cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.18462/iir.gl.2018.1379
title: New CO2 gas cooler for dry and wet operation.

description: The use of CO2 as working fluid is now a well-established reality in the refrigeration industry, Air cooled CO2 gas coolers have to ensure high performance both in sub-critical as well as in transcritical operation. The gas cooler outlet temperature is a key parameter for a high-efficiency CO2 cycle. However, when the ambient temperature is high the traditional dry products start to give an outlet temperature which is too warm for efficient operation. To limit these drawbacks, LU-VE has developed an innovative solution named EMERITUS. This technology has an air-cooled exchanger on which two additional water cooling systems are used in sequence: treated water is sprayed onto the heat exchanger coil and the remaining non-evaporated water is collected and used on an adiabatic panel. This combination of the two techniques has positive effects on both the thermal capacity exchanged and the quantity of water consumed. The article describes the functional principle of the new product and its important beneficial effect on the performance of the CO2 plant, illustrating a case study in which the running costs of a plant equipped with the new product are compared with the running costs of a traditional solution.
DOI: 10.18462/iir.gl.2018.1392
title: Experimental and numerical investigation on an ejector for CO2 vapor compression systems.

description: The use of two-phase flashing ejectors to improve the COP and capacity of CO2 vapor compression systems has become a key research topic in recent years. Although many experimental investigations focused on both the ejector performance and overall energy efficiency have been carried out, further efforts devoted to significantly enhance this device are necessary. In the present paper, the authors experimentally investigated the performance of a two-phase ejector as its main parameters, such as pressure lift and entrainment ratio, are varied. The results are finally compared with a CFD model based on a commercial solver.
DOI: 10.18462/iir.gl.2018.1104
title: Minimum airflow rates to dilute R290 concentrations arising from leaks in room air conditioners.

description: Currently R290 is used to a limited extent in room air conditioners, such as split, portable and window types. The product standard IEC 60335-2-40 currently specifies requirements to limit the charge of flammable refrigerants in such a way that it obstructs the wider use of R290. This is particularly challenging in warm countries where the heat load is greater and thus charge sizes need to be larger for a given room size, inferring higher concentrations in the event of a leak. Relying on the airflow of an indoor unit can be used to dilute a refrigerant leak and thus prevent flammable concentrations forming, despite the charge quantity being substantially greater than that currently permitted in the current standard. Research has been carried out to determine the minimum airflow rate from an air conditioner necessary to achieve sufficient dilution. A numerical model based on entrainment theory was developed and supported by experimentally analysing the behaviour of releases under various conditions with RACS airflow.
DOI: 10.18462/iir.gl.2018.1109
title: Effects of a thermodynamic non-equilibrium two-phase flow of R-600a at subcooled temperature condition on the performance of a vapor compression refrigeration system.

description: Some previous research demonstrated the existence of a thermodynamic non-equilibrium two-phase flow of the refrigerant between the condenser outlet and the expansion device inlet even at thermodynamic subcooled temperature condition where the refrigerant temperature is below the corresponding saturation temperature. In the present study, experiments are carried out to investigate the effects of the thermodynamic non-equilibrium two-phase flow of R-600a at the subcooled condition on the performance of a vapor compression refrigeration system. The enthalpy of the non-equilibrium state refrigerant is calculated using three different methods. Based on the enthalpy values at the outlet of the condenser, the condenser heat rejection rate and the coefficient of performance (COP) of the refrigeration system are evaluated.
DOI: 10.18462/iir.gl.2018.1191
title: Natural refrigerant in public transport HVAC application.

description: In recent years, the HVAC&R (heating ventilation air-conditioning and refrigeration) industry has been actively investigating usage of natural refrigerants for many applications. Carbon dioxide (R744) is a potential candidate due to the low GWP, low toxicity and non-flammability. The R744 refrigerant use in public transport HVAC application (bus and rail) opens new challenges and opportunities if used in heat pump applications. Efficiency losses in air-conditioning operating mode at high ambient air temperatures could be offset by higher efficiency in heat pump operation. As a result, the overall HVAC systems energy consumption could reach similar or be even better to currently used hydrofluorocarbon (HFC) systems in the specific geographical areas where heating demands are a significant portion of energy use for the year. This paper will reveal a manufacturers experience in exploration of possible R744 heat pump solution for public transport HVAC applications (bus and rail). An overview of system design challenges, test findings, and outcomes from ongoing investigations will be presented in the paper.
DOI: 10.18462/iir.gl.2018.1217
title: Ejector characterization for refrigeration applications with natural refrigerants.

