DEW Line Research Articles

Experimental study of leakage characteristics and risk prediction of N2-containing dense-phase CO2 pipelines in real transportation conditions

In the background of pipelines being widely used as a critical transportation chain for the carbon capture, utilization and storage (CCUS) process, studying the leak diffusion characteristics and risks of high-pressure impure CO2 pipelines in real transportation conditions is critical for process safety. Due to the limitations of the capture process and economic cost, the CO2 used for sequestration contains impurities in the range of 3% molar ratio, mainly N2. In this paper, the first leakage experiments involving dense-phase CO2 with a 3% molar ratio of N2 impurity were conducted on a large CO2 pipeline (258 m long and 233 mm inner diameter) using initial leakage orifices of 50 mm and 100 mm. Data concerning the thermodynamic properties of the impurity-containing leakage source were gathered for the analysis of phase transitions and flow alterations within the pipeline, as well as near-field temperature and the progression of the far-field concentration. The pressure-temperature curve in the pipe shifted along the dew line and then slowly shifted to the saturation line of pure CO2 with the influence of N2 impurities during the multiphase leakage phase. In the near-field region, cryogenic diffusion was governed by the boundary of the jet, with the control distance decreasing as the leakage orifice increased. In addition, an accurate prediction model of CO2 concentration on the leak axis was established based on the virtual source theory and the concentration decay law, and the predicted locations of CO2 concentrations at the 5% were 169 m and 210 m. As the leak orifice increases, the risk of low temperatures and high concentrations escalates, albeit with a sharp decrease in duration. These data provide accurate leakage characteristics and risk assessment for safely operating high-pressure CO2 processes under real conditions with impurities.

High-pressure liquid refrigerant injection for reciprocating compressors

Isentropic (adiabatic) compression of superheated vapor in vapor compression refrigeration cycles usually results in some discharge superheat, i.e. the discharge temperature exceeding the condensing temperature. Large discharge superheat reduces both operating range and compression efficiency. Sub-isentropic compression with heat rejection to the heat sink is therefore superior to adiabatic compression, as it results in lower discharge superheat and improved efficiency. However, significant temperature reduction by heat transfer through the working chamber walls is difficult to facilitate in common refrigeration compressors, particularly reciprocating compressors. Refrigerant and oil injection is a well-established method for reducing temperatures and increasing efficiency in screw and scroll compressors, as well as multi-stage systems. In comparison, effective methods for temperature reduction in single-stage reciprocating compressors are fairly limited. Therefore, a concept for high-pressure liquid injection is proposed. By means of a pump and injection valve, high-pressure liquid refrigerant is injected into the working chamber and atomized. The compressed gas is cooled through the evaporation of the injected liquid. The injection valve allows for control over the injection timing and quantity, enabling adjustment of the temperature profile, which is a major distinction from existing refrigerant injection methods. The coupled compression-injection process is evaluated for various refrigerants using an energetic chamber model. The injection is found to be particularly suitable for refrigerants with a large evaporation heat and a shallow dew line slope. For the example of ammonia, a theoretical reduction in compression work of 8.9% at an evaporation temperature of −10 °C and a condensing temperature of 45 °C is found.

Ongoing legacy contamination from a military radar station in Iceland: a case study

The Dew line radar station at Heidarfjall in 1958 (https://www.radomes.org/museum/acwgrnland.php).

Thermal Conductivity Calculation Model for Refrigerant Mixtures in the Vapor Phase

Thermal conductivity measurements of ten refrigerant mixtures (R-404A, R-406A, R-407C, R-409A, R-410A, R-415A, R-507A, R-227ea/R-134a 61.5/38.5, R-227ea/R-134a 88.8/11.2 and R-227ea/R-134a 45/55) in the gas phase are analyzed. The thermal conductivity was studied with the same experimental setup, which improved the reliability of the results, excluding thereby systematic errors caused by using different methods to measure thermal conductivity. The reported experimental data have 1.5 % to 2.5 % uncertainty at 0.95 confidence level with a coverage factor of k = 2. Equations for calculating thermal conductivity depending on temperature and pressure are given for each mixture. The equations for thermal conductivity on the dew line and in the ideal gas state are obtained. A model for predicting thermal conductivity on a wide range of state parameters is proposed based on obtained experimental data and the theory of thermodynamic similarity. A comparison of the experimental data with the calculation model gives the standard deviation at 0.4 % to 2.1 %, which does not exceed the measurement error.

