Analytical and Numerical Calculation of the Orifice Minimum Temperature Due to Joule - Thomson Effect
Mohammed Mohammed Said,
Abdelrahem Dohina,
Lotfy Hassan Rabie
Issue:
Volume 3, Issue 5, September 2017
Pages:
33-43
Received:
7 June 2017
Accepted:
19 June 2017
Published:
16 August 2017
Abstract: High pressure drop generated by a restriction orifice may result in a very low temperature, which can affect the piping material and may cause catastrophic piping failure if the operating temperature becomes lower than the minimum design temperature. This minimum design temperature is stated by piping ASME B31.3 code as -48°C. In such piping research branch, there has been relatively little investigation of very low temperature effect on pipelines. As well as, sizing the orifice with implementing temperature control to match piping material has a few analytical explanations, particularly in investigating the influence of Joule - Thomson effect on piping damage. Most commercial orifice sizing software ignore Joule - Thomson effect even though in choked flow condition. The objective of the present research is to compare a derived analytical equation with 3-D computational calculations by using ANSYS 16.0 for Joule - Thomson temperature drop through the orifice. As well as correlate the analytical equation to be safely considered as a good prediction tool for the lowest temperature at orifice throat instead of misleading ISO 5761 fully developed Joule - Thomson temperature drop. The analytical equation correlation has been carried out based on non-linear regression by grouping flow conditions, fluid properties, and orifice geometry, for minimum temperature prediction at orifice Vena-contracta. The numerical temperature differences in the fully developed flow regime after the office have been compared with EN ISO 5761-Part 3 Joule - Thomson temperature drop equation. Three orifices with β ratios, 0.3, 0.4, and 0.5 have been chosen for such study and numerical simulations have be carried out using k-ε and k-ω turbulence models. As a corollary of this study, it was concluded that the k-ε and k-ω models predict well both the flow and the fully developed temperature drop as compared with ISO 5761 equations. The errors are generally accepted at all conditions and both values give good agreement. The derived equation successfully predicts the lowest minimum temperature at Vena-contracta and can supersede ISO 5761-Part 3 Joule - Thomson temperature drop at fully devolved region.
Abstract: High pressure drop generated by a restriction orifice may result in a very low temperature, which can affect the piping material and may cause catastrophic piping failure if the operating temperature becomes lower than the minimum design temperature. This minimum design temperature is stated by piping ASME B31.3 code as -48°C. In such piping resear...
Show More
Establishing Mathematical Model to Predict Ship Resistance Forces
Do Thanh Sen,
Tran Canh Vinh
Issue:
Volume 3, Issue 5, September 2017
Pages:
44-53
Received:
18 October 2017
Accepted:
9 November 2017
Published:
5 December 2017
Abstract: Resistance forces of water affecting to the ship hull at every single time during ship motions change very complexly. For simulating the ship motion in 6 degrees of freedom on a bridge simulator, these forces need to be calculated. Previous studies showed that resistance forces were estimated by empirical or semi-empirical methods, basic hydrodynamic theory has not solved all components of resistance forces. Moreover, for simulating the ship motions at the initial design stage when experimental value is not available it is necessary to estimate resistance forces by theoretical method. Fully estimating damping forces by theoretical method is a practical challenge. This study aims to find out general equations to reasonably estimate all damping coefficients in 6 degrees of freedom for simulating ship motions on bridge simulators.
Abstract: Resistance forces of water affecting to the ship hull at every single time during ship motions change very complexly. For simulating the ship motion in 6 degrees of freedom on a bridge simulator, these forces need to be calculated. Previous studies showed that resistance forces were estimated by empirical or semi-empirical methods, basic hydrodynam...
Show More
