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We have developed a new automatic apparatus for the measurement of the phase equilibrium and pVT properties of natural gas mixtures in our laboratory. Based on the isochoric method, the apparatus can operate at temperature from 200 K to 500 K at pressures up to 35 MPa, and yield absolute results in fully automated operation. Temperature measurements are accurate to 10 mK and pressure measurements are accurate to 0.002 MPa. The isochoric method utilizes pressure versus temperature measurements along an isomole and detects phase boundaries by locating the change in the slope of the isochores. The experimental data from four gas samples show that cubic equations of state, such as Peng-Robinson and Soave-Redich-Kwong have 1-20% errors in predicting hydrocarbon mixture dew points. The data also show that the AGA 8-DC92 equation of state has errors as large as 0.6% when predicting hydrocarbon mixture densities when its normal composition range is extrapolated.

We have developed a new automatic apparatus for the measurement of the phase equilibrium and pVT properties of natural gas mixtures in our laboratory. Based on the isochoric method, the apparatus can operate at temperature from 200 K to 500 K at pressures up to 35 MPa, and yield absolute results in fully automated operation. Temperature measurements are accurate to 10 mK and pressure measurements are accurate to 0.002 MPa. The isochoric method utilizes pressure versus temperature measurements along an isomole and detects phase boundaries by locating the change in the slope of the isochores. The experimental data from four gas samples show that cubic equations of state, such as Peng-Robinson and Soave-Redich-Kwong have 1-20% errors in predicting hydrocarbon mixture dew points. The data also show that the AGA 8-DC92 equation of state has errors as large as 0.6% when predicting hydrocarbon mixture densities when its normal composition range is extrapolated.

The work explains how the dynamics of the release of water vapors from flux during the Control Atmosphere Brazing influences the process conditions important for the quality of the brazed product. The process involves sequential events such as continuous ramp-up heating, flux and filler melting, reactive flow, isothermal dwell and rapid quench solidification performed under the controlled atmosphere. During this complex process effluents are released. Some effluents are detrimental for the product quality (water vapor) and some are harmful for the environment (HF). We selected to study water vapor emissions with an objective to quantify these emissions and to consider their influence on the manufacturing process. Experiments were conducted using different fluxes. Findings are presented to compare the vapors released in each case. The objective is not necessarily to develop a metric for sustainability, but to understand the kinetics of an effluent release. A simple predictive model has been devised to approximate experimental data behavior. The data from the TGA analysis obtained from other sources, and the dew point temperature history from the controlled atmosphere brazing experiments performed in course of this work, have been used for the purpose of comparison and analysis.

The hygroscopic and electrical resistance characteristics of lithium chloride are investigated. Then an evaluation is made of the lithium chloride characteristics that would be suitable in development of a dew point hygrometer with measurement accuracy of + 0. 3 c. The development of a 12 volt battery-powered hygrometer is presented with circuit details and performance characteristics. Lithium chloride phase transition hygrometers tend to oscillate under certain conditions. A damping control is presented as part of the circuit details and recordings of the response characteristics and effectiveness of damping are presented showing effective control of the oscillations with a wide range of humidity transients.

Thesis (Ph.D.)--Ohio University, November, 2002. / Title from PDF t.p. Includes bibliographical references (leaves 175-177)

