cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.18462/iir.nh3-co2.2019.0033
title: Simulation and validation of a CO2-based pumped loop cooling system.

description: In high physics applications, silicon trackers form the innermost layer of particle detectors. These trackers require a complex active cooling system: tight space constraints, stringent requirements of low mass, a radioactive environment and the need for very stable evaporation temperatures complicate the cooling system design. Cooling systems based on Two-Phase Accumulator Controlled Loops have proven to be excellent in dealing with these challenges. In such systems, the liquid refrigerant is mechanically pumped and cooling is achieved through flow boiling inside the evaporator. A two-phase accumulator is used to control the evaporation temperature. In this study, a component library has been developed in EcosimPro to model such cooling systems. This library is used to simulate the complex startup and temperature step change dynamics of a test plant at CERN. The simulation results are compared against measured data. The results show that the library is able to predict well the transients considered.
DOI: 10.18462/iir.nh3-co2.2019.0035
title: Numerical investigation on the thermal performance of a new cooling unit for refrigerated transport using CO2 as the working fluid.

description: Refrigerated trucks are an essential link in the cold chain, since they are in charge of guaranteeing the delivery to the market of perishable freights in safe and high-quality conditions. The choice of the refrigerant in transport refrigeration is undergoing a though revision, as an indirect consequence of the phase down of synthetic refrigerants imposed by the F-gas regulation. In order to explore natural refrigerant options, a refrigerated unit with CO2 as working fluid was designed, with the possibility of using a new configuration with a two-phase ejector in place of an expansion valve. This paper presents a modelling approach to predict the system performance identified by the expected COP curves at different ambient conditions.
DOI: 10.18462/iir.nh3-co2.2019.0039
title: Experimental evaluation of ice storage inside a helical coil heat exchanger integrated into a R744 refrigeration system.

description: In this paper, an experimental evaluation of the ice storage inside a concentric helically coiled tube heat exchanger is presented. The main findings will be useful to suggest an efficient integration of the cold storage (CTES) unit into a R744 refrigeration system for food storage in supermarket cabinets. The free space at the top of the cabinets will be valuable to house the CTES and make good use of the thermosiphon working principle to operate the cold discharging process. The cold charging process is carried out through a CO2 trans-critical refrigeration system. For cold discharging, the CTES is connected to a glycol loop through a double-pipe helically coiled tube heat exchanger (HEX) to simulate the supermarket cabinets. The HEX consists of a three concentric helically coiled tubes of different diameters in order to maximize the heat transfer surface. The coils have the same length in order to ensure the same pressure drop at the HEX outlet and fulfill the thermosiphon circulation conditions. The tests are carried out under different heat transfer fluid (R744) flowrates and temperatures. The cold storage characteristics are investigated.
DOI: 10.18462/iir.nh3-co2.2019.0005
title: Ammonia refrigeration : what can we expect in the future ?

description: Ammonia is the long-time refrigerant of choice in industrial refrigeration systems; but that may come to an end if the industry does not innovate. A number of things call for a change – for instance, in no specific order: safety, simplicity and efficiency just to mention a few. Ammonia is a very efficient refrigerant, probably the most efficient we have at our disposal. However, if the general perception is that ammonia is a dangerous technology, and we do not do anything to change this – even more than we have done over the past years - we may well see the end of this great refrigerant. As for the entire refrigeration industry, the number of qualified craftsmen is decreasing. At the moment, a good qualified technician can get a new job within hours if he wants to, and the salaries increase due to the situation. We have been witnessing how companies “steel” workforce from competitors just by spreading the word of good compensation packages and conditions. One way to overcome the challenges with the lack of craftsmen is to simplify the systems, so the customer or owner only need one switch to turn on and off the system. The rest is taken care of automatically. Also, the service intervals need to be significantly increased without compromising the safety and reliability of the system.
DOI: 10.18462/iir.nh3-co2.2019.0010
title: New sensor technology optimizes evaporator performance especially during part load on both DX, flooded and pump circulation systems.

