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Ammonia Refrigeration Technology for Today and Tomorrow
International Conference |
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ABSTRACTS
ASPECTS
INVOLVED IN THE REPLACEMENT OF REFRIGERANTS BY LOW GWP GASES
Lambert Kuijpers
Technische Universiteit, Eindhoven, The Netherlands
Co-chair UNEP Technology and Economic Assessment Panel
Co-chair UNEP TOC Refrigeration, AC and Heat Pumps
Lead Author IPCC WG III Fourth Assessment Report
In the early 1990’s, when the replacement of CFCs was the important issue, the
discussion was dominated by how fluorocarbons –whether HCFCs or HFCs- could
be phased in quickly in order to comply with Montreal Protocol schedules. In
several sectors consideration of non-fluorocarbon solutions occurred. This started
in 1992 with the development of isobutane as a refrigerant for domestic refrigerators
in Europe and the consideration of carbon dioxide for several applications (initiated
by the late Gustav Lorentzen). The “natural refrigerant” conversion became an
important driver and in several refrigeration sectors new technological developments
were started during the last decade. Next to carbon dioxide and HFC-152a, low-GWP
alternatives were recently announced as HFC replacement for mobile air conditioning.
The paper summarises a number of aspects involved: the Montreal and Kyoto Protocol
regimes, reporting by TEAP and IPCC, the impact of regulatory frameworks, initiatives
by industry and ENGOs, as well as technological and cost potentials and barriers.
It summarises the current status and considers some ways forward.
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AMMONIA’S FUTURE AS A REFRIGERANT
Anders
Lindborg
Ammonia Partnership AB, Nyponv. 24, 260 40 Viken, Sweden
There is a belief that ammonia is both poisonous and explosive. This is not
true if one examines the definition of “poisonous” and of “explosive".
This belief has often been a hindrance to profitability in the refrigeration
industry. Most people have experienced, to a greater or lesser extent, the smell
of ammonia, while only a few people have actually been injured by ammonia. Furthermore,
although flammable, ammonia does not explode. It “flash burns” like confined
smoke does in a building fire.
As a refrigerant, ammonia is unsurpassed, and it has excellent thermodynamic
qualities that also have environmental advantages. All life is dependent on
the recirculation of nitrogen, in which the breaking down of natural substances
to ammonia is an essential part. Ammonia will continue to be used as a refrigerant
in the future since society cannot afford not to use it.
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EXTENDING THE LIFE OF AMMONIA REFRIGERATION SYSTEMS
Andy Pearson
Member of IIR Commission
E1, IIAR Board of Directors
Star Refrigeration Ltd., Thornliebank, Glasgow, G46 8JW, UK
This paper addresses issues related to the useful working life of ammonia refrigeration
equipment. It considers the economic case for extending the life of equipment
and reviews the factors which affect the condition of equipment. Key issues
in the design, operation and maintenance of plants are explained, with examples
to illustrate the effect of earlier decisions on later life. Some recommendations
are given as guides to good practice when equipment is being modified or reconfigured,
with the objective of finding ways in which existing systems can be brought
into line with current international safety standards without incurring an excessive
investment cost.
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IN-TUBE HEAT TRANSFER AND PRESSURE DROP CHARACTERISTICS OF PURE NH3
AND CO2 IN REFRIGERATION SYSTEMS
Pega Hrnjak, C.Y. Park
Professor and Co-Director Air Conditioning and Refrigeration Center; IIAR
Board of Directors
University of Illinois, Urbana Champaign
1206 W. Green St., Urbana, IL 61801, USA
This paper analyzes the differences and similarities between heat transfer in
ammonia and carbon dioxide from the perspective of NH3 two-stage, CO2/NH3 cascade,
NH3 direct expansion, and CO2 direct expansion systems heat exchanger designer.
The focus is on differences in thermophysical properties and thus different
performance. Besides a literature review of available correlations some new
experimental data are presented. Because of large deviation of calculated values
with exiting correlations from measured results, two new correlations to predict
flow condensation heat transfer coefficients are developed based on experimental
results for NH3 at 35 °C and CO2 at –15 °C. With comparison of measured and
predicted values, it is shown that some correlations, previously published in
open literature, can be used to calculate flow boiling heat transfer coefficients
for NH3 at –20 °C, CO2 at –30 °C and heat transfer coefficient for CO2 gas cooling
process. It is shown that some correlations proposed by previous studies can
predict pressure drop with NH3 and CO2 two-phase flow, and with CO2 gas cooling
process, relatively well. The NH3 and CO2 flow evaporation heat transfer and
pressure drop characteristics at –40 °C are compared with predicted values.
