cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.18462/iir.gl.2018.1401
title: Natural refrigerants for low temperature power cycles.

description: Working fluid selection determines various characteristics of low temperature Rankine cycles. Among other factors, the selected working fluid affects thermal performance, apparatus size and economic feasibility of the cycle. Beyond only affecting characteristics of the system, unrealistic preconditions for the working fluid of the system may force the designers in using environmentally harmful mixtures and force the outcome beyond boundaries of environmental regulations. There has been numerous research and scrutiny on various working fluids, but due to the unstructured and unorganized orientation of previous studies, there is no comprehensive insight on relationship of different characteristics of the working fluid and overall performance of the system. This work intends to develop a numerical evaluation approach, using a modified stochastic optimization algorithm as a search engine. The paper further explores and questions the existing criteria for optimization of working fluids in Rankine cycle. Rather than just finding the optimum fluids for different cases, this study aims to investigate the behavior of different fluids around optimum points and see the bigger picture to find trends in different fluid behaviors. Analysis of results show two main behaviors among the fluids in subcritical cycles. In the first type behavior, the optimum points for output work, thermal efficiency and exergy efficiency lie very close to each other, while in second type, these optimum points are not close. There is a transition from first type behavior to second type for a ratio of critical temperature around 0.9 of heat source inlet temperature. These results also show the importance of key performance parameter determination.
DOI: 10.18462/iir.gl.2018.1129
title: A new defrosting method using the thermosyphon principles.

description: Finned coil air coolers in cold storage rooms need to be regularly defrosted to remove frost witch grows on the tubes and fins during operation and would otherwise lead to deterioration in heat transfer and blockage of air through the coolers. Common methods used in defrosting are use of hot discharge refrigerant gas from the compressor and insertion of electric heaters in the coolers. In Japan water spraying the coolers is very common. None of these methods are energy efficient. To improve energy conservation and efficiency of the cooling system we developed a defrosting method using the principles of the thermosiphon with CO2 the secondary refrigerant. CO2 within the cooler is heated with hot brine. The heated CO2 evaporates but since it is in contact with frost it condenses and while the CO2 condenses frost is melted.
DOI: 10.18462/iir.gl.2018.1134
title: Reviewing new refrigerant options for industrial refrigeration systems.

description: In the light of the Kigali Amendment, while focusing on the EU F-gas regulation, most manufacturers of industrial refrigeration equipment are under pressure to find new refrigerant alternatives for many types of applications, to enable a phase-down of the well-known HFC refrigerants with high Global Warming Potentials (GWP). The 2014 UNEP RTOC assessment report1 estimated the market value for large industrial refrigeration installations as well as the proportion of R717 used as refrigerant in these installations. The latter is at 90-95%, with some variations that are related to the continent where the installation has been established. For small industrial refrigeration installations, the proportion of R717 is estimated to be between 5 and 25%, once again related to the continent where the equipment is operating. The rest of the market applies a number of different refrigerants, including HCFC-22, HFC-134a and R404A/R507A. With the introduction of the EU F-gas legislation, there has been an increased interest in CO2-based systems and in systems based on a combination of CO2 and other refrigerants in cascade. Furthermore, new refrigerants with lower or very low GWPs are now entering the market. This paper will consider options for industrial applications on sites with large-scale cold production, including breweries, dairies, abattoirs and meat processing factories. Cold store systems are defined as industrial systems, but supermarket and hypermarket systems are considered commercial systems. This paper will particularly consider which refrigerant options can come into play in industrial applications applied for food preservation with temperatures below 0°C.
DOI: 10.18462/iir.gl.2018.1206
title: The R744 multi-ejector hybrid CFD and experimentally-based reduced-order model.

description: The proposed hybrid reduced-order model (HROM) of the four R744 fixed ejectors installed in the multi-ejector module is presented. The ejectors HROM was built by use of the proper orthogonal decomposition together with the radial basis function interpolation to obtain high-accuracy model for a wide range of the subcritical and transcritical operating regimes. The input data for the proposed model was the combination of the experimental data of the investigated ejectors together with the numerical results obtained by use of the ejectorPL platform. The proposed HROM of each R744 vapour fixed ejector obtained a satisfactory accuracy of the motive and the suction nozzle mass flow rates for most validated points and significantly reduced the computational time. Hence, the proposed HROM of the R744 vapour fixed ejectors was successfully implemented to the Modelica dynamic simulations of the R744 refrigeration system to evaluate the system energy performance corresponding to the real ejector performance at different operating conditions.
DOI: 10.18462/iir.gl.2018.1227
title: Hydrocarbons as natural refrigerants for heat pump water heating applications.

