1
FORUM
THE TRADE JOURNAL FOR REFRIGERATION TECHNOLOGY
2007
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REFRIGERATED ROSES How to manage the challenge
ON THE ROAD Best practice for experts | CARROTS Complex produce | HOTEL REFRIGERATION Ideal
integrated solutions | EXPANSION VALVES Superheating under control | CORROSION Best material protection
02 | EDITORIAL | CONTENTS | INTERVIEW | INTERNAL | ACCESSORIES | INSIDE | REPORT | EVENTS | PRACTICE | SERVICE
EDITORIAL
CONTENTS
03 | INTERNAL
Küba on the road. Expert lectures from the Küba
Roadshow 2007 with a practical focus.
08 | PRACTICE
Keeping roses sweet. Perfect refrigeration from the start
ensures a long life in the vase for the queen of ﬂowers.
11 | EXPERT KNOWLEDGE
Set right. Proper superheating is the key to the optimal
utilization of the cooling capacity.
12 | REPORT
The carrot challenge. Despite robust appearances,
the carrot is very sensitive to refrigeration.
14 | Chilled treats for the taste buds. For the Hotel
Schloss Fuschl in Austria, a protected historical building
poses the biggest challenge to refrigeration
17 | FAQ
Corrosion protection. The corrosion resistance of the
stainless steel used for air coolers is especially important
for refrigeration applications.
18 | REPORT
Tapas and toreros. The Hotel Sol Meliá in Berlin
solves its complex refrigeration tasks with an intelligent
integrated solution.
02 | STANDARDS
Editorial/Contents
Imprint
DEAR READERS,
“On the road again“ is a famous album by Dr Feelgood, the
British rhythm and blues band. Küba is also “on the road again“
– even if we cannot offer any R&B. Instead, we preferred to offer you information on the latest developments from our company and in refrigeration engineering in general at this year‘s
roadshow. We would like to thank you for visiting us in such
large numbers and allowing us to show you our applicationoriented range of products that is tailored to the practical needs
of users.
However, this issue is not just about our roadshow lectures; it
also contains a number of interesting technical articles on speciﬁc refrigeration engineering solutions. As you know, we place
great value on a logical system focused on real-life applications.
We therefore make a distinction between simple and complex
refrigeration tasks and – with our Economy Line and our Classic
Line – are able to offer you the right high-performance cooler for
every need. Küba sees itself as a manufacturer with a deﬁned
variety of air coolers, and condensers. Complex organic carrots,
precious roses or the tasty treats of a ﬁrst-class hotel kitchen are
thus always cooled to perfection. Enjoy the articles!
As a brand with a long tradition, Küba sees itself as a strong
partner for refrigeration wholesalers and refrigeration system
contractors. We are there to support you with our application
expertise, our quality and our service. Continuous R&D and
the ongoing improvement in our products and production processes are a natural part of our business.
Enjoy your reading,
Christoph Korinth
IMPRINT FORUM
The trade Journal for Refrigeration Technology
PUBLISHER: Küba Kältetechnik GmbH, Oberdiller Straße 23, D-82065 Baierbrunn,
Tel.: +49/(0)89/74473-264, Fax: +49/(0)89/74473-107. MANAGING EDITOR: Michael
Münch (Küba Kältetechnik) CONTRIBUTORS TO THIS EDITION: Peter Strauß, Ralf
Jesumann, Gabriele Klages, Markus Neuhold, Christoph Korinth, Dr. Volkmar Pätzold,
Carola Baumgartner, Fritz Brenner, Dr. Gabriele Lüke, Jeff Barﬁeld, Mark Dietrich,
Richard Stapley EDITING, LAYOUT & PRODUCTION: imprime corporate publishing,
Perchtinger Str. 10, 81379 München, Tel.: +49/(0)89/309052650 PRINTING & SHIPPING:
artconcept Werbeagentur GmbH, Martinsried/München
Reproduction only by written permission from Küba Kältetechnik GmbH. Copyright reserved. We do
not accept responsibility for unsolicited manuscripts, pictures and ﬁles.
FORUM 01/2007
SERVICE | PRACTICE | EVENTS | REPORT | INSIDE | ACCESSORIES| INTERNAL | INTERVIEW | CONTENTS | EDITORIAL |03
Küba on the Road
As a strong partner for the refrigeration engineering
and retail industries Küba has always used its road
shows to present its application knowledge, product
innovation as well as important legal developments
and technological advances.
Refrigeration engineering and installation companies are facing increasing competition and greater price pressure. The demands of the customers and legal requirements are also rising
all the time. Engineering and installation companies have to
master both these aspects if they want to be seen as competent partners and remain successful in the future. They need
new arguments in their sales presentations in order to acquire
new and lucrative orders. For this reason Küba has engaged
top external specialists in addition to its in-house experts for the
Roadshow 2007.
HOW CAN IDEAL REFRIGERATION ENGINEERING ENHANCE PROFITABILITY FOR USERS?
This was slogan for the lectures by top industry speakers on a
variety of topics ranging from the planning of refrigeration systems to their implementation.
After some welcoming words from Thomas Millbrodt, managing director of Reiss Kälte-Klima, the roadshow began with the ﬁrst lecture.
The factor chilled goods
Maintaining maximum value
of sensitive chilled goods
The best proﬁts can be realized by satisfying the demands of the chilled goods to perfection. Expensive
initial investments thus start to pay for themselves
very quickly.
All relevant factors have to be taken into account in the design and
planning of the system to ensure that the users remain happy with
the supplier in the long term. Particularly, when it comes to complex refrigeration tasks, it is worthwhile to invest a little more at the
start to maintain ideal quality and value of the products. Only in this
way can the best price and so also the best proﬁt be achieved later
when the chilled goods is sold.
• “Maintaining maximum value of sensitive chilled
goods“ (see page 3) by Dr Volkmar Pätzold, owner of Fruit
Storage Consulting.
• Questions on speciﬁc implementation were answered by the
presentation “Designing and planning refrigeration systems for optimum results“ (see page 5) by Dipl.-Ing. Gabriele Klages of Klages Ingenieurkontor.
• Dipl.-Ing. Christoph Korinth, Technical Manager of Küba Kältetechnik, addressed the question of how to choose the right air cooler
in his keynote speech, “Küba air coolers can enhance your
customers’ success.“ (see page 6).
