Environmental Engineering Reference
In-Depth Information
For each liquid the following data were evaluated:
1. the TDR-measured apparent liquid level,
H
app
;
2. the measured reflection coefficient,
meas
;
3. the corrected reflection coefficient according to (4.4),
ρ
ρ
corr
;
4. the square root of the calculated dielectric constant
√
ε
app
; and, finally,
5. the actual liquid level,
H
meas
.
To provide a simple performance assessment of the method, the relative percentage
difference between reference and measured liquid levels was calculated:
Δ
H
=
|
H
ref
−
H
meas
|
100
/
H
ref
.
(4.5)
The results for level and dielectric constant estimation are summarized in Table 4.1:
it is worth noting that the experimental results for the level measurements show a
very good agreement with the reference levels; similarly, the measured dielectric
constant values agree with those reported in [18].
Ta b l e 4 . 1
Summarized results obtained from TDR measurements for the estimation of levels
and dielectric constants of liquid samples reported in Fig. 4.4 (de-ionized water, acetone, fuel,
and diesel oil)
√
ε
app
H
ref
probe end
probe-to-liquid
H
app
ρ
meas
ρ
corr
H
meas
Δ
H
(cm)
point
interface point
(m)
(cm)
(%)
(cm)
(cm)
deionized water
41.3
776.5
401.0
375.5
-0.75
-0.80
8.97
41.8
1.2
acetone
27.2
546.5
416.7
129.8
-0.61
-0.65
4.71
27.6
1.5
fuel
32.1
459.0
411.0
48.0
-0.18
-0.19
1.47
32.6
1.5
diesel oil
27.8
457.2
415.0
42.7
-0.19
-0.20
1.50
28.1
1.1
4.2.3.1
Measurements on Stratified Liquids
The proposed measurement system was also validated for measurements of the lev-
els of stratified liquids (which can be particularly useful in the field of petrochem-
ical, chemical, or agro-food, industrial processing control purposes). In this case,
measurements were performed with the probe-end termination short-circuited.
A 27.5 cm-high diesel oil layer was considered on a 9.5 cm-high tap water
sample: the corresponding TDR waveform is reported in Fig. 4.5. The measured
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