description: Growing awareness of the potential environmental impacts of conventional refrigerants (CFCs and HFCs) has led to efforts to identify suitable refrigerants for various heat pump applications with minimum environmental impact. This study is focused on the performance evaluation of pure propane and isobutane as drop-in-replacement for R134a for heat pump water heating (HPWH). A component-based model is used to predict the performance. Key performance parameters such as unified energy factor, first hour rating and thermal stratification in the water tank are investigated. Appropriate experiments are conducted to validate the finding from model. Simulation and experimental findings suggest that both alternative refrigerants could provide comparable system performance to that of the baseline system containing R134a. System refrigerant charge and the condenser discharge temperature are established to investigate the potential of hydrocarbon refrigerants to substitute R134a without significant system modifications.
DOI: 10.18462/iir.gl.2018.1228
title: Investigation on flow pattern, particle size and clogging during the expansion of CO2 into the solid-gaseous region below the triple point.

description: In this study, we experimentally investigated the throttling of preconditioned liquid carbon dioxide (CO2) to atmospheric pressure. As throttling devices a standard thermostatic expansion valve, a capillary tube and other non-standard geometries were used. It can be shown that the outflow patterns of the produced solid CO2 particles are strongly dependent on the type of used expansion device and the temperature as well as pressure conditions at the inlet. Additionally, we measured the distribution of CO2 solid particles size under various boundary conditions. The obtained averaged particle size in finest dispersed solid-gaseous fluid flow can be expected to be in the range of a few microns.
DOI: 10.18462/iir.gl.2018.1247
title: Further research of partial hybrid compression technology applied to ultra-low temperature refrigeration and hydrogen liquefaction.

description: The concept of Hybrid Compression (HC) is a two-technology synergy, introduced lately by the author. It aims at improving the feasibility of heat pumping applications, mainly in ultra-low temperature refrigeration (ULTR) and ultra-high temperature heating (UHTH), (Staicovici, 2015 a, b, c, 2016 a, b, 2017 a). The synergy technologies lay down the operation of an Absorption Technology Section (ATS) and a Mechanical Vapor Compression Technology Section (MVCTS), so that MVCTS plays the role of sink and heat or just the heat source for ATS, while ATS performs the useful task of cooling or heating, respectively. Recently, HC was completed with the Partial Hybrid Compression (PHC). PHC benefits of a free heat source heating of ATS generator-rectifier. This work presents further PHC-ULTR research and its application. PHC-ULTR results are given for single-stage NH3-H2O ATS and NH3 two-stage MVCTS using TWRC (Staicovici, 2014). [ ] Similar to the former studies, PHC-ULTR shows promise this time in HL cryogenics.
DOI: 10.18462/iir.gl.2018.1369
title: Low GWP conversion: an energy efficiency issue ?

description: Energy efficiency receives global attention today related to the decreasing of CO2 emissions. This also particularly concerns the R/AC sector, because Montreal Protocol parties, when adopting the Kigali Amendment, requested the Technology Panel to investigate energy efficiency opportunities when converting to low-GWP alternatives. Other initiatives such as (1) the Kigali Cooling Efficiency Program (K-CEP) “to help the Kigali amendment succeed by making cooling more energy efficient”, and (2) a “Cooling for All” policy undertaking, are likely to play a role in minimizing R/AC emissions. An initial analysis is imperative now in regards to what the R/AC sector can achieve via adequate new designs and technology approaches, resulting in significantly lower energy consumption values. In a first instance, this is related to the use of low-GWP alternatives. The paper describes how the energy efficiency issue has been dealt with during the last 30 years, when several types of refrigerant conversions took place. It provides a comprehensive analysis of the potential for equipment energy efficiency improvement achievable when converting to low-GWP alternatives. Using the technological possibilities as a reference, it estimates the impact of other factors that could contribute to increasing energy efficiency. This notion also includes claims in policy statements for increasing R/AC energy efficiency at the present.
DOI: 10.18462/iir.gl.2018.1378
title: Integration of heat pump in combined heat and power plant. Comparison of vapor compression and absorption technology.

description: Paper published in poster form during the conference. A central combined heat and power plant based on extraction steam turbines may operate in a range of modes. The operating map is defined by boiler load and maximum (back-pressure mode) to zero (condensation mode) heat production. The paper investigates the potential of expanding the map by integrating a heat pump in the cycle of the Avedøreværket Power Station in Copenhagen to preheat the return of district heating. The analysis was made for both vapor compression or absorption technology by numerical simulations of the plant. In both cases power was sacrificed to produce heat. For the vapor compression heat pump electricity from the generator was consumed, while for the absorption unit low pressure steam was used for the heat pump generator instead of producing power. Both heat pumps extend the heating capacity of the plant. The vapor compression unit produced 85.9 MJ s−1 additional heat while sacrificing 17.1 MW power. The absorption heat pump produced 74.5 MJ s−1 heat at a COP of 1.75, while sacrificing 8.9 MW power. Hence the compression heat pump produced a higher amount of heat, while the absorption heat pump provided a little better electric and exergy efficiency. In addition to the better performance of the absorption heat pump, its lower investment meant that it was estimated to have a payback period of 8.6 years compared to 16.8 years for vapor compression unit.
DOI: 10.18462/iir.gl.2018.1157
title: Performance evaluation of two stage mechanical vapour recompression with turbo-compressors.

