ABSTRACTS
Making ammonia
refrigeration plants safer
Andy Pearson
Star Refrigeration
Ltd., Thornliebank, Glasgow, UK
The use of ammonia as a refrigerant introduces some significant
hazards; toxicity, flammability, low temperatures and pressurised
volatile liquid are the most obvious. It has an excellent safety
record but there is undoubtedly still room for improvement.
This paper reviews some anecdotes of ammonia incidents and accidents
over the last twenty years and considers where the real danger
came from. This is contrasted with the requirements of our existing
safety codes, standards and regulations to establish whether
there are any deficiencies in the current approach. Ways in
which we could improve the safety record of ammonia are considered
and a proposal for a new approach to refrigeration safety is
outlined.
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DX
ammonia evaporators – flow regimes, charge and heat transfer
Predrag Hrnjak
University of Illinois (USA)
This article discusses the heat transfer and pressure drop in
evaporation of ammonia. An example of an experiment with DX
evaporator is presented. The evaporator was equipped with partially
transparent tubes so that visualization of the flow regimes
and estimation of the void fraction was done in real application,
with actual oil present in the system. Visualization indicated
flow regimes like at a bit lower mass flus than Zürcher at al.
would predict but reasonably close. The flow is characterized
with very high void fraction. These flow regime visualizations
indicated that any mechanism that would spread liquid to the
walls would be extremely beneficial.
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Current
and future trends in Ammonia refrigeration systems and control
components
Niels Vestergaard
Danfoss (Denmark)
The global refrigeration industry has during several years been
undergoing several changes. In particular the global environmental
impact of some refrigerants, such as the ozone depletion, global
warming and the greenhouse effect, has changed the industry
considerable. The environmental impact is mainly focused on
the synthetic refrigerants like CFC, HCFC, HFC and HFO.
Natural refrigerants, like Ammonia, Carbon Dioxide (CO2) and
Hydro Carbons are not affected by environmental restrictions;
however toxicity and flammability are issues that restrict the
use of these refrigerants.
This paper will mainly focus on Industrial Refrigeration, and
applications utilizing the natural refrigerants.
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Past,
present and future of ammonia as refrigerant, from a leading
industrial end-user perspective
Rene van Gerwen
Unilever Engineering Services (Netherlands)
Unilever, being one of the largest fast moving consumer goods
companies in the world, is one of the largest end-users of refrigeration
throughout its supply chain. In view of Unilever’s Sustainable
Living Plan, application of natural refrigerants is strongly
encouraged. Ammonia is the preferred refrigerant in its manufacturing
facilities.
Five value drivers called ’5C’, being ‘Core design, Carbon/costs,
Cash, Capability & Compliance’ are defined and applied for
continuous improvement of almost all processes in product manufacturing.
A specific set of value drivers has been defined for ammonia
refrigeration. These drivers provide an outlook for future trends,
from an FMCG end-user perspective. Increased focus on standardisation,
modularisation, sustainability, leveraging scale of business,
competence of personnel and process safety standard compliance
are identified as common trends.
In order to create a robust system across all the Unilever sites
utilising ammonia refrigeration, these ‘5C’ value drivers form
a consistent and integrated package attributing to value creation
throughout the value chain. Global implementation of this package
is structured through global and regional Communities of Practice.
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PRACTICAL
EXPERIENCES WITH AMMONIA REFRIGERATING SYSTEMS IN THE BALKAN
REGION
Franc Kosi
University of Belgrade (Serbia)
The paper gives an overview of ammonia industrial refrigeration
plants in Balkan countries. A brief chronology of the development
of industrial refrigeration in the countries of the former Yugoslavia
and current status of refrigeration equipment which has been
dominating in the Balkan market for the last fifty years are
presented. Based on personal insights of author acquired within
many years of experience in the planning, designing and construction
of industrial refrigeration installations, and including appropriate
examples, the basic technical features of the relevant systems
are given. In particular analyzed are the problems related to
the renovation and reconstruction of existing ammonia installations,
with special emphasis on the charging and the possibility of
improving energy transformation of refrigeration systems. A
short summary of suggestions for improving the existing status
of ammonia refrigeration systems in the Balkan region is also
stated.