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CURRENT AND FUTURE PROSPECTS OF ENHANCED HEAT TRANSFER IN AMMONIA SYSTEMS
Zahid Ayub
Member of ASHRAE Research
Committee;Member of IIR Commission B2
Isotherm, Inc., 7401 Commercial Blvd., East, Arlington, Texas 76001, USA
In the last decade a moderate headway has been made in the application of enhanced
surface heat exchangers in ammonia refrigeration systems. This has been a result
of the persistent issue of ozone and global warming which has resulted in keen
interest in natural refrigerants such as ammonia that has played a prominent
role in the refrigeration industry for years, particularly in the field of food,
beverage and marine. The only drawback with ammonia is the toxicity; hence,
if smaller heat exchangers could be introduced in order to reduce ammonia charge,
this negative aspect about ammonia can be pacified to a great extent. In order
to achieve this goal, novel and compact heat exchangers with enhanced surfaces
have to be introduced. This paper presents an over view of the status of ammonia
as a refrigerant. It also discusses the present and the future trends in the
development of compact heat exchangers for use in ammonia refrigeration.
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AMMONIA IN SMALL CAPACITY REFRIGERATION AND HEAT PUMP SYSTEMS
Bjorn Palm
Vice-President of IIR Commission
B1
Royal Institute of Technology,
S 100 44, Stockholm, Sweden
Ammonia has been used as refrigerant in large systems continuously since the
beginning of the era of refrigeration. In small systems, it has hardly been
used at all since the introduction of the halogenated hydrocarbons around 1930.
Lately, with the search for alternatives with less influence on global warming,
the use of ammonia in small systems has come into focus again.
In the present paper, we will describe the work done at the Royal Institute
of Technology with the aim of developing a prototype of a domestic water to
water heat pump with a heating capacity of around 6 kW. It has been shown that
such a system can be designed to operate with less than 100 g of ammonia. The
main obstacle for introducing this technology commercially is the lack of components.
Particularly, there seem to be no hermetic or semi-hermetic compressor available
in this size range.
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ULTRA-EFFICIENT AMMONIA SYSTEMS
S. Forbes Pearson
Star Refrigeration Ltd,
Thornliebank Industrial Estate, Glasgow G46 8JW, UK
The paper describes a proven method of producing chilled water by means of ammonia
refrigeration. The method uses special valves and heat transfer surfaces to
allow heat to be rejected to ambient when conditions are suitable, without running
the compressor.
Yearly average coefficients of performance of 13 – 15 have been achieved in
North European climates.
About twenty such systems have been installed over the past twenty years. There
are many existing conventional systems providing the same function with lower
reliability at about one third of the efficiency that could have been achieved
by using the Star system.
The system is particularly suitable for providing refrigeration for chilled
ceilings but its major application has been to the cooling of main frame computer
centres.
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AMMONIA WATER SOLUTION AS SECONDARY REFRIGERANT, ADVANTAGES AND DRAWBACKS
Valerie Gibert
Axima Refrigeration,
6 rue de l’atome, 67800 Bischheim, France
Because of environmental reasons one should normally try to reduce refrigerant
load under pressure. This approach promotes use of brines in combination with
primary refrigeration loop.
This leads to the development of ammonia water solution – also called alkali
- in some European countries and more especially in France. One could estimate
that about 50 installations with alkali have been implemented in France within
the last 5 years. The aim of this paper is to show the advantages of alkali
as brine compared to mono-ethylene glycol but also to address the authorities
about the contradictions between regulations governing use of ammonia and use
of alkali.
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CALCULATION OF THE ENERGY CONSUMPTION OF A REALISED NH3-BRINE PLANT
AND COMPARISON OF THE CALCULATION WITH METERED VALUES
Roland Handschuh
Guntner AG & Co. KG, Hans-Guntner-Strasse 2 - 6, 82256 Furstenfeldbruck,
Germany;
Bernd Kaltenbrunner
KWN Engineering, Sommerweg 13, 5201 Seekirchen, Austria
In the scope of the presented research, the energy consumptions of an indirect
NH3 refrigerating plant were calculated. During the first year, the plant was
operated with dry drycoolers, but later on it was changed over to heat dissipation
by means of wet cooling towers. The electric energy consumptions of both heat
dissipation systems were registered over a period of one year. In both cases,
the metered values exceeded the calculated energy consumptions by about 20 %.
An interpretation of the results will be presented in the scope of the lecture.
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AMMONIA REFRIGERATION SYSTEM WITH HEAT RECOVERY FOR RETROFIT COLD WAREHOUSES
Vasile Minea
Hydro-Quebec Research Institute, Laboratoire des Technologies de L’energie (LTE),
600, avenue de la Montagne, Shawinigan, G9N 7N5, Canada
Ammonia refrigeration systems in medium and large cold warehouses operate with
discharge and condensing temperatures allowing efficiently recovering heat for
space and industrial hot water heating. This paper presents the thermal design
of a heat recovery system from five retrofit ammonia compressors totalling 2
361 kW of maximum heat rejection with desuperheater/condenser and cascading
heat pumps. About 33.5% of the available thermal power is recovered and used
for heating 12 250-m2 service and office areas with brine-to-air heat pumps
connected on a brine reverse closed-loop. When at least two compressors simultaneously
are operating, whole available sensible heat and up to 93.9% of condensing enthalpy
have to be recovered to satisfy the building peak heating demand.