Systematic study of vapour–liquid equilibria in binary mixtures of fluids with different polarity from molecular simulations

ABSTRACT For engineering applications, one of the most important characteristics of fluid mixtures is the vapour–liquid equilibrium (VLE). Knowledge of the VLE of mixtures containing simple model components like Lennard-Jones (LJ) and Stockmayer (ST) fluids can offer insight into how different modes of molecular interaction shape the phase behaviour of mixtures. However, studies investigating such mixtures are still scarce in the literature, especially for mixtures with an LJ fluid as the high boiling substance. In this work, the VLE of mixtures consisting of LJ and ST fluids are studied with molecular simulation using the Grand Equilibrium method. The energy parameter and length parameter of the LJ fluids and the dipole moments of the ST fluids are varied systematically to generate different types of mixtures. These mixtures are investigated within a broad temperature range. VLE envelopes and molarities are reported as well as additional data on the bubble and dew line including enthalpies, chemical potentials, and activity coefficients. These data fill a gap in the literature by furthering the understanding of how polarity affects phase behaviour in mixtures and are therefore of critical importance, e.g. for the development of theoretical approaches for the description and prediction of phase behaviour for polar mixtures.

Experimental study of R-32/R-125 (75/25 wt.%) thermal conductivity in the vapor phase

The article presents the investigation of the thermal conductivity of binary mixture R-32/R-125 (75/25) in the gas state. Measurements were taken with a coaxial cylinders method in the temperature range of 305-426 K and the pressure range of 0.1-1.8 MPa. The dependence of thermal conductivity on pressure and temperature was discussed. The equations for thermal conductivity on the dew line and in the ideal gas state were obtained.

Thermal conductivity of R-32/R-125 (40/60 wt. %) mixture in the vapor phase

The gaseous thermal conductivity of binary mixture of R-32/R-125 (40/60) was measured with a coaxial cylinders method in the temperature range of 305–426 K and the pressure range of 0.1–1.8 MPa. The thermal conductivity as a function of pressure and temperature was considered. The correlations for thermal conductivity on dew line and in ideal gas state are presented.

Experimental Study of Thermal Conductivity of R-125/R-134A (39/61) Mixture in Vapor Phase

The coaxial cylinders method was used to measure the thermal conductivity of the R-125/R-134A (39/61) gas mixture. The experiments were carried out in the temperature range of 320–415 K and in the pressure range of 0.1–1.8 MPa. Coefficients were determined for an equation describing the thermal conductivity as a function of pressure and temperature. Thermal conductivity on the dew line and in ideal-gas state was calculated.

Vapor pressure, density, and speed of sound of the R134a-R227ea refrigerants in the vapor phase

The pressure on the dew line and density of the gas-phase 69.2 wt.% R134a / 30.8wt.% R227ea refrigerant were investigated using a constant volume piezometer in the temperature range from 293 to 373 K and at pressures from 0.45 to 3.1 MPa. The speed of sound of the 70.1 wt.% R134a / 29.9 wt.% R227ea mixture (323-373 K, 1.2-1.5 MPa) was also measured using an ultrasonic interferometer. The measurement errors of the temperature, pressure, density, and speed of sound were ±20 mK, ±4 kPa, ± (0.15–0.25)%, and ± (0.2–0.3)%, respectively. Approximation dependences of the studied properties were obtained and their errors were estimated. The obtained results were compared with the calculations using the REFPROP program.

Vapor thermal conductivity of R-125/R-134a (84.6/15.4) mixture

The vapors thermal conductivity of binary mixture R-125/R134a (84.6/15.4) was measured with a coaxial cylinders method in the temperature range of 305–412 K and the pressure range of 0.1–1.7 MPa. The thermal conductivity as a function of pressure and temperature was considered. The correlations for thermal conductivity on dew line and in ideal gas state are presented.

Dale and the Bomb: Exploring the Nuclear Future and Cold War Anxiety in 1950s Canadian Children’s Literature

Between 1950 and 1962, Joe Holliday wrote an adventure series called Dale of the Mounted, which consisted of 12 novels featuring Dale Thompson, a young constable of the Royal Canadian Mounted Police. Written for children and adolescents at a time when few books were directed toward young Canadians, these books stood out. What is more remarkable about this series is the author’s use of contemporary Cold War headlines in Dale’s adventures, such as nuclear meltdowns and atomic research, espionage plots, refugee crises, and the construction of northern radar systems. Holliday presented Cold War dramas to children as a means of educating them about their country and current events in an entertaining manner. This article focuses on two of Holliday’s Cold War adventures in particular, Dale of the Mounted: DEW Line Duty (1957) and Dale of the Mounted: Atomic Plot (1959). Both books express excitement for the future of Canadian science, technology, and industry, while the storylines are weighted in Cold War anxieties about espionage and nuclear disaster. This article explores the balance between fear and hope in the nuclear era. Holliday’s books stress the importance of control and order in a period of uncertainty and potential chaos. As rare examples of Canadian atomic culture in a decade dominated by American film and literature, DEW Line Duty and Atomic Plot are unique displays of Canadian Cold War society during the 1950s.

