This study was conducted to examine the effect of flow turbulence on sound waves propagating across a velocity field. The resulting information can be used to determine the potential for increasing the accuracy of an ultrasonic flowmeter, and understand the data scatter typically seen when using an ultrasonic flowmeter. A modification of the Ray Trace Method was employed which enabled the use of multiple rays in a very fine grid through a flow field. This technique allowed for the computation of the statistical variation of the propagation times for sound pulses traversing a flow field. The statistical variation was studied using two flow fields: 1) a uniform flow field with a superimposed vortex street and 2) an experimentally measured channel flow. The uniform flow field with a superimposed vortex street allowed for the examination of the effects of a large-scale flow structure on sound wave propagation, and for the verification of the analysis technique. Next by using the measured turbulent channel flow, as an example, the statistical variation of sound pulse propagation time was computed for flow likely to be encountered in actual flow measurement situations. Analysis was also conducted to determine the maximum allowable repetition rate of measurements with regard to the optimal time of flight measurements. Both the propagation time of a sound pulse moving across a uniform flow field with superimposed vortex street, and the resultant computed flow were observed to vary at the same frequency of the vortex street. Further, the magnitude of the variations was proportional with the strength of the individual vortices in the vortex street. A sound pulse propagating back and forth across a measured turbulent channel flow, afforded individual time difference variation from the mean propagation time of up to 5%. It was shown that a minimum variation occurred when the sound pulses were transmitted at a 75 degree angle to the flow axis. It was also determined that the average speed of sound in a flow field affected the final flow measurements by decreasing the measured delta time difference between the upstream and downstream propagating sound waves, and therefore the measured flow. The width of the sound path also contributed to decreasing the variation of the individual measurements by integrating over a larger sound path. These findings suggest that turbulence in a flow field affects ultrasonic flowmeter measurements by creating differences in the propagation times of individual sound pulses. Thus, turbulence and large-scale flow structures can result in variations in volumetric flow rate determination made by an ultrasonic flowmeter system.

This thesis presents a procedure to optimise the shape of a coaxial transducer ultrasonic flow meter. The technique uses separate numerical simulations of the fluid flow and the ultrasound propagation within a meter duct. A new flow meter geometry has been developed, having a significantly improved (smooth and monotonic) calibration curve. In this work the complex fluid flow field and its influence on the propagation of ultrasound in a cylindrical flow meter duct is investigated. A geometric acoustics (ray tracing) propagation model is applied to a flow field calculated by a commercial Computational Fluid Dynamics (CFD) package. The simulation results are compared to measured calibration curves for a variety of meter geometries having varying lengths and duct diameters. The modelling shows reasonable agreement to the calibration characteristics for several meter geometries over a Reynolds number range of 100...100000 (based on bulk velocity and meter duct diameter). Various CFD simulations are validated against flow visualisation measurements, Laser Doppler Velocimetry measurements or published results. The thesis includes software to calculate the acoustic ray propagation and also to calculate the optimal shape for the annular gap around the transducer housings in order to achieve desired flow acceleration. A dimensionless number is proposed to characterise the mean deflection of an acoustic beam due to interaction with a fluid flow profile (or acoustic velocity gradient). For flow in a cylindrical duct, the 'acoustic beam deflection number' is defined as M g* (L/D)^2, where: M is the Mach Number of the bulk velocity; g* is the average non-dimensionalised velocity gradient insonified by the acoustic beam (g* is a function of transducer diameter - typically g* = 0.5...4.5); L is the transducer separation; and D is the duct diameter. Large values of this number indicate considerable beam deflection that may lead to undesirable wall reflections and diffraction effects. For a single path coaxial transducer ultrasonic flow meter, there are practical limits to the length of a flow meter and to the maximum size of a transducer for a given duct diameter. The 'acoustic beam deflection number' characterises the effect of these parameters.

[pt] No Brasil, a medição de petróleo é regulada pela ANP e pelo INMETRO. O Regulamento Técnico de Medição de Petróleo e Gás Natural exige que os medidores de vazão de petróleo sejam calibrados nas condições mais próximas das encontradas no local de medição, tanto para o fluido (massa específica e viscosidade) quanto operacionais (vazão, pressão e temperatura). Replicar todas estas condições nos laboratórios de calibração nacionais é muito complicado e dispendioso. Assim, neste trabalho foram avaliados os comportamentos de 7 medidores Altosonic V calibrados com 5 tipos de fluidos (oural, condensat, fuel, heavy fuel e água). Os fatores de calibração dos medidores foram submetidos a avaliações estatísticas e curvas de calibração foram ajustadas buscando identificar possíveis tendências de comportamento. Após supor-se que vazões e viscosidades teriam influência na aleatoriedade dos fatores, chegou-se à conclusão que, utilizando as calibrações de fábrica (fingerprint) do medidor, que cobrem toda a faixa de viscosidade e vazão de medição com a utilização do número de Reynolds, os limites requeridos por norma de erros para medição fiscal de são atendidos. Assim, sugere-se que as verificações periódicas do Altosonic V sejam feitas com o fluido disponível no laboratório de calibração, observando a coerência dos fatores obtidos nesta calibração e na calibração inicial, buscando o atendimento aos limites legais da aplicação. / [en] In Brazil, the measurement of oil is regulated by ANP and INMETRO. The Technical Regulation for Petroleum and Natural Gas requires that the oil flow meters be calibrated in conditions close to those found at the measurement site, both regarding the fluid (density and viscosity) and operational conditions (flow rate, pressure and temperature). It is very difficult to replicate all these conditions in national calibration facilities and expensive too. Thus, this study evaluated the behavior of 7 Altosonic V meters calibrated with 5 types of fluids (oural, condensat, fuel, heavy fuel and water). The calibration factors of the meters were subjected to statistical evaluation and calibration curves were fitted looking for possible behavior trends. Supposing that flow rates and viscosities would influence randomly the factors, a conclusion was reached that, by using the factory meter calibrations (fingerprint), that cover the entire measurement range of viscosity and flow rates, by using Reynolds number, the required by norm fiscal measurement error limits are met. Thus, it is suggested that periodic checks of Altosonic V could be made with the fluid available in the calibration facility, verifying the consistency of the factors obtained in this calibration and in the fingerprint, aimed at complying with the legal limits of the application.

In the first part of master thesis is presented general introduction to district heating system (DHS) and hydraulic calculation for DHS. The next part deals with analysis operation of DHS and the pressure diagram for certain time interval. Subsequently, the thermohydraulic characteristics for the hydraulic main branch (comparing manual calculation with software calculation) and also the selected thermal and hydraulic characteristics for the whole DHS are shown. The last part is focused on the determination of the amount of heat supplied based on the ultrasonic flowmeter and the temperature probes. Subsequently, the computer simulation is also carried out, aiming at approximating the real heat supply from heat source to solved thermal network in winter.

The diploma thesis deals with the design of the heating and cooling system, inclu-ding hot water preparation for the administrative part of the production hall. The first part of the thesis briefly discusses the history of heating and cooling of office buildings, legislative requirements and current solutions. The second part contains the design of the entire heating and cooling system with heat pump as a source of heat and cold. The final part of the thesis describes the experimental measure-ment and evaluation of the efficiency of the ice rink source.