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LIQUID HAMMER IN INDUSTRIAL AMMONIA SYSTEMS
H. T. HAUKAS
Consulting engineer, Lingavegen 225, N-5630 Strandebarm, Norway
Instantaneous stop of liquid flowing at high velocity, e.g. against a closed
valve, is designated liquid hammer, after the hammering sound from the impact.
The energy released may in severe cases cause damage to the pipe system, e.g.
disrupt a valve. Therefore liquid hammer is a possible cause of serious accidents.
The paper presents two practical cases where industrial ammonia refrigeration
systems suffered from strong liquid hammer. In one system the problems were
related to the wet return line, while in the other case the hammering occurred
in the liquid feed line. In both cases the mechanical impact on the systems
was very strong, with obvious risks of damage to piping and components and possible
ammonia release. A brief, general discussion of potential causes and con-sequences
of liquid hammer is given, together with a more detailed presentation of the
cases men-tioned above and how the problems were solved.
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CONTAMINANTS IN AMMONIA REFRIGERATION SYSTEMS
Dermot Cotter,
Star Refrigeration Ltd, Derby, UK, Wincanton Close, Ascot Drive, DE24 8NB, UK;
John Missenden, Graeme Maidment
London South Bank University, London, UK
Contaminants (mainly air, water, dirt and lubricants) effect the performance
of refrigeration systems. When air enters a refrigeration system it contains
moisture (water). In refrigeration systems the air is usually found in the high-pressure
side of the system, while the water will find its way to the low-pressure side
of the system through the expansion valve. The air will cause the condensing
pressure to increase in the high side of the system. The water in the low-pressure
side of the system will result in a lower pressure in the evaporators to achieve
the desired evaporating temperature. This explains some of the shortcomings
of ammonia in DX low temperature applications.
The breakdown of lubricants (ie sludge) differs for mineral, alkyl benzene,
hydro-cracked, PAO and PAG lubricants. This has the effect of reducing the evaporator
performance as it coats the internal heat transfer surfaces
The paper will numerically assess the effects of each contaminant and their
accumulative effect on refrigeration system performance, outline the steps to
be taken to reduce contaminants entering ammonia refrigeration system and describe
how the contaminant can be removed.
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EXPERIENCE OF OPERATING AN OLDER AMMONIA PLANT AND THE ENERGY CONSUMPTION
Andrew Gigiel
CCC Consultants, Fairview, Moorlynch, Bridgwater, Somerset, TA7 9BY, UK;
Judith Evans
FRPERC University of Bristol, Churchill Building, Langford, Bristol, BS40 5DU,
UK
Most refrigeration plants operate efficiently when new and at their design condition.
However, plant if often changed to meet changed circumstances often with little
emphasis on energy efficiency. Recent increases in energy costs have raised
interest in the efficiency of of such plants.
This paper presents results from a survey of a large cold store complex with
a small amount of blast freezing. The survey specifically excluded measuring
the cooling loads. The site had two ammonia refrigeration systems with two-stage
screw compressors, one with a closed and one an open flash intercooler. The
refrigerant was pumped to the evaporators at high level in the cold stores.
Both plants had evaporative condensers.
The plant had been gradually adapted to its present configuration. The Coefficient
of System Performance (COSP defined as kW of electricity to extract 1kW of cooling)
of the two plants on the site if used as originally designed would have been
0.53 and 0.64. However, because of economising on capital cost and a lack of
maintenance the efficiency of the plants has been reduced and they are currently
operating at a COSP of 0.66 and 1.03.
The reasons for the reduced efficiency were, wear in the compressors, inefficient
operation at part load, inefficient defrost programs, reduced recirculation
in some evaporators, inaccurate instruments, poorly optimised intermediate pressure,
deterioration of insulation on refrigerant pipe work and vessels and hot gas
valves leaking. The estimated cost of the extra energy consumed because of these
faults was ?115,300 per annum (ˆ173,000) plus the unquantified cost of the energy
due to faulty hot gas valves.
