Commercial Kitchen
Ventilation
Slide 1 14.9.2004
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How can we define a Professional
Kitchen ?
IT’S A UNIQUE SPACE WHERE :
• Meals are prepared
(Hot and cold kitchen)
• Dishes and
equipment are washed
• Foodstuff is stored
Slide 2 14.9.2004
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Why do we need a ventilation system
in commercial kitchens ?
TO ENSURE THE MOST PLEASANT WORKING ENVIRONNEMENT
1. Remove immediately
excess heat
2. Remove particules of
grease , odours, exhaust
gases ...
3. Remove moisture
4. Renew the air to refresh
the working place and
replace exhausted air
Slide 3 14.9.2004
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Where do the heat loads generated in
a commercial kitchen come from ?
Mainly from COOKING PROCESS’ and
1. Convective
COOKING EQUIPMENT.
Heat
1. Convective heat => can be captured
by a hood.
(totally or partly depending on hood
efficiency)
2. Radiated heat => can not be
captured by any hood.
3. Other :
• heat transfer through windows,
walls, ceiling
• occupants
• lights
• other appliances
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2. Radiated
Heat
How are exhaust rates calculated in a
commercial kitchen ?
•
•
EXHAUST AIR FLOW (Qve) rate is DIRECTLY related to :
quantity of CONVECTIVE HEAT (Qvc) generated by the cooking equipment
EFFICIENCY (Heff) of the hood system
Qve
IT’S A HEAT LOAD BASED DESIGN !!!
Qvc = Output of Cooking Equipment
Qvc = Qvc1 + Qvc2 + Qvcn
Qve = H.eff x Qvc
Qvc1
Qvc2
This means :
That design methods not based on cooking
appliances (m3/h/m, m3/h/m², m3/h/meal, face
velocity) can not provide accurate results.
Cooking equipment
Slide 5 14.9.2004
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Qvc3
How convective heat loads are calculated
for each piece of cooking equipment ?
•
According VDI 2052* standard
Qs,k = P ⋅ Qs ⋅ b ⋅ϕ
Convective
Heat Flow
(W)
Appliance
Input Power
*Verein Deutscher Ingenieure
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Simultaneous
Factor
Convective
Fraction of the total
amount of heat release (0,5)
Appliance
Sensible
Factor
VDI Standard (continued)
Exhaust
Flow
Convective
Heat Flow
Hydraulic
Diameter
Reduction
Factor
1/ 3
=
⋅
Vth k Qs ,k ⋅ ( z + 1.7 ⋅ d hydr ) ⋅ r
Height
Above
Appliance
Slide 7 14.9.2004
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Supply ventilation also
affects the exhaust flow
required
What are the strengths and
weaknesses of VDI ?
C
•
•
•
Accounts for convective plume
from cooking appliance.
Accounts for different ventilation
strategies (e.g. mixing versus
displacement).
Neutral method not coming from
a hood manufacture.
D
•
Slide 8 14.9.2004
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Does not account for differences
in hood design and hood
efficiency between different
manufacturers
How to measure hood efficiency ?
SPILLING
CAPTURING
ASTM 1704 HEAT
GAIN CURVE –
GENERIC EXAMPLE
CAPTURE &
CONTAINMENT
Heat
Gain
CONVECTIVE
RADIANT
Slide 9 14.9.2004
Exhaust rates
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RADIANT
How can we define hood efficiency ?
Exhaust only hoods (traditional system)
If excess heat and impurities are not captured by
the hood and are spread to the occupied zone.
The hood effciency is not good.
Not a comfortable working area.
Common Solution
Increase exhaust air flow (Qve) to
guarantee front velocity especially in
Critical Zone.
Higher dilution of room air to remove load.
Higher energy consumption.
Slide 10 14.9.2004
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Qvc / Heff = Qve
?
