Effect of Flow Rates on Operation of a Solar Thermochemical Reactor for Splitting CO2 Via the Isothermal Ceria Redox Cycle

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Brandon J. Hathaway ◽  
Rohini Bala Chandran ◽  
Stephen Sedler ◽  
Daniel Thomas ◽  
Adam Gladen ◽  
...  
Keyword(s):  
Heat Recovery ◽  
Gas Flow ◽  
Gas Flows ◽  
Energy Costs ◽  
Redox Cycle ◽  
External Energy ◽  
Flow Rates ◽  
Computational Fluid Dynamics Cfd ◽  
Solar Thermochemical ◽  
The Impact

A prototype 4 kW solar thermochemical reactor for the continuous splitting of carbon dioxide via the isothermal ceria redox cycle is demonstrated. These first tests of the new reactor showcase both the innovation of continuous on-sun fuel production in a single reactor and remarkably effective heat recovery of the sensible heat of the reactant and product gases. The impact of selection of gas flow rates is explored with respect to reactor fuel productivity and external energy costs of gas separation and pumping. Thermal impacts of gas flow selection are explored by coupling measured temperatures with a computational fluid dynamics (CFD) model to calculate internal temperature distributions and estimate heat recovery. Optimized gas flows selected for operation provide a 75% increase in fuel productivity and reduction in parasitic energy costs by 10% with respect to the design case.

The Impact of Volute Versus Collector on Centrifugal Compressor Performance

2002 ◽  
Author(s):  
Y. I. Biba
Keyword(s):  
3D Model ◽  
Internal Flow ◽  
Performance Measurements ◽  
Cross Sectional ◽  
Flow Rates ◽  
Computational Fluid Dynamics Cfd ◽  
Compressor Performance ◽  
The Subject ◽  
Cfd Analyses ◽  
The Impact

As part of a revamp or rerate study, an investigation was undertaken to assess the impact of a collector design versus a volute on compressor performance. The subject compressor was a single stage, axial inlet configuration with a discharge collector rather than the more commonly used scroll volute. The primary distinction between the collector and volute is that the collector cross sectional area is constant at all circumferential locations. A complex 3D model containing the inlet, impeller, low solidity diffuser (LSD), and collector was built. A similar model was also created where the volute was substituted for the collector. Computational Fluid Dynamics (CFD) analyses were performed using these models with results generated at different flow rates. Computational results are presented and compared to test data for collector configuration. The test included standard performance measurements as well as more detailed internal flow data, allowing a credible comparison with the CFD results. Conclusions are drawn with respect to potential compromises in choosing a collector versus a volute.

scholarly journals A survey of the choice of general anaesthetic agents in Australia and New Zealand

2019 ◽  
Vol 47 (3) ◽  
pp. 235-241 ◽  
Author(s):  
Forbes McGain ◽  
Jason R Bishop ◽  
Laura M Elliot-Jones ◽  
David A Story ◽  
Georgina LL Imberger
Keyword(s):  
Nitrous Oxide ◽  
New Zealand ◽  
Gas Flow ◽  
General Anaesthetic ◽  
Gas Flows ◽  
Environmental Costs ◽  
Flow Rates ◽  
Intravenous Anaesthesia ◽  
Anaesthetic Agents ◽  
End Tidal