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THE BEHAVIOUR OF HEATING SYSTEMS AT OFF-DESIGN CONDI-TIONS AND THE INFLUENCE
ON HEAT PUMP DESIGN PERFORMANCE
Gert Nielsen
Opticonsult AS,
Storetveitveien 98, N-5072 Bergen, Norway
The behaviour of heating systems, working at off-design conditions, has as a
whole been neglected by practitioners and researchers alike. With increasing
use of heat pumps in heating systems, this lack of knowledge leads to systems
that in their overall design has serious flaws, i.e systems that are run poorly,
systems where the heat pump capacity is too high, systems with unnecessary big
radia-tors and systems where the heat pumps are designed for unnecessary high
pressure levels. In this paper we will show that for a typical office building
the use either of low temperature heating sys-tems or high pressure class NH3
heat pumps, will only give an extra heat delievery of app. 3%. The point is
then, is the 3% worth the extra investment? We will show that usually, from
an economic point of view, it is not.
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TEST RIG FOR AMMONIA BASED ABSORPTION CHILLER COMPONENTS
A. Lecuona, M. Venegas, A. Zacarias
Departamento de Ingenieria Termica y de Fluidos, Universidad Carlos III de Madrid,
Avda. Universidad 30, 28911 Leganes, Madrid, Spain,
J. Roa
PID Eng&Tech, C. Plomo, 15, Poligono Industrial Sur, 28770 Colmenar Viejo,
Madrid, Spain
The paper presents the design of a test rig for components from absorption machines
using ammonia solutions. A thermochemical compressor of an absorption machine
forms the core of the rig. Main components include: adiabatic absorber, generator,
two sub-coolers and heat recoverer. Last four components are based on plate
heat exchangers. Thermal oil drives the generator simulating a low temperature
heat source, below 120 ?C. Auxiliary equipment include: solution pump, thermal
oil reservoir, Coriolis and Vortex flowmeters, PT100 sensors, pressure transducers,
valves and piping. The rig integrates an on-line acquisition and control system
to allow high quality data throughput. Special attention has been paid to safety
issues and the flexibility of the layout, including two reservoirs for solution
calibration and control. Experiments to be conducted in the test rig will allow
characterizing solutions performance in a wide range of concentrations, temperature
and pressure conditions. Two phase and single phase heat exchanger flow and
performances using the ammonia-based solutions also will be evaluated.
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COABSORBENT CYCLE TECHNOLOGY FOR AMMONIA/WATER HEAT PUMPING APPLICATIONS
Mihail-Dan Staicovici
S.C. Varia Energia S.R.L. & S.C. Incorporate Power-Absorption Engineering
S.R.L.,
str. Mihail Eminescu, nr. 81 B, floor 4, apart. 9, sector 2, 020 072 Bucuresti,
Romania
Based on the coabsorbent cycles, recently introduced by the author (Staicovici
M.D., 2006 a, Coabsorbent cycles, Proc. Gustav Lorentzen Natural Working Fluids
International Conference, IIF/IIR: 219-222), a particular new technology can
be developed for efficient and feasible heat pumping applications. The technology
could be very effective with respect to already known cycle improvement (e.g.
the advanced absorption cycles) and to the elaboration of new ones, with high
COP. These issues are emphasized here, presenting some typical coabsorbent applications
for heat pumps and refrigeration, with flow charts and theoretical model results,
for hybrid and absorption cycles, operated by the ammonia/water.
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REVISION OF THE STANDARD EN 378 AND THE REFRIGERANT AMMONIA
Bernhard Schrempf
TUV SUD Industrie Service GmbH,
Center of Competence for Refrigeration and Airconditioning, Ridlerstrasse 65,
80339 Munich, Germany
The revision of the Standard EN 378 now implanted fully the refrigerant Ammonia.
The refrigerant Ammonia is very often used in refrigerant plants in the industry
for many years.
In Germany are in operation approx. 5000 refrigeranting plants which use Ammonia
as refrigerant.
If you know, how to handle this refrigerant, it will not be dangerous.
Now in the new Standard EN 378 it will be described the safety efforts completely,
so you can be sure, that this refrigerant plant is safely.
The main part for Ammonia was a German national standard for many years .
So that there are existing experience for many years.
This experience is now integrated in the Standard EN 378.
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A COMPARATIVE EU NATIONAL LEGISLATION & PROBLEMS ENCOUNTERED BY
END USERS SUCH AS COLD STORE OPERATORS
Carole Prier
ECSLA,
Avenue de Broqueville 272, Bte 8, 1200 BRUSSELS, Belgium
ECSLA is the European Cold Storage and Logistics Association It is the voice
of the European Union (EU) cold storage industry.
ECSLA’s members represent a temperature controlled storage capacity close to
45 million cubic meters throughout the EU.
Public cold store facilities (hereafter referred to as cold store) are specifically
built to receive, freeze (if applicable), chill (if applicable), store, and
dispatch essentially food and feed products or any other goods owned by third
parties at the appropriate temperature.
An Ecsla survey in 2006 showed that, with the noticeable exception of France
and Holland, ammonia is most widely used refrigerant in the food industry. In
addition, this survey highlighted a lack of harmonization in EU. Some countries
are very strict (France and The Netherlands), thereby creating an unfair competition
for cold store and food operators across EU.
