Kitchen Design Practice Introduction It is still quite

By admin on November 22nd, 2007

Kitchen Design Practice

Introduction

It is still quite common practice to estimate exhaust
air flow rates based on rough methods. The
characteristic feature of these methods is that the
actual heat gain of the kitchen appliance is neglected.
Thus, the exhaust air flow rate is the same: even
when a heavy load like a wok or a light load like a
pressure cooker is under the hood. These kinds of
rough estimation methods do not produce optimal
solutions; the size of the whole system will be
oversized and so the investment costs and running
costs will increase.
The layout of the kitchen ventilation design was
complex due to the provision of a logical structure
combined with good air flow distribution and
performance.
Technically it was a question of designing and
providing an air conditioning installation offering
conditions and a minimal variable temperature in the
surrounding area ie: 23 C, 0/3 C whilst also keeping a
negative pressure between the kitchen and all
adjacent areas.
The most sensitive space to be handled turned out to
be the working zone, where the airflow to extract heat
and steam produced by ovens or cooking pots were
important.

The steam emitted in the opening of cooking pots or
the brat pan should also be captured immediately.
In this case of providing sufficient efficiency in
capturing polluants, the necessity of having the lowest
energy consumption for the end user had to be
considered.
In tackling these constraints, it has been decided to
select a model of hood using high technology offering,
for the same connecting power installed in the
kitchen, maximum efficiency and important energy
savings.
Kitchen Design Process
The design of the professional kitchen environment
follows the methodology of the industrial design
process.

Effect of Kitchen Air Distribution System Equation 4

By admin on November 21st, 2007

Effect of Kitchen Air Distribution System

Equation 4 assumes that a mixing air distribution
system is being utilised and that the exhaust/return air
temperature is equal to the kitchen air temperature
(assuming fully mixed conditions). Conversely, a
displacement ventilation system can supply low
velocity air directly into the lower part of the kitchen
and allow the air naturally to stratify. This will result in
a higher temperature in the upper part of the kitchen
while maintaining a lower air temperature in the
occupied zone. This allows for improvement of the
kitchen indoor air quality without increasing the capital
costs of the air conditioning system.
Picture 35 demonstrates a CFD simulation of two
kitchens with mixing and displacement ventilation
systems. In both simulations the kitchens have the
same appliances contributing the same heat load to
the space. The supply air flow and temperatures, and
the exhaust air flow through the hoods are the same
in both cases. The air is supplied through the typical
ceiling diffusers in the mixing system. In the case of
the displacement system, air is supplied through
specially designed kitchen diffusers located on the
walls. As one can see, the displacement system
provides temperatures in the kitchen occupied zone
from 22 to 26 C while the mixing system, consuming
the same amount of energy as displacement, results
in 27 32 C temperatures. This 2 C temperature
increase in the kitchen with the mixing air distribution
system will result in approximately 10% reduction in
productivity (see picture 6. page 9).
Halton HELP
TM
program allows kitchen ventilation
systems for both mixing and displacement ventilation
systems to be designed.

Kitchen Hoods Comparison Studies In this section a

By admin on November 21st, 2007

Kitchen Hoods Comparison Studies

In this section a variety of techniques and research
findings are presented that demonstrate the
performance and value that Halton s products offer the
end-user. There is a discussion on the ineffectiveness
of some hood designs offered by Halton s competitors
followed by a discussion of how capture efficiency
impacts the energy use, and energy bills, of the end-
user.
KVI Case Study
Halton is using state-of-the-art techniques to validate
hood performance. These include modeling of
systems, using CFD, Schlieren imaging systems, and
smoke visualization. All the test results presented here
have been validated by third-party research.
Halton s standard canopy hood (model KVI) utilizes
Capture Jet technology to enhance hood
performance, and consequently hood efficiency,
versus the competition.
In this case study, the KVI hood has been modelled
using CFD software. Two cases were modelled for this
analysis: one with the jets turned off in effect this
simulates a generic exhaust only canopy hood and a
second model with the jets turned on. As can be seen
from observing figures 13 and 4, at the same exhaust
flow rate, the hood is spilling when the jets are turned
off and capturing when they are turned on.
The same studies were conducted in the third party
laboratory. The Schlieren Thermal Imaging system was
used to visualise the plume and effect of Capture
Jet. As one can see the CFD results are in good
agreement with the Schlieren visualisation