Qve
Exhaust only
hood
CRITICAL
ZONE
Qvc
Short Cycle system,
50 to 70% Induction
Designed first in the USA when high exhaust
rate followed exclusively the model codes.
Large volumes of untreated air is supplied
directly in the hood (50 to 70% of exhaust air).
Qvc + Qvi = Qve
!
Qvi
Qve
High air flow rates to guarantee acceptable
efficiency and to exhaust ”short circuit” air.
Thermal Plume (Qvc) is disturbed
and big problems occur during winter time.
Qvc
Inefficiency and poor working conditions.
System not advocated any more in Europe
and USA.
Slide 11 14.9.2004
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HALTON Capture Jet Hoods
= High Efficiency
Capture Jet technology designed by HALTON
in 80’s to prevent spillage at low exhaust rates.
Qvc + Qcj = Qve
Qcj
Qve
Use of high velocity Capture Jets to increase
face velocity of the hood with lower air flow.
Capture Jets push the thermal plume
towards the filters without interfering with the
convective flow.
Qvc
Efficiency is higher and air flow rates 35%
lower compared to exhaust only hood
system.
Supply/make up air is reduced as well.
Technological and energy efficient system.
Slide 12 14.9.2004
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20 l/s/m
is about
10%
Capture
Jet Air
Capture Jet Demonstration
Slide 13 14.9.2004
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Demonstration n°1 :
Tracer Gas Study
Qcj
Qve
me
eff =
260ºC
eff
%
70 %
83 %
Exhaust only
Qcj=0
Qve=600 m3/h
mtg
Slide 14 14.9.2004
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me
mt
g
84 %
90 %
Capture jet
Qcj=0
Qcj=60 m3/h
3
Qve=1000 m /h Qve=600 m3/h
Qcj=100 m3/h
Qve=1000 m3/h
Demonstration n°2 :
Computer Modeling (CFD*)
KVI with Capture Jets OFF
(same as hood exhaust only)
(Surface Temperature : 315°C)
*Computational Fluid Dynamics
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KVI with Capture Jets ON
(Surface Temperature : 315°C)
Demonstration n°3 :
Schlieren Thermal Imaging
•
•
•
Visualizes changes in air density
More sensitive than visualizing smoke
Quickly see impact of design changes
KVI with Capture Jets OFF
(same as hood exhaust only)
(Appliance : 315°C)
KVI with Capture Jets ON
(Appliance : 315°C)
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Schlieren Thermal Imaging Video :
KVL case study
Slide 17 14.9.2004
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Demonstration n°4 :
ASTM F1704
KVL laboratory test to measure how much heat is released into
the kitchen :
Full Load cooking conditions
SPILLING
CAPTURING
HOOD TYPE EXHAUST RATE CAPTURE AIR TOTAL EXHAUST
Capture Jet 620 m3/h (172 l/s) 37 m3/h (10,2 l/s) 657 m3/h (182 l/s)
No Capture Jet 850 m3/h (236 l/s)
0 m3/h
850 m3/h (236 l/s)
Test set up using a electric Griddle (17,1 KW)
Idle conditions (non-cooking)
HOOD TYPE EXHAUST RATE CAPTURE AIR TOTAL EXHAUST
Capture Jet 510 m3/h (142 l/s) 37 m3/h (10,2 l/s) 547 m3/h (152 l/s)
No Capture Jet 1037 m3/h (288 l/s)
0 m3/h
1037 m3/h (288 l/s)
Test set up using an electric Griddle (17,1 KW)
Heat
Gain
CAPTURE &
CONTAINMENT
CONVECTIVE
RADIANT
RADIANT
Exhaust rates
”Under the full-load cooking scenario, the capture jet technology reduced the
airflow required for complete capture and containment by 27% and for the idle
(non-cooking) situation, the jet reduced C&C by 51%.”
