Mass Flow Data Research Articles

Estimation of extreme mass flowrate in district heating systems

This paper focuses on how extreme mass flowrate conditions, i.e. T year events, in district heating systems can be estimated by extreme value analysis, namely the method based on annual maximum values and the peaks over threshold (POT) method. Only a few years of mass flowrate data are available, which is far too short a time to be of any practical use for extreme analysis. However, 42 years of climate data are available, which are used to generate daily mass flow data using an autoregressive external (ARX) model. The simulated mass flow contains uncertainty which must be considered in the analysis. This is not possible using a traditional analysis without some modifications. Furthermore, it is also of interest to consider the uncertainty in the climate. A bootstrap technique is applied in order to answer these questions and a comparison is made of the traditional analysis and the bootstrap approach. The results show that when using the bootstrap method the estimated T year events and their uncertainties are always higher compared to traditional methods, whether based on the annual maximum or the POT method. The difference is, however, quite moderate in most cases. The POT method yields somewhat higher estimates than the annual maximum method. It turns out that the predicted load in severe cold spells is not drastically higher compared to, for example, what has been experienced in Reykjavik over the last ten years when the climate has been quite normal. For instance, the 100 year event is estimated to be approximately 20 per cent higher than the average maximum mass flowrate during the last ten years.

Reconciliation of mass flow rate measurements in a chemical extraction plant

AbstractSince measurements of flow rates in a steady state chemical process are subject to errors, the laws of conservation and other constraints are violated. Total mass flow data from a chemical extraction plant are used to determine whether the process operated at steady state and to estimate the variances of the measurements. The data are then reconciled so as to minimize the weighted sum of squares of the adjustments and to test for gross error. Deletion of either of two particular flow rates is shown to remove all of the apparent gross errors in the data.

Unique Conveyor Massflow Measurement and Mass Balancing Techniques

This paper describes the development and testing of an integrated plant-wide materials massflow measurement and reporting system. The system, which employs some unique features, was developed to meet the needs of mineral processing plants, particularly those that employ a large number of inclined conveyors.The system collects massflow data from a large number of massflow transducers and manipulates, analyses, archives and produces printed reports of these data.During the development of the system use was made of a technique whereby the power drawn by an inclined conveyor drive motor was used to provide a very low-cost massflow measurement. Considerable attention was paid to this aspect and the applicability of this technique is described in some detail.The prototype system was installed on a diamond mine and has proved to be both reliable and useful. The mine staff are now using the system on a day-to-day basis.

Effect of an industrial ammonia discharge on the dissolved oxygen regime of the Willamette river, Oregon

Studies completed by the Department of Environmental Quality demonstrate that an industrial discharge of 7000–10,000 kg day −1 ammonia nitrogen can exert a very great impact on the oxygen regime of the lower Willamette River, Oregon through the microbially mediated process of nitrification. This conclusion is based upon the following evidence: (1) inorganic nitrogen mass flow data; (2) measured reductions in Willamette River dissolved oxygen during ammonia discharge as compared to non-discharge conditions; (3) the presence of nitrifying bacteria in mud and attached to aquatic vegetation and river cobbles; (4) verification of a dissolved oxygen model based upon nitrification as a primary ammonia sink and a dominant deoxygenation process; and (5) 15N heavy isotope tracer studies indicating significant conversion of ammonia to nitrate. An analysis of the data indicates that the observed average increase of 15% in dissolved oxygen saturation of the lower river during the period 1973–1979 is primarily a result of a drastic reduction of an industrial ammonia discharge in a relatively shallow surface active reach of the lower Willamette River, Oregon, U.S.A.

Superfluid onset in4He films adsorbed on pyrolytic graphite

Third-sound velocities and superfluid onsets have been studied for /sup 4/He films adsorbed on pyrolytic graphite. The present onset data are compared with previous experiments on graphite substrates. The third-sound onset data are found to be significantly different from superfluid mass-flow and heat-flow data. A value of 3.19 +- 0.52 x 10/sup -9/ g cm/sup -2/ K/sup -1/ is obtained for the superfluid arreal density at onset divided by the transition temperature. This value is consistent with the Kosterlitz-Thouless-Nelson picture of the phase transition in a two-dimensional superfluid.

Superfluid onset in 4He films adsorbed on pyrolytic graphite

Third-sound velocities and superfluid onsets have been studied for4He films adsorbed on pyrolytic graphite. The present onset data are compared with previous experiments on graphite substrates. The third-sound onset data are found to be significantly different from superfluid mass-flow and heat-flow data. A value of 3.19±0.52×10−9 g cm−2 K−1 is obtained for the superfluid areal density at onset divided by the transition temperature. This value is consistent with the Kosterlitz-Thouless-Nelson picture of the phase transition in a two-dimensional superfluid.

Estimation of interlocking mass-balances on complex mineral beneficiation plants

The difficulties encóuntered when sampling mineral processes for a detailed analysis in terms of interlocking mass-balances are outlined. The calculation of an overall balance from the process data is examined and a statistical method of taking into account all the data simultaneously, using computer programs, is introduced where weighting factors are used to specify the degree of confidence applicable to individual measurements. The estimation method has been developed for both the linear case involving mass-flow data and a non-linear case, where process measurements in terms of mass flow, pulp density and size/assay distribution are available. Practical results for both the above cases are given.