# 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
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
• 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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