Slide 18 14.9.2004
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Demonstration n°4 (continued) :
ASTM F1704
KVI Laboratory test to measure how much heat is released
into the kitchen :
HOOD TYPE EXHAUST RATE
Capture Jet
1530 m3/h
Exhaust Only
2210 m3/h
CAPTURE AIR
90 m3/h
0 m3/h
TOTAL EXHAUST DUCT T° RISE HEAT GAIN
1620 m3/h
24°C
998 W
2210 m3/h
17,5°C
980 W
Test set up using an under fired charbroiler, 600 F surface temperature
Equivalent heat gain, but capture jet hoods use 30% less
exhaust air to do the same job.
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Demonstration n°5 :
EDF*
Heat gain for different hood systems
3000
Heat Gain (W)
2500
2000
50% induction
10 % capture jet
1500
Exhaust hood only
1000
500
0
3 700
4 200
4 800
5 300
3
Exhaust rate (m /h)
” the 50% induction hood creates a lot of turbulences in the thermal flow
especially when extract rate increases. The efficiency is even worse than a
traditional exhaust only hood ”
Independent test made by Electricité De France
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Demonstration n°5 (continued) : EDF
Capture efficiency benefit
Capture efficiency benefit (%)
60
40
20
0
-20
50% induction
-40
10% induction
-60
-80
-100
-120
-140
3 200
3 700
4 200
4 800
5 300
Exhaust rate (m 3/h)
” The test shows that performances of the hood is depending very much on the % of
induction air. If it’s too high (50%, 70%), turbulences prevent the hood from having a
good efficiency. If it’s about 10%, efficiency can be improved by 20 to 50%, that
means an equivalent reduction of extract rates.”
”Performances are not coming from the fact we are supplying untreated
air, but from a better capture efficiency of the hood”.
Slide 21 14.9.2004
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KSA Multi Cyclone Grease Filter
Halton Patented Design
•
•
•
•
•
•
Uses cyclonic effect to
improve filtration efficiency
Non-clogging design
Low and constant pressure
drop
Easy to clean
All stainless steel
93% to 98% efficient
on particules between
5 and 10 microns
ƒ
ƒ
‚
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•
KSA filter :
The Cyclonic Effect !
Slide 23 14.9.2004
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What about other conventional filters ?
BAFFLE
FILTER
•
•
•
•
MESH
FILTER
•
•
•
Slide 24 14.9.2004
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Higher pressure drop (125-150
Pa)
Lower grease extraction
efficiency
Higher noise level
Low pressure drop when clean,
but when dirty pressure drop
increases quickly
Difficult to wash
Risk of fire when grease collected
in the filter
Short life cycle
T.A.B. Test & Balance Ports
KVF-3000(E)
2001.02
qv(dpm) E
a
k
0
1
2
79.00 70.30 52.00
2
300
1
0
200
100
pm
[Pa]
50
30
20
10
• EASE OF BALANCING
5
200
300
500
qv [l/s]
• FIELD SYSTEM FOR BALANCING AIR FLOW RATES
Slide 25 14.9.2004
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1000
Make-up Air with Mixing Ventilation
(CFD)
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Make-up Air with Displacement
Ventilation (CFD)
•
Slide 27 14.9.2004
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According to new VDI 1999, mixing ventilation
system requires 15 to
20% higher exhaust
rate than displacement
system for the same
efficiency.
Make-up Air : Select the Best System !
Low velocity
Mixing
•
Low supply velocity (<0,7 m/s).
•
High discharge velocity (>8m/s).
•
Based on natural convection effect.
•
Grilles or ceiling diffusers.
•
Displacement unit can be included
in the hood = KVF or in cupboards.
•
•
No mixing between new air and
room air, but room air is displaced
from the occupied zone to the
hood.
Purpose is to mix new air with
room air as much
as possible.
•
Thermal plume is disturbed
especially when supply units are
close to the hood => SPILLAGE.
•
Thermal plume is not disturbed =>
SlideASSIST
28 14.9.2004 THE CAPTURE.