description: Employing natural fluids in refrigerating plants at warm climate conditions sometimes impacts negatively on the system performance. Ejectors can play a key role in configurations aiming at improving the efficiency of such systems, however their geometry has to be optimized in order to gain the best benefit. Scope of this work is a numerical investigation on the geometry of the ejector in a cascade plant configuration with natural refrigerants, aiming at identifying the influence of various geometry aspects on the performance of the system. A one-dimensional model is employed for the ejector, while the performance of the refrigerating plant is evaluated in different operating conditions in order to seek the optimal configuration.
DOI: 10.18462/iir.gl.2018.1226
title: Ammonia and propane as natural refrigerants for heat pump applications.

description: Paper published in poster form during the conference. Interest in the use of natural refrigerants in to minimize the environmental impact of air conditioning and refrigeration equipment is gaining strength. This article focuses on the performance of two candidate natural refrigerants: ammonia and propane for heat pump applications. Cycle configurations include: (1) basic vapor compression, (2) two configurations with different liquid-line/suction-line heat exchanger arrangements, and (3) a two-stage flash economizer cycle for evaluation of ammonia and propane in comparison to R-134a and R410A. The objective is to evaluate the relative performances of current and natural refrigerants and gauge which class is better suited to address the global energy and environmental challenges.
DOI: 10.18462/iir.gl.2018.1351
title: An effective corrosion inhibitor for H2O/LiBr - absorption refrigeration machines.

description: Industrial facilities and power plants produce a lot of waste heat. Absorption refrigeration machines can use this heat effectively for cooling. Currently, absorption machines use the working medium combinations water/lithium bromide or ammonia/water. Under the influence of water and salt, for instance lithium bromide, the components of the machines corrode very strongly. Chemicals such as chromates and molybdates can reduce this corrosion processes. The European law forbids the use of chromates since September 2017. However, molybdates only protect iron components of the machines but not copper and other non-ferrous metal parts. Therefore, ILK Dresden started a project in 2015 to establish new inhibitors and strategies to protect the metals of absorption machines working with lithium bromide solutions. New inhibitor combinations were tested successfully. The present paper summarizes the results from one promising inhibitor system which is based on a combination of ternary antimony molybdenum oxides. Applied test methods are presented as well.
DOI: 10.18462/iir.gl.2018.1372
title: Energy analysis of CO2 refrigeration systems using measured values of compressor efficiency.

description: The strong demand for phasing out high GWP refrigerants has pushed research towards the study of other sustainable alternatives like natural refrigerants and in particular carbon dioxide. Because of CO2 low critical point, when the ambient temperature is high the cycle has to work in a transcritical configuration. This leads to a different operation mode, potentially with higher losses and consequently lower performances. The purpose of this paper is to study two different solutions and their performance during the transcritical operation and see which one can perform better from the yearly analysis point of view. Transcritical booster system and transcritical booster with parallel compression system will be analysed, with and without heat recovery for sanitary hot water production and space heating. Temperature data in Milano (Italy) and Valéncia (Spain) are considered for the external conditions; measured values of compressor efficiency are used for the analysis.
DOI: 10.18462/iir.gl.2018.1384
title: Alternative suction groups configuration to improve efficiency of advanced CO2 commercial refrigeration systems.

description: CO2 is one of the most promising natural refrigerants in commercial refrigeration systems. A basic two-stage CO2 transcritical booster system can operate with better or comparable efficiency in cold and mild climates, compared to a traditional HFC DX system. Advanced CO2 transcritical systems, such as adding intermediate suction group (parallel compression) and parallel compression with ejectors, have been developed and installed in commercial refrigeration systems for hot climates. This paper will discuss the opportunities to additionally improve the efficiency of advanced CO2 transcritical systems by alternative configuration of suction groups: LT discharges to parallel compressor suction; Split LT suction into two different suction groups and split MT suction groups with liquid ejector. The additional system efficiency improvement is estimated to be 5-10%.
DOI: 10.18462/iir.gl.2018.1400
title: Design and optimization of the heat exchanger network for district heating ammonia heat pumps connected in series.

description: Denmark presents ambitious climate policies, and in order to fulfil these visions electrically driven large-scale heat pumps (HP) are often mentioned as an important technology for future district heating (DH) systems. To reach the high temperatures needed in current DH systems, the suggested HP installations become complex systems, where heat transfer between the HP cycle and the heat sink takes place at several temperature levels. In this study the heat exchanger network (HEN) between a HP installation consisting of two serially connected two-stage ammonia HP units and a heat sink being heated from 50 °C to 80 °C was investigated. The study applied pinch analysis to estimate the highest attainable Coefficient of Performance (COP) with the given HP configuration. Based on the result of the pinch analysis, a HEN reaching the highest COP was suggested and compared with COPs obtained with three other solutions for a HEN. The result revealed an estimated highest COP of 3.46. The three other design suggestions yielded reductions in the COP of -2.3%, -2.0%, and -1.8% compared to the highest. From this it was concluded that the HEN has an influence on the COP, and that the pinch analysis can be used to estimate the highest COP for a given HP installation. Furthermore, the COP obtained by practical installations was accordingly shown to come close to the target.
DOI: 10.25489/6bt8ee
title: DOI for test
DOI: 10.18462/iir.gl.2018.1143
title: Vortex control for motive flow rate modulation of transcritical R744 ejector systems.

