cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.18462/iir.nh3-co2.2019.0013
title: Personal protective equipment for safety when working with NH3 and CO2.

description: This presentation provides assistance to facilities who store and use anhydrous ammonia (NH3) and/or Carbon Dioxide (CO2) as a refrigerant. Knowing the PPE that is necessary to keep your employees working safely should be a primary concern. This paper will discuss the need to perform a safety assessment at your facility to determine the type of PPE required. It will then cover the different types of PPE available, why they are necessary, and their pros and cons, and any periodic maintenance requirements. The paper will conclude with a discussion related to respiratory protection, and the importance, and possible consequences of, making the proper selection.
DOI: 10.18462/iir.nh3-co2.2019.0017
title: Revamping and expansion of milk chilling centre.

description: In this paper we have elaborated about revamping of the old refrigeration system for a milk chilling center at Lingnoor 300 km from Mumbai. This is a classic example of how old inefficient milk chilling centers can be revamped and modernized in India. The main diary process 1,500,000 lit milk every day. This chilling center is one of the four chilling center where 70000 to 80000 LPD (litter / day) milk was processed since 1985. The major problems faced were, inadequate milk handling capacity, very high energy consumptions, high discharge pressure, high milk temperature ( 3 Deg C required , actual was 5 to 7 Deg C ), and safety related issues such as frequent ammonia leak. In last twenty years the population density around chilling center increased and safety became a very critical issue. In addition, energy cost also increased substantially. Entire plant was operated manually. The approach/ methodology selected were, to carry out technical evaluation and to conduct safety audit. Study and understand day to day operation as compare to present / future milk processing requirement. Asses and evaluate route cause of problem. Find out areas of improvement to make existing chilling center energy efficient, safe and has capacity to handle 200,000 LPD milk. The entire operation was executed on fast track of six months without affecting the operation and business. Key achievements were substantial reduction in energy consumption, improved safety, and plant operation is atomized, increased milk handling capacity to 200,000LPD, Last one year no breakdown as compare to every two to three months breakdown. The return on investment as planned was achieved in first year.
DOI: 10.18462/iir.nh3-co2.2019.0023
title: End user perspective on transitioning away from HFC towards natural refrigerants.

description: End user perspective on the use and application of natural refrigerants to reduce the global CO²-footprint (along the integral coldchain) of a global food retail company with 6500 stores. Transitioning away from HFC’s, fossile fuels towards natural refrigerants, renewable energy and energy efficiency to become a sustainable retailer.
DOI: 10.18462/iir.nh3-co2.2019.0045
title: Market & technology trends for CO2 and ammonia in commercial and industrial refrigeration.

description: The changing legislative landscape for fluorinated refrigerants is underpinning the market trends for natural refrigerants in various sectors globally. With an increasing uptake of HFC-free technologies there is a growing competition between different natural refrigerant-based systems. While ammonia has been widely used as the standard refrigerant in large industrial refrigeration for more than a century, new technologies using low-charge ammonia and CO2 challenge the status quo. With more than 16,000 CO2 transcritical stores in Europe and close to 20,000 globally, CO2 transcritical technology is gradually gaining ground in different parts of the world. At the same time, low-charge ammonia represents the leading disruption in the traditional industrial refrigeration market. This new technology is also leading to ammonia being considered for application where it has traditionally not been used, such as HVAC and food retail. The paper evaluates the key market, technology and policy trends for CO2 and ammonia, presenting data on the number of installed applications and comparing the evolution in Europe, North America and Asia / Pacific.
DOI: 10.18462/iir.nh3-co2.2019.0050
title: Analysis of a gas-fired absorption heat pump with different cycle configurations and superheated refrigerant at the absorber inlet.

description: State-of-the-art fuel driven heating systems are equipped with a condensing boiler technology. Commonly the flue gas is cooled by the return flow of the heat distribution system. If the temperature in the heating system is higher than the dew point, which happens in the retro-fit market, water vapour condensation of the flue gas cannot take place. Studies have shown that implementing a refrigerant cooled flue gas heat exchanger in a GAHP can avoid this issue under all operating conditions. However, superheated ammonia vapour entering the absorber potentially affects the absorption process. Measurements were carried out to determine the influence of different cycle configurations (internal heat exchangers, dephlegmator, …) on the efficiency under various operating conditions. An additional heat exchanger was installed between the evaporator and the absorber in order to investigate the influence of superheated ammonia vapour entering the absorber on the absorption and the overall heat pump process.
DOI: 10.18462/iir.nh3-co2.2019.0004
title: Parallel operation of ammonia screw compressors: the practical way.

