum rate of flow allowable becomes a factor of viscosity versus the pressure drop across the flowmeter. As the product viscosity increases, the maximum flow rate decreases in accordance with the maximum allowable pressure drop across the flowmeter. In order to arrive at the minimum and maximum rate of flow limits for a particular turbine flowmeter size and application these factors must first be determined:
· The viscosity of the product to be metered (or maximum value of viscosity for products with varying viscosity’s at 37.8B (100BF).
· The degree of accuracy required.
· The maximum amount of pressure drop allowed across the flowmeter.
Using an area-of-operation diagram for a particular turbine flowmeter size and charting the factors for viscosity accuracy and pressure drop will determine the minimum and maximum flow rates.
Operating the flowmeter within this flow range will meet the operating requirements unique to that application. Technical bulletins providing area of operation for turbine flowmeter sizes with varying viscosity fluids can be obtained from the various meter manufacturers.
CAVITATION
Cavitation in a turbine flowmeter will take place when the local pressures fall close to or below the vapor pressure of the liquid product. The formation of bubbles and their collapse or local vaporization of product as it passes over the rotor blade surface can cause erratic behavior in the turbine flowmeter and excessive wear due to over speeding. Maintaining a system backpressure of 2 times the flowmeter pressure drop plus 25 times the product vapor pressure is sufficient to prevent cavitation as shown by the following formula:
BP= (P x 2) + (VP x 1.25)
Where,
BP= Required back pressure
P= Pressure drop at maximum flow.
VP= Absolute vapor pressure at maximum temperature.
Cavitation usually causes the rotor to speed up at the high flow rate due to the increased flow volume and causes the accuracy curve of the turbine flowmeter to be adversely affected.
INSTALLATION
The term swirl is used to describe the rotational velocity or tangential velocity component of fluid flow in a pipe or tube. Depending on its degree and direction, swirl will change the angle of attack between the fluid and the turbine rotor blades, causing a different rotor speed at a constant flow rate to non-swirling conditions at the same flow rate. Liquid swirl and non-uniform velocity profiles may be introduced upstream of the turbine flowmeter by variations in piping configurations or projections and protrusions within the piping. Swirl may be effectively reduced or eliminated through the use of sufficient lengths of straight pipe or a combination of straight pipe and straightening vanes installed upstream of the turbine flowmeter.
APPLICATIONS
Turbine flowmeters, when first introduced, were used mainly by the aircraft industry in small sizes. Turbine flowmeters are now used on many applications (figure 3). Reasons for this increased used are sizes up to 12″, weight and size versus flow rate, extended flow ranges, operating pressures up to 10,000 pounds per square inch, temperature range of -450° to 1000°F and a wide variety of construction materials including stainless steels.
In recent years, turbine flowmeters have been competing successfully with positive displacement flowmeters in many applications due to the economy of installation, low maintenance costs, weight, size and high flow rates per comparable connection size. You must exercise caution when making this comparison, especially on viscous products. Following the parameters outlined previously will prevent most misapplications of the turbine flowmeter.
When products are used in which viscosity changes with seasonal temperature, a proving run should be done at a time when the product temperature would be changing. For instance, fuel oil may change 50°F in ambient temperature between summer and winter. A change of this magnitude would affect the flowmeter curve and directly affect the flow range.
Increased expertise with electronics such as linearization is permitting turbine flowmeters to be used more widely (figure 4).
PROVING
Proving is a method of checking a measuring device against an accepted standard to determine the accuracy and repeatability of that measuring device. Turbine flowmeters should be proven immediately after installation, after repair, following removal from service (for any reason) when changing products, when product viscosity changes, or to chart the flow patterns of the flowmeter during a period of time.
METHODS
There are several different methods of proving. Volumetric proving consists of a measured volume of fluid being compared to a known standard, such as a seraphin can or piston prover.
Gravimetric proving entails measuring weight of a fluid by scale or load cell, then converting it by a known formula.
Master-meter proving is the comparison of a test flowmeter to another flowmeter previously calibrated in one of the above methods.
CONCLUSION
Turbine flowmeters are becoming more prominent in the field of liquid flow measurement. Turbine flowmeter manufacturers continue to respond to industry interest with improvements.
