Operational Behaviour of Supersonic Separators for Real Gas Mixtures of Methane and Carbon Dioxide, From the Homogeneous Nucleation Point of View

2019 ◽  
Author(s):  
Julián Restrepo ◽  
Jose R. Simões-Moreira
Keyword(s):  
Carbon Dioxide ◽  
Phase Change ◽  
Homogeneous Nucleation ◽  
New Technologies ◽  
Molar Fraction ◽  
Temperature Drop ◽  
Gas Mixtures ◽  
Point Of View ◽  
Operating Conditions ◽  
Operation Conditions

Abstract One of the several challenges of the oil and natural gas offshore extraction in pre-salt reserves in Brazil, is the high content of carbon dioxide inside the wells, reaching values close to 80% in a molar fraction. This issue has a big impact on the crude extraction, due to the necessity of further expensive equipment occupying considerable deck space in platforms. Therefore, it is necessary to research and find new technologies, which allow separating high contents of carbon dioxide at low energy consumption and low maintenance. The supersonic separation concept fulfils all these requirements due to the absence of moving parts and simple operation, because its working principle is based on the strong temperature drop of gas mixtures at supersonic expansion as it occurs in de Laval nozzles. Eventually, at the right operating conditions, the mixture starts to nucleate and, therefore, it will drive the phase change. Nevertheless, the physical phenomena involved in this device is complex, because it involves phase change at supersonic speeds, which comprise compressible, multispecies, and multiphase flow. This paper analyses the threshold of the phase change at supersonic speeds. The objective of this work is to calculate the influence of operation conditions (pressure, temperature and composition) in the phase change performance in supersonic separators. The phase change was modelled using the classical theory of homogeneous nucleation. In this approach allows to estimate the phase change inside the supersonic flow for different operating conditions and allows to establish operating strategies to ensure low Mach numbers (M < 1.5) in the phase change region, allowing a further pressure recovery.

scholarly journals Lumped parameter modelling of two-phase ejectors: numerical implications of the equilibrium assumptions

2021 ◽  
Vol 2116 (1) ◽  
pp. 012089
Author(s):  
Giorgio Besagni
Keyword(s):  
Carbon Dioxide ◽  
Critical Temperature ◽  
Operating Conditions ◽  
Cutting Edge ◽  
Technical Solution ◽  
Two Phase ◽  
Operation Conditions ◽  
System A ◽  
Lumped Parameter ◽  
Major Shortcoming

Abstract The use of carbon dioxide as refrigerant is attracting a growing attention and is a cutting-edge research topic. In spite of its many advantages, carbon dioxide has a major shortcoming, viz., low critical temperature. Owing to the low critical temperature, carbon dioxide cycles encompass both the sub-critical and the trans-critical operation conditions; the trans-critical operating conditions are characterized by high thermodynamic losses, requiring particular attention in the integrated component/system design criteria. In this perspective, in recent years, ejector technology has been widely recognized as a promising technical solution to support the deployment of carbon dioxide cycles, by reducing throttling losses. Unfortunately, the large variation in system operations as well as the changes in sub-critical and trans-critical operating conditions makes the numerical simulation of carbon dioxide ejector-based system a cutting-edge challenge. This paper contributes to the present day discussion on the validation of lumped parameter models for carbon dioxide ejectors. A model taken from the literature has been tested against literature data and the equilibrium assumptions, underlying the modelling approach have been tested.

scholarly journals Functional Feasibility in Optimal Evaluation of Water Distribution Network Performances

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3404
Author(s):  
Flavia Fuso ◽  
Maria C. Cunha ◽  
Gianfranco Becciu
Keyword(s):  
Water Distribution ◽  
Network Performance ◽  
Traditional Approach ◽  
Water Distribution Network ◽  
Distribution Networks ◽  
Point Of View ◽  
Operating Conditions ◽  
Worst Case ◽  
The Real ◽  
Operation Conditions

The traditional approach for the optimization of water distribution networks (WDNs) does not always lead to consistent solutions from an operational point of view. The latest optimization algorithms identify solutions that are “the best solutions” in mathematical terms but that can be less than robust against changes in operating conditions, resulting in the worst case in hydraulically infeasible configurations. Thus, this paper aims to provide a methodology that can synthesize the network performance capabilities under the change in operating conditions with two convergent strategies. The first consists of the implementation of new performance indices (PIs), the demand deficit and the pressure range, and the evaluation of their ability to criticality highlight in operating conditions. The second is the introduction of a new approach to weight the infeasible solutions in the final result, which are those inconsistent with the real hydraulic network performances. The analysis shows that the use of these new indices makes it easier to understand the behavior of the network and to identify any weaknesses. This is true if these indices consider the hydraulically inconsistent solutions that may arise from the simulations of different operation conditions; otherwise, results that poorly represent the real behavior of the network would be obtained.

