Near-Critical CO2 Flow Measurement and Visualization

2013 ◽  
Author(s):  
Farzan Kazemifar ◽  
Dimitrios C. Kyritsis
Keyword(s):  
Pressure Drop ◽  
Critical Point ◽  
Flow Structure ◽  
Greenhouse Gas Emission ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Inlet Temperature ◽  
Mass Flow Rates ◽  
Inlet Conditions ◽  
Co2 Flow

Near-critical CO2 flow has been studied because of its potential application in carbon dioxide capture and sequestration, which is one of the proposed solutions for reducing greenhouse gas emission. Near the critical point the thermophysical properties of the fluid undergo abrupt changes that affect the flow structure and characteristics. Pressure drop across a stainless steel tube, 2 ft long with 0.084 in ID, at different inlet conditions and mass flow rates have been measured. The effects of variations of inlet conditions have been studied. The results show extreme sensitivity of pressure drop to inlet conditions especially inlet temperature in the vicinity of the critical point. Also, shadowgraphs have been acquired to study the flow structure qualitatively.

Near-Critical CO2 Flow Measurement and Visualization

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Farzan Kazemifar ◽  
Dimitrios C. Kyritsis
Keyword(s):  
Pressure Drop ◽  
Critical Point ◽  
Flow Structure ◽  
Greenhouse Gas Emission ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Inlet Temperature ◽  
Mass Flow Rates ◽  
Inlet Conditions ◽  
Co2 Flow

Near-critical CO2 flow has been studied because of its potential application in carbon dioxide capture and sequestration, which is one of the proposed solutions for reducing greenhouse gas emission. Near the critical point the thermophysical properties of the fluid undergo abrupt changes that affect the flow structure and characteristics. Pressure drop across a stainless steel tube, 2 ft long with 0.084 in. ID, at different inlet conditions and mass flow rates have been measured. The effects of variations of inlet conditions have been studied. The results show extreme sensitivity of pressure drop to inlet conditions especially inlet temperature in the vicinity of the critical point. Also, shadowgraphs have been acquired to study the flow structure qualitatively.

Effect of Compressor Inlet Condition on Supercritical Carbon Dioxide Compressor Performance

2019 ◽  
Author(s):  
Haoxiang Chen ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Hongdan Liu
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Critical Point ◽  
Inlet Pressure ◽  
Inlet Temperature ◽  
Inlet Condition ◽  
Compressor Inlet ◽  
Compressor Performance ◽  
Inlet Conditions ◽  
Compressor Power

Abstract Supercritical carbon dioxide (S-CO2) Brayton power cycle has attracted a lot of attention around the world in energy conversion field. It takes advantage of the high density of CO2 near the critical point while maintaining low viscosity to reduce compressor power and achieve high cycle efficiency. However, as CO2 approaches to its critical point, the thermodynamic properties of CO2 vary dramatically with small changes in temperature or pressure. As a result, the density of the working fluid varies significantly at the compressor inlet in the practical cycle if operating near the critical point, especially for small-scale cycles and air-cooled cycles, which leads to compressors operating out of the flow range, even being damaged. Concerns of large density variations at the inlet of the compressor result in S-CO2 compressor designers selecting compressor inlet conditions away from the critical point, thereby increasing compressor power. In this paper, a criterion to choose inlet pressure and inlet temperature of compressors as the design inlet condition is proposed, which is guaranteeing ±50% change in inlet specific volume within ±3 °C variation in inlet temperature. By the criterion, 8 MPa and 34.7 °C is selected as the design inlet condition. According to design requirements of the cycle, a S-CO2 centrifugal compressor is designed through 1-D design methodology. Based on the two-zone model, the effects of compressor inlet condition including inlet pressure and inlet temperature on the compressor performance are analyzed in detail. In practical operation, the compressor inlet condition is varied. Thus, an accurate prediction of compressor performance under different inlet conditions is necessary. The traditional correction method is not suitable for S-CO2 compressor. Dimensionless specific enthalpy rise is used to correct pressure ratio by the real gas table. And the S-CO2 compressor performance can be predicted correctly under different inlet conditions.

Effect of Mass Flow Rate on Dryer Room Radiator Pressure Drop and Heat Transfer

2016 ◽  
Vol 836 ◽  
pp. 102-108
Author(s):  
Mirmanto ◽  
Emmy Dyah Sulistyowati ◽  
I Ketut Okariawan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Electrical Power ◽  
Maximum Temperature ◽  
Inlet Temperature ◽  
Mass Flow Rates ◽  
Room Model

In the rainy season, in tropical countries, to dry stuffs is difficult. Using electrical power or fossil energy is an expensive way. Therefore, it is wise to utilize heat waste. A device that can be used for this purpose is called radiator. The effect of mass flow rate on pressure drop and heat transfer for a dryer room radiator have been experimentally investigated. The room model size was 1000 mm x 1000 mm x 1000 mm made of plywood and the overall radiator dimension was 360 mm x 220 mm x 50 mm made of copper pipes with aluminium fins. Three mass flow rates were investigated namely 12.5 g/s, 14 g/s and 16.5 g/s. The water temperature at the entrance was increased gradually and then kept at 80°C. The maximum temperature reached in the dryer room was 50°C which was at the point just above the radiator. The effect of the mass flow rate on the room temperature was insignificant, while the effect on the pressure drop was significant. Moreover, the pressure drop decreased as the inlet temperature increased. In general, the radiator is recommended to be used as the heat source in a dryer room.

