flow by xiaohuicaicai

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									Flow Measurement and
     Tank Design
       MARI-5432
 AQUATIC SYSTEM DESIGN
              Objectives
• Describe various ways in which Q, or flow
  rate, can be determined for both liquids
  and gases
• Introduction to design concepts
• Lab: Introduction to AutoCadTM
Flow Estimation/Measurement
•    Understanding of flow measurement in aquatic
     systems is necessary for:
    1. maintenance of water levels in tanks
    2. monitor water flow from tanks
    3. adjustment of flow rates to maintain water quality
•    There are various ways to sense and maintain
     water levels in tanks and measuring water flow
     rates through pipes
•    Some are used to measure volumetric flow
     rates (Q) directly or velocity (V)
          Classification of Flow
              Measurement
• Either direct or indirect
• Direct involves measuring
  a quantity of flow per unit
  time
• Flow measured either by
  volume or by weight
• Example: using a
  impeller rotations to
  determine Q in a
  hydraulic stream
 Indirect Flow Measurements
• Involve measurement of
  some change in pressure
  or other variable relative
  to rate of flow
• Examples: venturi
  meters, orifices, nozzle
  meters, weirs, flumes,
  electromagnetic
  flowmeter
• The EM flowmeter uses
  voltage generated when a
  conductor passes through
  a magnetic field
  Measuring Flow in Pipelines
• Numerous devices:
  differential pressure,
  electromagnetic, rotating
  mechanical, bypass,
  ultrasonic, insertion, variable
  area, anenometer (gases)
• Differential flow meters create
  a pressure difference
  proportional to the square of
  the volumetric flow rate (Q)
• Differential created by passing
  the flow through a contraction
  in the pipe
• Most common is the venturi
  tube meter
         Venturi Tube Meters
• Venturis contain three
  sections: 1) converging
  (upstream), throat
  (constriction) and
  diverging (downstream)
• Pressure drop created
  between converging and           Q = Cd2K√P1 – P2
  throat sections as fluid
  passes through the throat                   1 – (d/D)2
• Lower pressure is created    Q = discharge, C = flow coefficient, d =
                               diameter of throat, D = diameter of
  by higher velocity through   converging section, P1 = pressure in
  the throat                   converging section, P2 = pressure in
                               throat section, K = unit constant (metric
                               vs. Eng.)
  Rotating Mechanical Meters
• Use rotating
  propellers, impellers,
  rotors, turbines,
  vanes, etc.
• Revolve at a speed
  proportional to Q
• Usually have displays
  indicating number of
  rotations
• Must be calibrated
  Other Types of Flowmeters
• Bypass: meter located in bypass section of
  piping
• Electromagnetic: liquids have conductivity and
  generate a voltage proportional to velocity, two
  electrodes
• Ultrasonic: also non-intrusive, two beams
  (upstream and downstream)
• Variable area: also called rotameters, vertical
  tapered glass or plastic tube, in-line, uses float
Part 2. Tank Design
      What Type of Tank???
• Aquatic systems typically contain tanks used for
  the culture or holding of aquatic organisms
• Tanks must reflect the needs of the organism
• Best design is usually identified from experience
  and what you hope to accomplish (display,
  research, maintenance, etc.)
• Display tanks are obviously constructed of clear
  glass
• Research tanks can be clear if objective is to
  observe animals, opaque if disturbance is an
  issue
       How Many Tanks????
• Biomass density is the primary issue
• Most commonly cultured aquatics have well-
  known criteria
• Most densities reflect natural conditions
• Exception: aquaculture production
• To a certain extent, biomass density can be
  exaggerated for effect (e.g., reef tanks)
• Problem with display tanks is typically high
  species diversity (caring for all animals in same
  environment is difficult)
      How Many Tanks???
• Also required is a fundamental working
  knowledge of how to estimate tank volume
• Tanks have variable shapes and volumes
• rectangular or square tanks = l × w × h
• cylindrical = π × r2 × h
• conical = ⅓ πr2h
• cylindroconical = (πr2h) + ( ⅓ πr2h)
       How Many Tanks???
• From an aquaculture perspective, the
  number of tanks required for the system
  depends upon anticipated production
  capacity
• Must take into consideration survival from
  initial stage of development to final stage
• Classic example is the production of
  postlarval shrimp in a hatchery
• Has strong impact on seawater demand
     Determining Seawater
       Demand/#Tanks
• Really a matter of number of tanks in facility and
  their turnover rate (T)
• Number of tanks depends on PL production
  capacity
• Let’s pick a medium-sized production facility: 50
  M PL8-12 per month
• Once you make this assumption, you must work
  backwards for sizing other tanks/facilities
      Determining Seawater
        Demand/#Tanks
50 million PL8-12/month
      70% SURV
71 million PL1/month      1430 MT water (@ 50 PL1/L)