description: The increased requirements to reduce global warming (GWP) lead to a desire for the use of natural refrigerants. The use of natural refrigerants is associated with major challenges, like safety (R717 & R290) and poor system efficiency (R744). New measurement methods make it possible to increase safety and achieve higher energy efficiency with both zero super-heat and demand driven defrost control. The use of Superheat control has for decades been necessary for safe operation of refrigeration systems. Superheat is however an area where a lot of energy is wasted without adding any value. A new revolutionary patented technology solves one of the main challenges when using CO2 and other refrigerants. CO2/NH3 refrigerant is very dynamic and reacts strongly on small changes in load and pressure-/temperature. With the new Vapor Quality Sensor solution measuring the dryness of the vapor and the phase of refrigerant flow (two-phase flow regime) it is possible to achieve a more balanced system performance with minimum Superheat and less pressure fluctuation (Semi-Flooded operation). By this solution it is possible to control the evaporator capacity faster and more accurate within a Superheat range of 0.5 to 1.0K. The sensor measures the Vapor Quality as the ratio of the vapor and liquid in a two-phase flow. The same measuring principle (capacitive) is also used for measuring ice build-up on air coolers at operating temperature below 0°C in form of a wire mounted between some of the evaporator fins and thus defrost cycles only starts when needed (On Demand) The sensor reacts as an "X" sensor that directly measures the dryness where “X”0.0 = 100% liquid and “X”1.0 = dry vapor gas. This paper and the following presentation will describe the sensor's measuring principle, system design and the location of the sensor, as well as experiences from tests performed on both NH3 and CO2 system. A brief presentation of tests performed on CO2 systems will also be included.
DOI: 10.18462/iir.nh3-co2.2019.0015
title: Using low charge ammonia heat pump as main cooling/heating energy source for ice hockey stadiums.

description: Modern ice hockey stadium year-round operation. Ice playground 56m x 26m and the background of the building. All demands on cooling and heating are done by ammonia heat pump with just 120 kg refrigerant charge.
DOI: 10.18462/iir.nh3-co2.2019.0028
title: Transcritical CO2 refrigerating systems applied to the cooling and heating of buildings reduce energy and cooling water.

description: The Kigali Amendment to the Montreal Protocol to phase down HFC production and consumption by 85% by 2036 in the G20 countries opens the door to the accelerated revival of the Natural Refrigerants (NR) CO2, NH3 and HCs for the efficient cooling and heating of the built environment. Using reported Specific Energy Consumption (SEC) data in kWh/m2/annum for cooling and heating in the EU built environment, projections are made on how the SEC may be reduced by retrofitting CO2 refrigerating systems to provide cooling and heating on demand separately or simultaneously, including the production of Domestic Hot Water (DHW). It is also observed that CO2 systems are suitable for cooling and heating new buildings with chilled and hot water for efficient hydronic building cooling and heating systems. Hybrid Evaporative Condensers (HECs) are used to save water compared to conventional evaporative condensers and cooling towers. It is furthermore pointed out that Multi-Function Two Stage Transcritical CO2 Systems with Parallel Compression are ideally suited to perform many simultaneous heating and cooling functions in food processing plants.
DOI: 10.18462/iir.nh3-co2.2019.0040
title: Entropic and statistical analysis of CO2 refrigeration plants for retail application.

description: The entropic and statistical method of the analysis (ESMA) allows calculating losses in different refrigeration plant components and comparing them to define the elements that need measures to increase their operation efficiency. The paper presents CO2 refrigeration cycles analysis for application in retail. The ESMA was applied to investigate four CO2 refrigerating systems and define elements for further optimization. The description of calculation method was given. The comparison with refrigeration systems using R404A as refrigerant was made. The degree of thermodynamic efficiency was calculated. This result couldn’t be achieved using a traditional method of comparison refrigeration systems by using a coefficient of performance (COP) or seasonal efficiency as an only efficiency criterion.
DOI: 10.18462/iir.nh3-co2.2019.0042
title: CO2 or R290 for Supermarket Applications – Pros and Cons.