Strategies to reduce the adverse environmental costs of anaesthesia include choice of agent and fresh gas flows. The current preferences of Australian and New Zealand anaesthetists are unknown. We conducted a survey of Australian and New Zealand anaesthetists to determine the use of volatiles, nitrous oxide and intravenous anaesthesia, lowest fresh gas flow rates, automated end-tidal volatile control, and the rationales for these choices. The survey was answered by 359/1000 (36%), although not all questions and multiple responses within single questions were answered by all respondents. Sevoflurane was preferred by 246/342 (72%, 95% confidence interval (CI) 67%–77%), followed by propofol, 54/340 (16%, 95% CI 12%–20%), desflurane 39/339 (12%, 95% CI 8%–16%) and isoflurane 3/338(1%, 95% CI 0–3%). When asked about all anaesthetics, low-risk clinical profile was the most common reason given for using sevoflurane (129/301 (43%, 95% CI 37%–49%)), reduced postoperative nausea for propofol (297/318 (93%, 95% CI 90%–96%)) and faster induction/awakening times for desflurane (46/313 (79%, 95% CI 74%–83%)). Two-thirds (226/340 (66%, 95% CI 61%–71%)) of respondents used nitrous oxide in 0–20% of general anaesthetics. Low fresh gas flow rates for sevoflurane were used by 310/333 (93%, 95% CI 90%–95%) and for 262/268 (98%, 95% CI 95%–99%) for desflurane. Automated end-tidal control was used by 196/333 (59%, 95% CI 53%–64%). The majority of respondents (>70%) preferred sevoflurane at low flows. These data allow anaesthetists to consider further whether changes are required to the choices of anaesthetic agents for environmental, financial, or any other reasons.

scholarly journals The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1997 ◽  
Author(s):  
Fredrik Leijonhufvud ◽  
Fredrik Jöneby ◽  
Jan G. Jakobsson
Keyword(s):  
Gas Flow ◽  
Anaesthetic Agent ◽  
Point Of View ◽  
Low Flow ◽  
Test Lung ◽  
Minimal Alveolar Concentration ◽  
Flow Rates ◽  
Optimal Flow ◽  
Gas Consumption ◽  
The Impact

Low-flow anaesthesia is considered beneficial for the patient and the environment, and it is cost reducing due to reduced anaesthetic gas consumption. An initial high-flow to saturate the circle system ( wash-in) is desirable from a clinical point of view. We measured the wash-in and wash-out times (time to saturate and to eliminate the anaesthetic agent, AA), for sevoflurane and desflurane, in a test-lung with fixed 3 MAC vaporizer setting at different fresh gas flow (FGF) and calculated the consumption of AA. We tried to find an optimal flow rate for speed and gas consumption, comparing two anaesthesia machines (AMs): Aisys and Flow-i. Time to reach 1 minimal alveolar concentration (MAC) (wash-in) decreased (p<0.05) at higher flow rates (1 – 2 – 4) but plateaued at 4-4.8 l/min. The consumption of AA was at its lowest around 4-4.8 l/min (optimal flow) for all but the Aisys /desflurane group. Wash-out times decreased as FGF increased, until reaching plateau at FGF of 4-6 l/min. Aisys had generally shorter wash-in times at flow rates < 4 l/min as well as lower consumption of AA. At higher flow rates there were little difference between the AMs. The “optimal FGF” for wash-out, elimination of gas from the test-lung and circle system, plateaued with no increase in speed beyond 6 l/min. A fresh gas flow of 4 l/min. seems “optimal” taking speed to reach a 1 MAC ET and gas consumption into account during wash-in with a fixed 3 MAC vaporizer setting, and increasing fresh gas flow beyond 6 l/min does not seem to confirm major benefit during wash-out.

scholarly journals Multiple propane gas flow rates procedure to determine accuracy and linearity of indirect calorimetry systems : An experimental assessment of a method.

2019 ◽  
Author(s):  
Mohammad Ismail ◽  
Alsubheen A Sana'a ◽  
Angela Loucks-Atlinson ◽  
Matthew Atkinson ◽  
Liam P Kelly ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Indirect Calorimetry ◽  
Energy Production ◽  
Gas Flow ◽  
Carbon Dioxide Production ◽  
Whole Body ◽  
Gas Flows ◽  
Flow Rates ◽  
Ventilation Rates ◽  
Body Energy