ECSLA members feel that the legislation concerning ammonia should be harmonized,
particularly on the 2 following elements:
- Safety distances between plants
- Containment for all new plants
The context of regulation towards other fluids such as HCFC and HFC make the
need to allowing easier use of ammonia even more urgent and necessary.
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HFCs OR THE OLD REFRIGERANTS?
Hermann Halozan, Rene Rieberer
Institute of Thermal Engineering, Graz University of Technology
Inffeldgasse 25 / B, A-8010 Graz, Austria
The alternatives for the HCFCs, which are still in use, and the HFCs are the
old refrigerants, substances like ammonia (R-717), the hydrocarbons (R-290,
R-1270, R-600a), water (R-718) and CO2 (R-744). The selection criteria for refrigerants
have to cover efficiency, safety, and environmental acceptability. Within these
criteria the environment expressed by the TEWI, i.e. refrigerant losses during
lifetime and CO2 emissions caused by the production of drive energy and the
drive energy, respectively, becomes a very important issue. In this context
efficiency gets the highest priority, and efficiency, as can be demonstrated,
is mainly the result of technology development and the correct integration of
units into systems.
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COMPARISON OF TOTAL ENERGY INTENSITY OF CONVENTIONAL CENTRAL AC SYSTEMS
WITH TRANSCRITICAL CO2 AC SYSTEMS
Klaas Visser
KAV Consulting Pty Ltd,
PO Box 1146, Kangaroo Flat VIC 3555 Australia
The revival of CO2/NH3 cascade technology has seen explosive growth with many
successful applications. It was mainly driven by Occupational and Public Health
and Safety (OPHS) issues
More recently, we have seen the development of transcritical CO2 applications
for Mobile Air Conditioning (MAC), supermarket refrigeration, domestic hot water
heat pumps, Coca-Cola drink coolers, etc. The European Commission’s Environment
Directorate has issued the EU F-gases Regulation and MAC directive. There are
therefore three significant forces at play.
One force is against the more widespread use of NH3. Another force is against
HFC’s. The third force favours maintaining the existing status quo.
In this paper, the advantages and disadvantages of transcritical CO2 systems
are compared with conventional industrial NH3 and HFC air conditioning systems
in terms of OPHS, water consumption for cooling, total system COP taking into
account all parasitic electrical and refrigeration loads like condenser and
cooling tower fans and pumps, air cooled gas coolers, tap-, heating- and AC
reheat water heating by the discharge gases of the transcritical CO2 compressors,
liquid refrigerant pumps, supply and return air fans, cooling water pumps, chilled
water circulating pumps, etc.
Suggestions are made on how to best take advantage of locally prevailing seasonal
climatic conditions to arrive at minimum energy and water consumption through
a year’s running.
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CASCADE TYPE REFRIGERATION SYSTEMS WORKING ON CO2/NH3 FOR TECHNOLOGICAL
PROCESSES OF PRODUCTS FREEZING AND STORAGE
G. Belozerov, N. Mednikova, V. Pytchenko, E. Serova
The All Russian Scientific Research Institute for Refrigerating Industry (VNIHI),
12, Kostyakova St., Moscow, 127422, Russia
To carry out technological processes in food processing industry the temperatures
of the cooling medium as low as minus 30 ? 350C are required, which correspond
to evaporation temperature of the refrigerant minus 40 ? minus 450C. To increase
the efficiency of processing, further reduction of evaporating temperature of
the refrigerant is often needed. Currently used pump-circulation systems with
ammonia supply to refrigerating devices are dangerous for service personnel
and people, who live nearby, because of a large amount of ammonia in the system.
For the solution of this problem a cascade refrigerating system CO2/NH3 has
been offered. We determine a range of evaporation temperatures, when the use
of a cascade scheme CO2/NH3 is more efficient than traditional ammonia pump
circulation systems due to less power consumption, for a set of real enterprises.
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NEXT GENERATION ADIABATIC CONDENSERS AND FLUID COOLERS
Ray Clarke
ISECO Consulting Services Pty Ltd,
723 Burwood Road, Hawthorn East, Victoria 3123 Australia
This paper presents the design approach adopted for the development and application
of a new range of adiabatic condensers and fluid coolers.
The design is based on making use of both the design wet and dry bulb weather
conditions for any given location. The concept employs the placing of evaporative
pre-cooler pads in front of a tube and fin heat exchanger. When operating in
pre-cooling mode, the dry bulb air temperature of the air passing through the
wetted pads is reduced prior to entering the condensing or fluid cooling heat
exchanger. A simple observation is that in this mode the operation is similar
to an air-cooled condenser or fluid cooler during low ambient dry bulb operating
conditions.