Five regional events conducted together with the refrigeration wholesalers Reiss Kälte-Klima attracted several hundred
engineering and installation companies. The interesting talks
were followed by lively discussions and a tasty buffet.
FRUIT AND VEGETABLES SHOW THEIR SENSITIVE SIDE WHEN REFRIGERATED
Apples “continue to live“ after being harvested. The natural ripening process ﬁrst leads to shrivelling and ﬁnally to decomposition. It
is the job of the refrigeration technology to retard these biological
processes so that fresh produce can be sold at high prices when
it comes to market. The cost-efﬁcient maintenance of the quality of
the chilled goods therefore represents a great challenge.
Breathing and respiration of the product is the main cause of the loss
of water, which naturally corresponds directly to a loss of mass and
thus of its value. This applies above all to those types of fruits and
vegetables that only fully ripen during storage such as apples and
pears . Poor storage conditions create the greatest damage here.
The lower the humidity during storage, the more moisture is drawn
out of the produce. The aim for the refrigeration system therefore is
to achieve the lowest possible decrease in partial pressure.
01/2007 FORUM
04 | EDITORIAL | CONTENTS | INTERVIEW| INTERNAL | ACCESSORIES | INSIDE | REPORT | EVENTS | PRACTICE | SERVICE
TEMPERATURE AND HUMIDITY ARE DECISIVE
Fruit such as the apples as shown in the next example require
special consideration of the refrigeration engineer.
The aim of storage is to slow down the ripening process
as much as possible.
The ripening process is directly dependent on the storage temperature. A reduction in the temperature by 10 K already retards
the process by half to one third. The lowering and maintaining of
temperature should be carried out in an intelligent manner that
is gentle on the produce.
Here, a high humidity of 92 to 95% ensures a minimal
loss of mass.
Evaporators which produce a low entry temperature difference DT1 between the air inlet temperature and the evaporation temperature (TL1 and T0) permit a minimal dehumidiﬁcation of the air. The upper limit of the entry temperature
difference of 5 K should not be exceeded in this process.
This is mainly ensured by an optimised tubing system and
an intelligent refrigerant distribution in the air cooler as well
as by an evaporator control with pre-, intermediate and postventilation.
Draw through type evaporators are recommended due
to the optimum air distribution over the heat exchanger
surface.
CHOOSING THE RIGHT EVAPORATOR MAKES
A DIFFERENCE
Every litre of water removed from the storage area
by the evaporators represents a ﬁnancial loss for
the operator!
Inefﬁcient evaporators dramatically reduce the produce quality
at the end of the storage phase and demonstrably result in a
substantial loss of product value. This is shown by the following
table:
mulates over the entire operating period of the system - in every
storage period! The added cost for an optimized refrigeration
system thus pays for itself after only a few operating periods.
ARRANGEMENT, CONTROL AND CONFIGURATION OF THE UNITS INCREASE EFFICIENCY
An optimum arrangement of the air coolers in the room helps
increase energy efﬁciency and cost effectiveness. Evaporators
should be positioned opposite the door. The air ﬁrst ﬂows along
the ceiling to the opposite wall and then back through the refrigerated product. It is important to maintain a uniform stacking
height and corresponding distances from the walls.
An ideal control requires the right starting values.
At least three temperature sensors should be installed per storage room to permit precise control:
• In direct proximity to the evaporators in the region of the return air ﬂow in order for the control of the refrigeration system
• Inside the stack for the measurement of the produce temperature
• Opposite the evaporators close to the ﬂoor
Only when the temperature difference - after the cooling phase
in the storage phase - is less than 1 K between the different sensors is an optimum maintenance of value of the total produce
ensured.
The system should be conﬁgured as follows if it is
to pay for itself:
• $t < 5 K between the air inlet temperature and the evaporation temperature (TL1 and T0)
• Efﬁcient parallel tubing system with optimized refrigerant distribution
• Hot Gas defrosting using the Böckstroem method
• Coordinated forced ventilation performance and throw
• Intelligent control (pre-, post- and intermediate ventilation)
Weight loss
Loss per 100 t
Value loss
per storage period
storage quantity
approx. price/kg fruit = 1 EUR
Good storage conditions
3%
3.000 kg
3.000 EUR
Poor storage conditions
6%
6.000 kg
6.000 EUR
>6%
100.000 kg
100.000 EUR
Total loss
The different types of produce each require speciﬁc storage
conditions with respect to storage time, temperature and humidity.
An unsuitable refrigeration system can result in a total loss of
value of the stored produce. Even a suitable refrigeration system whose dehumidiﬁcation is only slightly above the optimum
can lead to substantial losses. The loss in value namely accu-
FORUM 01/2007
If the requirements of the chilled goods are ideally met, it is possible to maintain the value of the chilled goods, which in turn
enables high proﬁts. An efﬁcient system lowers operating costs
and thus ensures the maximum economic success for the user.
Source: Summary of a lecture during the Küba Roadshow 2007by Dr Volkmar Pätzold, owner of
Fruit Storage Consulting in Dresden.
05
All factors considered
Ideal design and planning
of refrigeration systems
Legislators, users and the chilled goods itself al place
ever higher demands on the makers of refrigeration
systems. This calls for experts who think and plan in
holistic terms.
After the spoiled meat scandals in Germany and the resulting tighter controls by the
food inspection authorities,
refrigeration engineers bear a
high responsibility for the safety of the chilled goods – toward
consumers, refrigeration users
and the law. To meet this challenge, they must coordinate
three levels of demands in the
design of new systems or the
expansion of existing systems.
THE CHILLED GOODS ARE THE BIGGEST
CHALLENGE
Finally, in addition to the technical conﬁguration and the operating safety, it is the precise matching of the refrigeration
system to the speciﬁc requirements of the chilled goods
which is decisive for product safety. This particularly includes
the temperature, humidity and the exchange of air. The type
and quantity of the chilled goods must be precisely deﬁned
Storage conditions for fruit and vegetables
GREEN VEGETABLES
ROOT VEGETABLES
FRUIT VEGETABLES
PROBLEMATIC
PARTIAL
COMPATIBILITY
NOT COMPATIBLE
SEPARATE STORAGE
STRICT SEPARATION
OF CHILLED GOODS
LEGISLATORS HAVE
THEIR SAY
• Occupational health and
safety laws: concerning the
avoidance of drafts in production areas, for example.
