Ammonia Refrigeration Technology

for Today and Tomorrow

International Conference
- Ohrid 2007 -

 

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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