description: Mechanical Vapour Recompression (MVR) is an open loop heat pump system using water (R718) as working fluid, one of the most abundant and safest refrigerant on the planet. The concept can significantly reduce the energy consumption for steam based processes like drying, pasteurization, evaporation or distillation but also for steam production itself. However, the compression technology is commonly not cost efficient especially for small scale productions in the capacity range from 500 kW to 4 MW. A two stage turbo-compression system was developed and tested based on mass produced automotive turbocharger technology. The turbo-compressor of the first stage reached a pressure ratio of 1.69 and is designed for a mass flow of 400-600 kg/h superheated steam. The second stage turbo-compressor had an identical design and achieved the same pressure ratio. Between compression stage one and two de-superheating is applied by water injection. With the developed system it is possible to compress superheated steam from atmospheric pressure to above 2.8 bar, where it can be condensed at a temperature of 131°C. The COP of the performed investigation was 7.8, when the achievable condensation energy is compared to the total amount of energy supplied to the system. The compressor efficiency is around 70% of the Carnot efficiency.
DOI: 10.18462/iir.gl.2018.1195
title: Comparative study on a dual temperature transcritical refrigeration cycle with two cascade ejectors.

description: Paper published in poster form during the conference. This paper presents a comparative study of performance of two natural refrigerants CO2 and N2O on a modified dual temperature transcritical refrigeration cycle using two cascade ejectors to enhance its performance. Thermodynamic analysis using energetic and exergetic methods are carried out. Effect of system performance parameters, namely COP, pressure ratios, entrainment ratios are evaluated for various warm weather operating conditions (heat rejection pressure within range 7 MPa to 12 MPa; heat rejection temperature 35°C to 50°C and evaporator temperatures -40°C to 0°C). Results show that the system using N2O as refrigerants have higher COP and lower heat rejection pressure compared to CO2 system. Exergy destruction is found to be highest in the gas cooler, followed by ejectors. Exergy efficiency of N2O system is found to be about 2.51% to 6.56% higher than CO2 system for the selected operating conditions.
DOI: 10.18462/iir.gl.2018.1231
title: Supermarket application with CO2. New solution and system design for the evaporators overfeeding in cabinet and cold rooms in transcritical booster.

description: Natural refrigerants are today more and more proposed as a ready to use solution in commercial refrigeration. For this reason there is a constant technological improvement of “green” system, with special reference to CO2 trans critical installations. The key to success is to simplify trans critical technology and enhance efficiency and reliability. This paper present a new solution called FTE (Full Trans critical Efficiency) that has been developed in order to increase reliability and efficiency in a simple design of the system. This solution adds to the system an intermediate liquid receiver located between refrigerated cabinet and the compressors which permits to overfeed the refrigerated loads operating without any superheat and, as consequence, to increase the evaporator temperature and the efficiency. This additional intermediate liquid receiver collects the liquid that’s coming out from the refrigerated loads and delivers the liquid accumulated directly to the frozen loads. FTE is a system solution that can be adopted in all the climates and that increase the efficiency during the whole year. This study has the scope to describe and demonstrate the benefit of the FTE comparing to standard trans critical system. To support the theoretical analysis real consumption of a store installed in South of Europe will be highlighted.
DOI: 10.18462/iir.gl.2018.1287
title: Performance investigation of a multi-ejector R744 heat pump.

description: Paper published in poster form during the conference. Carbon dioxide (CO2, R744) is a natural refrigerant which is emerging as a potential substitute for Hydrofluorocarbons (HFCs) and FCs nowadays because of its eco-friendliness, non-flammability, high volumetric capacity and good heat transfer properties. The demand for domestic water heating is growing rapidly in India for applications like dairies, hotels, hospitals etc. Trans-critical R744 system with heat recovery seems to be appropriate for such application. The drawbacks of lower efficiency and the demand mismatch can be improved by incorporating ejectors; while, the mismatch is addressed by suitable control and standby gas cooler respectively. The paper presents an experimental evaluation of an R744 multi-ejector based system with heat recovery for hot water production. The effect of high ambient temperature (36-46°C) on the overall performance of the system and heat recovery is also evaluated. It is observed that the COP of the multi-ejector R744 system with heat recovery for domestic production at high ambient context is high. Also, the opportunity of maximum heat available for recovery is encouraging to accept this technology for high ambient context.
DOI: 10.18462/iir.gl.2018.1364
title: Design of a gas-fired carbon-ammonia adsorption heat pump.