• Fire prevention: NH3 systems with special accident prevention regulations or emergency phones for staff in freezer
rooms > 20 m²
• Food ordinances: all companies in the food industry which
process products of animal origin will require an EU licence
by January 1, 2009.
• Food hygiene laws: HACCP, ISO 9000.
• Region-speciﬁc construction laws: individual regulations on
building plans or noise emissions, for example
TECH. REFRIG.
CALCULATION
NOT A PROBLEM
STORAGE
COMPABILITY
WITH FRUIT
TEMPERATURE
HUMIDITY
EVAPORATOR
TEMPERATURE
in the planning stage. One must differentiate between packed
goods, wrapped goods or unpacked goods, between the type
of transport and the transport packaging and between the type
of storage – that is long-term storage, package transfer storage or shipping storage. The demands on refrigeration engineers are high. Users need them to be their partner with comprehensive knowledge – as experts able to consult, plan and
implement the system
USERS MAKE DEMANDS TOO
Users are primarily interested in the safety of the chilled goods.
That is expressed in their requirements for guaranteed and
documented temperatures for the respective chilled goods.
Product safety goes hand in hand with the operating safety of
the system. The company that installed the refrigeration system is liable to the user for its safety. Guaranteed safety aspects
today include as standard qualiﬁed malfunction alarms with a
remote polling facility. In addition, emergency plans have to be
developed and the operator‘s staff trained in them.
Chilled goods
Storage temp. [°C]
Remarks
Deep frozen goods
–22 °C
Packed goods, storage
Meat
+2 °C
Packed goods
Fish
Dairy products
Fruits, vegetables
0 bis +2 °C
Usually cooled in ice
+4 bis +7 °C
Packed goods
Dependent on type
High demands on temperature and humidity
Source: Summary of a lecture during the Küba Roadshow 2007 by Dipl.-Ing. Gabriele Klages
of Klages Ingenieurkontor.
01/2007 FORUM
06 | EDITORIAL | CONTENTS | INTERVIEW| INTERNAL | ACCESSORIES | INSIDE | REPORT | EVENTS | PRACTICE | SERVICE
The right choice
Küba air coolers enhance
your customers’ success
Choosing the right air cooler is the prime consideration for the maximum maintenance of the value of the
chilled goods, for the efﬁciency of the refrigeration system and, ultimately, for the success of the customer.
doors. Long storage periods or the use of aggressive cleaning
agents, as necessary in the processing of meat or ﬁsh, also
increase the degree of complexity.
Choosing the “Green World“ or the “Blue World“
The decision as to which product line is the right one depends
on the degree of complexity of the two factors of chilled goods
and environment. The “Blue World“ is Küba`s Classic Line for
complex refrigeration. The “Green World“ is Küba’s Economy
Line for simpler applications.
Refrigeration engineering companies are not only responsible for product and operating safety. Their choice of a speciﬁc
brand also has a great inﬂuence on the proﬁtability. The Küba
brand has been a guarantee for maintaining and increasing
the value of chilled goods during storage and processing for
more than 80 years. Users of refrigeration systems attain sustainable success with high-quality Küba products.
THE FAST WAY TO THE RIGHT AIR COOLER
But which air cooler is the right one? Does it have to be the
technically best unit or is a simpler cooler sufﬁcient? Which
solution is the most economical? The application-focused
product range of high-performance Küba air coolers supplies
the answers to these questions. Küba offers the right air cooler
for every cooling task, from the very simple to the most complex. Choosing between the “Blue World“ of the Küba Classic
Line and the “Green World“ of the Küba Economy Line depends on the chilled goods and on the overall refrigeration
environment.
Simple or complex chilled goods?
The chilled goods’s demands on temperature, humidity and air
speed represent the ﬁrst criteria for the selection of the right air
cooler. Simple chilled goods primarily include packed goods
and beverages. The complexity of the chilled goods increases
with unpacked products, which react sensitively to dehumidiﬁcation. Examples of such products include fruit, vegetables,
ﬂowers or baked goods. The same applies when aging processes take place, which is the case in the ripening of cheese or
bananas. Meat and ﬁsh or acidic products such as marinades
and tropical fruits are also considered complex chilled goods.
The role of the refrigeration environment
The application environment is the second factor for the selection of the right air cooler. Design requirements may well
make air coolers with a long throw necessary or ones with a
ﬂat design or special accessories (textile tubes, etc.). The people on site and the way they use the system create a complex environment if a large amount of humidity is introduced
into the refrigerated space by frequent or long opening of the
FORUM 01/2007
ECONOMY LINE
CLASSIC LINE
THE PERFECT AIR COOLER FOR EACH
APPLICATION
Every refrigeration task has its own special characteristics
and challenges. Some examples will make clear how quickly
and how directly the right air cooler can be selected.
1. Delicate refrigeration for sensitive ﬂowers
The sensitivity of the delicate chilled goods of cut ﬂowers is
a true challenge. Flowers like it cool, but cold drafts damage
the leaves and buds. High humidity levels are indispensable if
the ﬂowers are to remain fresh for a long period of time. These
complex demands make ﬂowers a complex chilled good. This
makes the blue Küba Classic Line the right choice even though
the environment of the refrigeration application is relatively
simple.
07
1
3
2
4
2. Cooled bottles, a simple case
Cooled bottled drinks is characterized by a simple chilled good
and a simple environment and is so predestined for the use
of the “Green World.“ The Economy Line is the prime choice
thanks to its economy in investment and operation.
3. A complex environment in slaughterhouses requires
robust coolers
The environment in slaughterhouses is considerably harsher. All
units must be cleaned thoroughly to satisfy the hygiene regulations. This naturally also includes the air coolers. The air coolers are not only subjected to frequent and intensive cleaning in
slaughterhouses and associated meat processing facilities, but
also come into contact with smoking materials or acidic products such as marinades, etc. This all makes the inﬂuence of the
environment very complex and the “Blue World“ provides the
ideal air cooler.
The shelf life of meat at different temperatures
Storage temperature
–1,5 °C
± 0 °C
+ 2 °C
+5 °C
Storage period
100 %
70 %
50 %
30 %
4. The long-term storage of fruit and vegetables
is complex
The previous articles have shown how complex the chilled
goods of fruit and vegetables is. The environment is likewise
complex due to the demands on air distribution and on the long
storage period. This is a clear case for the Küba Classic Line.