In general, provings should be quite frequent in the early history of an installation. When sufficient results have been gathered to establish meter factor versus flow rate curves for each product, frequently proving can taper off unless one of the aforementioned reasons for proving occurs.
Non-invasive Flowmeter with Integrated Heat Quantity Calculation
Thermal energy is mainly distributed by fluid media to the points of consumption. The energy manager is not only interested in the total energy required, but also in the consumption of individual heat consumers and the flow of energy in the plant in general. The EESIFLOâ„¢ EF portable ultrasonic flowmeter with integrated heat quantity calculator has been developed to compliment permanently installed devices.
The flowmeter EESIFLOâ„¢ EF is especially appropriate for measurements in large variable supply networks, e.g. to register the heat distribution in a large complex of buildings or to review the heat balances in a process engineering facility. This device is particularly useful in situations where temporary, non-intrusive inspections of heat consumption and distribution need to be made quickly. The advantages of this portable instrument are its flexibility, enabling it to be used in a wide range of applications, and the low installation and running costs.
Principles of Heat Quantity Measurement
The differential method is the basis for the precise measurement of heat quantity. This method considers the enthalpy that enters and leaves a system. The difference between the two values gives the heat consumption. Since the enthalpy difference cannot be measured directly, the value is calculated from the volumetric flow, the inflow and outflow temperatures and the heat coefficient for the medium.
The newly developed flowmeter EESIFLOâ„¢ EF incorporates all these features and in contrast to conventional flow meters, it allows the user to measure heat flow and distribution from the outside of pipes without the necessity of disrupting the process in the plant. This is achieved by using a clamp-on ultrasonic flow meter together with two surface temperature sensors.
Temperature Measurement
The EESIFLOâ„¢ EF ultrasonic flowmeter features two input channels to connect resistance temperature sensors Pt100 in four wire circuit. This sensor type has been chosen because of its popularity in industrial applications and ready availability in a variety of versions. Two surface sensors are supplied with the unit to measure the temperature of the inflow and outflow. The user may, however, connect other types of sensors of a compatible type according to specific application requirements. This is particularly advantageous where temperature sensors are already installed in the pipe. In such cases, an input correction for each sensor is required to obtain a linear resistance temperature curve. These correction values can be stored in the non-volatile memory of the flowmeter and are therefore always available. When using the supplied sensors, the ability to correct may serve to compensate for the temperature gradient of the pipe.
The so-called energy temperature, which represents the temperature for the transportation of energy, is of special interest for measuring heat flow. According to Adunka[1], this temperature corresponds to the temperature in the middle of the pipe in case of turbulent flow. Under laminar flow conditions, it is more difficult to determine this temperature and the energy temperature is calculated as the mean of the temperatures of the wall and the centre of the pipe.
When using surface temperature sensors, it is the pipe wall temperature which is measured not the energy temperature. In practice however, the temperature difference is important in the calculation of heat flow not the absolute temperatures. The absolute temperatures are only required to determine the heat coefficients. Studies at the University of Rostock[2] showed that the difference between the surface temperatures approximates to the difference between the energy temperatures. The pre-condition is, that the pipe has sufficient insulation to limit the heat loss through the pipe walls. Both the inflow and outflow temperatures should always be measured with the same type of sensor.
These systems are ideal for energy efficiency optimization in industrial sectors and buildings. EESIFLOâ„¢ offers a highly accurate, low cost and robust Energy Management Solution.
The BTU (or Energy) Flow measurement systems can be readily configured for almost any size of pipe and are completely non-intrusive, since all the sensors are installed on the outside of the pipes being measured.
Advantages over traditional type flowmeters are seen by the accuracy ,sensitivity and longevity of the meters since they are able to measure both high and low flow rates with the same accuracy, due to the fact that the transit time technology is not dependant on moving parts and frictional wear and tear.
The co-efficents, which the instrument needs to know, in order to measure the heat flow of various media are pre programmed into the flowmeter.In cases where the temperatures of inflow and/or outflow are known , or are constant during the whole measuring period, you may enter these fixed temperatures manually into the instrument.
