Viumdal H.,Tel Tek |
Viumdal H.,Telemark University College |
Mylvaganam S.,Telemark University College
Ultrasonics | Year: 2014
Buffer rods (BR) as waveguides in ultrasonic time domain reflectometry (TDR) can somewhat extend the range of industrial applications of ultrasonics. Level, temperature and flow measurements involving elevated temperatures, corrosive fluids and generally harsh environments are some of the applications in which conventional ultrasonic transducers cannot be used directly in contact with the media. In such cases, BRs with some design modifications can make ultrasonic TDR measurements possible with limited success. This paper deals with TDR in conjunction with distance measurements in extremely hot fluids, using conventional ultrasonic transducers in combination with BRs. When using BRs in the ultrasonic measurement systems in extreme temperatures, problems associated with size and the material of the buffer, have to be addressed. The resonant frequency of the transducer and the relative size of the transducer with respect to the diameter of BR are also important parameters influencing the signal to noise ratio (SNR) of the signal processing system used in the ultrasonic TDR. This paper gives an overview of design aspects related to the BRs with special emphasis on tapers and cladding used on BRs. As protective cladding, zirconium oxide-yttrium oxide composite was used, with its proven thermal stability in withstanding temperatures in rocket and jet engines up to 1650 C. In general a BR should guide the signals through to the medium and from and back to the transducer without excessive attenuation and at the same time not exacerbate the noise in the measurement system. The SNR is the decisive performance indicator to consider in the design of BR based ultrasonic TDR, along with appropriate transducer, with suitable size and operating frequency. This work presents and analyses results from extensive experiments related to fine-tuning both geometry of and signals in cladded/uncladded BRs used in high temperature ultrasonic TDR with focus on overall performance based on measured values of SNR. © 2013 Elsevier B.V. All rights reserved.
Wang T.,Telemark University College |
Hovland J.,Tel Tek |
Jens K.J.,Telemark University College
Journal of Environmental Sciences (China) | Year: 2015
Amine scrubbing is the most developed technology for carbon dioxide (CO2) capture. Degradation of amine solvents due to the presence of high levels of oxygen and other impurities in flue gas causes increasing costs and deterioration in long term performance, and therefore purification of the solvents is needed to overcome these problems. This review presents the reclaiming of amine solvents used for post combustion CO2 capture (PCC). Thermal reclaiming, ion exchange, and electrodialysis, although principally developed for sour gas sweetening, have also been tested for CO2 capture from flue gas. The three technologies all have their strengths and weaknesses, and further development is needed to reduce energy usage and costs. An expected future trend for amine reclamation is to focus on process integration of the current reclaiming technologies into the PCC process in order to drive down costs. © 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.
Ihunegbo F.N.,Telemark University College |
Ratnayake C.,Tel Tek |
Halstensen M.,Telemark University College
Powder Technology | Year: 2013
An emerging process analytical technology (PAT) technique, acoustic chemometrics, was applied for monitoring of heated fluidised bed drying process. The feasibility of quantitative on-line monitoring of the drying progress and end-point determination of silica gel dried in a heated fluidised bed was investigated. Silica gel was used owing to its high water adsorption property and stability to heat. Acoustic signals were acquired using four accelerometers mounted at different locations on the wall of the fluidised bed. The accelerometer located close to the base was the best based results from this study. Prediction models validated with independent acoustic data (test set validation) were developed using partial least square regression, PLS-R. Some data pre-preprocessing techniques were applied to improve the developed prediction model. The final prediction results were satisfactory for monitoring of the drying progress and end point determination. The prediction results based on the independent data indicated a slope=0.97, correlation coefficient, R2=0.99 and the root mean square error of prediction was 1.71 water %, within the range 0-35.69 water % of sampled reference. It was concluded that the results from this feasibility study show that acoustic chemometrics is a viable on-line technique for monitoring the drying progress and for determining the end-point during drying of particulate matter. This on-line monitoring technique for the drying process developed in this study can be applied in many relevant industries in order to improve the overall economics of material drying by optimising fluidised bed drying technology using this decisive end-point determination approach. © 2013 Elsevier B.V.
Ellingsen L.A.-W.,Norwegian University of Science and Technology |
Majeau-Bettez G.,Norwegian University of Science and Technology |
Singh B.,Norwegian University of Science and Technology |
Srivastava A.K.,Tel Tek |
And 2 more authors.
Journal of Industrial Ecology | Year: 2014
Summary: Electric vehicles (EVs) have no tailpipe emissions, but the production of their batteries leads to environmental burdens. In order to avoid problem shifting, a life cycle perspective should be applied in the environmental assessment of traction batteries. The aim of this study was to provide a transparent inventory for a lithium-ion nickel-cobalt-manganese traction battery based on primary data and to report its cradle-to-gate impacts. The study was carried out as a process-based attributional life cycle assessment. The environmental impacts were analyzed using midpoint indicators. The global warming potential of the 26.6 kilowatt-hour (kWh), 253-kilogram battery pack was found to be 4.6 tonnes of carbon dioxide equivalents. Regardless of impact category, the production impacts of the battery were caused mainly by the production chains of battery cell manufacture, positive electrode paste, and negative current collector. The robustness of the study was tested through sensitivity analysis, and results were compared with preceding studies. Sensitivity analysis indicated that the most effective approach to reducing climate change emissions would be to produce the battery cells with electricity from a cleaner energy mix. On a per-kWh basis, cradle-to-gate greenhouse gas emissions of the battery were within the range of those reported in preceding studies. Contribution and structural path analysis allowed for identification of the most impact-intensive processes and value chains. This article provides an inventory based mainly on primary data, which can easily be adapted to subsequent EV studies, and offers an improved understanding of environmental burdens pertaining to lithium-ion traction batteries. © 2013 by Yale University.
Ying J.,Tel Tek |
Ying J.,Telemark University College |
Eimer D.A.,Tel Tek |
Eimer D.A.,Telemark University College
Industrial and Engineering Chemistry Research | Year: 2012
The molecular diffusivities of nitrous oxide (N2O) with aqueous monoethanolamine (MEA) solutions up to 12 M were studied over a temperature range from 298.15 to 333.15 K under atmospheric pressure using a laminar liquid jet absorber. The diffusivities of CO2 in aqueous MEA solutions were calculated by the "N2O analogy" method. A simple and effective thermal control technique was used to control the temperatures of gas and liquid in the laminar liquid jet absorber. The rates of absorption were determined by measuring the flow of gas needed to replace the gas absorbed. The results showed that the diffusivities of both N2O and CO2 into aqueous MEA solution decrease with the increase of the concentration of MEA, and increase with an increase of the temperature of the solution. The relationship between the diffusivity and the viscosity of the solution roughly agrees with the modified Stokes-Einstein equation, but an exponent mathematical model was employed to simulate the diffusivity data and shows a better agreement between data and model for the diffusivity of N2O and CO2 in the monoethanolamine + water system. © 2012 American Chemical Society.