THE RIGHT MODEL FOR THE EACH LOCATION
Once a decision has been made between the “Green World“ and the
“Blue World“, it is necessary to select the model. This is very simple
for the Küba Economy line: for the junior DF small cooling rooms; the
compact DF in the cooling room; the market plus SP in the supermarket or refrigeration store; and the comfort DP in the workroom area.
In the “Blue World”, the DE is particularly suitable for smaller cooling and refrigeration rooms; the SC commercial for refrigeration
rooms, the SG industrial for larger refrigerated warehouses and
storage rooms, and the DZ for production and workroom areas.
The wide range and the many variants in the Classic Line also
make it possible to match the unit to speciﬁc refrigeration tasks
beyond this simpliﬁed association.
SUMMARY
To enhance the commercial success of the customer, refrigeration systems must be ideally adapted to their designated applications. Only in this way can the best possible balance be
achieved between investment and operating costs, on the one
hand, and maintaining and increasing the value of the chilled
goods, on the other hand. This optimum balance is the main
sales argument for refrigeration engineering companies to their
customers. Solutions that initially appear to be cheaper can turn
out to be the more expensive choice later. And Küba offers highperformance air coolers for all refrigerating jobs - from very simple to complex - with the “Green World“ and “Blue World.“
Source: Summary of a lecture during the Küba Roadshow 2007by Christoph Korinth, Technical
Manager of Küba Kältetechnik GmbH.
01/2007 FORUM
08 | EDITORIAL | CONTENTS | INTERVIEW | INTERNAL | ACCESSORIES | INSIDE | REPORT | EVENTS| PRACTICE | SERVICE
Keeping roses sweet
Fotos: pixelio.de
Keeping roses cool and sweet requires an ideal coordination of humidity and temperature as provided by an efﬁcient evaporator.
IT WILL ALWAYS BE THE QUEEN of ﬂowers: the precious
rose, the proud rose, the traditional symbol of love. The refrigeration engineer today uses special storage and refrigeration
processes to ensure that this summer ﬂower is available all year
round and also remains fresh for a long time after it is sold.
The challenge: The longer roses are stored and transported, the
more time there is between the cutting of the ﬂower and the start
of its life in a vase. The installed cooling system must therefore
ensure ideal conditions over the entire storage period so that
the rose also looks its best as long as possible in the home.
Refrigeration engineers must therefore ﬁrst fully familiarise themselves with the special features of the rose as a chilled product.
Cut roses are living parts of plants, which have been separated
from their root systems. The supply of water is interrupted and
the wilting process begins. The fact that the rose’s ratio of surface to mass is signiﬁcantly larger than for a vegetable also affects refrigeration requirements.
It is the aim of the refrigeration system to maintain the rose in
its initial cut state, usually as a bud, while still allowing its further development. The bloom should continue to unfurl during refrigeration and then ﬂower completely in the vase. This
requires reserves of sugar, proteins and minerals which are in
FORUM 01/2007
short supply and can no longer be supplied because the roots
have been removed. Nevertheless, cutting the ﬂowers from
their roots actually promotes ﬂowering. The “amputated“ rose
attempts to perpetuate the species and does everything in its
power to bloom and form seeds. It breathes more after cutting
and breaks down oxygen. Its reserves are used to nourish and
develop the bloom.
The actual ﬂowering also leads to another transformation of the
rose during refrigeration, the formation of ethylene. The ﬂowering rosebud produces this ripening gas which not only induces
the further development of the bloom and the production of
seeds, but also promotes the ripening process in other plant
organs. For instance, the leaves turn yellow and the colour of
the ﬂowers changes.
Refrigeration engineers can now manipulate this process. The
most important measure is the absolutely strict observation of
the speciﬁed temperature. This is because the biological processes are slowed down as the temperature reduces – admittedly with different intensities, but nevertheless substantially in
part. Low temperatures result in a reduction in breathing, largely
prevent the formation of ethylene, stop changes in shape and
colour, inhibit decomposition due to infections and slow unde-
CLASSIC LINE
01/2007 FORUM
10| EDITORIAL | CONTENTS | INTERVIEW | INTERNAL | ACCESSORIES | INSIDE | REPORT | EVENTS| PRACTICE | SERVICE
Storing cut roses
1. Only suitable for healthy roses still budding
2. Rapid chilling directly after cutting
3. The temperature distribution in the cold room must be as precise and
constant as possible
4. Maintain a maximum temperature difference (product/ cold room)
of 0.5 K
5. Maintain relative humidity of 90% (watch defrosting cycle)
6. Disinfect and ventilate storage room regularly
7. Important: NEVER store fruit or vegetables together with roses
8. Prevent wilting due to dehumidiﬁcation; slow down aging
9. Ensure the roses can breathe: otherwise they can neither be preserved
nor develop
sired growth. Although the cell water of plants, and also that of
the rose, does not freeze at 0 °C like normal water, but usually at
–1 to –2 °C due to the substances dissolved in the cell sap, there
is still a risk when storage temperatures are below 0°C. Bacteria
can act as condensation nuclei for the formation of ice, thus
raising the freezing point and permitting damage to the tissue.
The lowest possible and also the safe storage temperature for
roses is therefore 0 to 2 °C.
It is furthermore important that the roses are cooled down as
quickly as possible. The faster the ﬁeld heat is removed from
the cut roses and the faster the organs themselves attain the
temperature of the refrigerated space, the fewer reserves are
lost. The respiration heat should also be considered in addition
to the product heat. The respiration of cut roses not only produces energy for the continuation of ﬂowering, it also generates
heat which has to be countered by chilling. It is also important
to ensure that the refrigeration process really chills every part of
the rose. The temperature difference between the rose and the
refrigerated space must be as small as possible. 0.5 K is recommended. To achieve this close temperature difference, the
evaporator, the control unit and the expansion valve must be
precisely matched to one another. An evaporator is therefore
to be recommended which satisﬁes the following parameters: a
large heat exchange surface, a ﬁn spacing of r 7 mm, controlled
refrigerant distribution [CAL] and superheat, a low air speed, an
Air Straightener for precise and constant air distribution and a
low number of defrosting cycles with a corrective control. The
air should not be blown directly onto the roses.