description: This paper presents results of a novel expansion device refrigerant flow control mechanism called vortex control. The key advantage of this control mechanism is being far less vulnerable to clogging than conventional expansion devices since the flow control is achieved without having to adjust the cross-sectional flow area in order to achieve the desired modulation effect. Vortex flow control is seen as particularly promising when applied to transcritical R744 ejectors, where flow control of the motive nozzle is known to substantially impact ejector and cycle efficiencies. Vortex control can potentially offer the advantage that overall ejector efficiency is less impacted than designs where a needle is used to modulate the motive nozzle flow. The effects of operating conditions were investigated experimentally. It is shown that vortex flow control appears to be feasible for two-phase ejectors using R744 and similar flow modulation ranges as with needle control were achieved.
DOI: 10.18462/iir.gl.2018.1144
title: Efficiency enhancement by combining the carbon dioxide process with a water-loop using water as refrigerant.

description: As a consequence of the F-Gas regulation R404A is no longer a viable option for commercial refrigeration applications. Therefore, this paper focuses on natural refrigerants. There are some alternatives like carbon dioxide, but with an energy efficiency penalty at increasing ambient temperatures. A promising alternative is the combination of carbon dioxide with a water-loop using water as refrigerant at the same time. The benefit is a constant heat sink temperature of the carbon dioxide process all over the year and consequently, the potential to optimize the system for constant operational conditions. Finally the annual COP values of a standard and water-loop system will be discussed.
DOI: 10.18462/iir.gl.2018.1300
title: Comparative life-cycle cost analysis of refrigeration systems in ice rinks.

description: Many ice rinks are facing renovations which require sound financial decision-making to improve their overall performance. Hence the concept of life-cycle cost (LCC) analysis is increasingly applied to estimate costs. However, a practical way to incorporate the concept when comparing the economic performances of refrigeration systems seems to be missing. This study addresses this issue by developing an LCC analysis model that is effective and capable of producing reliable results when comparing refrigeration systems in ice rinks. The LCC model is developed to automatically perform economic analysis based on simulated energy performance together with investment and service cost data gathered from the field. Different tools are included in the model to critically evaluate the input data. The model is applied to real cases in Sweden, where the LCC analysis often concludes that installing a CO2-based system with a heat export function would yield the best financial results. This paper further discusses the potential reasons behind these recurring findings. Results indicate that the sensitivity and scenario analyses play a crucial role when evaluating the quality of input data. The reliability and robustness of calculated results can therefore be assessed, which demonstrates the applicability of the developed model in comparative LCC analysis of refrigeration systems in ice rinks.
DOI: 10.18462/iir.gl.2018.1348
title: Exergy analysis of adsorption cooling system.

description: Exergy analysis is a great tool to identify the details of energy degradation in each process and components. However there was a critical limitation in the previous exergy analysis which assumed no spatial variation in adsorption beds based on lumped capacity method. We have conducted both the energy and exergy analysis of an adsorption cooling system working with silica gel/water. Firstly, the energy analysis has been conducted based on axisymmetric 2-dimensional CFD simulation, and then the exergy analysis has been conducted based the detailed information obtained by the CFD results. The numerical results give the detailed information varying in time and space in adsorption beds. This approach also includes the effects of geometric consideration and operating conditions, which will definitely enhance the accuracy of the exergy analysis.
DOI: 10.18462/iir.gl.2018.1359
title: The LOGAS hot gas defrost system.

description: The paper describes the development of a new hot gas defrost system for central type, dual compression stage, low NH3 inventory refrigeration systems for refrigerated storage facilities and other applications. Conventional hot gas defrost in ammonia refrigeration systems designed with focus on low refrigerant inventory require a refrigerant reservoir that can accommodate the condensate returning from the evaporators during defrost. The LOGAS defrost system eliminates this by employing a phase change defrost fluid that is capable of utilizing a range of heat sources including the glycol loop commonly used for subfloor heating. The paper describes the laboratory test rig and the defrost test results compiled during a series of hot gas defrost tests. Using an existing system as the basis for the calculation example, the paper further details the refrigerant inventory reductions that are possible by implementing the LOGAS defrost system in combination with a new intercooler design that replaces the conventional closed coil flash intercooler. The paper further describes specific refrigerant inventories in kg/kW for more than ten existing, central type, dual compression stage, low refrigerant inventory refrigeration systems constructed in Australia between 2012/13 and 2018. The potential for further NH3 inventory reductions through implementation of LOGAS defrost in these systems is discussed as are the recorded energy performances over a number of years.
DOI: 10.18462/iir.gl.2018.1376
title: Integrated R744 ejector supported parallel compression rack for supermarkets. Experimental results.