[pt] Recentemente, a umidade vem sendo um dos parâmetros cujas necessidades de medição e controle mais se desenvolvem especialmente em processos os farmacêuticos, de biotecnologia, automobilísticos, além de instalações de ar condicionado. A necessidade de expansão da rede de laboratórios de calibração de umidade, rastreados à Rede Brasileira de Calibração, torna-se cada vez maior para atender a demanda da indústria, além de contribuir para a melhoria dos níveis de incerteza de medição. Este trabalho tem como objetivo uma análise crítica das diferentes metodologias de medição de umidade para uso em laboratórios de calibração. Foram avaliadas as mais utilizadas expressões para a pressão parcial de vapor, visando o cálculo de umidade, e foi realizada uma comparação com a formulação de Sonntag, a mais aceita na comunidade metrológica internacional. Foi também analisada uma comparação entre alguns dos softwares disponíveis na internet para o cálculo dos principais parâmetros de umidade, tomando como referência a mesma formulação. Dentre os fatores de possível influência nas medições de umidade, foi avaliado o comportamento da mistura ar seco-vapor d´água como gás ideal e real, bem com as alterações na composição do ar. Foi feita uma análise das principais fontes de incerteza de medição seguindo a metodologia de medição de umidade a partir da temperatura de ponto de orvalho. Finalmente, o objetivo deste trabalho é apresentar aos laboratórios de calibração de umidade uma análise crítica das metodologias disponíveis para medição de umidade, juntamente com as incertezas alcançadas. / [en] Recently, the need of humidity measurement and control has been shown to be of growing interest, especially in processes like pharmaceuticals, biotechnology, automotives, as well as in air conditioning installations. Increasing the number of laboratories, which are traceable to the Brazilian Calibration Network, is a requirement for attending the industry demands, besides contributing towards improving the measurement uncertainty level. This work has as an objective to critically analyze different methods for humidity measurement, to be used by calibration laboratories. The mostly used expressions for calculating vapor partial pressure were evaluated, aiming humidity determination in comparison with Sonntag´s one, the most accepted formulation by the international metrological community. Also, a comparison was made between different softwares, which were available through internet, for calculating the most important humidity parameters, in comparison with results obtained by the same formulation. Among several factors, the dry air and water vapor mixture properties were calculated, considering it as an ideal or a real one, as well as the effect air composition changes on humidity measurement. The contribution of several sources of errors on the combined uncertainty of humidity measurement was examined, following the methodology that uses the dew point as a starting measurement parameter. Finally, the objective of this work is to present the humidity calibration laboratories a critical analysis of the available methodologies for measuring humidity, together with the achieved uncertainties.

Diploma thesis submit processing and evaluation of experiment which was made at University of Hertfordshire. Aim of this experiment was practically confirm and compare efficiency of drying bottles with blower and compressor. The next purpose was to suggest solution against recondensation on dry surface of bottles. Diploma thesis involves also economy calculation. In the diploma thesis was described issues of drying and condensation, realized analysis of drying equipment and methods of air conditioning. As the most suitable and the most cost effective way of drying was at the base on experiment and energy and economy calculation chosen tested turbo blower 587. As the solution, against recondenzation was created anticondensation tunnel. As the most suitable way for condition the dew point inside the tunnel for require value was chosen desiccant rotor Munters.

A modified dew point method for measuring vapor pressures of condensed phases is applied to solid mixtures of benzene and cyclohexane. From the measured vapor pressures, activity coefficients and excess Gibbs energies are derived. Much less accurate information about excess entropy and excess enthalpy is obtained. A comparison is made with the known properties of liquid mixtures of the same molecules. / Thesis / Master of Science (MSc)

Thermal resistance per unit thickness for Vacuum Insulation Panel (VIP) is 5 to 10 times higher than conventional insulation materials. This makes VIP an attractive option for retrofitting exterior building envelopes. Insulation can be added in an exterior wall either on the interior side, exterior side or in the available stud cavity. VIP has high vapor diffusion resistance factor and could lead to moisture management risk in the wall layers because of the steep temperature gradient in the wall generated due to very high thermal resistance of VIP. VIP is a relatively new insulation material for building envelope construction, thus the hygrothermal or moisture management performance of VIP-insulated exterior building envelopes need to be critically analyzed before its application. This study aims to evaluate the moisture management risk associated with wood-frame stucco-cladded exterior walls retrofitted with VIP using a 2-D hygrothermal simulation tool WUFI-2D. Eight North American locations were considered, based on Moisture Index (MI) which varied between 0.13 and 1.17, and two different indoor hygrothermal loading conditions as prescribed by the ASHRAE 160P and EN 13788, respectively. The outputs from hygrothermal simulations (water content, relative humidity and temperature) were critically analysed and expressed further using freeze-thaw cycles and RHT indices. The results show that the appropriately designed VIP retrofitted walls can have superior moisture management performance as compared to conventional stucco-cladded wall. / Graduate