In these instances, the temperature sensors need not be connected.
the following information is available:
• Volume flow
• Heat flow
• Flow velocity
• Total flow volume or heat quantity (if total counting activated)
• Temperature T1 (inlet temperature)
• Temperature T2 (outlet temperature)
• Temperature difference T1-T2
EESIFLOâ„¢ heat meters give the option of displaying two of these measured values (one in each line of the display) and of configuring the display readings according to your requirements.
The flow measurement of the heat carrying fluid is based on the ultrasonic transit time technique. This method utilises the transmission of sound waves in the fluid. Sound pulses are sent alternatively downstream and upstream through the liquid. The ultrasonic signal has different transit times for the two directions comparable to a swimmer in a river who swims faster downstream than upstream. The resolution of the signal time difference is 0.1 ns with a transit time of the sound from 16 µs and 1.6 ms. If these values together with details of the profile of the pipe section are known, the volumetric flow rate can be calculated.
The transducers for coupling the sound signals through the pipe clamp from the outside onto the pipe ensuring that there is no disturbance to the flow nor any expensive installation costs. This method of flow measurement implies that the pipe diameter and tolerances are part of the measuring conditions. Often the inner diameter and wall thickness of the pipe are unknown although this information is required to calculate the volumetric flow from the flow velocity. The input of incorrect pipe parameters will result in measurement errors. For this reason, an device for measuring the wall thickness of the pipe was incorporated into the flowmeter.
Heat Quantity Calculation
The microprocessor within the flowmeter computes the heat flow from the measured inflow and outflow temperatures and the volumetric flow rate. The specific enthalpy and the density of the fluid can be internally calculated depending on the measured temperature.
As various liquids may be used as heat carriers, the portable ultrasonic flowmeter EESIFLOâ„¢ can be adapted for specific tasks using an in-built database. The database contains information on pipe materials and fluids frequently used and requiring measurement. As well as information on sound velocity and viscosity, the database also stores the coefficients necessary for calculating the heat quantity.
The database can be specifically adapted and extended by the manufacturer to meet specific customer requirements. It is also possible for the customer to enter set-up values and make changes to the stored data. Special software has been designed for use with a Personal Computer to generate the coefficients used for calculating the heat flow and to transfer them via a serial interface to the flowmeter where they are stored in non-volatile memory. These data are available even when the instrument has been repeatedly switched off, the batteries have been changed or a cold start has been performed.
Applications
The EESIFLO™ EF can measure volume flow, flow velocity, mass flow or heat quantity of liquids within a temperature range from -30 °C up to 130 °C. With specially designed high temperature transducers, the temperature range can be extended up to 250 °C, and for short periods up to 300 °C. The ultrasonic sensors are small, lightweight and very robust. Pipe diameters may range from 10 up to 3,000 millimetres.
The instrument can always be used where the pipewall and the liquid to be measured are sonically conductive. This is true for pipewalls consisting of homogeneous material, such as steel, synthetic material, glass or copper, and for liquids which carry not an excessive amount of solid particles or gas bubbles. There is no dependency on electrical parameters of the fluid such as conductivity or dielectric constant.
To assist the user in obtaining a complete profile of the flow conditions in the plant, the EESIFLOâ„¢ EF features an in-built data logger which can record up to 150,000 measuring values and up to 15 different sets of site parameters. The data can either be transferred to a Personal Computer (PC) or to a printer as numerical values or in graphic format.
The device allows the operator dialogue in different languages and guides the user through the menus for parameter set-up, measurement or data storage.
The instrument can feature an integrated measuring point multiplexer which allows for the connection of up to four independent flow sensor sets with one transmitter. EESIFLOâ„¢ automatically recognises the connected sensors through Intelligent Sensor Identification. This means that all calibration parameters are stored in the sensor and automatically transferred to the instrument at the time when the sensors are connected.
EESIFLOâ„¢ can also be fitted with various process inputs and outputs. The instrument can be equipped with a maximum of four temperature inputs whereby the temperatures can be freely assigned to the available flow channels. This makes it possible to configure, for example, a 3-channel heat flow measuring system with a common inlet temperature and three independent outlet temperatures