description: Paper published in poster form during the conference. Ammonia – carbon adsorption heat pumps for domestic use have been a focus of research at the University of Warwick for many years. The continuing challenge is to devise a sorption generator which has excellent heat transfer to an inherently poor conducting medium, minimal thermal mass and low manufacturing cost. This paper presents the design and manufacturing of a novel carbon-ammonia adsorption generator heat pump for application to an air source domestic gas fired heat pump and also shows preliminary testing results of the complete heat pump system. This laminated generator has the characteristic of delivering high heating power at a high efficiency but having an inexpensive manufacturing cost.
DOI: 10.18462/iir.gl.2018.1381
title: Energy saving on solar air-conditioning system using single-double effect combined absorption chiller at Universitas Indonesia.

description: Since further energy saving for global environmental protection becomes a matter of urgency, the utilization of renewable energy is needed for realizing a low-carbon society. Especially, in Indonesia, according to the economic growth, the measures for the reduction of the greenhouse gas emissions and energy consumption are requested. Under these situations, a single-double effect combined absorption chiller for "Solar airconditioning system" has been developed. This chiller is composed of a highly-efficient gas absorption chiller as the main machine which is equipped with a solar heat recovery unit comprising a heat recovery heat exchanger and special condenser. It enables low temperature solar hot water at 75 °C under operation at the cooling rating of load factor: 100%. Solar air-conditioning system using single-double effect combined absorption chiller 239 kW was installed in the University of Indonesia Faculty of Engineering building located in Depok city in the vicinity of Jakarta, aiming to reduce greenhouse gas emissions. We have collected and analyzed data from this air-conditioning system to comprehend its performance and fuel gas reduction by around 20% could be achieved. The results are reported here.
DOI: 10.18462/iir.gl.2018.1389
title: Experimental pool boiling heat transfer coefficients of ammonia on two dual-enhanced carbon steel tubes.

description: Pool boiling on the external surface of the tubes is a complex process for theoretical analysis, so in many occasions the boiling heat transfer coefficients (HTCs) need to be experimentally determined. Carbon steel tubes are commonly employed in shell-and-tube heat exchangers when ammonia is used as refrigerant, due to their compatibility. This work reports the experimental determination of the ammonia pool boiling HTCs on two dual-enhanced carbon steel tubes of 18.8 mm diameter at saturation temperatures of 10 °C and 0 °C. Experimental facility and data acquisition system are described, experimental procedure is explained, data reduction methodology is detailed, and experimental results are presented and discussed.
DOI: 10.18462/iir.gl.2018.1397
title: Development of high performance air-conditioning system combined liquid desiccant and R718 centrifugal heat pump.

description: General implementation of air conditioning in buildings and facilities is such that in order to keep room temperature and humidity within predetermined range, heat pump is used to lower the air temperature to achieve desired humidity and then the air is heated to the specified temperature. From energy-saving perspective, this process is inefficient.

To overcome such inefficiency, separation of latent heat and sensible heat has been proposed. This is a two-step process in which temperature and humidity are adjusted separately in two steps by combining desiccant dehumidifier and heat pump. Theoretically, the system is known to be effective in reducing energy consumption, but in practical application, this technology can be further improved.

For this research, we have chosen liquid desiccant dehumidifier as the desiccant can be regenerated at low temperature. For heat pump system, we have chosen R718 centrifugal as it is suited for increasing efficiency for such combination of desiccant and heat pump. By improving each element of the system and seeking optimization of operating conditions, we aim to develop a high efficiency air-conditioning system. The result is reported here.
DOI: 10.17632/mdhbx6rctp.1
title: Data for: Interstitial nitrides revisited - a simple synthesis of MxMo3N (M = Fe, Co, Ni)

description: Raw X-ray diffraction data for interstitial nitrides.
DOI: 10.18462/iir.gl.2018.1139
title: Measures to minimize entropy production in compression-resorption heat pumps.

description: Compression-resorption heat pumps (CRHP) enhanced by wet compression are considered a very promising option to upgrade low grade waste heat from the industry. This is especially true for applications where the heat source and/or sink have a large temperature glide. But commercial solutions using wet compression are not yet available on the market. Compared to the classically used vapor compression heat pumps (VCHP), CRHP can provide much better performance but only if the efficiency of the compressor exceeds 0.7. In this respect, a twin screw compressor has been identified as a potential solution to reach this efficiency goal. This study makes use of the entropy production minimization to identify where the major irreversibilites are located in a CRHP system operated with an ammonia-water mixture. A detailed model of the wet compressor and the resorber are coupled with simplified models of other components of the HP cycle to analyze where potential improvements can be made. The results show that significant benefits can be obtained using CRHP.