description: In a previous article titled “Parallel operation of ammonia screw compressors – the optimum way”, presented during the 6th IIR Conference in Ohrid, 2015, the theory behind parallel operation of ammonia screw compressors and how it can maximize part load efficiency and offer high degree of redundancy was described. This paper will continue the work with focus on how to achieve optimum efficiency from a practical perspective. The importance of correct sizing of components and the use of an intelligent control system to utilize the theoretical advantage shown earlier will be discussed. The control system must find the optimum operating mode for a given application taking into account many variables namely, compressor size, capacity regulation (speed vs. slide vs. on/off), ability to react on changing loads, avoiding frequent cycling of compressors, balancing of running hours, power availability and price on the grid. In static operating conditions the optimum operation of each compressor may be relatively easy to find, but it is the ability to offer a high efficiency of the system, even under dynamic and transient load conditions, that challenge the control system.
DOI: 10.18462/iir.nh3-co2.2019.0008
title: Thermodynamic modelling of liquid overfeed and dry expansion feed central NH3 refrigeration plants to determine differences in energy performance.

description: This paper presents preliminary results of thermodynamic modelling to determine the differences in energy performance between liquid overfeed and dry expansion central two stage ammonia refrigeration plants. Models of both plant types are created and influences of part load, ambient temperature and evaporator return line are discussed.
DOI: 10.18462/iir.nh3-co2.2019.0012
title: Investigation of CFD models for ammonia ejector design.

description: In this work the flow structures inside a transonic- single phase ammonia ejector is investigated using CFD. The efficiency of ammonia (R717) vapor compression cycles can be improved by including an ejector component in the system. A good understanding of the flow phenomena inside the ejector is required for proper design of these components. In the present work a 2D axisymmetric CFD model using ANSYS Fluent software is used to investigate the flow characteristics of the ejector. The model uses a steady-state coupled pressure-based solver together with the k-omega SST turbulence model. A mesh refinement study has been done to investigate grid independency. Results indicate that the model can predict the correct trends of ejector operation, however, fails to accurately reproduce the experimental results. The results suggest that a more advanced multiphase models may be required to accurately model super-sonic ammonia ejectors.
DOI: 10.18462/iir.nh3-co2.2019.0046
title: Climate considerations for R/AC equipment operation: is the answer in energy efficiency ?

description: Since a long time, energy efficiency has been an important issue in R/AC equipment development; currently its relation to climate is considered most important. Energy efficient use of ammonia or hydrocarbons in equipment relates to a number of aspects already realised; this also applies to CO2, which is under further development. In the case of fluorocarbons, it is different since direct emissions (i.e., from high GWP HFCs) are typically to be considered in light of the Kigali Amendment. However, even with the “Kigali” HFC phase-down, addressing of energy efficiency related indirect GHG emissions often receives a lot of emphasis in that context. “Kigali” is strictly related to regulatory measures to phase down and to compliance; “Kigali” and efficiency are two different things. If one aims at a substantial reduction of all climate relevant emissions for all applications, efforts need to be undertaken from a broader perspective. Priorities are on energy efficiency, but even more on initiatives focused to achieve capacity reductions within comprehensive frameworks. Lowering demand via influencing outside parameters, guaranteeing adequate, high-efficient equipment operation, shall be considered priority number one, and can be defined as using energy efficiently. Even though the total capacity of large units is lower than the capacity in other sectors, food production, cold storage and chillers can contribute to savings via efficient energy use. While the efforts under the Montreal Protocol are important, a different or perhaps enhanced framework will be required to effectively address a more efficient use of energy in R/AC equipment, aiming at the highly emphasised ‘low carbon profile’ for the R/AC sector.
DOI: 10.18462/iir.nh3-co2.2019.0048
title: Heat pumps for energy efficient breweries.

description: The article analyses and describes the energy flows in a modern brewery, as planned to be realized in the southern part of Norway. Based on the heating and cooling demands a new concept is developed to enable an innovative and efficient surplus heat upgrade, applied to eliminate current fossil fuel burners. Initially focus is given to minimizing the necessary steam demand in the plant, since the energy efficiency can be increased by substituting this high-quality energy source by pressurised hot water, which can be directly produced by heat pumps. As a result of different system evaluations, the final recommendation is to install an energy storage tank and two heat pump systems with different supply temperature levels. Both heat pumps are utilising the residual heat generated in the tank farm (fermentation) and from the residual water. The first system should be an ammonia heat pump followed by a butane heat pump to produce steam, which also can be stored in a steam accumulator. The second unit should be a carbon dioxide heat pump applied to produce water at 100 ºC. The hot water is stored in a stratified tank with water at temperature levels above 85 ºC.
DOI: 10.18462/iir.nh3-co2.2019.0019
title: Extreme low charge units with ammonia blend R723 applications in practice.