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Heat
pumps and their economics
Alexander Pachai
JCI - Sabroe (Denmark)
Heat pumps have attracted a great deal of attention in different
parts of the world. Energy prices are high, very high, at the
moment and have been for quite a while. Energy prices have been
high before, historically, but never this high and for as long
as they have been over the past 5 years. This generates great
pressure on production where heating and cooling make an essential
part of the product price. Energy prices vary tremendously all
over the world. It is therefore relevant to figure out the relationship
between different price levels on electricity, oil and gas.
This information can be gathered from different sources, but
local high volume customers can get better prices than the ones
stated in the tables available on the internet. In the
past, heat pumps were mainly used for domestic heating using
different energy sources. The industrial market has many other
sources than the domestic market. New products are becoming
available for production of water at temperatures as high as
90°C. The Coefficient of Performance (COP) is high thus ensuring
a high Return Of Investment (ROI). The price of energy is regulated
in different ways in different countries. The challenge is to
look at the system implementation and figure out how to get
the most out of the heat pump and where it would make sense
to use the technology.
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Heat
recovery in fish meal industry by high temperature hybrid heat
pumps
Stein Nordtvedt
Institute for Energy Technology (Norway)
The fish meal industry uses large amount of heat for drying,
and this paper presents results from a feasibility study of
the possibilities for energy recovery by means of a hybrid heat
pump. By hybrid heat pump means a vapour compression heat pump
with a solution circuit. The working fluid is mixture of ammonia
and water which gives many benefits where high temperatures
are required and where the heat sink and heat source fluids
have large temperature glides. A simulation model was developed
to explore the possibilities for heat recovery using hybrid
heat pumps, and results from parametric studies with simulation
model are presented. The results show that hybrid heat pumps
have promising capabilities for use in the fish meal industry.
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Ammonia
heat pump optimization through two condensers in series
Claus Madsen*, B. Pijnenburg, R. Christensen
*Danish Technological Institute (Denmark)
With a relatively large difference in temperature of water in
and out of a condenser, it is possible to reduce the required
area of the condenser by splitting the condenser into two sections.
An alternative is to use the same area but increase the COP
by lowering the condensing temperature.
This article describes the potential of splitting the condenser
into two sections and under which circumstances this is possible.
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Towards
"environmentally sound” refrigeration as defined under
the Montreal Protocol
Lambert Kuijpers
Technical University of Eindhoven (Netherlands)
Since 2009 many efforts have been undertaken internationally
to study limits to HFC consumption. In that year the Montreal
Protocol experienced first discussions of the so-called HFC
Amendment to the Montreal Protocol, discussions which are still
ongoing. In fact, the European F-gas regulation and the MAC
directive were the first international HFC regulations that
entered into force; the F-gas regulation has already been reviewed
recently and a new proposal is currently under discussion. In
2011, in Decision XXIII/9, the Montreal Protocol Parties requested
a new report on environmentally benign or friendly ODS alternatives,
which was published in 2012. The beginning of 2012, a group
of countries established the CCAC, the Climate and Clean Air
Coalition, the efforts of which are focused on the reduction
of emissions of short-lived climate gases --including HFCs--
via various initiatives, including workshops and conferences.
Late in 2012, the Parties to the Montreal Protocol took Decision
XXIV/7 in which they request a TEAP Task Force to produce a
new report on “environmentally sound” ODS alternatives in 2013.
This paper summarises main assessments environmentally acceptable
alternatives, and elaborates on the refrigerant alternatives
described in two recent TEAP Task Force reports, where the XXIV/7
Task Force report will be subject for discussions at the Montreal
Protocol OEWG meeting in Bangkok, June 2013. Refrigerant alternatives
should be “environmentally sound”, a definition probably related
to refrigerant alternatives having a low GWP, which includes
natural refrigerants.
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Status and analysis of ammonia refrigeration technology for
cold stores in China
Jianyi Zhang
Jimei University (China)
Ammonia is widely used in refrigerating plants in China, where
more than 92% of cold stores have adopted it as the refrigerant.
The energy efficiency of cold stores is introduced, and the
status of equipment used in ammonia refrigeration plants reviewed.
The author’s investigations reveal a continuing increase in
the size of cold stores and progressive application of screw
compressors. Based on field surveys, safety issues around ammonia
refrigeration still present a challenge in China. National standards
for safety and charging of ammonia systems have recently been
issued to address these problems, and the measures in these
standards are introduced.