However, the evaporator is not only crucial for maintaining the
temperature, it is also responsible for the regulation of the humidity, which is equally important for the refrigeration of roses.
After its cut a rose cannot stop evaporation, i.e. it still gives off
water vapour. Perforated transport foils can at least limit this loss
of water. The degree of transpiration is thus reduced; however,
water is still lost over the whole storage time depending on the
temperature. To prevent the total loss of the rose due to this loss
of water, the transpiration must be inhibited. This is done by ensuring the proper humidity, which – in addition to rapid chilling is of utmost importance for rose storage. While most cut ﬂowers
prefer a relative humidity of 85% to 90%. The ideal spectrum is
much narrower for the demanding rose. The cooling system, in
particular the evaporator, must ensure a relative humidity of 90%
± 2 %. If the relative humidity drops below the optimum level,
wilting soon becomes evident. If the humidity is too high, on the
other hand, fungus will form and result in mould. Like temperature, humidity must also be kept in the ideal range.
Conclusion: A perfect climate for the storage of cut roses can
only be achieved by an interaction of temperature and relative
humidity. So that roses stay sweet smelling longer.
Klages Ingenieurkontor
The author of this article is Gabriele Klages, joint owner of Klages
Ingenieurkontor in Wedemark, Germany. Klages is a design and engineering bureau for industrial construction. More information at:
www.klages-ingenieurkontor.de
Climate demands of cut roses during storage
2. Relative humidity
1. Temperature
• < 87 %:
Dehumidiﬁcation = Wilting = Total loss
• 0 bis +2 °C: Ideal storage temperature
• 90 %:
Optimum humidity
• Über +5 °C: Storage life much reduced
• > 94 %:
Risk of fungal infection inside the rose bundles
due to condensation = total loss
• > –1,5 °C:
FORUM 01/2007
Risk of freezing of any water on the roses
SERVICE | PRACTICE | EVENTS | REPORT | INSIDE | ACCESSORIES | INTERNAL | INTERVIEW | CONTENTS | EDITORIAL |11
EXPERT KNOWLEDGE: Expansion valve
1
Photo 1: The
evaporator superheat is too high there is already no
refrigerant in the
tubing for the remaining two thirds
of the evaporator
surface.
Photo 2: An
incorrectly set
expansion valve
results in insufﬁcient refrigerant ﬂow and the
formation of icing
on the ﬁns and
too much refrigerant vapour in the
tubes.
Right: The KÜBA
Superheat calculator is now available again – see
contact below.
2
Set correctly
The superheating of the refrigerant is decisive for the ideal utilisation of the evaporator surface
and therefore a 100% cooling capacity.
WHAT IS SUPERHEAT? Superheat is the term used to describe
the difference between the vapour point (i.e. the temperature at
which the refrigerant evaporates at a given pressure) and the
actual temperature of the refrigerant exiting the evaporator coil.
The correct superheat temperature is decisive for the refrigerating process. This can be only achieved with the correct setting
of the expansion valve: Expansion valves regulate the amount of
supercooled liquid refrigerant to be injected into the evaporator
distributor in accordance with the superheating of the refrigerant vapour at the evaporator outlet. In each case, only so much
refrigerant can be injected as is required - or can be evaporated
- under the respective operating conditions while utilising the
heat-transfer surface of the evaporator.
Incorrectly set expansion valves result either in too high or too
low a superheating. The required refrigerated space temperature
is not reached or is only reached with an increased expenditure
of energy. Under certain circumstances, the cooling system itself can become damaged. If the superheating is insufﬁcient,
drops of liquid, for example, can be carried over into the suction
line, which can then cause damage to the compressor . On the
other hand, excessive superheating reduces the performance
of the evaporator because the heat exchanger surface is not
completely utilised. If the intake vapour temperatures are too
high, the compressor is frequently subjected to increased wear
and tear. It is therefore important to correctly match the evaporator performance and the size of the expansion valve, the nozzle
used and the setting of the expansion valves to one another.
$t0h/$tL1 = 0,65
$t0h = t0h – t0
DT1 = tL1 – t0
The ideal evaporator performance is reached at a superheating
ratio of 0.65. This is calculated from the difference of the evaporation temperature t0 to the superheating temperature t0h in relationship to the difference between the air inlet temperature into
the evaporator tL1 and the evaporation temperature t0.
Order now!
Ask Küba to send you the easy-to-use Superheat calculator slide.
You can now order this practical calculator slide from Küba at no
charge by sending a fax to +49 (0)89 74473-107 or an e-mail to
[email protected].
01/2007 FORUM
12| EDITORIAL | CONTENTS | INTERVIEW | INTERNAL | ACCESSORIES | INSIDE| REPORT | EVENTS | PRACTICE | SERVICE
The carrot challenge
Foto: Stock Food
Carrots represent a difﬁcult product for refrigeration. Vegetable wholesalers need
reliable refrigeration to minimize moisture losses.
MARCHFELD to the northeast of Vienna between the Danube
and the Morava (March) Rivers is also known as the garden of
Austria. This region accounts for around a quarter of Austrian ﬁeld
vegetable cultivation. The bountiful ﬁelds stretch as far as the eye
can see, interrupted only by windbreaks. The Marchfeld region
is also famous beyond the borders of Austria for its asparagus.
However, the main crops are potatoes, onions, celery, fresh vegetables such as spinach, peas, strawberries – and carrots.
Carrots in particular are very sensitive to cooling and so provide
a great challenge to refrigeration engineers. The main problem
is maintaining correct moisture levels. A loss of moisture of only
10% already results in a substantial loss of quality and therefore
also of value.