Types of Kitchen Hoods Kitchen ventilation hoods are

By admin on November 20th, 2007

Types of Kitchen Hoods

Kitchen ventilation hoods are grouped into one of two
categories. They are defined by their respective
applications:
TYPE I: Is defined for use over cooking processes that
produce smoke or grease laden vapours and meet the
construction requirements of NFPA-96
TYPE II: Is defined for use over cooking and
dishwashing processes that produce heat or water
vapour.
Additional information on Type I and Type II hoods can
be found in Chapter 30 of the 1999 ASHRAE HVAC
Applications Handbook. This section presents
information on engineered, low-heat hoods and
commodity classes of hoods as well as an overview of
the most common types of grease removal devices.
Engineered Hood Systems
This subsection presents the engineered hood
products offered by Halton. These systems are factory
built and tested and are considered to be high-
efficiency systems.
These systems have been tested using the tracer gas
technique, Schlieren visualization, and computer
modeling to measure system efficiency. Common to
these designs is the use of Capture Jet technology
to improve the capture and containment efficiency of
the hood.
Capture Jet Canopy Hoods
These wall style canopies incorporate the Capture Jet
technology to prevent spillage of grease-laden vapor
out from the hood canopy at low exhaust rates.

Ultraviolet Light Technology Ultraviolet Light What Is

By admin on November 20th, 2007

Ultraviolet Light Technology

Ultraviolet Light What Is It ?
Light is the most common form of the
electromagnetic radiation (EMR) that the average
person is aware of. Light is only a very small band
within the electromagnetic spectrum. Cosmic rays, X-
rays, radio waves, television signals, and microwave
are other examples of EMR.
EMR is characterised by its wavelength and frequency.
Wavelength is defined as the length from the peak of
one wave to the peak of the next, or one oscillation
(measured in metres). Frequency is the number of
oscillations in one second (measured in Hertz).
Sunlight is the most common source of ultraviolet
radiation (UVR) but there are also many other sources.
UVR emitting artificial light sources can be produced
to generate any of the UVR wavelengths by using the
appropriate materials and energies.
Ultraviolet radiation is divided into three categories
UVA, UVB, and UVC. These categories are determined
by their respective wavelengths.
Ultraviolet A radiation is the closest to the
wavelengths of visible light .
Ultraviolet B radiation is a shorter, more energetic
wave.
Ultraviolet C radiation is the shortest of the three
ultraviolet bands and is used for sterilisation and
germicidal applications.
UV technology has been known since the 1800 s. In
the past it has been utilised in hospital, wastewater
treatment plants, and various industry applications.
HALTON has now developed new applications to
harness the power of Ultraviolet Technology in
commercial kitchens.

How Does the Technology Work?
Ultraviolet light reacts to small particulate and volatile
organic compounds (VOC) generated in the cooking
process in two ways, by exposing the effluent to light
and by the generation of ozone (UVC).
As is commonly known, the effluent generated by the
cooking process is a fatty substance. From a chemical
standpoint, a fatty substance contains double bonds,
which are more reactive than single bonds. By using
light and ozone in a certain manner, we are able to
attack these double bonds and consequently break
them. This results in a large molecule being broken
down into two smaller ones. Given enough reactive
sites, this process can continue until the large
molecule is broken down
into carbon dioxide and
water, which are
odourless and harmless.
Unlike the grease that
results in these small
molecules, CO2 and H2O
will not adhere to the
duct and will be carried
out by the exhaust air flow.

Grease Extraction The convection plume from the cooking

By admin on November 19th, 2007

Grease Extraction

The convection plume from the cooking operation
underneath the hood contains grease that has to be
extracted as efficiently as possible. The amount of
grease produced by cooking is a function of many
variables including: the type of appliance used for
cooking, the temperature that food is being cooked at,
and the type of food product being cooked.
The purpose of a mechanical grease filter is twofold:
first to provide fire protection by preventing flames
from entering the exhaust hood and ductwork, and
secondly to provide a means of removing large grease
particles from the exhaust stream. The more grease
that can be extracted, the longer the exhaust duct and
fan stay clean, resulting in better fire safety.
From a practical standpoint, grease filters should be
easily cleanable and non-cloggable. If the filter
becomes clogged in use, the pressure drop across the
filter will increase and the exhaust airflow will be
lower than designed.