This paper will discuss the design, operation, construction and advantages of
this type of condenser or fluid cooler.
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EXPERIMENTAL INVESTIGATION OF NON-CONDENSABLE GASES INFLUENCE ON CONDENSERS
OPERATION OF HIGH-CAPACITY REFRIGERATING SYSTEM AT THE AMMONIA TERMINAL
A. Andrusenko
Odessa Port Plant, P.O. Box 304, Odessa, 65000, Ukraine;
G. Mnatsakanov
Odessa State Academy of Refrigeration, Dvorianskaya str. 1/3, Odessa, 65082,
Ukraine
Operating conditions of high-capacity refrigerating system for ammonia terminal
is highly influenced by non-condensable gases coming into the condensers. Experimental
study of air-cooled condensers operation in the presence of high concentration
of non-condensable gases is carried out. Characteristic of non-condensable gases
influence on the ammonia vapor condensation inside horizontal tubes are determined.
Further results of mathematical modeling for ammonia vapor condensation in the
presence of air inside horizontal tubes for various velocities of vapor-gas
mixtures are presented. Recommendations are given for the effect of non-condensable
gases concentrations on the length of horizontal tubes for air-cooled ammonia
condensers.
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SYSTEM AND COMPONENT SOLUTIONS, TO SIGNIFICANT REDUCTION OFF OIL-FOULING
IN AMMONIA REFRIGERATION PLANTS, part 1 and part 2
Titus Bartholomeus,
GEA, Grasso Products b.v.
Parallelweg 27, 5223Al, ’s-Hertogenbosch, The Netherlands
Apart from the occasional special application, oil is used to lubricate all
refrigeration compressors. An annoying side effect of this is that oil residues
enter the plant with the compressed gas, in vapour and liquid form. This oil
will contaminate the heat exchanger present, with a negative impact on performance
and operation. This article presents a few ideas on how simple installation
and/or adjustment of components can significantly reduce the oil concentration
and therefore increase the operation and performance of the refrigeration plant.
The theory of how the oil film builds up with ring flow is explained, based
on the boundary layer [2, 3], theory, and several practical equations are developed.
There is a concrete example for calculation the average oil film thickness in
a DX evaporator pipe.
A reduction of the contaminating influence of the lubricating oil in the refrigeration
plant is described for soluble oil, and in more details for insoluble oil such
as the cases at the ammonia plants. The reduction of oil concentration in the
ammonia plants is elaborated in several ideas: by choosing a compressor with
low oil consumption, using a high-efficiency oil separator, using a compressed
gas cooler for the oil separator, choosing proper oil type, arranging the liquid
tank where the oil can settle and be returned to the compressor, using intermediate
tank at 2-stage plants, by regularly draining off the oil, automatically or
otherwise.
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ADVANCES IN PLATE HEAT EXCHANGERS USED AS DX EVAPORATORS
A. Bhadsavle
GEA, FES Systems Inc., 3475 Board Road, York, PA 17406, USA
H. Kumar
APV, 1200 W. Ash Street, Goldsboro, NC 27530, USA
Many designers have attempted to use plate heat exchangers as direct expansion
evaporators. Direct expansion type of evaporator is desirable for a low cost
system design with the lowest amount of refrigerant charge. This is more important
when ammonia is used as a refrigerant. There are two major obstacles that limit
the use of these exchangers for large duty chillers. The distribution of two
phase refrigerant through the inlet port of plate heat exchanger and the availability
of proper expansion devise. Many heat exchanger manufacturers have tried different
types of distributor tubes. This author has not seen a successful installation
above 600 TR (2100KWR) using direct expansion plate and frame evaporators.
A research will be presented on existing literature on actual installations
or theoretical designs of such DX evaporators. The paper will concentrate the
work done with Ammonia evaporators.
A new idea which was patented recently for a specially designed Plate and Frame
heat exchanger will be presented. This design includes a special feeding tube
for each Welded Pair (Cassette). The idea is to reduce the pressure drop taken
at the expansion valve and there by reduce the amount of flash gas entering
the port. The design and performance of a 1000 TR (3500 KW) system recently
installed at a Chemical plant will be discussed. The Author believes that this
is the first Chiller of this size designed with Ammonia DX evaporator. Discussions
in the meeting will reveal if others have done such a large chiller using DX
evaporator.
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CHARGE MINIMIZATION IN A MULTI - STAGE AMMONIA REFRIGERATION SYSTEM
BY INTRODUCING CARBON DIOXIDE
M. Peran, K. Jelusic, B. Pavkovic
University of Rijeka - Faculty of Engineering,
Vukovarska 58, Rijeka, 51000, Croatia
Preliminary analyses aimed to ammonia charge minimization in an existing two
stage ammonia refrigeration system of a cold storage are presented in the paper.
