Calibration fluids

Another fluid standard used in the literature is a suspension of colloidal noble-metal particles in a solvent [96]. The method is explained starting on p. 134. The application of such calibration methods is in particular feasible, if polymer solutions are studied and thus the measurement of a calibration fluid does not require to modify the setup. 

For benzene - one of the best-suited calibration fluids - the error is 4% at room temperature. For polymers errors of up to 65% (polystyrene at room temperature) have been verified both theoretically and experimentally. 

Pressure and air-assist atomizers. Derived from calibrating fluid (MIL-F-7041 l)-air spray data using Parker Hannifin spray analyzer... 

To avoid the apparent complications with absolute rheologic measurement techniques, a number of investigators (4,5). have used relative measurement systems to make rheologic measurements. The major difference between the relative and absolute measurement techniques is that the fluid mechanics in the relative systems are complex. The constitutive equations needed to find the fundamental rheologic variables cannot be readily solved. Relative measurement systems require the use of Newtonian and non-Newtonian calibrations fluids with known properties to relate torque and rotational speed to the shear rate and shear stress (6). 

The use of Newtonian and non-Newtonian calibration fluids allows the determination of constants relating the measured torque and speed to viscosity and shear rate. Silicone oil and glycerin (Newtonian) with viscosities of 1.024 and 0.912 Pa s, respectively, were used to determine the impeller constant, c, while xanthan and guar gum solutions (non-Newtonian) were used to determine the shear rate constant, k. 

For the impeller ribbon viscometer technique, the power number of an impeller is inversely proportional to the impeller Reynolds number (Eq. 1). As the impeller rotational speed increases, the flow will gradually change from laminar to turbulent, passing through a transition region. Parameter c can be obtained from the calibration fluids. If the same value for c is assumed to apply to a non-Newtonian fluid, then Eq. 4 can be used to calculate the apparent viscosity of that fluid. The range of the impeller method is determined by the minimum and maximum torques that can be measured (5). 

Using Newtonian calibration fluids the value for the constant, c, was determined to be 135 (12). The deviation in the value of c between Reynolds numbers from 1 to 10 was <5%. 

Index Entries Distiller s grain slurries rheologic properties wet grains calibration fluids helical impeller. 

The impeller method is a technique commonly used to determine rheologic properties of fluids subject to particle settling. The impeller method utilizes a viscometer along with Newtonian and non-Newtonian calibration fluids to obtain constants that relate shear stresses and shear rates to experimentally measured values of torque and rotational speed. Newtonian calibration fluids are used to determine the impeller constant, c, and non-Newtonian calibration fluids are used to calculate the shear rate constant, k. These constants are then used to aid in the determination of rheologic properties of a selected non-Newtonian fluid, such as wet grains. 

Howeever, inaccuracies were apparent for non-Newtonian calibration fluids and distiller s grain slurries up to 10% of the full-scale torque. Therefore, only measurements above 10% and below 90% torque were utilized for guar gum solutions and distiller s grain slurries. The experiments were conducted at a constant temperature of 25 0.1°C. 

Newtonian and non-Newtonian calibration fluids were used to determine the necessary calibration constants for the impeller method. It has been previously determined that the impeller method is only valid for a Reynolds number (Re) <10. Impeller rotational speed and torque data from Newtonian calibration fluids of known viscosity were employed to determine the Newtonian calibration constant, c. Cone-and plate-viscometer data from non-Newtonian calibration fluids were used to determine a viscosity vs shear rate relationship. Impeller rotational speed and torque data of the non-Newtonian calibration fluids combined with a determined viscosity vs shear rate correlation were utilized to calculate the shear rate constant, k. The impeller method calibration constants allow the calculation of viscosity, shear rate, and shear stress data of non-Newtonian suspensions. Metz et al. (2) have thoroughly discussed the equations utilized in the impeller method. 

To calculate the shear rate constant, k, a relationship must be established between shear rate and viscosity of a non-Newtonian calibration fluid. A cone-and-plate viscometer is used to determine a correlation between shear rate and viscosity that can be fit to a power law model. The power law correlation is then applied to viscosity data calculated from the impeller viscometer and Eq. 4. The shear rate constant can be calculated as follows ... 

