Mass flow measurement steps

Step 2—acquisition of mass flow rate data some experimental precautions must be taken in order to obtain the proper data since the objective is to determine the two-phase critical flow rate by measuring the emptying time ATe, and... 

The objectives of this project are consistent with the objectives (1) and (4) above. The general objective of this project has been to verify a new measurement method to analyse the thermochemical conversion of biofuels in the context of PBC, which is based on the three-step model mentioned above. The sought quantities of the method are the mass flow and stoichiometry of conversion gas, as well as air factors of conversion and combustion system. One of the specific aims of this project is to find a physical explanation why it is more difficult to obtain acceptable emissions from combustion of fuel wood than from for example wood pellets for the same conditions in a given PBC system. This project includes the following stages ... 

Two new efficiencies are deduced in the context of the three-step model that is, conversion efficiency and combustion efficiency, which can be very useful in the optimization of existing PBC system and in the design of new advanced environmental-friendly PBC systems. However, to be able to quantify these new parameters, the mass flow and stoichiometry of the conversion gas need to be measured. 

Based on the three-step model, a hypothetical mathematical model has been formulated to measure the mass flow and stoichiometry of conversion gas as well as the air factors of conversion and combustion system. 

Some new concepts have been deduced in the context of the three-step model, for example, the conversion system, the conversion gas, the conversion efficiency, and the combustion efficiency. Two new physical quantities have been associated with the conversion gas. The physical quantities are referred to as the mass flow and the stoichiometry of the conversion gas. The conversion efficiency is a measure of how well the conversion system performs, that is, the degree of solid-fuel convertibles that are converted from the conversion system to the combustion system. The combustion efficiency is defined as the degree of carbon atoms being oxidised to carbon dioxide in the combustion system. In other words, the combustion efficiency is a measure of the combustion system performance. 

However, it is possible to directly or indirectly measure the mass flux (mass flow) of conversion gas. Several authors have measured the mass loss of the fuel bed as function of primary air velocities and biofuel [12,33,38,53] by means of a balance. Most of them have used the over-fired batch conversion concept. They utilise the relationship illustrated by Eq. 16 (formulised in amounts instead of flows) above and the assumption that no ash is entrained. As a consequence, the mass loss of the batch bed with time equals the conversion gas. In the simple three-step model [3], an assumption of steady state is made, which is not relevant for batch studies. If it is practically possible, the method of using a balance to measure the conversion gas rate is especially appropriate for transient processes, that is, batch processes. 

Flow measurement will be performed in most cases at the low-pressure side of a process step. For this reason, such devices are only available for moderate pressures. In research, the use of flow measurement devices in the high-pressure loop of a process step in small-scale plants is necessary to check the mass balance. These applications normally need the measurement of small mass-flow rates. Therefore the development of these devices for higher pressures ends normally in the range up to approx. 400 bar. Different kinds of measuring principles are in applied. The different methods of flow measurement are presented in Table 4.4-2, together with the range of pressure. 

Preparations, conducted at 40°C, take place in a stirred glass vessel equipped with sensors (pH, temperature, torque motor measurement of the stirrer shaft) allowing the control of the diffrrent steps of the preparation. Reactants pretreated at Ae preparation temperature, are introduced in the reactor at defined mass flow rates by means of calibrated peristaltic pumps. Reactants can be introduced in the reactor, successively (batch process) or simultaneously (semi-continuous process). In the later case reactants are mixed in the feeding pipe. 

The measurement of melt mass-flow rate and density is usually the first step in the specification and identification of polyethylene materials. It should be noted that the density of the base polymer differs from the density of the finished geomembrane mixed with carbon black. The confusion, which can occur in the classification of the PE resin, has briefly been dealt with in Sect. 2.1. As a rule, only geomembianes coloured black by carbon black, and not their natural-coloured resin, reach a density which properly meets the classification of HOPE plastic material (see Sect. 2, Tables 2.2 and 2.3). However, one may not consider these classification limits as strict technical criteria even if the density of the black geomembianes is just below 0.940 g/cm, it may correspond to what is ealled HOPE geomembrane over the whole spectrum of its characteristics. 

Fig. 10 Above chemical structure of the PEO-PCl-ssDNA conjugate (with the 22-mer oligonucleotide sequence arm ) and representation of a DNA micelle. Below DNA-controlled attachment of block copolymer micelles on surfaces monitored by measuring the time-dependent frequency and dissipation changes induced by mass adsorption on the QCM sensor in the flow mode. Step 1 addition of the anchor -thiolated oligonucleotide. Step 2 addition of the micelles bearing the linker oligonucleotide, followed by rinsing. Step 3 treatment with the as-arm oligonucleotide (competitive displacement to detach the micelles) [84] (figure adapted with permission of Wiley-VCH)...

The gravimetric method depends on the sampling of flowing, particulate-laden gas from different positions across the exhaust gas duct and the determination of the mass of the particulate material. The sample is collected over a certain time period from each point. The volumetric gas flow is measured. The result is obtained by the following steps ... 

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