Thermal conductivity calculation model of refrigerant mixtures on the dew line

The results of the thermal conductivity measurements of ten mixture refrigerants in the gas phase are analysed. An equation for calculating the thermal conductivity is given for each mixture as a function of temperature and pressure. Basing on experimental information and the theory of of corresponding states a model for predicting thermal conductivity on dew line is proposed.

Thermal conductivity investigation of R-227ea/R-134А (45/55) mixture in the vapor phase

Thermal conductivity of the gaseous R-227ea/R-134A (45/55) mixture was investigated by the coaxial cylinders method within the temperature range of 306–426 K and the pressure range of 0.1–1.6 MPa. Approximating dependence of thermal conductivity on pressure and temperature was obtained. Thermal conductivity on dew line and in ideal gas state was calculated.

Measurement of sorption phenomena near dew points of fluid mixtures: concept for the combination of gravimetric sorption analysis and Raman spectroscopy

Near dew points of fluid mixtures, measurements of thermophysical properties such as density are distorted by sorption phenomena on the internal surfaces of the experimental setup. The reason is that such phenomena change the composition of the gas mixture under study. Here, we present a new experimental approach, which enables density and composition measurements in the vicinity of the dew line at the same time. Density measurements will be carried out utilizing a state-of-the-art gravimetric sorption analyzer incorporating a magnetic-suspension balance, and for in situ composition analysis, a compact Raman backscattering setup will be employed. The goals are to expand the basic understanding of sorption phenomena on non-porous media and to improve the accuracy of density measurements at dew-point conditions.

Vapour-phase (p, ρ, T, x) behaviour and virial coefficients for the (ethane + carbon dioxide) system

Accurate density measurements on three binary (ethane + carbon dioxide) mixtures with ethane mole fractions of 0.05023, 0.20031, and 0.49954 were carried out at temperatures from T = (273.15 to 323.15) K with pressures up to the dew-point pressure or 6.0 MPa, whichever was lower. The gas mixtures were prepared gravimetrically and a well-proven two-sinker magnetic suspension densimeter was utilized for the measurements. It was observed that sorption effects have an impact on the reproducibility of the density measurements of up to 0.04%. Considering all measurement uncertainties in temperature, pressure, density, and composition, the relative combined expanded uncertainty (k = 2) in density was estimated to be less than or equal to 3.8 × 10−4. Relative deviations of the experimental densities from the GERG-2008 equation of state were less than 0.5%, which is clearly within the uncertainty of this equation. Values and uncertainties of the second and third virial coefficients were calculated by correlating the isothermal experimental data to a third-order virial equation. Second interaction virial coefficients were determined as well, and excellent agreement with literature was obtained. The new experimental data presented in this work can be especially used to further improve the performance of multi-parameter equations of state for mixtures, particularly in the vicinity of the dew line.

Densimetry for the Quantification of Sorption Phenomena on Nonporous Media Near the Dew Point of Fluid Mixtures

Phase equilibria of fluid mixtures are important in numerous industrial applications and are, thus, a major focus of thermophysical property research. Improved data, particularly along the dew line, are needed to improve model predictions. Here we present experimental results utilizing highly accurate densimetry to quantify the effects of sorption and capillary condensation, which exert a distorting influence on measured properties near the dew line. We investigate the (pressure, density, temperature, composition) behaviour of binary (CH4 + C3H8) and (Ar + CO2) mixtures over the temperature range from (248.15 to 273.15) K starting at low pressures and increasing in pressure towards the dew point along isotherms. Three distinct regions are observed: (1) minor sorption effects in micropores at low pressures; (2) capillary condensation followed by wetting in macro-scale surface scratches beginning approximately 2% below the dew-point pressure; (3) bulk condensation. We hypothesize that the true dew point lies within the second region.