Increasing production volumes resulting in lower prices of devices will push the whole market and open additional ones. The expectations of using small samples as well as small reagent volumes, minimization of time expenditure of skilled clinical people, minimization of calibration fluid consumption and waste are still key advantages of such a micro technology. 

Calibration fluids were water, ethylene glycol, and liquid oxygen. The results shown in Table II represent at least two independent measurements for each viscosity reported. 

A comparison of experimental CO2 viscosities obtained over a wide range of temperatures and pressures with that of previously reported viscosites (14) taken over that same range is illustrated in Figure 3. The three different experimental curves shown correspond to a particular calibration fluid, water or CO2, or the constant derived from the Navier-Stokes equation. 

Use Organic synthesis, refrigerant, motor fuels, aerosol propellant, synthetic rubber, instrument calibration fluid. 

Many experimental apparatus require calibration with substances whose properties are accurately known. Water (see Section 1.2.3) is the most common calibration fluid for liquid-phase properties, but other fluids such as toluene are sometimes used. Vapor-phase properties are often calibrated with helium, argon, nitrogen, or air. An lUPAC book [92] describes recommended... 

Another method of measuring density relies on the change in the resonant frequency of a tube (often U-shaped) when it is filled with a fluid. Vibrating-tube densimeters are commercially available they can be a convenient measuring tool in many circumstances. These instruments must be calibrated (usually with water if liquids are being measured, although for liquids whose density is significantly different from water a calibration fluid with a similar density is preferable) at the temperature and pressure of interest. While the precision of these instruments is often better than... 

The calibration fluid is stirred. Probes showing less than 0.5% change in reading are retained. 

The quantity on the right side of this equation must be evaluated for the test fluid and the calibration fluid. This ratio (i.e., test fluid/calibration fluid) represents the calibration factor, which one must multiply by the mass flow rate of the calibration fluid at a given rotameter float height to obtain the mass flow rate of the test fluid when the float is in the same position. 

Biochemical analysis on nanoliter scale is precisely carried out by micrototal analysis system (pTAS) which consists of microreactors, microfluidic systems, and detectors. Performance of the pTAS depends on micromachined and electrochemically actuated micropump capable of precise dosing of nanoliter amounts of liquids such as reagents, indicators, or calibration fluids [28]. The dosing system is based on the displacement of the liquid from a reservoir which is actuated by gas bubbles produced electrochemically. Electrochemical pump and dosing system consist of a channel structure micro-machined in silicon closed by Pyrex covered with novel metal electrodes. By applying pulsed current to the electrodes, gas bubbles are produced by electrolysis of water. The liquid stored in the meander is driven out into the microchannel structure due to expansion of gas bubbles in the reservoir as shown in Fig. 11.8. 

Brookfield viscosimeters also belong to the group of rotational viscosimeters. In contrast to the devices described earlier, this viscosimeter does not generate a defined shear field. The Brookfield viscosimeter consists mainly of a disc or a pin that is rotating with a defined velocity in the sample fluid. The torque that is required to achieve this rotational speed directly yields a viscosity through comparison with a calibration fluid. The range of measurable viscosities can be adjusted by variation of the disc geometry. 

The determination of the viscosity with this device is done according to DIN 53015. The relative flow around the sphere is similar to the flow through a gap. In the Hoppler viscosimeter, the slope of the falling tube is 10° and its diameter is 16 mm. In this case, a sphere with a diameter of approx. 15 mm is used to achieve a sliding state. Evaluation of the state of flow is very difficult and in some cases impossible. For this reason, a calibration of the device with a calibration fluid is very important. With these calibration measurements, a constant K can be obtained ... 

For both methods, maintaining of a constant temperature is of great importance. A good review of calibration fluids for viscosimeters is given in [25]. 

A calibration system, capable of performing 20 calibration of 100 nl each, must contain 2 pi of calibration fluid. This 2 pi of calibration fluid is stored in the meander channel. A meander channel of 100 pm x 200 pm must therefore have a length of 10 cm. To push all the calibration fluid out of the meander channel, there must be at least 2 pi of electrolyte in the reservoirs. To have sufficiently electrolyte left for electrolysis when the 20 calibration is performed a reservoir volume of 5 pi is chosen. 

Kestin et al (1980) used triple-distilled water as the calibration fluid. 

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