1,720,973 research outputs found
Car air conditioning system
No full textConsulta en la Biblioteca ETSI Industriales (Riunet)Sánchez Espín, C. (2013). Car air conditioning system. https://riunet.upv.es/handle/10251/32354.Archivo delegad
The Influence of the Spatial Discretization Methods on the Nozzle Impulse Flow Simulation Results
No full textAbstractVibration and noise caused by pressure pulsations in the volumetric compressor manifolds are one of the most important problems in the volumetric compressor's operation. For pressure pulsation attenuation, different types of mufflers are applied using a design based on the Helmholtz resonator approach. This design is not effective for variable revolution speed compressors and in this case other pressure pulsations attenuation methods are required. Nowadays, due to the increasing application of variable speed compressors new design methods are developed. One of the possibilities to attenuate pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow directly after the compressor outlet chamber. It is well known that a nozzle can attenuate pressure pulsations, however, it increases the compressor power at the same time. The main criterion for the nozzle selection is the highest possible attenuation of pressure pulsations coupled with the lowest possible effect on the compressor pumping power. In some cases 25-30% of the pressure damping is good enough to reach the standard requirements. The method applying CFD impulse flow simulations has been developed for the estimation of the nozzle influence on pressure pulsations for all frequencies. The FLUENT/ANSYS software has been used for the simulation. The CFD simulation requires a lot of effort for proper selection of the boundary conditions, solution methods, turbulence models, discretization methods, mesh design etc. The results are in some cases surprisingly different between different methods. In this paper the flow simulations for the nozzle flow with the connecting pipe using impulse function as a mass inflow excitation is shown. In this investigation project various models and methods have been compared and results in 2D and recalculated into 0D time only dependent functions are presented
Calculation, desing and optimization of condenser for a food industry
No full textConsulta en la Biblioteca ETSI Industriales (Riunet)[EN] In this project is tried to explain the working of a condenser, as well as the
types of condenser that we can find in the typical applications and especially in
the food industry. Also we are going to improve the design using the less
quantity of matter for transfer the most quantity of heat possible, by means of
a really powerful Excel program that we have implemented for this case.
Furthermore we will explain how to do the calculations in order to obtain the
finally design of the condenser; also we will include the plans of the condenser
finally designed.Vicente Martin, S. (2014). Calculation, desing and optimization of condenser for a food industry. https://riunet.upv.es/handle/10251/35526.Archivo delegad
The CFD Based Estimation of Pressure Pulsation Damping Parameters for the Manifold Element
No full textAbstractVibrations and noise caused by the pressure pulsations in the volumetric compressor manifolds have a high impact on the compression power requirement and the reliability of manifold operation. For the pressure pulsations attenuation, different types of mufflers are applied using a design based on the Helmholtz resonator model approach. This is particularly effective for the constant revolution speed compressors. For the widely introduced variable revolution speed compressors, other pressure pulsation attenuation methods are required. One of the possibilities to attenuate the pressure pulsations over a wide range of frequencies is the introduction of specially shaped nozzles in the gas duct flow. The CFD impulse flow simulations can be used as a tool for the estimation of the nozzle influence on the pressure pulsations damping. The direct 3D or 2D CFD simulation results are difficult to apply for this estimation. A new method has been worked out to obtain the damping coefficient for the diverse nozzle type, using the numerical simulation results of the impulse flow propagation. In this paper the application of the Levenberg-Marquardt method for damping parameter estimation is shown. This method allows fitting the attenuation curves described by damped equations to obtain damped oscillation functions from CFD results. In this paper the CFD based estimation method of pressure pulsation damping parameters is illustrated with an example of its application for a nozzle
Selected issues of the multistage evaporator thermodynamics
Get PDFThe well known multi-stage evaporation is an energy efficient process applied for concentrate juice production. There are however, some important issues concerning its thermodynamics which are not commonly revealed by the producers. The multi-stage design requires a properly designed control system to achieve maximum efficiency and capacity of the evaporator. In this paper, results of the author’s practical experience concerning the thermodynamics of the operation of the multi-stage evaporator in the industrial environment are presented. The report describes problems concerning the steady-state evaporator operation, choice of control parameters, and thermodynamics of the transient states
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The hybrid sorption-compression refrigeration cycle control system
Get PDFThe requirements for environmentally friendly refrigerants promote the application of both CO2 and water as working fluids. Both solutions have disadvantages resulting from the high temperature limit for CO2 and the low temperature limit for water. This can be avoided by the application of the hybrid adsorption-compression system, where water is the working fluid in the adsorption cycle which is used to cool down the CO2 compression cycle condenser. The adsorption process is powered with a low-temperature renewable heat source such as solar collectors or waste heat sources. This solution has been developed by the authors of this paper and has not been reported in any other literature source. The different ambient conditions over the course of the year require specially designed controlprocedures and the automation system. The algorithm has to control positive and negative heat sources operation, valve actions, pumps, fans and compressor operation. In the control algorithm, the ambient temperature and solar conditions or other waste heat sources have to be introduced as control parameters, optimised to achieve maximum efficiency of the whole system. The refrigeration effect as a parameter has to be considered both for the refrigeration capacity as well as the CO2 evaporation temperature
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