The ammonia – carbon dioxide cascade system, ammonia two-stage system with carbon
dioxide or ammonia two-stage system with potassium acetate as secondary fluids
have been considered as possible solutions. At this preliminary stage of the
study, the heat transfer in existing evaporators has been analyzed for carbon
dioxide or potassium acetate as heat transfer fluids and compared with the heat
transfer of ammonia. Stresses in pipelines and evaporators which appear due
to increased pressure in the case of carbon dioxide application have been evaluated
for the analyzed fluids. Pressure drop in pipelines has been determined for
ammonia, carbon dioxide and potassium acetate. All the analyses have been performed
with the goal to avoid the replacement of existing evaporators and distribution
pipelines. The possible reduction of ammonia charge has been calculated as well.
Efficiency of different processes has been evaluated in order to determine consequences
of retrofitting on energy consumption.
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ANALYSIS OF CYCLE OF CASCADE REFRIGERATION MACHINE WITH USING MIXTURES
OF REFRIGERATION FLUIDS
Mykhaylo Khmelnyuk, Evgeniy Korba, Vitaliy Chepurnenko
Odessa State Academy of Refrigeration, 1/3 Dvoryanskaya Str., 65026 Odessa,
Ukraine;
Valery Vozny
Ukrainian Research Institute “VESTA”, 26 Degtyarivska Str., 01119 Kyiv - 119,
Ukraine
Investigation results of cycle analysis of cascade refrigerating machine using
as refrigerant ammonia mixtures with hydrogen and carbon dioxide mixtures with
hydrogen are given in the article. Calculation results make it possible to conclude
that the addition of hydrogen to ammonia and carbon dioxide increase the cascade
refrigerating machine energetic efficiency.
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USE OF AMMONIA/DIMETHYL ETHER (SCHICK R723®) BLEND IN MEDIUM REFRIGERATION
PLANTS
Dieter Krauss
Schick GmbH + Co. KG,
Wernerstr. 28, D-70469 Stuttgart, Germany
With schickR723® we offer a natural refrigerant mixture which provides you with
an easy way to eliminate the considerable drawbacks of ammonia.
The refrigerant schickR723® is made up of 60 mass% ammonia and 40 mass% dimethyl
ether, it is environmentally-friendly (zero ODP, insignificant GWP), and available
in adequate quantities in returnable steel tanks and containers.
schickR723® is used in small and medium refrigeration systems as a working fluid
in a similar way to R717. The pressure is almost identical but this blend has
a number of interesting advantages over pure ammonia.
With schickR723® the discharge temperature can be reduced by approximately 15
– 25 degrees.
The solubility for mineral oils is considerably improved and can be extended
to the area of very low temperatures.
Continuing our poster presentation of the previous conference /1/ we demonstrate
now the applicability of this refrigerant in real refrigeration plants and under
various ambient conditions.
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EXPERIMENTAL RESEARCH OF THE REFRIGERATING MACHINE WORKING ON MIXES
ON THE BASIS OF AMMONIA
Mikhaylo Khmelnyuk, Volodymyr Zhyvytsya, Vadim Shevchenko
Odessa State Academy of Refrigeration, 1/3, Dvoryanskaya Str., 65082 Odessa,
Ukraine;
Valery Vozny
Ukrainian Research Institute “VESTA”, 26, Degtyarivska Str., 01119 Kiev - 119,
Ukraine
One of the most perspective directions allowing promoting ammonia refrigeration
machines is search for new working agents (refrigerant mixtures) based on ammonia.
The improvement of working agent properties was offered in the way to mix pure
ammonia with hydrocarbons having low values of GWP and ODP. The preliminary
analysis has shown that some additives of hydrocar-bons to pure ammonia could
improve energy efficiency, reduce discharge temperature of compres-sor, provide
solubility (oil return) of working agents.
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CARBON-AMMONIA ADSORPTION CYCLE MOBILE AIR CONDITIONING SYSTEM
S.J. Metcalf, R.E.Critoph, and Z. Tamainot-Telto
School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
The European Commission (EC) has estimated that the use of automobile air-conditioning
in the EU increases the annual fuel consumption of cars by 4-8% (EC, 2003).
In addition, the HFC refrigerant R134a currently used in mobile air conditioning
applications has a high global warming potential. Replacement of these systems
could therefore result in significant reductions in global greenhouse gas emissions.
The University of Warwick is currently developing an adsorption air-conditioning
system as part of the EU TOPMACS project, which is driven by the waste heat
from the engine. This system therefore causes no direct increase in fuel consumption.
Additionally, the ammonia refrigerant to be used has no global warming potential.
This paper presents the design and computational modelling of the system.
