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CHAPTER 6 FLOW MEASUREMENT & MEASUREMENT OF LIQUID LEVEL, Re = (ρ u2)…
CHAPTER 6
FLOW MEASUREMENT & MEASUREMENT OF LIQUID LEVEL
FLOW MEASUREMENT
A technique used in any process requiring the transport of a material from one point to another.
Elements needs to consider during FLOW MEASUREMENT
1) Clean or dirty
2) wet or dry
3) hazardous/corrosive or safe
4) laminar or turbulent
5) pressure
6) temperature
7) flow rate
measuring devices categories
Primary devices (quantity meter)
Measure the amount of fluid in terms of mass or volume
Advantages: Simple, economic and extremely accurate.
commonly used device
Nutating Disc Meter
application:
domestic water system.
description of the process
1) water flows directly into meter housing
2) water flows through the meters internal strainer before it enters measuring chamber
3) strainer do protects measuring chamber due to debris in the water
3 more items...
Sliding Vane Type Meter
application:
dispensing petrol/diesel in the fuel filling station.
is vane type positive displacement flow meter, creating high accuracy measurement and low pressure loss by decreasing rotation resistance.
due to small revolution resistance, it gives large volume measurement with low pressure loss.
Lobed Impeller Flow Meter
application:
metering of gas and refined petroleum products.
A type of positive displacement meter in which a fluid stream is separated into discrete quantities by rotating, meshing impellers driven by interlocking
gears.
Secondary devices (rate meter)
Variable head meter
pitot tube
know as the air-speed indicator used in aircrafts.
advantages
1) Simple and low cost.
2) No pressure loss in the flow system.
1 more item...
Re = (ρ u2) / (µ u / L)
If 2000<= Re <= 4000 = Critical zone between laminar & turbulent.
If Re > 4000 = turbulent flow.
If Re < 2000 = laminar flow.
P1 + (ρv1)^2 /2 + ρgh1 = P2 + (ρv2)^2 /2 + ρgh2
Bernoulli Equation
Re = Reynolds Number
ρ =density
u = velocity based on the actual cross section area of the duct or pipe
µ =dynamic viscosity
L = characteristic length
ν =kinematic viscosity
static pressure + dynamic pressure = total pressure
(Ps + ρ x (V^2)/2 ) = P1