description: Extreme low charge ammonia blend R723 chillers with direct expansion is the way how to use all advantages of natural refrigerant NH3 in ranges where ammonia is not or hard to use. Applications in food industry, commercial and public. Just 0.04 kg of refrigerant for one cooling kW.
DOI: 10.18462/iir.nh3-co2.2019.0020
title: Thermodynamic properties of ammonia-oil-mixtures that influence the efficiency of an evaporator.

description: Typically, hydrocarbon oils like mineral oil (MO), polyalphaolefine (PAO) and alkyl benzene (AB) are used for lubricating R717 compressors. It is known and confirmed by our previous experiments as well as the latest literature that ammonia dissolves in these oils not only at high temperatures but also at low temperatures. This partial solubility affects the viscosity and the pour point of the oil. There is a huge interest to understand the cold-flow properties of oil in the evaporator. This also includes the mass flow of liquid on the inner surface of the evaporator, that influences the heat transfer coefficient significantly. However, the heat transfer in evaporators is not influenced by the mass flow alone. There are three phases in the R717 evaporator, the liquid refrigerant with a low load of oil, the oil-rich phase and the gaseous ammonia phase. To develope refrigeration cycles with low energy demand, the knowledge of the interaction between the three phases and their influence on the efficiency of the plant becomes more important.
The presentation deals with measurements of low temperature solubility and thermal conductivity of different oils mixed with ammonia. The goal of our presentation is to show how difficult it is and what have to be done in future to predict which oil is the best and most effective regarding heat transfer in an ammonia evaporator.
DOI: 10.18462/iir.nh3-co2.2019.0026
title: Optimization of two-stages CO2 transcritical cycles for low temperature water-cooled cabinets application.

description: Nowadays the use of carbon dioxide (CO2) as a working fluid is widespread in commercial refrigeration, especially for remote packs and cabinets. Regarding plug-in and self-contained water cooled cabinets, innovative solutions are available, but further research and development are required. This paper deals with the optimization of self-contained transcritical cycles for low temperature applications, where the use of a two-stages cycle is mandatory to contain the CO2 compressor discharge temperature. A simulation model for the liquid injection cycle (LIC) and split cycle (SC) was developed, highlighting the variables that mostly influence the system, in terms of optimal operation. The theoretical results show that an optimal gas cooler pressure still exists in transcritical regime, but can significantly differs from the one given by single stage simple correlations (e.g. Liao et al., 2000). Moreover, variables such as intermediate pressure and/or intermediate superheat have a non-negligible impact on the efficiency, and must be taken into account during the design and optimization process. Finally, new correlations are presented, so that they can be easily implemented on case controllers.
DOI: 10.18462/iir.nh3-co2.2019.0029
title: Effect of the operating conditions on a transcritical CO2 refrigeration systems efficiency.

description: CO2 refrigeration systems, as used e.g. for supermarket applications, often encounter a drastical decrease of COP when operation moves into a transcritical mode. There are several options to enhance the system efficiency to reduce this penalty. All of them influence the optimum value for discharge and intermediate pressure. This paper discusses these influences for parallel compression and for an additional booster compressor. For comparison a system simulation was performed. The compressor model in the simulation is based on a data map of a currently available compressor. As a result the system’s efficiency improvement potential of both methods is presented under consideration of optimized operation conditions.
DOI: 10.18462/iir.nh3-co2.2019.0031
title: Trade-offs between design complexity and performance impacts for transcritical R744 ejectors.

description: It is well known that the transcritical CO2 cycle has higher intrinsic throttling losses than comparable subcritical cycles. Replacing the expansion valve with a two-phase ejector greatly improves cycle performance by reducing throttling losses. However, ejectors have yet to be successfully applied to low-capacity systems (approximately 1 to 5 kW), such as bottle coolers, window air conditioners, beverage dispensers, heat pump water heaters or similar. It is a real challenge to integrate ejectors into mass produced systems of small capacity in a cost-effective manner due to the relatively complex design of an ejector in comparison to simpler expansion devices. In addition to presenting system level results obtained with a transcritical CO2 bottle cooler with ejector, another aim of this paper is to systematically determine the possibilities for cost reduction by identifying performance trade-offs of less complex ejector designs. In a first step, a simplified diffuser design was investigated in combination with a conventional motive nozzle having converging-diverging design. Resulting system COPs and the impact on ejector efficiency are reported.
DOI: 10.18462/iir.nh3-co2.2019.0034
title: Eco-friendly, energy- and cost-efficient A/C system with heat pump functionality using R744 for rail applications.