Objective: Indirect calorimetry (IC) systems measure the fractions of expired carbon dioxide (FECO2) and oxygen (FEO2) recorded at the mouth in order to estimate whole body energy production (EP). The fundamental principal of IC relates to oxidative mechanisms, expressed as rate of oxygen uptake (V̇O2) and carbon dioxide production (V̇CO2). From these volumes we calculate energy production and respiratory exchange ratio which is used to estimate substrate utilization rates. The accuracy of IC systems is critical to detect small changes in respiratory gas exchanges. The aim of this technical report was to assess the accuracy and linearity of IC systems using multiple propane gas flow rates procedure. Approach: A series of propane gas with different flow rates and ventilation rates were run on three different IC systems. The actual experimental V̇O2 and V̇CO2 were calculated and compared to stoichiometry theoretical values. Results: showed a linear relationship between gas volumes (V̇O2 and V̇CO2) and propane gas flows (99.6%, 99.2%, 94.8% for the Sable, Moxus, and Jaeger metabolic carts, respectively). In terms of system error, Jaeger system had significantly (p < 0.001) greater V̇O2 (M = -0.057, SE = 0.004), and V̇CO2 (M = -0.048, SE = 0.002) error compared to either the Sable (V̇O2, M = 0.044, SE = 0.004; V̇CO2, M = 0.024, SE = 0.002) or the Moxus (V̇O2, M = 0.046, SE = 0.004; V̇CO2, M = 0.025, SE = 0.002) metabolic carts. There were no significant differences between the Sable or Moxus metabolic carts. Conclusion: The multiple flow rates approach permitted the assessment of linearity of IC systems in addition to determining the accuracy of fractions of expired gases.

Selective Catalytic Reduction Impact on Heat Recovery Steam Generator Design and Operation

1986 ◽  
Author(s):  
James S. Davis ◽  
G. C. Duponteil
Keyword(s):  
Selective Catalytic Reduction ◽  
Gas Turbine ◽  
Steam Generator ◽  
Heat Recovery ◽  
Gas Flow ◽  
High Efficiency ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Heat Recovery Steam Generator ◽  
The Impact

Selective Catalytic Reduction (SCR) is a post-combustion method to reduce the oxides of nitrogen (NOx), present in flue gases such as gas turbine exhaust streams, to N2 and water. It involves the injection of ammonia and the use of a catalyst module to promote the reaction to obtain high efficiency (60–86+%) NOx reduction. Several operating parameters can influence catalyst performance to include temperature, gas flow distribution, presence of sulfur compounds and catalyst age. This paper examines the impact of a SCR integration in a gas turbine heat recovery steam generator (HRSG) design/operation. Limitations on HRSG load and following capabilities, effect on capital cost and overall performance and current SCR system experience represent a number of areas that are examined.

scholarly journals Impact of Gas Flow and Humidity on Trans-Nasal Aerosol Deposition via Nasal Cannula in Adults: A Randomized Cross-Over Study

Pharmaceutics ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 320 ◽  
Author(s):  
Luciana Alcoforado ◽  
Arzu Ari ◽  
Jacqueline Barcelar ◽  
Simone Brandão ◽  
James Fink ◽  
...  
Keyword(s):  
Gas Flow ◽  
Healthy Adults ◽  
Nasal Cannula ◽  
Lung Deposition ◽  
Gas Flows ◽  
Aerosol Delivery ◽  
Upper Airways ◽  
Fill Volume ◽  
Heated Humidification ◽  
The Impact

