Chapter 4
Flow measurement
Viet Dung Nguyen
Department of Electronic Technology and Biomedical Engineering, Hanoi University of Science and Tech
Sensors and Measurements in Biomedicine Chương 4: 2/
4.1. CÁC ĐẠI LƯỢNG CẦN ĐO
4.2. ĐO LƯU LƯỢNG MÁU TRONG MẠCH MÁU
ĐƠN
4.3. PHÉP ĐO DÒNG MÁU MÔ
4.4. ĐO LƯU LƯỢNG KHÍ HÔ HẤP
Sensors and Measurements in Biomedicine Chapter 4: 3/
4.1. OBJECT QUANTITIES
4.1.1. Unit in Flow Measurements
- For fluid flow
+ Volume flow rate: m3/s, kg/s; l/s, l/min, ml/min
+ Mass flow rate: m3/s.kg; ml/(min.100g): volume flow rate per unit
mass of tissue
+ Volume flow rate per unit volume of tissue: number of turnovers in
the unit of time interval: s-1, min-1...
+ Flow velocity: m/s
- For gas flow: pressure and temperature are known
+STPD (Standard Temperature and Pressure, Dry): 10C, 101,325 kPa
(1 atm), zero water vapor pressure
+ BTPS (Body Temperature, ambient Pressure and Saturated with
water vapor):
+ ATPS (Ambient Temperature and Pressure Saturated with water
vapor)
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4.1.2. Requirements for Measurement Range
- Flow rate: ~ (2R)3
- Mean velocity: ~ (2R)
- Different flow rate or velocity →
different measurement
4.1.2.1. Blood flow in a single vessel
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- Flow velocity: not uniform but distributed
Assumption: conduit is a long straight, cylinder tube, flow is steady and
laminar
➔parabolic velocity profile
−= 2
2
mR
r
1U)r(U
==
R
0
m
2UR
2
1
rdr2).r(UQ
Parabolic velocity profile in long circular conduit
with steady laminar flow