For almost a quarter of a century, however, carrots have been
in good hands with Walter Lengheim. The refrigeration engineer
from Vienna has specialised in demanding refrigerated produce
such as onions, potatoes, celery, berry fruits, strawberries, asparagus – and carrots. He mainly designs and installs direct expansion systems using the most common refrigerants, and, on
FORUM 01/2007
request, systems that use secondary refrigerants such as Glycol. Lengheim also installed the perfect refrigeration system for
the production and retail operations of Walter Schick in Wittau,
Austria. Up to 250,000 kg of carrots can be stored in a 240-m²
large refrigerated warehouse. The vegetable is harvested from
the ﬁeld at a temperature of around +15 °C to +20 °C. The carrots are then stored in wooden crates, which hold around 800
kg each. The refrigerated space is then loaded over a period of
three to four days. After that the carrots are cooled down to a
temperature of +1 °C at a relative humidity of 96 to 98% over a
period of around two weeks. The refrigerated warehouse serves
as a long-term storage from October to early summer; in the
summer months it is also used for short-term and intermediate
storage (only a few days) of treated, washed raw produce and
packed goods. The refrigerated warehouse was equipped with
a high performance SGAE 56-F84 air cooler. It is designed for
a cooling capacity of approximately 40 kW with a low operating
temperature difference of 5 K (DT1). This is a direct expansion
system with R404A refrigerant.
CLASSIC LINE
The essential aspects for the preservation of ideal
carrot quality include:
• Harvesting of healthy, ripe, storable raw produce with sufﬁcient soil
covering
• Refrigerated storage immediately after harvesting
• Harvest temperature max. 15 °C
• Observation of the ﬁxed stacking plan for ideal ventilation
• Cooling of the produce to the core temperature in the box in around two
weeks
• Exact selection and calibration of the expansion valve for direct evaporation
Another example that proves Walter Lengheim‘s sure touch with
carrots is a production operation for organic carrots in Marchegg.
The storage capacity of the refrigerated space for carrots here is
800,000 kg. A Glycol system was selected when designing the
plant. It ensures both load-dependent operation of a hydro-cooler
and the operation of the refrigerated space. The system employs
R134a refrigerant in the primary circuit and the anti-freeze agent
propylene glycol (33%) in the secondary circuit. Two DZAE123
Dual Discharge air coolers are installed with an ideal air/surface
ratio. Eight large wooden boxes can be stacked on top of one
another thanks to the low proﬁle construction of the air coolers.
Storage likewise takes place at +1°C room temperature and a
relative humidity of 96 to 98%. The installed cooling capacity totals approx. 65 kW. The air coolers work at a DT1 which is as low
as possible of approx. 2.5 to 3 K. On the one hand, this system
is also designed so that freshly harvested raw produce such as
early carrots can be cooled for short-term processing from June.
On the other hand, produce already prepared for export, washed,
sorted, rapid chilled in the hydro coolers to 4°C and then packed
in big packs of approx. 1,000 kg each can also be stored for fairly
long periods here. Since the facility is near a residential area, low
noise emissions were important when selecting the condensers.
Thus, the installation features two CAV E09-1x3 A condensers
with a sound pressure level of 33 dB(A) in each case at a distance
of ﬁve meters.
Both the direct expansion system and the Glycol system are
controlled by an SPSS control. CO2 extraction and external ventilation are also integrated in the system concept. The defrosting
of the air coolers takes place by circulating air up to a room
temperature of +4°C; at lower room temperatures, the electrical
defrosting is automatically activated. In order to save energy the
defrosting interval is determined by the control as defrosting on
demand, depending on the operating time over the machine
running time. This results in more defrosting operations with a
long machine running time, fewer operations with shorter running times. Both systems are designed so that no further humidiﬁcation is necessary.
A third example: a processing operation for organic carrots
stores 1,000,000 kg of carrots over an area of 510 m². The re-
DZAE 123 air coolers ensure high product quality and low weight
loss of the carrots and pay for themselves very fast - which greatly
pleases the users.
frigeration system here is similar to system 2 in its basic concept, but was conﬁgured as a direct expansion system with
R134a refrigerant. It takes the room conﬁguration, the ceiling
design and the loading capacity into account. Two DZAE 123C
Dual Discharge air coolers and the refrigeration system with two
separate refrigeration circuits were installed in the refrigerated
room. The long throw of the air coolers is particularly advantageous here. The whole room can thus be ventilated and so also
utilised to the full.
Walter Lengheim comments, “Our customers are very happy
with the respective refrigeration systems due to the high product quality of their carrots. The systems amortize very quickly
due to the lower weight loss and the higher quality of the product, despite the somewhat higher initial investment expenses of
air coolers with large cooling areas because of the design with
a small temperature difference.“
The observation of optimum storage and conﬁguration conditions as described applies not only to carrots, but also to related
produce such as celery and parsley root, in particular, and root
vegetables in general.
Customer requirements in the planning phase are very
similar due to the similarities of the refrigerated produce:
• Exact temperature control to a precision of 1 K
• High humidity in the range of 96 to 98% relative humidity
• Large cooling areas and uniform air distributiong
• Ideal space utilisation for maximum stacking and storing
• Minimal dehumidiﬁcation of the produce; high maintained quality
• Coverage of a wide cooling capacity range because daily quantities put
into storage cannot be exactly deﬁned (depending on harvest)
Ing. W. Lengheim Kühlanlagenbau
Ing. W. Lengheim Kühlanlagenbau in Vienna, Austria specializes in refrigeration engineering and construction, above all for custom refrigeration
More information at: www.lengheim.at
system designs for vegetables.
01/2007 FORUM
14 | EDITORIAL | CONTENTS | INTERVIEW | INTERNAL | ACCESSORIES | INSIDE| REPORT | EVENTS | PRACTICE | SERVICE
FORUM 01/2007
ECONOMY LINE
CLASSIC LINE
Chilled treats for
the taste buds
The Hotel Schloss Fuschl offers its guests ﬁrst-class
service and so also requires ﬁrst-class refrigeration
technology. Küba evaporators form the backbone of
this technology.
THE HOTEL SCHLOSS FUSCHL IN HOF near Salzburg, Austria, is not only a treat for the eyes of its guests, but also for their
taste buds. Since 2002, Thomas M. Walkensteiner, a chef who
has been awarded three chef‘s hats, has revolutionized the gastronomic side of the picturesque palace with a fantastic location.
“My cuisine is light and healthy, my products are ﬁrst-rate, my
creations are remarkable,“ is how the master chef characterises
his philosophy.