description: Emerson Climate Technologies GmbH has commissioned to Institute für Luft- und Kältetechnik (ILK) an energy comparison and a life cycle cost analysis (LCC analysis) for two different supermarket refrigeration systems at the Munich, Barcelona and Gothenburg sites. The first concept is a traditional refrigeration system consisting of a compressor pack refrigeration system with the refrigerant R744 (CO2) and remote display cabinets. The 2nd concept consists of refrigeration cabinets with an integrated refrigeration system (plug-in refrigeration system) with the refrigerant R290 (propane) in which the dissipation of heat from the refrigeration process takes place via an external brine circuit. For the energetic considerations the normal cooling range was considered, since the deep-freezing, cold storage rooms and the air conditioning/heating is assumed to be identical for both supermarket concepts. The calculation results for the electrical energy demand showed that the energy demand is strongly dependent on the chosen location and the associated temperature profiles during summer.
DOI: 10.18462/iir.nh3-co2.2019.0044
title: Development of a high efficient NH3/CO2 refrigeration system.

description: Environmental problems such as ozone layer depletion and global warming are widely known as global issues. The Montreal Protocol totally prohibits use of HCFC from 2020 and Kigali revision of the protocol calls for gradual reduction of use of HFC by 85% towards 2036. In the industrial refrigeration, HCFC-22 refrigerant has been used for many years and HFC refrigerants are widely used as alternatives, however, conversion to refrigerants with less environmental impact is urgently required. Mayekawa developed and introduced a highly efficient refrigeration system called ‘NewTon’, applying the natural refrigerants ammonia (NH3) and carbon dioxide (CO2) as the primary and secondary refrigerants. The refrigeration system demonstrates a high energy saving compared to systems with traditional working fluids and in addition its direct environmental impact can be neglected since only natural working fluids are applied. These kind of units are widely used in freezing- and cold storage applications. In this work, the specific features of the ‘NewTon’ unit are described and energy consumptions are compared with historical demands of the systems, which have been replaced.
DOI: 10.18462/iir.nh3-co2.2019.0049
title: Compressors for ammonia-water hybrid absorption-compression heat pumps.

description: In this paper, investigations on the development of industrial high temperature heat pumps are carried out based on the analysis of the current available compressors. The compressor used for the ammonia compression is a major component of ammonia-water hybrid absorption-compression heat pump. Furthermore, the compressor is the dominant constraint on achievable process conditions due to the limitation of high pressure and discharge temperature. Ammonia-water hybrid heat pumps combine technologies of an absorption and compression heat pump with a mixture of ammonia and water as working fluid. The heat is extracted and emitted at non-constant temperature glides and the necessary ratio of compression is lower compared to conventional compression heat pumps. These properties make the hybrid heat pump interesting for use in industrial high temperature applications. In this study, currently available compressors are being investigate for a utilization of them in a hybrid heat pump test facility able to operate at high side pressures to achieve exit temperatures on the secondary side of 140 °C to 180 °C. For this purpose, available compressors are identified and evaluated based on performance indicators such as the maximum pressure and discharge temperature.
DOI: 10.18462/iir.nh3-co2.2019.0002
title: Packaged ammonia refrigeration units continuously improve. How to measure and present performance ?

description: This paper talks about recent developments in penthouse, packaged low charged units with ammonia as refrigerant. A special attention is given to clarification of the definition of various ways to present efficiency providing insights to opportunities for improvements of COP in design stage as well in operation. The schematics drawing of the facility for performance evaluation of the penthouse unit presents various balances when defining capacity and efficiency. Definition of the performance (Q and COP) and its measurements is very important at this point when new technology, packaged low charged units with ammonia is trying to fully establish position among units with synthetic refrigerants and industrial refrigeration systems with ammonia.
DOI: 10.18462/iir.nh3-co2.2019.0006
title: Charge reduction in pump circulating ammonia systems.