Thermal conductivity of R-410A mixture in the vapor phase

Thermal conductivity of R-410A mixture in the vapor phase (314–428 К and 0.1–2.0 MPa) has been studied by the steady-state method of coaxial cylinders. Experimental uncertainties of temperature, pressure, and thermal conductivity measurements did not exceed 0.05 K, 4 kPa, and 1.5-2.5 %, respectively. The approximating equation has been obtained for thermal conductivity depending on temperature and pressure. Thermal conductivity on dew line and in ideal-gas state has been calculated.

Speed-of-sound measurements in (argon + carbon dioxide) over the temperature range from (275 to 500) K at pressures up to 8 MPa

The speed of sound of two (argon+carbon dioxide) mixtures was measured over the temperature range from (275 to 500)K with pressures up to 8MPa utilizing a spherical acoustic resonator. The compositions of the gravimetrically prepared mixtures were (0.50104 and 0.74981) mole fraction carbon dioxide. The vibrational relaxation of pure carbon dioxide led to high sound absorption, which significantly impeded the sound-speed measurements on carbon dioxide and its mixtures; pre-condensation may have also affected the results for some measurements near the dew line. Thus, in contrast to the standard operating procedure for speed-of-sound measurements with a spherical resonator, non-radial resonances at lower frequencies were taken into account. Still, the data show a comparatively large scatter, and the usual repeatability of this general type of instrument could not be realized with the present measurements. Nonetheless, the average relative combined expanded uncertainty (k=2) in speed of sound ranged from (0.042 to 0.056)% for both mixtures, with individual state-point uncertainties increasing to 0.1%. These uncertainties are adequate for our intended purpose of evaluating thermodynamic models. The results are compared to a Helmholtz energy equation of state for carbon capture and storage applications; relative deviations of (−0.64 to 0.08)% for the (0.49896 argon+0.50104 carbon dioxide) mixture, and of (−1.52 to 0.77)% for the (0.25019 argon+0.74981 carbon dioxide) mixture were observed.

Thermal conductivity of the R-227ea (61.5 mass %)-R-134a (38.5 mass %) mixture in vapor phase

Recently, in the air conditioning and refrigeration industries, fluorohydrocarbons (HFC) have replaced fluorchlorinecontaining hydrocarbons (HClFC); the latter should gradually go out of use. To replace the forbidden chlorinecontaining refrigerants, the search for and development of the new mixtures has been undertaken; these mixtures should be suitable in use, costefficient, and not reduce the efficiency of the refrigerating unit. For the active and largescale implementation of the new mixtures, the exact ther� mophysical properties of such systems should be known (1). In the present work, we propose a mixture of 61.5 mass % of 1,1,1,2,3,3,3�heptafluorpropane, C 3HF7 (R�227ea), and 38.5 mass % of 1,1,1,2�tet� rafluorethane, C2HF4 (R�134a); the mixture belongs to the ozonesafety refrigerant group with the ozone depletion potential ODP = 0. The values of the ther� mal conductivity in the vapor phase were obtained experimantally and the temperature dependence of the thermal conductivity in the idealgas state and on the dew line was calculated.

Assisted Revegetation Following Contaminated Site Remediation in the Arctic: Four-Year Case Study of a Former Radar Site

Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies in the late 1990s and early 2000s determined that extensive soil contamination existed across the site, and excavation of six landfills and subsequent reshaping of the area in 2008 disturbed approximately 19,700 m2. A four-year pilot project was conducted between 2009 and 2012 to investigate feasibility of, and determine methods to, accelerate revegetation of the disturbed area through assisted seed dispersal of native and non native species and selective transplantation of slow-growing shrub species. Prior to revegetation efforts, plant surveys conducted in July 2009 determined that 15 species were present in the undisturbed areas, of which Salix arctica (~11%), Vaccinium uliginosum L. (~8%), and Empetrum nigrum L. (~5%) were the predominant species. A total of 14 species (three new) were observed growing on the disturbed areas between 2010 and 2012. The majority of Lolium multiflorum (annual ryegrass) seeds planted as a nurse species in 2009 grew in 2010, but most were stunted and only observed in furrows or sheltered areas at a low density. Salix arctica Pall. (willow) cuttings planted in “islands” of 20-30 cuttings in fall 2009 had a three-year survival rate of 82%, while a second set of cuttings planted in fall 2011 had a one-year survival rate of 93%. Visual observations indicate that patches of new vegetation are becoming more predominant on the disturbed area, especially around the willow islands, indicating the importance of microtopography for successful reclamation in arctic environments. Monitoring over ten or more years will be required to determine the long term success of this project.