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Energy
conservation in ammonia refrigeration system installed for meat
processing unit in india
Anil Gulanikar
Dag-Tech Refrigeration (India)
In this paper we have elaborated the renewal and improvement
carried out in ammonia refrigeration plant installed for a meat
processing units in India from energy conservation perspective.
We selected two out of four refrigeration systems installed
in one meat processing unit for revamping as they were 15 year
old. Plant consist of reciprocating compressors, atmospheric
condensers, inefficient air cooling units (ACU), and was manually
operated without any automation. The discharge pressures were
high due to presence of air in the system. The approach/ methodology
selected was, formulation of design parameters, introduce automatic
compressor capacity control system, replace existing overdesigned
compressor jacket cooling pumps, install air purger, replace
existing inefficient atmospheric condensers by S & T condensers,
replace old inefficient ACU by efficient ACU, install controls
to minimize manual operation and educate manpower for safe/efficient
plant operation. Designed and installed heat recovery system
using compressor discharge gas and using 85°C waste fluids from
rendering plant to generate hot water. As all above revamping
work to be executed without any production loss, we meticulously
planned and executed all above in about four years. Similar
activities were successfully carried out in two others meat
processing units simultaneously for the same group. The plant
is running successfully for last two years. Key achievements
were , only 15 out 22 No. compressors were required to operate
during peak load, 57% reduction achieved in ACU fan motor installed
kW , replacement of 20 No. overdesigned jacket cooling pump
achieved 114,624 kW/year energy saving and saved 98,000 lit/year
furnace oil due to heat recovery.
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Use
and misuse of standards in refrigeration
Gert Koster
GEA Refrigeration (Netherlands)
This paper is intended as an introduction to the workshop on
use and misuse of standards for commercial reasons. It shows
how standardization is organized, what the benefits of standardization
can be and what threats can occur in unguarded moments.
INTRODUCTION: Worldwide standards are developed and used for
many purposes and applications. It may have been started by
agreements on length and weight. These agreements were of local
interest in order to be “sure” that on the market place you
got delivered the right amount of goods. From this time as example
the measure “foot” is known, as if all feet are alike. Normally
it was referred to the length of the foot of the king. So, the
value could change when the king was succeeded with confusion
all over.
Internally in companies and organizations standards are used
not only to prevent and/or avoid repetitive work, but also to
reduce the risk of making mistakes. By applying standards, in
many cases it also results in cost reduction in design and manufacturing.
In after-sales service and maintenance it also has advantages
because of the interchangeability of parts. In daily
life, we also see the advantage in having standards for e.g.
electrical power supply and the physical dimensions of electrical
sockets, traffic signs, etc. During the years the purpose of
standards has changed. Some 40 years ago, standards were mainly
dealing with dimensioning of e.g. construction elements. Apart
from these types of standards, now standards are setting the
objectives to be met with regard to safety and safeguarding
the environment. The latter in the broadest sense of the word;
directly and indirectly by setting a standard for e.g. efficiency
and energy consumption. This paper deals with the organization
how standards are being set up, how they are approved and how
the industry can participate in this and to create awareness
of possible misuse of standards.
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Ammonia
chillers in different industrial plants in Switzerland
Jan Boone
Mayekawa Europe (Belgium)
This paper presents the results of operation of CHILLERS with
natural refrigerants in Switzerland. PLANT 1 - NH3-chiller is
designed to produce 367 kW chilled ethylene glycol/water at
-2/-6˚C with an evaporating temperature of -9˚C. The plant started
in the fruit-season 2012 and operated approx. 3716 hrs at an
overall COP of 4 to 5.
PLANT 2 uses 2 piston compressors to produce 500kW chilled water
at 6°C and 350kW glycol-water at -3°C in a coldstore by using
NH3 direct expansion type chillers. The plant was started in
2010 and operated approx. 18000 hrs at an overall COP of 3~4.5.
PLANT 3 - NH3 chillers use piston compressors to produce 250kW
cooling in a fruit cold storage plant with ethylene glycol at
-7°C by using combined plate in shell evaporators. The plant
started in 2011 and operated approx. 16000 hrs at an overall
COP of 2.9.
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Operating
ammonia refrigeration systems at peak efficiency
Sergei Khoudiachov
S K Energy Consulting (Canada)
There are several ways to improve energy efficiency of ammonia
refrigeration systems. To save energy, many companies invest
in additional condensers, sophisticated PLC’s, and VFD’s. Unfortunately,
optimization of the refrigeration plant operation is often overlooked.