      50% SURV            715 MT if tanks used 2x/m


                          36 x 20 MT postlarval
                          rearing tanks
142 million N5/month      1420 MT water (@ 100 N5/L)
     Determining Seawater
       Demand/#Tanks
142 million N5/month     1420 MT water (@ 100 N5/L)

                         710 MT water if tanks used
                         twice per month

                         72 x 10 MT larval rearing
                         tanks
200 million eggs/month     1,333 spawning females/m
                           @ 150,000 eggs/spawn
      Determining Seawater
        Demand/#Tanks
1,333 spawning females/m
@ 150,000 eggs/spawn
      @ 30 d/month

45 spawning females/night
      @ 10% spawning/night

 450 females in maturation
      @ 30 females/tank

15 active maturation tanks
       (8 MT)
                             20 maturation tanks
                             (5 non-active)
       Determining Seawater
         Demand/#Tanks
45 spawning females/night   72 x 10 MT larval rearing
       @ 2 females/tank     tanks
                                   10% or 5% factor
23 spawning tanks
                            72 MT large volume algae
                            tanks (low cell density) or
24 spawning tanks (500 L)   36 MT large volume algae
                            tanks (high density)
Estimating Reservoir Volume
Hatchery Area        Volume   Turnover   Daily
                     (MT)     Rate       Volume
                                         (MT)
Maturation           160      2.25       360

Spawning             12       10         120

Larval rearing       720      1          720

Postlarval rearing   720      1          720

Large volume algae   72       1          72

                              Total      1,992 MT
         Construction Materials
• Tanks used in aquatic systems are constructed from a
  variety of materials
• Fiberglass, concrete and glass are most common
• Some are constructed of wood with plastic liners
• Basic criteria
   –   smooth inner surfaces to reduce abrasion
   –   nontoxic surfaces
   –   durability and portability
   –   long life
   –   ease of cleaning, sterilizing and repair
   –   affordable!!!
Various Hatchery Systems
• Seawater abstraction/treatment
• Seawater distribution/drainage
• Production areas
   – Quarantine
   – Maturation/reproduction
   – Larval rearing
   – Postlarval rearing
   – Algae production
   Feed/Artemia prep
• Aeration
• Electrical
Construction Materials: wood
• Very inexpensive
• lightweight, easy to work
  with
• 3/4 in, marine plywood
  most common
• thick sections = no flex in
  walls, but needs some
  bracing
• no treated wood
• seal internal surfaces with
  epoxy or fiberglass resin
          Construction Materials:
                concrete
• Used for constructing large
  tanks or pools
• Easy to work with and shaped
• Due to weight, installation is
  permanent
• Use special cement for
  seawater tanks
• Must cure and apply slick
  glaze coat
• Gunite: very compact
  cement-like material that can
  be blown in a 5-10 cm-thick
  layer over metal frame (rebar,
  rabbit wire, chicken wire)
 Construction Materials: plastic
• "Plastic" refers to a
  number of polymers
  including polypropylene,
  polyethylene,
  polybutylene, polyvinyl
  chloride (PVC), acrylics
  and vinyl
• All have their good and
  bad characteristics
• Good: lightweight,
  portable, easy to repair,
  various shapes and sizes
• Most are non-toxic or
  initially toxic
         Construction Materials:
               fiberglass
• Usually the material of
  choice for most research
  tanks, but not aquaria
• lightweight, strong,
  durable, moderately
  priced, inert to both fresh
  and saltwater
• Withstands effects of UV
  if outdoors
• Very slick gel-coat on
  inner surface, various
  colors
• New designs will require
  new mold = $$$

								
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