Background: Trans-nasal pulmonary aerosol delivery using high flow nasal cannula (HFNC) devices is described with the administration of high gas flows exceeding patient inspiratory flow (HF) and with lower flows (LF). The aim of this pilot clinical trial was to compare deposition and distribution of radiolabeled aerosol via nasal cannula in healthy adults across three rates of gas flow delivered with active heated humidification, and to further identify the impact of aerosol administration without heated humidity. Methods: Twenty-three (23) healthy adults (16F) were randomized to receive aerosol with active heated humidification or unheated oxygen at gas flows of 10 L/min (n = 8), 30 L/min (n = 7), or 50 L/min (n = 8). Diethylenetriaminepentaacetic acid labeled with 1 millicurie (37 MBq) of Technetium-99m (DTPA-Tc99m) was mixed with NaCl to a fill volume of 1 mL, and administered via mesh nebulizer placed at the inlet of the humidifier. Radioactivity counts were performed using a gamma camera and the regions of interest (ROIs) were delimited with counts from the lungs, upper airways, stomach, nebulizer, circuit, and expiratory filter. A mass balance was calculated and each compartment was expressed as a percentage of the total. Results: Lung deposition (mean ± SD) with heated humidified gas was greater at 10 L/min than 30 L/min or 50 L/min (17.2 ± 6.8%, 5.71 ± 2.04%, and 3.46 ± 1.24%, respectively; p = 0.0001). Using unheated carrier gas, a lung dose of aerosol was similar to the active heated humidification condition at 10 L/min, but greater at 30 and 50 L/min (p = 0.011). Administered gas flow and lung deposition were negatively correlated (r = −0.880, p < 0.001). Conclusions: Both flow and active heated humidity inversely impact aerosol delivery through HFNC. Nevertheless, aerosol administration across the range of commonly used flows can provide measurable levels of lung deposition in healthy adult subjects (NCT 02519465).

On the Use of Computational Fluid Dynamics (CFD) to Assess the Impact of Low-Load Operations on Heat Recovery Steam Generator (HRSG) Tube Module Integrity

2019 ◽  
Author(s):  
Andreas Fabricius ◽  
David S. Moelling ◽  
Jan Rusaas
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Recovery ◽  
Power Plants ◽  
Large Temperature ◽  
Plant Design ◽  
Low Load ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
Load Conditions

Abstract As the electricity market has evolved with the addition of renewables to the generation mix, Heat Recovery Steam Generators (HRSGs) that were originally designed for base load conditions are now frequently forced to operate in a cycling and/or low-load regime. This can lead to front end tube-to header fatigue, creep or creep-fatigue failures, often induced by Gas Turbine (GT) flow imbalances causing locally-elevated tube temperatures and/or bending stresses on joints due to large temperature differences between tube rows. This paper focuses on the use of Computational Fluid Dynamics (CFD) as a tool to analyze the risks of shifting operation mode. Exhaust gas flow profiles were analyzed for various low load conditions in two power plants with differing vertical designs. One of the plants had already moved into cycling mode and suffered tube failures that were directly related to low-load (and start-up) exhaust flow patterns, the other plant is projected to operate in a frequent cycling mode in the near future. The contribution of CFD to identifying the conditions that lead to failure for the first plant is presented, along with projections on the potential impact of lowload operation on the second plant design in terms of risk of hotend tube failures. Mechanisms to reduce the failure risk, such as addition of flow-conditioning devices, are also investigated.

scholarly journals Experimental Characterization of the Jet Wiping Process

2018 ◽  
Vol 180 ◽  
pp. 02064
Author(s):  
Miguel Alfonso Mendez ◽  
Adriana Enache ◽  
Anne Gosset ◽  
Jean-Marie Buchlin
Keyword(s):  
Gas Flow ◽  
Detection Algorithm ◽  
Gas Flows ◽  
Experimental Characterization ◽  
Data Set ◽  
Time Resolved ◽  
Numerical Studies ◽  
Image Velocimetry ◽  
The Impact

This paper presents an experimental characterization of the jet wiping process, used in continuous coating applications to control the thickness of a liquid coat using an impinging gas jet. Time Resolved Particle Image Velocimetry (TR-PIV) is used to characterize the impinging gas flow, while an automatic interface detection algorithm is developed to track the liquid interface at the impact. The study of the flow interaction is combined with time resolved 3D thickness measurements of the liquid film remaining after the wiping, via Time Resolved Light Absorption (TR-LAbs). The simultaneous frequency analysis of liquid and gas flows allows to correlate their respective instability, provide an experimental data set for the validation of numerical studies and allows for formulating a working hypothesis on the origin of the coat non-uniformity encountered in many jet wiping processes.