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Thermal Comfort, Productivity and
Kitchen Ventilation
*
Results from a study conducted in Finland
100
Productivity, %
90
80
70
60
50
40
Recommendations:
T = 26 – 27 °C
HR = 65 %
45 dB (A)
30
20
22
23
24
25
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27
Room Temperature, °C
With bad system :
•The temperature can increase
•Employees can feel more uncomfortable
•This can affect both efficiency of staff and turnover
Slide 29 14.9.2004
26
28
30
32
How to measure thermal comfort in a
professional kitchen ?
•Utilizes a breathing thermal
mannequin
•Measures skin temperature and
power to maintain temperature.
•Mean thermal vote calculated at
25 body locations.
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Satisfaction Measurement
Exhaust only hood
V = 0 m/s
Hood with low velocity local supply
20% people
satisfied
Hood with low velocity local supply
directed downwards
V = 0,1 m/s
25% people
satisfied
Hood with low velocity supply + Personal
air supply Nozzle
80% people
satisfied
V = 0,25 m/s
50% people
satisfied
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V = 0,40 m/s
IDEAS: Integrated Design, Exhaust
and Supply
•
•
•
•
•
•
•
Slide 32 14.9.2004
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From 100 kWh energy consumption in
a kitchen, 56 kWh are for heating of
make-up air (Electricité de France)
31% of restaurants expenses are for
wages and salaries
5 to 10% of restaurants expenses are
for energy bills
A 2 °C temperature increase can
decrease productivity 10%
Improved thermal comfort through
integrated design approach
Improved indoor air quality = higher
retention of valuable employees
Reduced training cost due to higher
retention
Halton HELP:
Hood Engineering & Layout program
•
•
•
•
Slide 33 14.9.2004
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Heat load based design on
kitchen exhaust.
Effect of air distribution type
factored for hood performance.
Accounts for non hooded
equipment.
Energy savings and improved
I.A.Q.
Factor Effect of Air Distribution System
Mixing ventilation
Displacement ventilation
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Halton HELP : Changing your
perspective
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Halton HEAT : Halton Energy Analysis
Tool
•
•
•
•
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Evaluate first cost and
operating cost between
Capture Jet and
competing systems.
Calculate “true” exhaust
rate for competing
systems.
Evaluate environmental
impact.
Determine R.O.I.
Halton HEAT : Annual Costs
Comparison
Capture Jet
hoods have a
short pay-back
time
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Halton HEAT : Saving Report
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KVI : Capture Jet Canopy
UK: Tesco store in Woodford Green
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KVF : Capture Jet Canopy, Supply and
Exhaust
France: LEP Chenevard
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KVL : Capture Jet Backself Hood
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Air Conditioning Ceiling with
Capture Jet
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Air Conditioning Ceiling with
Capture Jet
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KWF : Capture Jet Water Wash Hood
with Supply Air
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KWI : Capture Jet Water Wash Hood
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KVV: Steam or Condensate Canopy
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Reference List :
Some Among the Others ...
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UK: Tesco Store in Woodford Green
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Ventilated Ceiling : KCE
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France: Centre AFPA -Douai-
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Steam Canopy : KVV
Slide 51 14.9.2004
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France: School -Lycée Allende,
Béthune-
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Capture Jet + Supply : KVF
Slide 53 14.9.2004
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Ventilated Ceiling : KCE
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UK: Tesco Store in Woodford Green
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USA: Tennessee Mountain in
New York
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UK: Tesco Store in Wokingham
-
Slide 57 14.9.2004
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Capture Jet + Supply : KVF
Slide 58 14.9.2004
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Ventilated ceiling : KCE
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Rolland-Garros Stadium - France KVF, KVI, KVV
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Lycée Armentières - France KCF, KVF
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Hotel Restaurant La Chartreuse France - KVF
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School Canteen - France KCF
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Ventilated Ceiling KCF –Hong Kong -
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