However, this optimization is the most cost-effective approach
to save energy in ammonia industrial refrigeration. By improving
the operation of ammonia systems, companies can get 10 – 20
times better return on investments compared to typical investments
in energy saving equipment. This technical paper will review
practical implementation of the optimized operation. Many existing
refrigeration systems can save 10- 20% of the energy use by
optimizing condensing pressure, suction pressure, hot gas defrosting,
etc. To achieve these energy savings, limited investments are
required. However, operators should work as a team with energy
efficiency experts to minimize energy use of their refrigeration
systems.
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New
developments on ammonia separation systems
Atte Aarnio
Vahterus Oy (Finland)
Vahterus is an inventor and manufacturer of fully welded Plate&Shell
Heat Exchanger since 1990. Recently the company has developed
two different kinds of evaporator / separating systems. The
target of the developing was to reach a low ammonia charge and
compact size unit combined to a safe and environment friendly
construction. The first newly developed construction has been
named the “Combined Evaporator”. This system performs two functions
in one compact cylinder type of round shell; the evaporating
section in the bottom and the droplet separating section on
the top. Vahterus has its own in-house testing laboratory. It
gives the possibility to run NH3 in the system producing a lot
of practical testing results; furthermore we have a lot of customer
experiences and test results from them. These data has been
used in the development process and heat exchanger dimensioning
software.
The “Combined Evaporator” was introduced in Chillventa fair
2008. The newest construction revision has been available from
the beginning of 2012. Tests have shown that the operation is
in line with expectations. Main benefits of using the “Combined
Evaporator” are to reach as small footprint and constructional
volume as possible; as small charge of ammonia as possible and
the possibility to save piping, insulating and transportation
charges. Another newly developed construction has been named
“Vahterus External System” (“VES”). It is a new version of the
two-vessel-system (evaporator + separator). “VES” works with
similar technical principle as the “Combined Evaporator”, giving
the possibility to minimize the size of the separator vessel
and the ammonia charge.
The dimensional size of the “Combined Evaporator” is limited,
so on very large duties the “VES” is preferred because it gives
the opportunity to reduce the size compared to the traditional
heat exchanger and separator. When using the “VES” it is now
possible to have a smaller construction for larger capacity
units.
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Gaining
“Lost Work” for a Greener Planet
Henry Bonar*, John Nuszkowski
*BONAR (USA)
During the refrigeration cycle – compression, condensing, expansion,
and evaporation – a process that occurs during the expansion
phase has become known as the lost work process. This process
releases energy (flash gas) which could be captured and used
to reduce the work by harnessing this energy to drive portions
of refrigeration equipment.
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Extended
operational flexibility of trigeneration systems with ammonia
water absorption chillers
Arnd Hilligweg
Nuremberg University of Applied Sciences (Germany)
In a contribution to the 2009 Ohrid Conference (Hilligweg, 2009)
a short-cut method for designing trigeneration systems for steady
state operation was explained. Here system modifications for
non-steady state operation shall be introduced. An interesting
approach to this problem was made by Lai and Hui (2010) who
suggested to integrate trigeneration systems and thermal storage.
However, the selected components were rather conventional: Chilled
water or ice storage units. Following the demands of power,
heat and cooling it shall be shown in this article that capacities
can be supported by store-and-boost-components. Completing cogeneration
system (IC-engine or gas turbine) and ammonia-water absorption
chiller these components make operation of trigene-ration systems
more flexible.
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First
operation data of a gas absorption heat pump at a test bench
Rupert Graf, Jose Corrales Ciganda, Simon Funk, Annett Kühn,
Felix Ziegler
Technical University of Berlin (Germany)
First operation data of a test site with four parallelly operated
natural gas driven absorption heat pumps (GAHP) using NH3/H20
as working pair and air as an environmental heat source will
be presented. Waste heat of an indoor pool hall is used to raise
the heat source temperature. The influence of the resulting
high ambient air temperatures - along with additional necessary
fans - on the system efficiency will be investigated. In this
paper gas utilization efficiencies, auxiliary energy factors
and primary energy ratios for high air inlet temperatures above
17 °C will be presented and compared to a system using ambient
air as heat source. In addition the influence of the load behaviour
on the gas utilization efficiency, auxiliary energy factors
and primary energy ratios will be revealed.
