Entropy – stagnation enthalpy interpolation tables for calculation of the critical flow properties of compressible fluids

High-pressure pipelines provide the most cost-effective and established method for long-distance transportation of large quantities of compressible fluids, such as natural gas, hydrogen and carbon dioxide. Given significant safety hazards associated with these pipelines, their design and operation requires using mathematical modelling tools quantifying consequences of accidental pipeline failure. Central to this is the accurate and robust prediction of the critical discharge flow from the pipeline, accounting for the real fluid thermodynamic behaviour, including the phase transition induced by the decompression process. In this work, a method of inverse interpolation tables is developed to calculate physical properties of compressible fluid, for use in a computational model of transient outflow from an accidently ruptured pipeline. In particular, the density – energy interpolation tables are applied to calculate the fluid pressure, temperature and phase composition as required for solving the mass, momentum and energy conservation equations describing the decompression flow inside pipeline, while the entropy – stagnation enthalpy interpolation tables are introduced to obtain the critical (choked) flow properties at the rupture section of the pipe. To construct the latter, the choked flow properties are calculated by solving simultaneously the total enthalpy conservation equation along with the constant entropy condition. The interpolation is performed using Akima splines fitted to the thermodynamic properties data predicted using highly-accurate Perturbed Chain-SAFT (PC-SAFT) equation of state. The interpolation tables are constructed for ethylene and carbon dioxide, covering pressures from 0.1 to 10 MPa and temperatures ranging from the triple point to 350 K. The study provides recommendations for the optimal resolution of the interpolation tables to achieve a balance between the accuracy and computational efficiency of the calculated physical properties. Practical implementation of the interpolation method in a pipeline decompression flow model is discussed. Acknowledgement. This research has received funding from the European Union’s Horizon 2020 Research & Innovation Programme under the Grant Agreement No 884418, and Qatar National Research Fund (a member of the Qatar Foundation) NPRP award 8-1339-2-569

CO2PipeHaz: Quantitative hazard assessment for next generation CO2 pipelines

Without a clear understanding of the hazards associated with the failure of CO2 pipelines, carbon capture and storage (CCS) cannot be considered as a viable proposition for tackling the effects of global warming. Given that CO2 is an asphyxiant at high concentrations, the development of reliable validated pipeline outflow and dispersion models are central to addressing this challenge. This information is pivotal to quantifying all the hazard consequences associated with the failure of CO2 transportation pipelines, which forms the basis for emergency response planning and determining minimum safe distances to populated areas. This paper presents an overview of the main findings of the recently completed CO2PipeHaz project [1] which focussed on the hazard assessment of CO2 pipelines to be employed as an integral part of CCS. Funded by the European Commission FP7 Energy programme, the project's main objective was to address this fundamentally important issue

Techno-economic assessment of CO2 quality effect on its storage and transport: CO2QUEST: An overview of aims, objectives and main findings

This paper provides an overview of the aims, objectives and the main findings of the CO2QUEST FP7 collaborative project, funded by the European Commission and designed to address the fundamentally important and urgent issues regarding the impact of the typical impurities in CO2 streams captured from fossil fuel power plants and other CO2 intensive industries on their safe and economic pipeline transportation and storage. The main features and results recorded from some of the unique test facilities constructed as part of the project are presented. These include an extensively instrumented realistic-scale test pipeline for conducting pipeline rupture and dispersion tests in China, an injection test facility in France to study the mobility of trace metallic elements contained in a CO2 stream following injection near a shallow-water qualifier and fluid/rock interactions and well integrity experiments conducted using a fully instrumented deep-well CO2/impurities injection test facility in Israel. The above, along with the various unique mathematical models developed, provide the fundamentally important tools needed to define impurity tolerance levels, mixing protocols and control measures for pipeline networks and storage infrastructure, thus contributing to the development of relevant standards for the safe design and economic operation of CCS

Intrinsic factors and the embryonic environment influence the formation of extragonadal teratomas during gestation

Background: Pluripotent cells are present in early embryos until the levels of the pluripotency regulator Oct4 drop at the beginning of somitogenesis. Elevating Oct4 levels in explanted post-pluripotent cells in vitro restores their pluripotency. Cultured pluripotent cells can participate in normal development when introduced into host embryos up to the end of gastrulation. In contrast, pluripotent cells efficiently seed malignant teratocarcinomas in adult animals. In humans, extragonadal teratomas and teratocarcinomas are most frequently found in the sacrococcygeal region of neonates, suggesting that these tumours originate from cells in the posterior of the embryo that either reactivate or fail to switch off their pluripotent status. However, experimental models for the persistence or reactivation of pluripotency during embryonic development are lacking. Methods: We manually injected embryonic stem cells into conceptuses at E9.5 to test whether the presence of pluripotent cells at this stage correlates with teratocarcinoma formation. We then examined the effects of reactivating embryonic Oct4 expression ubiquitously or in combination with Nanog within the primitive streak (PS)/tail bud (TB) using a transgenic mouse line and embryo chimeras carrying a PS/TB-specific heterologous gene expression cassette respectively. Results: Here, we show that pluripotent cells seed teratomas in post-gastrulation embryos. However, at these stages, induced ubiquitous expression of Oct4 does not lead to restoration of pluripotency (indicated by Nanog expression) and tumour formation in utero, but instead causes a severe phenotype in the extending anteroposterior axis. Use of a more restricted T(Bra) promoter transgenic system enabling inducible ectopic expression of Oct4 and Nanog specifically in the posteriorly-located primitive streak (PS) and tail bud (TB) led to similar axial malformations to those induced by Oct4 alone. These cells underwent induction of pluripotency marker expression in Epiblast Stem Cell (EpiSC) explants derived from somitogenesis-stage embryos, but no teratocarcinoma formation was observed in vivo. Conclusions: Our findings show that although pluripotent cells with teratocarcinogenic potential can be produced in vitro by the overexpression of pluripotency regulators in explanted somitogenesis-stage somatic cells, the in vivo induction of these genes does not yield tumours. This suggests a restrictive regulatory role of the embryonic microenvironment in the induction of pluripotency