To ensure that the meals reach the table fresh and in the best
quality, the hotel management and the chef use produce from
local organic suppliers and rely on modern refrigeration engineering. “When the hotel was completely renovated in 2006, the
refrigeration systems were also fully modernised,“ explains Peter
Strauss, managing director of Strauss Kälte-Klimatechnik in Thalgau, Austria, who was responsible for the refrigeration design and
the installation. “The old system was 15 years old, technologically
obsolete and too small; the new system satisﬁes all the demands
on a modern hotel restaurant service.“
The hotel has a total of 76 refrigeration systems. They are spread
over various locations wherever refrigeration is required: in the
cooling and freezer rooms in the storage area, the blast freeze
area, the wine store, the various under counter refrigerators in the
main kitchen and in the gourmet kitchen, in the service and buffet
area as well as in the delivery area in the annex. Küba evaporators
were used in all units. Let us start with a look at the great variety of
evaporators in the storage area beneath the main kitchen:
A famous ﬁlmsetting: The Hotel Schloss Fuschl
was where the legendary German ﬁlms about the
Austrian Empress Elizabeth („Sissy“) were made
in the 1950s. There is still a Sissy room to commemorate this.
Application
Patisserie Chill
Dairy product Chill
Pre- Chill room
Beer Chill
Beverage Chill
Vegetable Chill
Meat Chill
Freezer
Kitchen Chill
Gourmet Chills
Room size
6.3 m2
2.2 m2
6.96 m2
3.1 m2
10.2 m2
8.64 m2
8.1 m2
9.54 m2
3.3 m2
3.6 m2
Air cooler
DFAE 33
DFA 61
DFA 33
DAF 61
DEA 72
DEA 91
DEAE 91
DEBE 92
DEAE 81
DEAE 81
DT1[K]
7
7
7
7
7
7
7
7
7
7
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The Hotel Schloss Fuschl is a truly ﬁrst-class location. This means: only the best refrigeration technology is used to guarantee the quality of
the food. Since part of the palace is a protected historical building, the installation of the system was a engineering challenge.
The DFA 061 and DEAE 081 were used in the Beer Chill and in the
Dairy Chill of the main kitchen due to their compact size. These
evaporators are also easy to clean thanks to the hinged fan plates.
The DEAE 081 was also installed in the two Gourmet Chills of the
gourmet kitchen. And last, but not least, in the delivery area. The
products are received here and then distributed to the individual
refrigeration rooms. Only the beverages for seminars and conferences are permanently stored – and cooled by the DEA 072 – in
the delivery area. This area also includes a Waste Chill whose cooling ensures that the fermenting organic waste does not develop
an unpleasant odour. A DEA 072 is also used there. Engineer Peter Strauss chose Küba evaporators for three reasons: “The units
have the required cooling capacity stages, are very economical
and can be delivered fast and without problem.“
Strauss spread the refrigeration units over three multi-compressor
refrigeration systems and four individual systems. The individual
systems provide the climate for the wine store, cool the Blast
Freezer area and the delivery area. The refrigeration desks and the
deep freeze area are each supplied by a multi-compressor refrigeration system. In addition, the refrigeration rooms in the gourmet
kitchen and in the main kitchen as well as the Chill Rooms beneath
the main kitchen are combined in one integrated system. Each
of the systems has three compressors. They require the cooling
capacity listed below and use the following refrigerants:
Cold Stores
Undercounter refrigerators
Deep freeze area
19,7 KW
13,5 KW
8,5 KW
R134a
R134a
R404A
Strauss describes the advantages of the integrated system as
follows: “It is more cost-effective, is an energy efﬁcient system,
is more reliable in operation and also easier to service.“
The technical side was only a part of the challenge to be mastered: the palace tower is also protected as a historical building. Strauss: “This means that the air-cooled condensers of the
installation could not be installed externally. The intake air was
therefore supplied via openings in the outer wall and the exhaust air was guided up and out via air ducts on the inside of
the building.” The hotel reopened in July 2006. The guests are
very pleased with the food and the hotel operators are equally
pleased with the refrigeration system.
Strauss Kälte-Klimatechnik – Perfection with Celsius
Strauss Kälte-Klimatechnik in Thalgau, Austria, was responsible for the design and installation of the refrigeration systems in the renovation of
the Hotel Schloss Fuschl. The company was founded in 1966 and is today managed in the second generation by the brothers Peter and Rudolf
Strauss. They currently have 20 employees and are specialist suppliers of customized refrigeration solutions for customers in all industries.
More information at: http://www.strauss-kaelte.at
FORUM 01/2007
FREQUENTLY ASKED QUESTIONS
SERVICE | PRACTICE | EVENTS | REPORT | INSIDE | ACCESSORIES | INTERNAL | INTERVIEW | CONTENTS | EDITORIAL |17
The corrosion resistance of stainless steel is particularly important when selecting the material
for demanding technical refrigeration applications with complex
environmental conditions. The
collective term “corrosion-resistant stainless steel“ encompasses
around 120 types of steel, which
have two common features as a
rule:
• They have a chromium alloy
component of at least 10.5 to
13%.
• They form a passive layer (or
corrosion layer, see below)
of chromium oxide when exposed to oxygen.
The most common corrosion-resistant types and brands of steel
include, for example, Cromargan,
V2A, V4A, Nirosta or Inox.
HOW DOES the anti-corrosion effect of stainless steel actually
work? A more or less closed surface layer, the corrosion-resistant passive layer, is formed from the more noble alloy components of the steel. Its regeneration capability is its most signiﬁcant speciﬁc property. Even if it is damaged by scratches, for
instance, the layer renews itself fast with the aid of the oxygen
in the air. The corrosion protection is thus effective again within
a short period.
The regeneration capability of the passive layer is noticeably
impaired by moisture. It is therefore recommended to rinse
stainless steel air coolers after cleaning and then to dry
them completely. In addition, the proper draining of the
condensation should be monitored during assembly. This
is because moisture prevents oxygen from reaching the defective areas. When this happens, the passive layer cannot
regenerate sufﬁciently, if at all. The damaged points are then
subject to corrosion attacks. This is a very critical issue for
refrigeration engineering: around a third of the downtime of
all refrigeration plants are due to such local corrosion. What
happens when the steel starts to corrode? Halogen ions, but
above all, chloride ions that are frequently found in cleaning
agents, remain deposited on the damaged parts (recesses)
and produce an electrochemical reaction. Tiny, microscopic
pits form in the protective oxide skin of the steels even before
corrosion actually occurs. Each of these pits generates small
current pulses, which are indications of the chemical reaction.
Pitting corrosion follows. Incidentally, the rate of corrosion can
increase very rapidly on even the slightest changes in the external conditions (temperature, concentration, etc.).