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Optimization
of a gas absorption heat pump system
Jose Corrales Ciganda, Rupert Graf, Annett Kühn, Felix Ziegler
Technical University of Berlin (Germany)
In the course of an energy-efficient modernization of a kindergarten
in Berlin a 35 kW gas absorption heat pump using NH3/H2O as
working pair has been installed in 2010. Domestic hot water
production and space heating are additionally supported by a
15 m2 solar collector. The low temperature heat is supplied
to the heat pump system by four 100 m long vertical ground probes.
In this paper operation data for the period 2011-2012 are presented.
Gas Utilization Efficiencies (G.U.E.) are calculated and compared
for different demand profiles. The comparison of measured G.U.E.
values with manufacturer data revealed potential for system
optimization. Based on operation analysis modifications of the
control strategy and alternative hydraulic set-ups for an improved
performance are presented.
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Hybrid
coabsorbent heat pumping cycles
Mihail-Dan Staicovici, Andrei-Marius Staicovici
S.C. Varia Energia s.r.l. (Romania)
The work presents model results of the nontruncated and simple
truncated ammonia-water hybrid coabsorbent heat pumping cycles
(Staicovici, 2007). The cooling cyles are run for sink temperatures
of 12ºC to 42 ºC and desorber temperatures of -60 ºC to -5 ºC.
The depleted heat source temperature has been considered to
be by 20 ºC to 40 ºC higher than the sink source. The effectiveness
with respect to the pumping and mechanical vapor compression
(mvc) work consumption, , shows values ranging within several
to one and two orders of magnitude higher as compared to the
single-stage mvc cooling cycles. The cooling effectiveness with
respect to the heat source consumption is and in case of the
nontruncated cycles and simple truncated cycles, respectively.
Concerning the heating cycles, these are run for heat source
temperatures of 5 ºC, 37 ºC and 70 ºC. The sink source temperature
ranges within -50 ºC to +50 ºC. The usefully heated fluid temperature
resulted in values of 40 ºC to 140 ºC. The values of the heating
cycles are quite similar to those of the cooling ones, whyle
the heating effectiveness with respect to the heat source consumption
is . The results are very encouraging for use of the hybrid
coabsorbent cycles in heat pumping applications with high primary
energy savings.
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Influence
of ejector performance on the overall efficiency of ammonia
ejector refrigeration cycle
Krzysztof Banasiak, Armin Hafner, Anne Karin Hemmingsen
SINTEF Energi AS (Poland, Norway)
The influence of ejector performance on the overall efficiency
of ammonia ejector refrigeration cycle in different operating
conditions was numerically assessed and discussed. A brief review
of experimental results reported in scientific literature was
performed and commented, specifically with reference to limited
values of ejector efficiency (up to 18%). Physically and technically
based thresholds for further increment of ejector performance
were presented.
Sample operation curves for the ejector layouts reported in
literature as well as potential degrees of freedom for optimization
of the ejector design were suggested and discussed, based on
the results of numerical simulations carried out by authors’
own one-dimensional ejector model.
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Exergetic
analysis of refrigeration cycles operating with natural refrigerants
C. Filipoiu, A. Dobrovicescu, V.Apostol, L. Drughean
University Politehnica of Bucharest (Romania)
Comparative analysis of the design and operation of two different
solutions for a supermarket cold chain located in Bucharest
Romania is presented. The actual system operates with R404A
in a single stage for cooling and two stages for freezing while
the replacing one (alternative) considers a cascade CO2/NH3
system. The analysis is performed based on the exergy concept.
The exergy analysis points out which are the exergy destructions
associated to every piece of equipment and processes offering
solutions for improvement. Based on the exergetic analysis an
exergoeconomic optimization can be developed. The conduct of
the cascade system at the variation of the operating parameters
is performed.
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Romania
– Ammonia traditional user
Gratiela Tarlea
Technical University of Bucharest (Romania)
This paper presents a study of the Romanian line up to the environment,
refrigeration and air-conditioning EU legislation with the recommendation
of using ammonia as a very eco-efficient alternative.
Romania has ratified the Vienna Convention for the Preservation
of Ozone Layer, the Montreal Protocol on ozone depleting substances
and its Amendment adopted in London in 1993, followed by ratification
of the Copenhagen and the Montreal Amendment in 2000 and 2001,
respectively. In the last years, the refrigeration, air conditioning
and heat pump industry made important technical progress and
complied with the Montreal and Kyoto Protocols.
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