Adapting the Existing District Heating Systems to Dynamic Operating Conditions

2015 ◽  
Vol 809-810 ◽  
pp. 688-693 ◽  
Author(s):  
Răzvan Corneliu Lefter ◽  
Daniela Popescu
Keyword(s):  
Energy Efficiency ◽  
District Heating ◽  
Point Of View ◽  
Operating Conditions ◽  
Flow Rates ◽  
Heating Systems ◽  
Operation Conditions ◽  
District Heating Systems ◽  
Dynamic Operating ◽  
Heating Networks

District heating systems operating under dynamic conditions without proper hydronic balancing is one of the causes of discomfort for heating consumers. Moreover, from the point of view of producers, unbalanced heating networks generate low energy efficiency. The study analyzes the operation conditions in three cases, on the same network: the first simulates the operating conditions of the network without balancing, the second when just balancing valves set to corresponding nominal flow rate values are used and the third when balancing valves and differential pressure controllers are used, the so-called total balancing method. Results highlight the importance of the hydraulic balancing under steady state and dynamic operating conditions, as a source to increase the energy efficiency and assure thermal comfort by better distribution of fluid flow rates between consumers.

Thermal Energy Storage Through Melting of a Commercial Phase Change Material in an Annulus with Radially Divergent Longitudinal Fins

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Tonny Tabassum Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Operating Conditions ◽  
Melting Time ◽  
Bottom Part ◽  
Change Material

This study reports on the unsteady two-dimensional numerical investigations of melting of a paraffin wax (phase change material, PCM) which melts over a temperature range of 8.7oC. The PCM is placed inside a circular concentric horizontal-finned annulus for the storage of thermal energy. The inner tube is fitted with three radially diverging longitudinal fins strategically placed near the bottom part of the annulus to accelerate the melting process there. The developed CFD code used in Tabassum et al., 2018 is extended to incorporate the presence of fins. The numerical results show that the average Nusselt number over the inner tube surface, the total melt fraction, the total stored energy all increased at every time instant in the finned annulus compared to the annulus without fins. This is due to the fact that in the finned annulus, the fins at the lower part of the annulus promotes buoyancy-driven convection as opposed to the slow conduction melting that prevails at the bottom part of the plain annulus. Fins with two different heights have been considered. It is found that by extending the height of the fin to 50% of the annular gap about 33.05% more energy could be stored compared to the bare annulus at the melting time of 82.37 min for the identical operating conditions. The effects of fins with different heights on the temperature and streamfunction distributions are found to be different. The present study can provide some useful guidelines for achieving a better thermal energy storage system.

Tertiary Nitrification Pilot Plants on Parisian Waste Water

1990 ◽  
Vol 22 (1-2) ◽  
pp. 347-352 ◽  
Author(s):  
C. Paffoni ◽  
B. Védry ◽  
M. Gousailles
Keyword(s):  
Waste Water ◽  
Metropolitan Area ◽  
Fixed Bed ◽  
Point Of View ◽  
Operating Conditions ◽  
Research Center ◽  
Daily Output ◽  
Practical Point ◽  
Fixed Bed Reactors

The Paris Metropolitan area, which contains over eight million inhabitants, has a daily output of about 3 M cu.meters of wastewater, the purification of which is achieved by SIAAP (Paris Metropolitan Area Sewage Service) in both Achères and Valenton plants. The carbon pollution is eliminated from over 2 M cu.m/day at Achères. In order to improve the quality of output water, its tertiary nitrification in fixed-bed reactors has been contemplated. The BIOFOR (Degremont) and BIOCARBONE (OTV) processes could be tested in semi-industrial pilot reactors at the CRITER research center of SIAAP. At a reference temperature of 13°C, the removed load is approximately 0.5 kg N NH4/m3.day. From a practical point of view, it may be asserted that in such operating conditions as should be at the Achères plant, one cubic meter of filter can handle the tertiary nitification of one cubic meter of purified water per hour at an effluent temperature of 13°C.

Micro-Thermal Field-Flow Fractionation

2002 ◽  
Vol 67 (11) ◽  
pp. 1596-1608 ◽  
Author(s):  
Josef Janča
Keyword(s):  
High Performance ◽  
Thermal Field ◽  
Temperature Drop ◽  
Point Of View ◽  
Constant Field ◽  
Field Flow Fractionation ◽  
Operational Mode ◽  
Experimental Conditions ◽  
Standard Size ◽  
Flow Fractionation

