UV disinfection Synergy By Normand Brais PEng PhD National Air Filtration Association NAFA TECH 2014 Kissimme FL April 3 2014 Content 1 UV Fundamentals 2 Cooling ID: 294825
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Slide1
Filtration and
UV
disinfection
Synergy
By: Normand Brais
P.Eng
,
Ph.D
.
National
Air
Filtration Association
NAFA TECH 2014,
Kissimme
, FL
April 3 2014
Slide2
Content
1) UV Fundamentals
2)
Cooling
C
oils
D
isinfection
3) Filtration
F
undamentals
4) Filtration + UV :
complementaritySlide3
1) Fundamentals of UV light
UV-A
(400-315 nm) Sun glasses
UV-B
(315-280 nm) Sun tanningUV-C (280-200 nm) Germicidal UVUV-V (200-30 nm) V = Vacuum : O2 O3 Slide4
DNA : Watson and Crick 1953Slide5
Reproduction:
a
molecular
copying machineSlide6
UV
Sterilization
mechanism
: Dymerisation of Thymines pairsSlide7Slide8Slide9
Fundamental
Principle
of UV disinfectionUV Dose = intensity x time joule/ m
2
watt/m
2
sec
The
larger
the
Dose
,
t
he more
alterations
to the DNA,
leading
to
Sterilization
Slide10
Direct
Mathematical
C
orrelation N0 = Initial number of micro-organisms N(t)
= Number of micro-organisms surviving at time “t”
I
= UV radiation intensity
i
n W/m
2
t
= exposure time in seconds
Dose = I x t
, in Joule/m
2
K = susceptibility coefficient in m2/jouleSlide11Slide12
k values:
Susceptibility
of microbes to GUV
Figure 2. General ranking of suceptibility to UVC inactivation of microorganisms by group.Slide13
2)
Cooling
Coils
Surface DisinfectionSlide14
Coil
without
adequate
FilterSlide15
Coil
with
good
Filters: is it clean ?Slide16
Samples
taken
on
Clean Looking CoilsSlide17
Difference
between
virus,
bacteria, fungi and inert mineral dust ?Slide18
i
nert
dust
can’t grow and multiply !Slide19
About multiplication…by 2
2 x 2 x 2 x 2 x….x 2 = ?
10 times = 1,024
20 times = 1 million +
30 times = 1 billion +Slide20
What
lives
on
cooling coils ?A) Mold spores UV Dose for 90% killAspergillus Niger D90= 448 mJ/cm2
Cladosporium
wemecki
D90= 448
mJ
/cm
2
Penicillium
D90= 224
mJ
/cm
2
B)
Bacteria
Legionella
Pneumophilia
D90=
2.5
mJ
/cm
2
Pseudomonas
Aeruginosa
D90
= 2.2
mJ
/cm
2Slide21
UV dose
required
against
Aspergillus and Cladosporium UV Dose: 448 mJ/cm2 for 90% kill = 1 log
UV Dose:
896
mJ
/cm
2
for
99%
kill
= 2 log
UV Dose:
1344
mJ
/cm
2
for
99.9%
kill = 3 logUV Dose: 1792 mJ/cm2 for 99.99% kill = 4 logUV Dose: 2240 mJ/cm2 for 99.999% kill
= 5
log
a
nd
so
on…Slide22
How
much
UV
does
it take to keep a coil clean ?Disinfecting
Aspergillus
at
99%
within
1
hour
r
equires
a UV
intensity
of :
Intensity
=
896 mJ/cm2/(3600 sec) = 0.25 mW/cm2 = 250
μ
W/cm
2Slide23
Just the tip
of the iceberg…Slide24
Example
:
coil
of 10 ft x 10 ft
10 inches thick, 10 fins/inchCoil face = 100 ft2 Total coil surface = 20,000 ft2 ! !Coil heat
transfer
surface –vs- face areaSlide25
Area ratio = 2 X
Fins per
inch
X Coil thicknessSlide26
Inter-Fins UV PropagationSlide27
Move away for better resultsSlide28
Inter-Fins UV Propagation
1 reflection : UV =
80%
2 reflection : UV = 80% x 80%=
64%3 reflection : UV = 80%x80%x80%= 51%4 reflection : UV = 80%x80%x80%x80%= 41%5 reflection : UV = 80%x80%x80%x80%x80%= 33%
6 reflection : UV = 80%x80%x80%x80%x80%x80%=
26%
7 reflection : UV = 80%x80%x80%x80%x80%x80%x80%=
21%
8 reflection : UV = 80%x80%x80%x80% x80% x80% x80% x80%=
17%
9
reflection : UV =
80%x80%x80%x80%x80%x80%x80%x80%x80%=
13%
10
reflection : UV =
80%x80%x80%x80%x80%x80%x80%x80%x80%x80%=
11%Slide29
Aspergillus Niger:
time to
reach
99%
disinfection inside a CoilAt Coil
face, 250
μ
W/cm2: 1
hour
At 2’’
depth
,
113
μ
W/cm2:
2.2
hours
At
4’’
depth
, 51.4 μW/cm2:
4.9
hours
At
6’’
depth
,
23.3
μ
W/cm2:
11
hours
At
8’’
depth
,
10.6
μ
W/cm2:
24
hours
At
10’’
depth
, 4.8
μ
W/cm2:
52
hours
At 12’’
depth
, 2.2
μ
W/cm2:
115
hours
At
14’’
depth
,
1.0
μ
W/cm2:
254
hours
At
16’’
depth
,
0.45
μ
W/cm2:
561
hoursSlide30
Aspergillus Niger:
time to
reach
99%
disinfection inside a CoilAt Coil face,
500
μ
W/cm2
: 0.5
hour
At 2’’
depth
,
227
μ
W/cm2:
1.1
hours
At
4’’
depth, 103 μ
W/cm2:
2.4
hours
At
6’’
depth
,
46.6
μ
W/cm2:
5.4
hours
At
8’’
depth
,
21.1
μ
W/cm2:
12
hours
At
10’’
depth
, 9.6
μ
W/cm2:
26
hours
At 12’’
depth
, 4.3
μ
W/cm2:
58
hours
At 14’’
depth
,
2.0
μ
W/cm2:
127
hours
At 16’’
depth
,
0.9
μ
W/cm2:
281
hoursSlide31
Aspergillus Niger:
time to
reach
99%
disinfection inside a CoilAt Coil face,
1000
μ
W/cm2
: 0.25
hour
At 2’’
depth
,
453
μ
W/cm2:
0.55
hours
At
4’’
depth, 205 μ
W/cm2:
1.2
hours
At
6’’
depth
,
93.1
μ
W/cm2:
2.7
hours
At
8’’
depth
,
42.2
μ
W/cm2:
5.9
hours
At
10’’
depth
, 19.1
μ
W/cm2:
13
hours
At 12’’
depth
, 8.7
μ
W/cm2:
29
hours
At 14’’
depth
,
3.9
μ
W/cm2:
64
hours
At 16’’
depth
,
1.8
μ
W/cm2:
140
hoursSlide32
UV
rules
of
thumb
–vs- Coil ThicknessCoil thickness Avg UV on face Gross PowerCoil ≤ 12’’ 250 μW/cm
2
1 Watt/ft
2
12’’<
Coil
≤ 14’’
500
μ
W/cm
2
2 Watt/ft
2
14’’<
Coil
≤ 16’’ 1 000 μW/cm2 4 Watt/ft216’’ < Coil ≤ 18’’ 2 000 μW/cm
2
8
Watt/ft
2Slide33
Coil
Disinfection
Elimination
of biofilms formation
Lower
pressure drop
better
heat
transfer
energy
savings
Improved
occupant’s
wellbeing
UV system design
criteria
:
I
ntensity
Homogeneity
Inter-fin
penetrationSlide34
UV COIL DISINFECTIONSlide35
10
ft
x 10
ft
CoilSlide36Slide37
Petri
dish
samples taken with UV ON Slide38
3) How
Filters
W
orkSlide39Slide40
The MPP
C
hasm
Most
P
enetrating
Particle
sizeSlide41
HEPA
Filters
: MPP
ChasmSlide42
Filters
MERV
efficiency
(source: NAFA)Slide43
4 -
Filling
the
Chasm
with UV Slide44
4) FILTER+UV SYNERGY
FILTERS: good on
small
or large microbes
Between 0.02 and 1 micron, filters efficiency drop HEPA filters
:
also
a drop of
efficiency
b
etween
0.1
and
0.4 micron
UV : efficient
in
this
size range
viruses are easy targets for UV.Slide45
UV
can
complete
the job Slide46
Example
of
Combined
efficiency: MERV 16 Filter + UV ≥ HEPASlide47
A proof by
e
xample
:
In-Vitro Fertilization ClinicsIVF clinics with best HEPA filtrationFertilization success rate
stagnated
at
20 to 30%
W
hen
UV
was
added
to HEPA
S
uccess
rate
jumped
at 70 to 85% ! !Slide48
Independent
Studies
Published
by : THE LANCET
Medical Journal
“Impact of Ultraviolet Germicidal Lights Installed in the Ventilation Systems of Office Buildings on Workers Health and Well Being”
Richard
Menzies
MD MSc1
,2
, Julia
Popa
BEng MEng
1
,
James A Hanley PhD
2
, Thomas Rand PhD
3
, Don Milton MD Dr. PhD
4
.
From
:
1.Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute,
2.Department of Epidemiology and Biostatistics of McGill University
3.Dep’t of Biology, St. Mary’s University, Halifax, Nova Scotia,
4.Department of Environmental Health,
Harvard School of Public Health, Boston
.Slide49
The LANCET paper highlights
771 Employees
from
3
office buildings participated in the study.UV ON for 4 weeksUV OFF for 12 weeks3
cycles totalling 48 weeks.
Repeated twice, over 2 years.
When UV were ON :
40% reduction in respiratory
symptoms
20
% overall reduction in all symptoms
30% reduction in mucosal symptoms
These benefits were greatest for
those
with known
allergies
.Slide50
Conclusions
When
properly
engineered with adequate software, UV eliminates coil biofilms and saves Energy $$$UV improves overall performance of filters
Just
like
for Filtration
,
UV Fundamentals are
also
well
defined
in
ASHRAE
Handbook
Slide51
Working
hand in hand
with
good filtration practice, a well engineered Ultraviolet system brings a boost tobuilding hygiene and energy
efficiency
. Slide52
Thank
you
!