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THE FEASIBILITY OF AMMONIA – WATER ABSORPTION REFRIGERATION FOR FISHING
VESSELS
J. Peranic, A. Bozunovic, B. Pavkovic
University of Rijeka - Faculty of Engineering,
Vukovarska 58, Rijeka, 51000, Croatia
Ammonia compression refrigeration system and ammonia – water absorption refrigeration
system powered by the heat recovered from engine exhaust gasses are designed
and compared on an example of sea water refrigeration for medium - sized fishing
boats. It has been shown in this paper that the single – stage absorption refrigeration
plant can achieve better results in energy efficiency and in terms of environmental
impact. Furthermore it has been demonstrated that even lower total costs of
absorption system compared to a compression system can be achieved for the analyzed
application. Drawbacks of absorption systems, such as high mass and volume do
not allow wide application but they can be overcome by further research in absorption
system optimization.
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AMMONIA-LIQUID DESICCANT BASED HYBRID AIR CONDITIONING SYSTEM
S.V.K.Reddy, G. I. Panchal, A. B. Salvi
Fr. C. Rodrigues Institute of Technology,
Sector 9A, Vashi, Navi Mumbai, Maharashtra, 400 703, India
The combination of vapor compression system and a liquid desiccant (LD) system
is the hybrid air conditioning system (HACS) which can be energy efficient and
environmental friendly. The HACS has received considerable attention due to
its inherent ability to use low grade thermal energy and reduce the latent cooling
load. These systems have the ability to provide the required humidity and temperature
for human comfort, while reducing the electrical energy requirement compared
to a vapor compression system (VCS) alone. This paper presents the simulation
results of a HACS, working with ammonia refrigerant and calcium chloride LD.
The capacity of the ammonia compressor selected is 42.5 kW with an evaporator
temperature of 15oC and condenser temperature of 50oC. As the evaporator temperature
is increased from 7.2oC of conventional air conditioner to 15oC, the COP of
HACS increases by 35 %. The process air is cooled and dehumidified in the absorber.
The heat rejected from the condenser is used to regenerate the LD in the regenerator.
The absorber and regenerator used incorporate a large heat and mass transfer
area and work without any carryover of LD. The simulation is carried out using
MATHCAD software.
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APPLICATION OF AMMONIA FOR HEAT-AND-COLD SUPPLY SYSTEMS IN PROCESSES
OF PURIFYING TECHNICAL GASES
Olga Diachenko, Tetiana Diachenko
Iceblick Ltd.,
29,Pastera Str., 65082 Odessa, Ukraine
The presented work is devoted to investigation of heat-and-cold supply (HCS)
systems in processes of purifying technical gases in temperature range of 150
to 350 K. The heat-and-cold supply system for an installation of purifying R216
was investigated by rectification method on the basis of vapour-compression
refrigerating machine (VCRM) and heat pump (HP). Coefficient of cycle efficiency
and exergetic COP are calculated under operation on refrigerants R717, R22,
R407b for VCRM as well as R114, R142b, R600a for HP.
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AMMONIA COLD STORES RENEWAL/REHABILITATION COUPLED WITH THE CLEAN DEVELOPMENT
MECHANISM
Risto Ciconkov, Ana Lazarevska
Faculty of Mechanical Engineering, Univ. “Sv. Kiril i Metodij”,
PO Box 464, 1000 Skopje, R. Macedonia;
Vasil Ciconkov
Energija doo, Londonska 1b, 1000 Skopje, R. Macedonia
One of the sectors contributing to the energy demand side is the refrigeration.
The nowadays refrigerating systems often utilize synthetic refrigerants significantly
contributing to climate change. In contrast, ammonia reemerges as an extremely
suitable refrigerant for medium and large refrigerating systems, due to its
excellent thermodynamic and physical properties.
In this paper we propose project activities which could be undertaken in the
frames of the flexible Kyoto Protocol Clean Development Mechanism project activity
defined as “Ammonia cold stores renewal towards higher energy efficiency”. In
line with this, we elaborate two origins - improved energy efficiency and replacement
of F-gas based cold rooms with an ammonia cold store - and give rough estimates
for possible green-house gases emission reduction resulting from the measures
encompassed in the proposed project activity.
The calculations point out that such project activity could fall under the classification
of a small scale CDM project in compliance with the Kyoto Protocol. Further
significance of such project is its agreement with the Montreal Protocol as
well.
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MAINTENANCE OF REFRIGERATING PLANTS: COSTS OR SAVINGS?
Gert J. Koster
Grasso International B.V.,
's-Hertogenbosch – The Netherlands
Very often in practice, maintenance on a refrigerating plant is restricted to
the mechanical components like compressors, pumps, etc. Of course this type
of maintenance should be executed according to the components manufacturer's
instructions. However, from a point of view of plant performance and energy
costs, system maintenance is just as important. This paper shows how costly
lack of system maintenance can be in terms of energy costs and preventing early
breakdown of a.o. compressors.
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