description: Within the national R&D project ”eco2jet” an environmentally friendly A/C system with heat pump functionality is being investigated. The system will be evaluated on a test rig as well as in regular operation in a train of the national railway operator (Austrian Federal Railways – ÖBB). The use of the natural refrigerant R744 (CO2) means a future-oriented technology for railway applications because of its negligible GWP and favourable thermodynamic properties for heat pump applications. Compared to conventional A/C systems, the eco2jet A/C system increases the energy efficiency significantly. The primary objective is to meet the comfort criteria of the passengers in a wide operating range with low environmental impact by using novel heat exchangers, an advanced system architecture and intelligent control strategy in the future. Furthermore, predictive maintenance strategies shall help to reduce the operating and maintenance costs. The manuscript describes the system design, first test rig measurements and simulation results of the eco2jet A/C system with heat pump functionality.
DOI: 10.18462/iir.nh3-co2.2019.0038
title: CO2-based water chiller for wineries: a case study.

description: This paper presents field results of a CO2 transcritical water chiller installed in a winery in North Italy. The unit is designed to cool down glycol, which keeps must temperature under control during fermentation; different water temperature level might be required according to specific step in the wine production process. Waste heat can also be recovered at high temperature, for cleaning purposes. A transcritical low pressure receiver design, with flooded, natural circulation evaporator is implemented. Data from the field are collected and analyzed to assess energy performance and useful effects under different boundary conditions and load requirements. Field data analysis, which are still ongoing, will allow for proper fine-tuning of the controller setup.
DOI: 10.18462/iir.nh3-co2.2019.0041
title: A CFD analysis for the performance assessment of a novel design of plates-in-tank latent storage unit for freezing applications.

description: In this paper, the charging and discharging processes of a recently developed cold thermal energy storage (CTES) unit integrated into a poultry processing plant is investigated. A mathematical model of the CTES was created based on the two-dimensional transient Navier-Stokes equations using the ANSYS Fluent commercial software package. Thermal storage is commonly designed either for full storage (to meet the entire needs during peak hours) or for partial storage (to meet a fraction of the needs when there is a time shift between the energy supply and demand). In this study, the storage unit is designed to operate in a full storage operational mode integrated in the R744 circuit of a R717/R744 cascade refrigeration system. The CTES unit consists of a stack of heat exchanger (HEX) plates immersed in a steel tank filled with a phase change material (PCM). The selection of the appropriate PCM is based on the operational temperature range required in the system. Water is chosen as the PCM for this study. It is characterised by a high energy storage density and well-defined thermal properties. The HEX plates are called pillow plates (PP-HEX), and consists of two spot-welded and inflated steel plates that allows the CO2 to circulate in a specific pattern and enhance the heat transfer. The CO2 circulates within the plates to freeze and melt the PCM during the charging and discharging processes, respectively. The pressure-based model was selected to model the phase change based on the enthalpy-porosity formulation. This study aims to evaluate the relevance of detailed modelling of the PP-HEX structure compared to flat walls for the melting/solidification process. Results show that the flat wall model have comparable melting/solidification time and heat transfer rate to the PP-HEX geometry.
DOI: 10.18462/iir.nh3-co2.2019.0003
title: Low charge ammonia packaged refrigeration systems: achieving ultra-reliable operation.

description: The refrigeration industry has been migrating to natural refrigerants at an accelerated pace due to the fast approaching deadlines set by the Montreal Protocol and subsequent Kigali agreement. Ammonia, one such natural refrigerant, has been widely used for decades but is also being burdened with increased regulation since traditional refrigeration systems utilizing central machine rooms require such large ammonia quantities. However, the benefits of ammonia cannot be dismissed. Within the last five years, a stronger focus has been on the development of industrial low charge ammonia packaged refrigeration systems for industrial refrigeration similar to how halocarbon based packaged refrigeration systems have evolved in the commercial industry. What has been critically dismissed in pursuing systems with ‘ultra-low charge’, in some cases, is reliability and efficiency. Achieving ultra-reliable, efficient operation with low ammonia charge is the key to success for low charge ammonia packaged refrigeration systems.
DOI: 10.18462/iir.nh3-co2.2019.0018
title: Modelling of a novel oil-free linear compressor for small ammonia refrigerator.

description: The global trend towards using natural refrigerants is intensifying recently. Ammonia (NH3, R717) has vaporization properties similar to Freons (CFCs) with an ODP rating of 0 and a GWP rating of 0. However, the toxicity and corrosivity restrict its domestic and small-scale use. The oil lubricant can also be a problem. A novel moving magnet linear compressor has been prototyped for oil-free refrigeration systems. By keeping the windings outside the pressure containment, it is possible to avoid the contact between copper or copper alloys and R717 as working fluid. This paper presented a mathematical model of the prototype oil-free linear compressor working with R717. The cooling capacity using R717 is 1.8 times higher than R134a. Pressure-volume diagrams show a higher mean cylinder pressure leading to higher piston offset/drift. The R717 model will be further validated by a future prototype linear compressor that can operate properly with R717.