Performance Calculation Model Research Articles

Assessing the accuracy of a simplified building energy simulation model using BESTEST: The case study of Brazilian regulation

This paper reports the use of an internationally recognized validation and diagnostics procedure to test the fidelity of a simplified calculation method. The case study is the simplified model for calculation of energy performance of building envelopes, introduced by the Brazilian regulation for energy efficiency in commercial buildings. The first step of the assessment consisted on evaluating the simplified model results using the BESTEST. This paper presents a straightforward approach to apply the BESTEST in other climates than the original one (Denver, USA). The second step of the assessment consisted on applying the simplified model to evaluate four building typologies, and compare the results with those obtained using a state of the art building energy simulation (BES) program. For some BESTEST cases, the simplified model presented results inside of a confidence interval calculated by the authors. However, the simplified model was found to yield significant difference in the four building typologies analysed. Moreover, in all four building typologies analysed, the simplified model led to a lower energy efficiency label when compared to the label obtained using BES. The paper concludes that the simplified model may require improvements to properly indicate the actual energy performance of commercial building envelopes.

On-line monitoring the performance of coal-fired power unit: A method based on support vector machine

This paper introduces a novel on-line monitoring performance method of coal-fired power unit. Support vector machine (SVM) is used to predict the unburned carbon content of fly ash in the boiler and the exhaust steam enthalpy in turbine, which are two difficulties in the real time economic performance calculation model in coal-fired power plant. Comparison between the output of SVM modeling and the experimental data shows a good agreement, and compared with conventional artificial neural network techniques, SVM can achieve better accuracy and generalization. This presented monitoring method is proven by the results of application cases in a practical coal-fired power plant.

Durability design of concrete structures—Committee report 130-CSL

The idea of the durability design of concrete structures is developed as statistical theory which is based on the probability of failure taking into account the time as a parameter of the performance function and of the loading function. The generalised loading includen environmental effects into the structure like mechanic loading and weathering (sun, temperature changes, frost, moisture, pollutants, oxygen etc.). As generalised capacities like loading capacity, tightness, deflections, cracking, smoothness of the surface and visual fitness are treated. The statistical theory is transformed into practical deterministic durability design applying partial safety factor method. Important addition into the ordinary partial safety factors is the lifetime safety factor which is introduced into a design for first time here. The static and dynamic performance parameters and the durability performance parameters are combined together in the final phase of design. Performance and service life calculation models is introduced into design method, and presented for six decradation processes. The article is based on the report of RILEM TC 130—CSL [31], where the author was serving as chairman.

A model for calculation of steam injector performance

Steam injectors can be used in many applications, but especially for security water injection in steam generators of nuclear reactors. Using a one-dimensional model, a steam injector with a centered liquid supply has been simulated. General relationships are presented from the nozzle exit to the steam injector outlet. It is shown that the flow contains a condensation shock. To achieve modelling of the mixing zone, and empirical correlation giving an equivalent pressure with value of condensation rate is found using experimental results obtained at the CETHIL. A parametric study is then made to determine the influence of significant parameters and the functioning range of the steam injector. Calculated values are compared with experimental results and are found to be in good agreement.

95/03345 A useful model for the calculation of the performance of batch and continuous jigs

95/03345 A useful model for the calculation of the performance of batch and continuous jigs

A Theoretically Based Mathematical Model for Calculation of Electrostatic Precipitator Performance

A mathematical model is described which relates collection efficiency to precipitator size and operating parameters. Procedures are given for calculating particle charging rates, electric field as a function of position in wire-plate geometry, and the theoretically expected collection efficiencies for various particle sizes and precipitator operating conditions. Methods are proposed for empirically representing the losses in collection efficiency caused by non-uniform gas velocity distributions, gas by-passage of the electrified regions, and particle reentrainment due to rapping of the collection electrodes. Incorporation of these proposed techniques into a mathematical model of precipitator performance results in reduction of the theoretically calculated overall collection efficiencies. The reduced efficiencies are compared with those obtained from measurements on precipitators treating flue gas from coal-fired generating stations. The effects of changes in particle size distributions on calculated collection efficiencies obtained from the mathematical model are also presented.

Discussion of incorrect equations in "A model for calculation of magnetron performance"

An error in the above-mentioned paper is noted. It is shown that the general conclusions of the paper remain valid, while the accuracy of the calculated dynamic impedance is substantially improved when the error is corrected.

A model for calculation of magnetron performance

A simplified model of the space charge in a magnetron is proposed, and the performance of the magnetron is calculated; the method differs from that of Welch in the space charge density assigned to the and from that of Hull in using energy conservation instead of the principle of induction to identify the operating point. The method is tested by applying it to four known magnetrons, covering a wide range of frequencies, operating voltages and power levels. In all four cases the method predicts the output power correctly within ± 0.5 dB, and the voltage within ± 2 percent, at the nominal operating current and field. It also predicts the frequency pushing, and provides information on the relative phase of the spokes, and other parameters. The spoke phase is found to be always within the range -20° to -60°.