CFD for Ballast Water & Bio-fouling Management

Transcription

1 CFD for Ballast Water & Bio-fouling Management Vivek V. Ranade Catalysis, Reactors & Separation Unit (CReST) Chemical Engineering Division National Chemical Laboratory Pune

2 OUTLINE Ballast Water & Bio-fouling Management Key issues Computational Fluid Dynamics What is CFD? Methodology Sample applications Closure

3 BALLAST WATER/ BIO-FOULING Filling/ draining: water hammer Sloshing Cleaning: high velocity jets Mixing/ exchange/ ballast water treatment Corrosion Microbial Flow assisted Film formation: stability & break-up Valves/ diodes/ piping circuit Handling large quantities of water/ complex protocols

4 BALLAST WATER EXCHANGE Replace coastal water with open ocean water during a voyage Emptying and refilling ballast tanks (sequential exchange) Flow-through dilution/ continuous exchange Concerns about Biological effectiveness Ship safety and operational issues Excess bending moment/ shear stress, propeller immersion, minimum forward draft, sloshing for sequential exchange Flushing by fresh water, stratification, over pressurization for continuous exchange

5 SLOSHING From Lee et al., Ocean Engineering 34 (2007) 3 9

6 WATER TREATMENT Use of Biocides Mixing of very small quantities in huge volume Heat Treatment UV Exposure time distribution Ultrasonic Cavitation Hydrodynamic Cavitation Pressure profiles, mixing

7 BALLAST WATER/ BIO-FOULING Filling/ draining: water hammer Sloshing Cleaning: high velocity jets Mixing/ exchange/ ballast water treatment Corrosion Microbial Flow assisted Film formation: stability & break-up Valves/ diodes/ piping circuit Handling large quantities of water/ complex protocols

8 BALLAST WATER/ BIO-FOULING Detailed Modeling of Fluid Dynamics is Essential Conventional Methods Analytical fluid mechanics Restricted to very simple flows Scale models Restricted validity/ difficult to extrapolate Time consuming/ expensive COMPUTATIONAL FLUID DYNAMICS (CFD)

9 WHAT IS CFD? Solution of Mass, Momentum and Energy Balances on Digital Computers Major Features No restrictive assumptions / approximations Can handle complex geometry of industrial process equipment Can incorporate variety of processes simultaneously Can lead to: Accurate insight of underlying fluid dynamics A bridge between theory and experiments Process data which can not be obtained from experiments

10 COMPUTATIONAL FLOW MODELING Enhanced understanding of theory through numerical experiments Bridge between theory and experiments Detailed analysis at early stage in design cycle for less money, less risk and less time May provide data which is not possible to obtain experimentally High pressure/ temperatures Corrosive conditions Screening of alternative design configurations Sounds too good to be true! Is there any catch some where?

11 COMPUTATIONAL FLOW MODELING Uncertainties / Limitations: Inadequacies of the underlying mathematical model & input data Turbulence Multiphase flows Complex Rheology Chemical reactions Inaccuracies of the numerical technique (discretisation and roundoff errors) Computational constraints Interpretation of results Despite the Limitations, CFD has Enormous Potential! Necessary to develop appropriate methodology to harness this potential

12 NCL Multi-scale Modeling Capabilities to Provide Complete Solutions for Reactor/ Product Engineering Simulation of Drop Impact on Flat Surface: Understanding wetting Separate model to simulate erosion of support hooks Top portion of industrial thermo-siphon loop reactor modeled using hybrid approach Simulation of Fluidized Bed Reactor: multi-scale approach

13 METHODOLOGY Development & Creative Use of Computational Models for Better Reactor, Process & Product Engineering

14 APPLICATIONS Optimizing Ballast Water Exchange Strategies Ballast Water Treatment Technology Based on hydrodynamic cavitation Modeling of cavitating flows Devising effective cavitating it ti chamber h b ffor destruction of microbes Adjust number density of cavities and intensity of collapse as per the requirements J-type side Ballast Tank Patented cavitating devices for water dis-infection

15 BALLAST WATER DISPOSAL Flow-Through Exchange Method 300% of a tank s full capacity of clean water from the deep ocean must be pumped into each tank to achieve an acceptable 95% volumetric exchange. Sequential Exchange (empty / refill) Involves emptying tanks of high-risk ballast water at sea before refilling them with clean water from the deep ocean. Dilution Method Tank is partially filled and filling deep ocean water will dilute to original ballast water to 5% Exchange to take place no less than 200 nautical miles from coast & at water depth of at least 200 m

16 FLOW THROUGH EXCHANGE From Eames et al., Mar. Pollut. Bull. (2007), doi: /j.marpolbul

17 TYPES OF BALLAST TANKS Hopper pp Upper pp Wing g Ballast Tank Regular Double Bottom tank J-type side Ballast Tank

18 DOUBLE BOTTOM BALLAST TANK 1.5 m Geometric Details : 1. Volume of tank = 410 m3 2. Flow rate = 1000 m3/hr 30 m 9.12 m 410 m3 Tank volume τ= = = 0.41 hrs = 1476 sec 3 pumping rate 1000 m hr

19 PORT CONFIGURATIONS Outlet-1 Outlet-1 Outlet-2 inlet Single port