Flow Pattern, Heat Transfer and Pressure Drop Behaviors of Micro-Channel Flow Boiling

2018 ◽  
Author(s):  
Sira Saisorn ◽  
Pochai Srithumkhant ◽  
Pakorn Wongpromma ◽  
Maturose Suchatawat ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Boiling ◽  
Flow Direction ◽  
Saturation Pressure ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Stainless Steel Tube

Two-phase flow of R-134a with high confinement number was experimentally carried out in this study. Flow boiling conditions for different orientations were controlled to take place in a stainless steel tube having a diameter of 0.5 mm. Based on a saturation pressure of 8 bar, a heat flux range of 2–26 kW/m2, and a mass flux range of 610–815 kg/m2s, a constant surface heat flux condition was controlled by applied DC power supply on the test section. The flow behaviors were described based on flow pattern and pressure drop data while heat transfer mechanisms were explained by using heat transfer coefficient data. In this work, nucleate boiling was observed, and the importance of the change in the flow direction was neglected, corresponding to the confinement number of around 1.7.

Paleoclimate Inferred from Concentration of Greenhouse Gas and Ratios of O2/Ar and N2/Ar in Ice Wedges in Northeastern Siberia and Northern Alaska

2021 ◽  
Author(s):  
Nayeon Ko ◽  
Ji-Woong Yang ◽  
Go Iwahana ◽  
Alexandre Fedorov ◽  
Andrei G. Shepelev ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Late Holocene ◽  
Greenhouse Gas Emission ◽  
Steel Tube ◽  
North Slope ◽  
Stainless Steel Tube ◽  
Gas Mixing ◽  
Climate Conditions ◽  
Mixing Ratios ◽  
Northeastern Siberia

<p>Global warming is drawing keen attention to people all over the people. Especially, the history of climate in permafrost area is of great interest to better understand greenhouse gas emission due to the thaw of permafrost in the future. In this context, formation of ice wedges and greenhouse gas was studied based on gas chemistry in permafrost ice wedges. The study areas are Batagay and Zyryanka in northeastern Siberia, and North Slope in Alaska. The gas was extracted using a dry extraction method that physically breaks down ice, and cryogenically collects gas in a stainless steel tube. The gas mixing ratios were analyzed by gas chromatography. N<sub>2</sub> and Ar occluded in the air bubbles in the ice are relatively unaffected by microbial activity, but if liquid water contacted atmospheric air and froze, the N<sub>2</sub>/Ar ratio in the ice will differ from the atmospheric value due to difference in the gas solubility in water. On the other hand, if O<sub>2</sub> was consumed by microorganisms in the ice, the concentration of O<sub>2</sub> will decrease and consequently the O<sub>2</sub>/Ar ratio will also decrease. Our results show that the δ(O<sub>2</sub>/Ar) and δ(N<sub>2</sub>/Ar) of the ice wedges in Zyryanka and North Slope areas range from -86.5% to -12.2% and from -16.0% to 5.5%, respectively with regard to modern air. The <sup>14</sup>C ages of Zyryanka and North Slope samples are 810±30 BP and 1920±30 BP, respectively, corresponding to the late Holocene. Because the late Holocene was a relatively warm period, it may be interpreted that the ice wedges formed predominantly from snow melt water, resulting in the negative values of δ(N<sub>2</sub>/Ar). This is in contrast with our earlier study on ice wedges in Central Yakutia region (Syrdakh, Cyuie, and Churapcha) (Kim et al., 2019). The Central Yakutian ice wedges formed during the Last Glacial Maximum (LGM) and the δ(N<sub>2</sub>/Ar) values of ~0% indicates that the ice did not form from snow melting. The δ(O<sub>2</sub>/Ar) of the Zyryanka and North Slope is much less depleted than that of Central Yakutian (close to -100%). Oxygen consumption by microorganisms in the Central Yakutian ice is more completed probably by the longer time period for the biogeochemical reaction compared to the Zyranka and North Slope ice (>20,000 years vs. < 2,000 years). The ages of Batagay ice wedges range to earlier part of the Late Pleistocene, and may allow us to study longer biogeochemical reactions in ice. The concentrations of CO<sub>2</sub>, N<sub>2</sub>O and CH<sub>4</sub> in the Batagay ice range 260-71,000 ppm, 0.11-68 ppm and 4.7-130 ppm, respectively. Further geochemical analyses are in progress. Future study will include scrutinizing correlations among the three greenhouse gas concentrations. Our study shows that the gas mixing ratios in ice wedges may hlep us better understand the biogeochemical reactions in the ice and climate conditions when the permafrost formed.</p>