What Is Grease?
According to the University of Minnesota, grease is
comprised of a variety of compounds including solid
and/or liquid grease particles, grease and water
vapours, and a variety of non-condensable gases
including nitrogen oxides, carbon dioxide, and carbon
monoxide. The composition of grease becomes more
complex to quantify as grease vapours may cool down
in the exhaust stream and condense into grease
particles. In addition to these compounds,
hydrocarbons can also be generated during the
cooking process and are defined by several different
names including VOC (volatile organic compounds),
SVOC (semi-volatile organic compounds), ROC
(reactive organic compounds), and many other
categories.
Grease Emissions By Cooking Operation
An ASHRAE research project conducted by the
University of Minnesota has determined the grease
emissions from typical cooking processes. Figure 7
presents total grease emissions for several appliances.

It appears at first as if the
underfired broiler has the highest grease emissions.
However when examining the figure closer you see
that if a gas or electric broiler is used to cook chicken
breasts, the grease emissions are slightly lower than if
you cook hamburgers on a gas or electric griddle. This
is the reason that we are discussing cooking
operation and not merely the type of appliance.
However, we can say that, for the appliances tested in
this study, the largest grease emissions are from
underfired broilers cooking burgers while the lowest
grease emissions were from the deep-fat fryers. The
gas and electric ranges were used to cook a spaghetti
meal consisting of pasta, sauce, and sausage. All of
the other appliances cooked a single food product. It
is expected that the emissions from solid-fuel (e.g.,
wood burning) appliances will probably be on the
same order of magnitude as under-fired broilers, but in
addition to the grease, large quantities of creosote and
other combustion by-products may be produced that
coat the grease duct. Chinese Woks may have grease
emissions well above under-fired broiler levels due to
high surface temperature of the Woks combined with
the cooking medium utilised for cooking (e.g. peanut
oil, kanola oil, etc.) which will tend to produce extreme
grease vaporisation and heat levels.

The components of grease were discussed earlier and
a breakdown of the grease emissions into the
particulate and vapor phases is shown in figure 8.
Upon examining figure 8, it becomes apparent that
the griddles, fryers, and broilers all have a significant
amount of grease emissions that are composed of
particulate matter while the ovens and range tops are
emitting mainly grease vapour. If you combine the
data in figure 7 with the data in figure 8 it becomes
evident that the broilers have the largest amount of
particulate matter to remove from the exhaust stream.
The final piece of information that is important for
grease extraction is the size distribution of the grease
particles from the different cooking processes.
On a mass basis, cooking processes tend to produce particles
that are 10 microns and larger. However, the broilers
produce significant amounts of grease particles that
are 2.5 microns and smaller (typically referred to as
PM 2.5) regardless of the food being cooked on the
broiler.

ASTM F1704 In 1990, AGA Laboratories was funded

By admin on November 19th, 2007

ASTM F1704

In 1990, AGA Laboratories was funded by the Gas
Research Institute to construct a state-of-the-art
kitchen ventilation laboratory and research the
interaction between cooking appliances, kitchen
ventilation hoods, and the kitchen environment.
In early 1993, the original Energy Balance Protocol
was developed to explain the interaction between the
heat loads in the kitchen. Mathematically, the energy
consumed by the cooking appliance can only go three
places:
to the food being cooked
out of the exhaust duct
into the kitchen as heat load
In late 1993, this was introduced as a draft standard to
be adopted by ASTM and was called the Energy
Balance Protocol. The original protocol was developed
to only examine the energy interactions in the kitchen
with the goal of determining how much heat was
released into the kitchen from cooking under a variety
of conditions. This standard was adopted by ASTM as
F1704.

Around 1995, the standard adopted new methods of
determining the capture and containment using a
variety of visualisation techniques including visual
observation, neutrally buoyant bubbles, smoke, lasers,
and Schlieren thermal imaging (discussed in more
detail later in this section).
The test set up includes a hood system operating over
a given appliance. Several thermocouple trees are
placed from 1.8 m to 2.5 m. in the front of the hood
system and are used to measure the heat gain to the
kitchen space. This enables researchers to determine
the temperature of room air being extracted into the
hood.
In theory, when the hood is providing sufficient
capture and containment, all of the convective plume
from the appliance is exhausted by the hood while the
remaining radiant load from the appliance is heating
up the hood, kitchen walls, floors, ceiling, etc. that are
eventually seen as heat in the kitchen.