description: R744 is currently the preferred solution in the commercial refrigeration sector for most regions, but the limited efficiency of such systems under high temperatures constrains its expansion. Technologies such as parallel compression and ejectors allow the CO2 horizon to be pushed closer to the equator, making CO2 systems an interesting solution even under these environmental conditions. An experimental facility that replicates the refrigeration system for a medium-size supermarket has been built and instrumented. The purpose of this setup is to study which of the potential CO2 vapour compression configurations (booster, parallel compression, ejectors) leads to the lowest power consumption as a function of the ambient temperature, with given refrigeration (and AC) loads. The paper also focuses on the benefits that are associated with increasing the medium-temperature evaporation level, possible due to the combined use of flooded evaporators and liquid ejectors, and with modifying the intermediate pressure (downstream of the ejectors and high-pressure valve).
DOI: 10.18462/iir.gl.2018.1404
title: Global warming potential of hydrocarbon refrigerants.

description: Whilst values for global warming potential (GWP) of widely used and atmospherically stable fluorocarbon refrigerants are well described within the literature, those for hydrocarbons (which are typically short-lived species) are seldom discussed. Arguably, this is due to hydrocarbons (excepting methane) being deemed as posing an insignificant contribution to climate change. This absence of readily available data has led to the adoption of “subjective” GWPs. In response to this, this article collates available data and proposes appropriate values for hydrocarbons commonly used as refrigerants.
DOI: 10.18462/iir.gl.2018.1113
title: Integrated energy concepts for high performance hotel buildings.

description: Integrated energy concepts with heat recovery are not widely applied for hotels, i.e. there is a huge potential to further reduce the specific primary energy demand in this kind of buildings. The development and implementation of such concepts would reduce the cost of ownership and the environmental footprints in the sector, significantly. A combined heat pump and refrigeration system applying carbon dioxide (CO2) and propane is presented for the main and backup system, respectively. Grey Water (GW) usage and thermal energy storage are included in the energy system. A model of the system has been developed and several simulations were carried out in order to investigate the energy demand of a hotel building in several scenarios and ambient temperatures. The integrated energy system can efficiently provide heating, Air Conditioning (AC), Domestic Hot Water (DHW) and refrigeration capacities at various temperature levels. The implementation of thermal storage resulted in both reduction and delay of peak loads.
DOI: 10.18462/iir.gl.2018.1160
title: Local NH3 condensation in a plate heat exchanger.

description: The availability of open source experimental data of NH3 condensation within plate heat exchangers (PHEs) is very limited. This work attempts to extend the database. For this purpose step by step experiments are carried out in a setup capable of local measurements. Temperature sensors have been installed along a PHE to obtain the temperature profile. The local heat flux and the heat transfer coefficient (HTC) are then calculated from the energy balances. Condensation of NH3 has been investigated with varying vapor quality at different mass fluxes. The experimental results are compared with the heat transfer models developed for the condensation of NH3 in tubes and for the condensation of HFCs in PHEs.
DOI: 10.18462/iir.gl.2018.1192
title: Analysis of an advanced R744 cycle and its impact on green house gas emissions by climate zone.

description: Transport (mobile) refrigeration applications offer designers unique application and hardware challenges in selecting new refrigerants. These systems are mobile and have to work efficiently and reliably in a wide range climatic conditions to include adapting to changing climate zone conditions as they move in country, in region and globally. A previous paper presented at the Gustav Lorentzen Conference by Finckh et al. (2016) provided a new evaluation methodology utilizing global climate zone data and a transport refrigeration products efficiency versus ambient profile to understand the impacts on the life cycle climate greenhouse gas (GHG) emission by climate zone. This paper presents a manufacturers analysis of testing of an advanced two stage compression R744 refrigeration unit. A simple thermodynamic model was developed to model this unit’s performance and to handle R744 transcritical operation and various cycle improvements. The R744 test unit performance data was used to calibrate the model and to validate various cycle improvements. The GHG emissions profiles of various R744 duty cycles and future potential cycle improvements will be provided and compared to R452A by climate zone using the methodology provide by Finckh.