What does this mean for refrigeration engineering? The
designer must always bear in mind that stainless steel can
corrode very quickly – even slight changes in the potential of
corrosive solutions applied or of the temperature sufﬁce. It is
therefore important to keep a close eye on the choice of the
steel. For example, 1.4301 steel (V2A) is unsuitable for applications where there is contact with salt water. In such cases,
1.4571 steel (V4A) should always be used. Nevertheless, mechanical work on the coolers such as the unhinging of the drip
trays or fans for cleaning can always cause damage to the
passive layer.
INSTALLATION TIPS: Additional electric defrost for junior DF air cooler series
Economic defrosting with a standard heater – Küba engineers paid particular attention to this feature in
the design of the junior DF series, which is relevant for nearly all typical applications for the junior DF. If
the junior DF air cooler series is used in a deep-freeze room with an adjacent kitchen or if the opening frequency of the deep-freezer is relatively high, additional electrical defrosting is necessary. Further details
on how to order the additional heater can be found in the current spare parts list.
01/2007 FORUM
18 | EDITORIAL | CONTENTS | INTERVIEW | INTERNAL | ACCESSORIES | INSIDE| REPORT | EVENTS | PRACTICE | SERVICE
Tapas and toreros
The Hotel Sol Meliá in Berlin uses an intelligent integrated compressor system to
cool refrigeration cabinets and cooling rooms over four ﬂoors.
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2
ECONOMY LINE
THE SOL MELIÁ HOTEL GROUP is based in Palma de Mallorca in Spain and operates more than 350 hotels in 30 countries
on four continents with a total of some 85,000 rooms. The group
is the market leader in Spain, the third-largest hotel group in
Europe and the world number twelve – a truly superlative hotel
chain. Since October 2006 Germany‘s capital, Berlin, now also
has its own Sol Meliá Hotel. The four-star hotel is situated at the
center of the city on Friedrichstrasse, just a few minutes from the
Brandenburg Gate, the Museum Island and Alexanderplatz. The
upper class hotel caters to business travellers and tourists in its
647 rooms and offers a relaxing atmosphere, the required touch
of luxury – and ﬁrst-class dining. Guests can choose between a
buffet, an à-la-carte restaurant and also excellent Spanish tapas
in the separate tapas bar. It is therefore not surprising that this
sumptuous gastronomic experience also requires a superior refrigeration solution. A good kitchen needs fresh and properly
chilled ingredients. The Berlin Sol Meliá refrigeration system
was planned and installed by the refrigeration engineering ﬁrm
Kühlanlagenbau Süd-West of Erfurt, Germany, which is a subsidiary of Dresdner Kühlanlagenbau, based in Dresden. Ralf
Jesumann, the manager of the sales and service ofﬁce in Greiz,
reports, “Big hotels always make a huge variety of demands on
refrigeration technology. In this case, the refrigerated cabinets
and rooms were spread over a number of ﬂoors and all had to
be linked to the refrigeration system. It was also necessary to
ﬁnd the ideal location for the condenser.”
Kühlanlagenbau Süd-West ﬁrst installed a semi-hermetic, linked
refrigeration system with three compressors. The integrated
system supplies 20 refrigerated cabinets spread throughout the
hotel, including, for instance, the salad bar, the tapas bar and
the buffet, as well as 13 cooling rooms belonging to the kitchen.
The cooling rooms for the kitchen are designed to pre-cool and
cool dairy products, vegetables, meat and convenience foods
Dresdner Kühlanlagenbau
The refrigeration engineering specialist can look back on a tradition
of more than 50 years and currently employs 540 people. It offers a
wide spectrum of services and ISO 9001 certiﬁcation for complete
refrigeration and air-conditioning solutions. The company places
great importance on using environmentally friendly technologies.
More information at: www.dka-dresden.de
as well as to chill beverages in two further refrigerated rooms.
The cooling rooms thus ensure that there are always enough
products in stock for the cooks. In addition, two single compressor sets were integrated into the total concept speciﬁcally
for deep freezing. The deep-freeze rooms are likewise located
in the vicinity of the main kitchen. The refrigerated cabinets and
rooms are spread over a total of four ﬂoors.
When selecting the evaporators for the integrated system, Ralf
Jesumann‘s team relied on units from the junior DF and market
plus SP series. Why? “We have been using Küba products with
excellent results for many years, and the price/performance ratio is also good.“
The main refrigeration concern besides the integrated system
was the condenser. “We had originally planned to install the condenser in the hotel building. However the dissipation of the heat
emitted by the refrigeration system from the building proved difﬁcult,“ Jesumann explains. For this reason, the customer even
considered using a water-cooled system. Finally, however, the
condenser was installed outdoors above the entrance to the
underground garage. “It was simply the best solution - ecologically and economically,“ the customer and the refrigeration engineers agreed.
The system has now been up and running with excellent results
for more than six months. The Berlin Sol Meliá Hotel is happy
– and so are its guests.
Dresdner Kühlanlagenbau installed high-performance Küba
evaporators to ensure best refrigeration results in all refrigeration spaces in Berlin’s Sol
Meliá Hotel. A junior DF is installed for beverage cooling, for
example (photo 1).
Also in use is the market plus
SP in the freezer room and a
further junior DF in the readyto-serve room (photos 2 and 3).
Glass cabinets for intermediate
storage and fast service for the
guests are a special feature of
the beverage cooling (photo 4).
3
4
01/2007 FORUM
Quality all the way through
CLASSIC LINE
Freshness that lasts longer
ECONOMY LINE
junior DF
Q0 up to 2,1 kW
DE
Q0 up to 9,4 kW
SG commercial
Q0 up to 32 kW
SG industrial
Q0 up to 170 kW
DZ
Q0 up to 78 kW
simple reliable fresh
The Küba
Classic Line
is the best
technical solution
for complex
refrigeration
applications.
It stands
for maximum
goods protection,
optimum maturing
or finishing
processes and
universal use
even in difficult
environmental
conditions.
The Küba
Economy Line
is the right
product line
for simple
refrigeration
applications.
With a clear
focus on
standardised
refrigeration
tasks, it
combines low
investment and
operating costs
with proven
Küba quality.
compact DF
Q0 up to 10 kW
market plus SP
Q0 up to 50 kW
comfort DP
Q0 up to 28 kW