The effect of miniaturization of the separation channel on the performance of thermal field-flow fractionation (TFFF) is substantiated theoretically. The experiments carried out under carefully chosen experimental conditions proved the high performance of the separation of polymers within an extended range of molar masses from relatively low up to ultrahigh-molar-mass (UHMM) samples. The new micro-TFFF allows to achieve high resolution when applying constant field force operation, it makes easy the programming of the temperature drop which is an advantageous operational mode from the point of view of the time of analysis, and it extends considerably the range of perfectly controlled temperature of the cold wall due to a substantial decrease in the heat energy flux compared with standard size channels.

scholarly journals Sustainable Electric Personal Mobility: The Design of a Wireless Charging Infrastructure for Urban Tourism

2021 ◽  
Vol 13 (3) ◽  
pp. 1270
Author(s):  
Sung Il Kwag ◽  
Uhjin Hur ◽  
Young Dae Ko
Keyword(s):  
Public Transportation ◽  
New Technologies ◽  
Point Of View ◽  
Urban Tourism ◽  
Electric Mobility ◽  
Wireless Charging ◽  
Efficient Design ◽  
Personal Mobility ◽  
Charging Infrastructure ◽  
Mobility System

Though new technologies have been applied in all industries, electric mobility technology using eco-friendly energy is drawing a great deal of attention. This research focuses on a personal electric mobility system for urban tourism. Some tourism sites such as Gyeongju, Korea, have broad spaces for tourists to walk around, but the public transportation system has been insufficiently developed due to economic reasons. Therefore, personal mobility technology such as electric scooters can be regarded as efficient alternatives. For the operation of electric scooters, a charging infrastructure is necessary. Generally, scooters can be charged via wires, but this research suggests an advanced electric personal mobility system based on wireless electric charging technology that can accommodate user convenience. A mathematical model-based optimization was adopted to derive an efficient design for a wireless charging infrastructure while minimizing total investment costs. By considering the type of tourists and their tour features, optimal locations and lengths of the static and dynamic wireless charging infrastructure are derived. By referring to this research, urban tourism can handle transportation issues from a sustainable point of view. Moreover, urban tourism will have a better chance of attracting tourists by conserving heritage sites and by facilitating outdoor activities with electric personal mobility.

scholarly journals It’s Our Fault: A Global Comparison of Different Ways of Explaining Climate Change

Human Ecology ◽  
2021 ◽  
Author(s):  
Michael Schnegg ◽  
Coral Iris O’Brian ◽  
Inga Janina Sievert
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Local Knowledge ◽  
Indigenous Communities ◽  
Point Of View ◽  
Global Comparison ◽  
Local Phenomenon ◽  
World Regions ◽  
Survey Results ◽  
Specific Factors

AbstractInternational surveys suggest people increasingly agree the climate is changing and humans are the cause. One reading of this is that people have adopted the scientific point of view. Based on a sample of 28 ethnographic cases we argue that this conclusion might be premature. Communities merge scientific explanations with local knowledge in hybrid ways. This is possible because both discourses blame humans as the cause of the changes they observe. However, the specific factors or agents blamed differ in each case. Whereas scientists identify carbon dioxide producers in particular world regions, indigenous communities often blame themselves, since, in many lay ontologies, the weather is typically perceived as a local phenomenon, which rewards and punishes people for their actions. Thus, while survey results show approval of the scientific view, this agreement is often understood differently and leads to diverging ways of allocating meaning about humans and the weather.

scholarly journals ZnOTe Compounds Grown by DC-Magnetron Co-Sputtering

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 570
Author(s):  
Olga Sánchez ◽  
Manuel Hernández-Vélez
Keyword(s):  
Molar Fraction ◽  
Variable Parameter ◽  
Point Of View ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sample Series ◽  
Solid Phases ◽  
The One ◽  
High Bulk ◽  
Substrate Sample

ZnOTe compounds were grown by DC magnetron cosputtering from pure Tellurium (Te) and Zinc (Zn) cathodes in O2/Ar atmosphere. The applied power on the Zn target was constant equal to 100 W, while the one applied on the Te target took two values, i.e., 5 W and 10 W. Thus, two sample series were obtained in which the variable parameter was the distance from the Te targets to the substrate. Sample compositions were determined by Rutherford Backscattering Spectroscopy (RBS) experiments. Structural analysis was done using X-Ray diffraction (XRD) spectrometry and the growth of the hexagonal w-ZnO phase was identified in the XRD spectra. RBS results showed high bulk homogeneity of the samples forming ZnOTe alloys, with variable Te molar fraction (MF) ranging from 0.48–0.6% and from 1.9–3.1% for the sample series obtained at 5 W and 10 W, respectively. The results reflect great differences between the two sample series, particularly from the structural and optical point of view. These experiments point to the possibility of Te doping ZnO with the permanence of intrinsic defects, as well as the possibility of the formation of other Te solid phases when its content increases. The results and appreciable variations in the band gap transitions were detected from Photoluminescence (PL) measurements.

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