description: Pump circulating systems are the dominant system type for large ammonia industrial installations. These systems are well-known over decades as very effective, flexible, easy to install, operate and easy to defrost, however these systems typical requires large ammonia charges. In classical pump circulating systems, the circulating rate is not controlled, but set to a given rate, sufficient for all operating conditions and load variations. This paper is focussing on resent laboratory test on a measuring principle for determining the circulating rate and controlling the liquid feed in over-feed ammonia systems, where the first results from these tests was presented in 2017 [1] [2]. Further laboratory test has been conducted on pump-circulating systems with controlled circulating rate, as well as field-test from a 20+ years old pump-circulating system.
DOI: 10.18462/iir.nh3-co2.2019.0009
title: Adiabatic condensers and fluid coolers: Impact of pad system design on saturation efficiency and unit operation.

description: Refrigerant condensers and closed circuit coolers which utilize air-cooled heat exchange are growing in popularity for various reasons, but mainly to conserve water. However, in climates with high ambient temperatures, air-cooled heat exchangers require too much capital cost, consume too much energy and/or require too much plan area. In many cases, incorporating adiabatic pads on an air-cooled heat exchanger (a.k.a., an adiabatic fluid cooler or refrigerant condenser) is the best solution to balance costs, energy consumption and the size or number of units required. The adiabatic pad test program included testing ten pad designs from four adiabatic pad suppliers. The independent research contained in this report is offered for the benefit of industry, and to de-mystify some of the variables surrounding adiabatic cooling technology which have been misrepresented in the marketplace. The adiabatic air pre-cooling system uses water to depress the ambient air dry-bulb to a lower value, reducing the necessary size of the heat exchanger compared to a 100% air-cooled equivalent. Main conclusions: Saturation efficiency changes with air velocity. The maximum saturation efficiency achieved for the various adiabatic pads in this test program was: 78% at 2.0 m/s, 76% at 2.5m/s, 74% at 3 m/s and 72% at 3.5m/s. Saturation efficiency and air side pressure drop are equally important in rating the thermal performance of an adiabatic unit. Furthermore it was proven that water flow rate and water temperature have very little impact on adiabatic pad saturation efficiency when measured on a full-size adiabatic fluid cooler or condenser.
DOI: 10.18462/iir.nh3-co2.2019.0014
title: Performance optimization of a large-scale ammonia heat pump in off-design conditions.

description: A thermodynamic model of a 5 MW test and demonstration heat pump, implemented in the district heating network of Copenhagen, is presented. A genetic algorithm was applied to the model for 27 different operating conditions, optimizing the system Coefficient of Performance (COP) by adjusting the available set points (SP) in the heat pump system. Analyzing the optimization result, new SP values depending on the operating conditions were proposed. The potential improvement in COP was between 0.4 % and 2.9 %. A performance map for all operating conditions was presented and discussed. In general the COP increased with decreasing forward temperatures, increasing source temperatures and further an optimum at 80 % heating load was observed within the investigated span of operating conditions.
DOI: 10.18462/iir.nh3-co2.2019.0016
title: Experimental stands for testing separation efficiency of unconventional separators for ammonia cooling units.