During the 1950 s Schlieren thermal imaging was used by AGA
Laboratories to evaluate gas combustion with several
different burner technologies. NASA has also made
significant use of Schlieren thermal imaging as a means
of evaluating shockwaves for aircraft, the space shuttle,
and jet flows. In the 1990 s Penn State University
began using Schlieren visualisation techniques to
evaluate heat flow from computers, lights, and people
in typical home or office environments. In 1998 the
kitchen ventilation lab in Chicago purchased the first
Schlieren system to be used in the kitchen ventilation
industry. In 1999, the Halton Company became the first
ventilation manufacturer globally to utilise a Schlieren
thermal Imaging system for use in their research and
development efforts.
By using the thermal imaging system we can visualise
all the convective heat coming off an appliance and
determine whether the hood system has sufficient
capture and containment. In addition to verifying
capture and containment levels, the impact of various
supply air and air distribution measures can be
incorporated to determine the effectiveness of each.
By using this technology a more complete
understanding of the interaction between different
components in the kitchen (e.g., appliances, hoods,
make-up air, supply diffusers, etc.) is being gained.

Evolution of Kitchen Ventilation System Tracer Gas Studies

By admin on November 18th, 2007

Evolution of Kitchen Ventilation System

Tracer Gas Studies
Halton pioneered the research on kitchen exhaust
system efficiency in the late 1980 s, commissioning a
study by the University of Helsinki. At the time there
were no efficiency test standards in place. The goal
was to establish a test protocol that was repeatable
and usable over a wide range of air flows and hood
designs.
Nitrous Oxide (tracer gas), a neutrally buoyant gas,
was used. A known quantity of gas was released from
the heated cooking surface and compared to the
concentration measured in the exhaust duct. The
difference in concentration was the efficiency at a
given air flow. This provided valuable information about
the potential for a variety of capture and containment
strategies. The Capture Jet system was tested using
the Tracer Gas technique and the results showed a
significant improvement in capture and containment of
the convective plume at lower exhaust air flows
compared to conventional exhaust only hoods.

Kitchen Hoods The purpose of kitchen hoods is

By admin on November 18th, 2007

Kitchen Hoods

The purpose of kitchen hoods is to remove the heat,
smoke, effluent, and other contaminants. The thermal
plume from appliances absorbs the contaminants that
are released during the cooking process. Room air
replaces the void created by the plume. If convective
heat is not removed directly above the cooking
equipment, impurities will spread throughout the
kitchen, leaving discoloured ceiling tiles and greasy
countertops and floors. Therefore, contaminants from
stationary local sources within the space should be
controlled by collection and removal as close to the
source as is practical.
Appliances contribute most of the heat in commercial
kitchens. When appliances are installed under an
effective hood, only the radiant heat contributes to the
HVAC load in the space. Conversely, if the hood is not
providing sufficient capture and containment,
convective and latent heat are spilling into the
kitchen thereby increasing both humidity and
temperature.
Capture efficiency is the ability of the kitchen hood to
provide sufficient capture and containment at a
minimum exhaust flow rate. The remainder of this
chapter discusses the evolution and development of
kitchen ventilation testing and their impact on system
design.

Integrated Approach Energy savings can be realised with

By admin on November 18th, 2007

Integrated Approach

Energy savings can be realised with various exhaust
hood applications and their associated make-up air
distribution methods. However with analysis the
potential for increased energy savings can be realised
when both extract and supply for the kitchen are
adopted as an integrated system.
The combination of high efficiency hoods (such as
Capture-Jet hoods) and displacement ventilation
reduces the required cooling capacity, while
maintaining temperatures in the occupied space. The
natural buoyancy characteristics of the displacement
air helps the C&C of the contaminated convective
plume by lifting it into the hood.
Third-party research has demonstrated that this
integrated approach for the kitchen has the potential
to provide the most efficient and lowest energy
consumption of any kitchen system available today.