scholarly journals Influence of mass transfer on bubble plume hydrodynamics

2016 ◽  
Vol 88 (1) ◽  
pp. 411-422 ◽  
Author(s):  
IRAN E. LIMA NETO ◽  
PRISCILA A.B. PARENTE
Keyword(s):  
Mass Transfer ◽  
Gas Flow ◽  
Low Flow ◽  
Integral Model ◽  
Bubble Plume ◽  
Flow Rates ◽  
Functional Relationships ◽  
Bubble Plumes ◽  
The Impact ◽  
Water Depths

ABSTRACT This paper presents an integral model to evaluate the impact of gas transfer on the hydrodynamics of bubble plumes. The model is based on the Gaussian type self-similarity and functional relationships for the entrainment coefficient and factor of momentum amplification due to turbulence. The impact of mass transfer on bubble plume hydrodynamics is investigated considering different bubble sizes, gas flow rates and water depths. The results revealed a relevant impact when fine bubbles are considered, even for moderate water depths. Additionally, model simulations indicate that for weak bubble plumes (i.e., with relatively low flow rates and large depths and slip velocities), both dissolution and turbulence can affect plume hydrodynamics, which demonstrates the importance of taking the momentum amplification factor relationship into account. For deeper water conditions, simulations of bubble dissolution/decompression using the present model and classical models available in the literature resulted in a very good agreement for both aeration and oxygenation processes. Sensitivity analysis showed that the water depth, followed by the bubble size and the flow rate are the most important parameters that affect plume hydrodynamics. Lastly, dimensionless correlations are proposed to assess the impact of mass transfer on plume hydrodynamics, including both the aeration and oxygenation modes.

scholarly journals The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1997 ◽  
Author(s):  
Fredrik Leijonhufvud ◽  
Fredrik Jöneby ◽  
Jan G. Jakobsson
Keyword(s):  
Gas Flow ◽  
Anaesthetic Agent ◽  
Point Of View ◽  
Low Flow ◽  
Test Lung ◽  
Minimal Alveolar Concentration ◽  
Flow Rates ◽  
Optimal Flow ◽  
Gas Consumption ◽  
The Impact

Low-flow anaesthesia is considered beneficial for the patient and the environment, and it is cost reducing due to reduced anaesthetic gas consumption. An initial high-flow to saturate the circle system (wash-in) is desirable from a clinical point of view. We measured the wash-in and wash-out times (time to saturate and to eliminate the anaesthetic agent, AA), for sevoflurane and desflurane, in a test-lung with fixed 3 MAC vaporizer setting at different fresh gas flow (FGF) and calculated the consumption of AA. We tried to find an optimal flow rate for speed and gas consumption, comparing two anaesthesia machines (AMs): Aisys and Flow-i. Time to reach 1 minimal alveolar concentration (MAC) (wash-in) decreased (p<0.05) at higher flow rates (1 – 2 – 4) but plateaued at 4-4.8 l/min. The consumption of AA was at its lowest around 4-4.8 l/min (optimal flow) for all but the Aisys /desflurane group. Wash-out times decreased as FGF increased, until reaching plateau at FGF of 4-6 l/min. Aisys had generally shorter wash-in times at flow rates < 4 l/min as well as lower consumption of AA. At higher flow rates there were little difference between the AMs. The “optimal FGF” for wash-out, elimination of gas from the test-lung and circle system, plateaued with no increase in speed beyond 6 l/min. A fresh gas flow of 4 l/min. seems “optimal” taking speed to reach a 1 MAC ET and gas consumption into account during wash-in with a fixed 3 MAC vaporizer setting, and increasing fresh gas flow beyond 6 l/min does not seem to confirm major benefit during wash-out

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