Conference Proceedings
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Item Numerical computation of Boil off Rate (BoR) in shipboard LNG tanks(IOP Publishing, 2022) Eswara, Arun Kishore; Sandilya, P.Natural gas is an environment-friendly fuel and a raw material for many chemicals. Its offshore transport is economical when the gas is transported in liquefied form as Liquefied Natural Gas (LNG) over distances (exceeding 2000 kilometers) by sea. LNG is stored at near-atmospheric pressure and about 112 K in these tanks. Heat inleak from the ambient into the stored LNG causes considerable boil-off of the LNG due to low latent heat of vaporization of LNG. Boil off Gas (BoG) generation should be reduced to minimize the loss of LNG as well as environmental pollution. Determination of the boil-off rate (BoR) poses a challenge because it involves interplay of multitude of phenomena and considerations, like liquid sloshing that is likely to generate heat and increases the interfacial area between the liquid and the ullage, variation in LNG composition due to BoG generation, and thermal stratification. In this paper we present a numerical analysis of the BoG generation, including some of the effects just mentioned. A model including transport phenomena based-equations and thermodynamic phase relations has been developed for this purpose.The simulation results would help in carrying out more in depth study of BoG generation that is useful in the design and operation of the prismatic membrane tanks.Item The prospects of dredging and indigenization of dredger design(Dredge India INAvation 2015 conference, 2015) Eswara, Arun Kishore; Ramesh, U. S.The scope for dredging in India is potentially vast, looking at the prospects of development and maintenance of existing major ports, building new ports, offshore resources exploration, demand from navy and more interestingly the projects envisaged for national waterways. The capital dredging demand during 2012-2017 is about 639 million m3 and that of maintenance dredging during the same period is about 521 million m3. This requires the employment of substantial number of dredgers of varying capacities. The minor sector dredging demand of about 100 million m3, during the said period, offers additional opportunity for dredging. The modal shift of cargo to inland and coastal waterways offers bright prospects for a sustainable economic prosperity. The government encouragement for “Make in India” has brought in a lot of economic interest as well. This is an excellent period to target for indigenization of dredger manufacture. Locally manufactured dredgers not only reduce costs of dredging but also encourage business climate. Further, it will enable India to produce globally competitive world class dredgers. The present paper is written in this context of presenting our study1 encompassing the scope for dredging activity, identifying suitable types and capacities of dredgers for employment in India. The paper also touches upon the present shipbuilding infrastructure, dredger equipment manufacturers and a road map for indigenization. The paper concludes with forecasting future dredging demands, scope for native dredgers manufacture, identifying a particular target range for indigenization.Item Some statistical relationships among dredger particulars observed in the Indian dredging fleet(The Royal Institution of Naval Architects, 2015-12-10) Eswara, Arun Kishore; Ramesh, U. S.Cutter suction dredgers (CSD), Trailing suction hopper dredgers (TSHD) and Grab dredgers form 88% of the total Indian fleet size, respectively in the order of individual share. Indian yards have achieved 90% indigenization in design and construction of grab hopper dredgers. However, there is a techno-economic backlog in India to manufacture some vital components for CSDs and TSHDs and companies are increasingly looking to buy foreign made dredgers at a high price. Dredging demand in India at ports and in navigable inland water ways is set to grow with the encouragement for water transport. Ministry of Shipping, Govt. of India has sponsored studies at Indian Maritime University-Visakhapatnam (formerly, NSDRC) for indigenization of dredger design and manufacture. The present paper aims to illustrate the existing dredger fleet of India and bring out some interesting correlations that aid the design of dredgers. Dredgers are built for a specific function. Due to this design objective, they differ from other marine vessels on the aspects of principle particulars, hopper capacities, powering and other functional data such as cutter power for CSD and dredge pumps power etc. The identified correlations among such parameters observed from the Indian dredging fleet are discussed. Certain ratios among the main dimensions for a TSHD such as length/breadth, breadth/dredge depth and breadth/draught, also known as ship ratios, are a key to dredger design and are known to vary with market conditions or time. They indicate design trends for future dredgers and require to be kept updated.Item Introduction to natural gas: A comparative study of its storage, fuel costs and emissions for a harbor tug(Society of Naval Architects & Marine Engineers, 2013-11-08) Eswara, Arun Kishore; Misra, S. C.; Ramesh, U. S.This paper discusses the science of natural gas, its composition and ways to determine and coherently express its physical and chemical properties. Pricing of natural gas is shown with regard to weight and energy. A 60 Ton harbor tug employing either a set of constant rpm engines for CPP operation, or a set of variable rpm engines for FPP operation, with a standard load profile is made the basis for discussion. Advantage of evaluating thermal efficiency of gas engines relative to the higher heating value of natural gas, as against its lower heating value is explained. A compendium of storage options and the resulting endurance with the use of natural gas forms such as liquified gas (LNG), compressed gas (CNG) and adsorbed gas (ANG) is presented. Steps to ascertain fuel consumption of the gas engines operated according to the load profile and an approach to evaluate and relate the quantities of LNG, CNG and ANG is shown. Fuel costs and emissions from the tug operation using natural gas as fuel are evaluated per month and compared with diesel and residual fuels. Green House Gas emissions as a summation of emission constituents from the natural gas fuelled tug operation is detailed, and its need emphasized. The concepts of useful work done, emission efficiency parameter and energy efficiency parameter, which may be helpful in the design of harbor tugs and similar service vessels are proposed. The emission efficiency parameter is evaluated and analyzed for the 60 ton harbor tug.