Heat Transfer and Pressure Drop During Condensation of Ammonia in Microchannels

2012 ◽  
Author(s):  
Brian M. Fronk ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Process ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Process Data ◽  
Improve Energy Efficiency ◽  
Tube Heat Exchanger ◽  
Component Size

An experimental investigation of condensation heat transfer and pressure drop of ammonia flowing through a single, circular, microchannel (D = 1.435 mm) was conducted. The use of ammonia in thermal systems is attractive due to its high latent heat, favorable transport properties, zero ozone depletion (ODP), and zero global warming potential (GWP). At the same time, microchannel condensers are also being adopted to increase heat transfer performance to reduce component size and improve energy efficiency. While there is a growing body of research on condensation of conventional refrigerants (i.e., R134a, R404A, etc.) in microchannels, there are few data on condensation of ammonia at the microscale. Ammonia has significantly different fluid properties than synthetic HFC and HCFC refrigerants. For example, at Tsat = 60°C, ammonia has a surface tension 3.2 times and an enthalpy of vaporization 7.2 times greater than those of R134a. Thus, models validated with data for synthetic refrigerants may not predict condensation of ammonia with sufficient accuracy. The test section consisted of a stainless steel tube-in-tube heat exchanger with ammonia flowing through a microchannel inner tube and cooling water flowing through the annulus in counterflow. A high flow rate of water was maintained to provide an approximately isothermal heat sink and to ensure the condensation thermal resistance dominated the heat transfer process. Data were obtained at mass fluxes of 75 and 150 kg m−2 s−1, multiple saturation temperatures, and in small quality increments (Δx∼15–25%) from 0 to 1. Trends in heat transfer coefficients and pressure drops are discussed and the results are used to assess the applicability of models developed for both macro and microscale geometries for predicting the condensation of ammonia.

scholarly journals Stabilizing Effects of Supercritical CO2 Fluid Properties on Compressor Operation†

2019 ◽  
Vol 4 (3) ◽  
pp. 20
Author(s):  
Alexander Johannes Hacks ◽  
Sebastian Schuster ◽  
Dieter Brillert
Keyword(s):  
Critical Point ◽  
Supercritical Co2 ◽  
Cooling Power ◽  
Inlet Temperature ◽  
Stabilizing Effect ◽  
Fluid Properties ◽  
Compressor Inlet ◽  
Applicable Range ◽  
Temperature And Pressure ◽  
Inlet Conditions

This paper aims to give an understanding of an effect which stabilizes the inlet conditions of compressors for supercritical CO2 (sCO2) operating close to the critical point. The effect was observed during testing of the turbomachine within the sCO2-HeRo project, and is caused by the sCO2 real gas properties close to the pseudocritical line. Under theoretical consideration, strong gradients in the fluid properties around this line—dependent on the static temperature and pressure of sCO2—can result in strong variation of compressor performance and finally lead to unstable cycle behavior. However, this paper demonstrates reduced gradients in density at the compressor inlet when varying the cooling power and taking advantage of a stabilizing effect. The applicable range and the significance of this stabilizing effect depended on the cooler inlet temperature and pressure, and was used to evaluate the relevance for individual cycles. Controlling the cooling power and the measurement of the inlet density allowed control of the compressor inlet conditions equally well, independent of the operating point, even close to the critical point.

scholarly journals CFD Analysis of a Tubular Heat Exchanger for the Conditioning of Olive Paste

2021 ◽  
Vol 11 (4) ◽  
pp. 1858
Author(s):  
Claudio Perone ◽  
Roberto Romaniello ◽  
Alessandro Leone ◽  
Pasquale Catalano ◽  
Antonia Tamborrino
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Extraction Process ◽  
Hot Water ◽  
Inlet Temperature ◽  
Cfd Analysis ◽  
Tubular Heat Exchanger ◽  
Inlet Conditions

The use of a heat exchanger for the conditioning of the olive paste could enhance the olive oil extraction process. Particularly, paste pre-heating could reduce the malaxation time and, most of all, improve the temperature control during this process (e.g., 27 °C). In this study, a three-dimensional computational fluid dynamics (CFD) analysis of a tubular heat exchanger was carried out to better understand the influence of the inlet conditions of the olive paste on thermal and hydrodynamic behavior within it. CFD analysis was performed with SOLIDWORKS Flow Simulation (ver.2016). The heat exchanger consists of a tube-in-tube module, in which the inner tube was fed with the olive paste, while the jacket was filled of hot water. The main aim was that to predict the heat transfer and pressure drop in paste side of the exchanger. Multiple analyses by varying the mass flow rate and inlet temperature of the paste were carried out, and temperature and pressure drop were estimated. The numerical model has proved very useful in identifying the main factors affecting the optimization of the heat exchanger in order to improve the extraction process of the olive paste.

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