description: Separators are commonly used in ammonia cooling installations. Their objective is to separate the liquid from the vapour before entering the compressor. This paper presents two experimental stands for testing efficiency of separation process. In particular, the stands are intended to investigate an unconventional separator for ammonia cooling units. The experimental test stands and the
measurement and control system are described. First experiments, in the laboratory scale, were performed with water droplets suspended in the air in order to simplify the process and establish the assumptions for construction of the separator. The research aimed at understanding the separation processes in the unconventional separator. The methodology of obtaining the required range of droplets diameters, in chosen locations, is presented. The second installation was made by modification of the ammonia chiller working in an industrial system. The ammonia cycle was equipped with additional measurement system. The aim of those changes was to prepare experimental procedure to evaluate the efficiency of prototype separator in typical working conditions. In the article, there are presented first results of experiments performed to verify a test procedure of checking separator efficiency. The tests were carried out for reference separator design. The obtained test results allowed to determine the efficiency of separation process.
DOI: 10.18462/iir.nh3-co2.2019.0027
title: Energy analysis of integrated CO2 commercial refrigeration systems under different climate conditions.

description: The strong demand for phasing out refrigerants with high GWP has pushed the research towards the study of sustainable alternatives like natural refrigerants. In the recent years, carbon dioxide has increased its market share in the field of commercial refrigeration and has proven to be a viable solution for the replacement of HFC systems. One of the most common approaches to make CO2 refrigerating systems economically and environmentally sustainable for all types of climate is to fulfil all the thermal demands with one single unit. The purpose of this paper is to study different solutions that can improve the performance of an integrated CO2 booster system for supermarket application. The refrigeration systems studied here integrate heat exchangers for the air conditioning and two stages heat recovery, for sanitary hot water production and space heating. In addition, parallel compression and flooded evaporators are considered in order to reduce the energy consumption of the compressors. Steady-state models of the refrigeration cycles are developed to simulate the hourly performance of the investigated solutions across a year. The boundary conditions are based on field-measurements of an existing system. Measured values of the compressor efficiency are adopted for this analysis. The yearly performance of the proposed solutions are compared in terms of energy consumption and working conditions in moderate and warm climates.
DOI: 10.18462/iir.nh3-co2.2019.0037
title: Improving performance of transcritical CO2 systems, using phase change materials (PCM) in a cold storage application.

description: Thermal energy storage is one of the most promising solutions for energy savings and increasing efficiency. To improve the performance of cold storage applications, incorporating phase change materials (PCM) to these systems, is a new approach. In this study, the performance of a transcritical CO2 refrigeration with a PCM incorporated supermarket refrigerator was investigated experimentally. The supermarket refrigerator was operated at evaporation temperature of -10 °C and cooling capacity of 4.2 kW. The PCM was chosen to have a melting and freezing point temperature of -4 °C. Differential Scanning Calorimeter (DSC) device was used to determine properties of salt solutions such as melting/freezing temperatures and latent heat of fusion and freezing. In order to determine the system performance, compressor on-off time and its duration were measured for the cases with and without PCMs. It is revealed that by addition of PCMs, the compressors runtime was decreased meaningfully.
DOI: 10.18462/iir.nh3-co2.2019.0047
title: Using good rack design and electrical step-up autotransformers to improve the stable operation and energy saving of multiple-compressor racks.

description: Within the F-Gas Regulation (EU) No. 517/2014 and the related phase down of the HFOs, CO2 and NH3 are becoming increasingly important as refrigerants again. Refrigeration systems with these refrigerants are often controlled by intelligent frequency inverters. These frequency inverters can adapt the compressor capacity to the required refrigerating capacity at any time with a good design of the compressor rack. This is referred to as optimum control of the refrigeration system (good Control Factor) which also extends the lifetime of refrigeration compressors in a rack. However, when operating CO2 compressor systems, a problem can arise that at some refrigeration operating points, the maximum permissible current of the frequency-controlled compressor is reached at a frequency lower than the maximum permissible mechanical frequency. The result is that the compressors of the refrigeration system start more frequently, which reduces the controllability of the system (poorer Control Factor) and detracts from the overall energy balance of the refrigeration system. This paper shows how this problem can be mitigated with a small modification of the electrical circuit. With the help of step-up autotransformers (3 AC 400 V → 3 AC 480 V), the maximum permissible mechanical frequency of the frequency-controlled, star-connected compressor can often be reached cost-effectively.