cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.18462/iir.gl.2018.1210
title: Low GWP working fluids for reversible systems of high temperature heat pump and organic Rankine cycle (HTHP/ORC).

description: Paper published in poster form during the conference. An innovative measure to recover low-grade waste heat is a reversible system based on a High Temperature Heat Pump (HTHP) and an Organic Rankine Cycle (ORC). This system can produce useful thermal energy and, in periods with no thermal demand, produce electricity. This study analyzes the influence of several working fluids (HFC-245fa, ammonia, isobutane, and HFO-1336mzz-Z) over the system using a theoretical model in basic and IHX cycles of HTHP/ORC architectures. The model has been optimized to use the more appropriate built-in ratio and the IHX effectiveness. Firstly, the built-in results highlight scroll and screw technologies as the most appropriate for the compressor-expander component and ammonia as the working fluid that requires minor size. Secondly, IHX effectiveness can be maximized for all the cases studied except for ammonia at lower evaporating temperatures. Finally, HFO-1336mzz-Z is the working fluid that leads to higher performance operating in both modes (net electrical efficiency for ORC and COP for HTHP).
DOI: 10.18462/iir.gl.2018.1212
title: Experimental investigation of the performance of a hydrocarbon heat pump for high temperature industrial heating.

description: A 20 kW heat pump test rig has been built to investigate and validate heat delivery up to 110 °C using a vapour compression cycle. The heat pump is a cascade cycle with propane as the working fluid in the low temperature cycle and butane in the high temperature cycle. The technology will recover low temperature (30 °C) waste heat from industrial processes and upgrade to high temperature heat for applications such as drying, sterilization, pasteurization and other heat demands within 100 – 120 °C. The heat pump will replace equivalent capacities of existing cooling towers and boilers or direct electricity heating systems in the industry. A modified compressor prototype was implemented for the high temperature cycle and was found to have an average total compressor efficiency of 71 %. The heat pump had a heating COP up to 2.6 and a combined heating and cooling COP of 4.1 for a temperature lift of 80 °C.
DOI: 10.18462/iir.gl.2018.1223
title: Experimental analysis of a R600 high temperature heat pump.

description: Heat pumps offer the possibility to improve industrial processes in terms of efficiency and the reduction of fossil fuel consumption. Therefore a vapour compression heat pump using n-butane (R600) for a supply temperature level up to 110 °C has been developed and investigated. Since R600 shows a so-called overhanging two phase region, a certain amount of superheat at the compressor inlet has to be secured in order to avoid wet compression and thus compressor damage. In a conventional cycle a high value of
superheat may decrease the evaporation temperature resulting in lower efficiencies. Hence three different cycle configurations in terms of superheat utilization have been analysed. The first two configurations correspond to a conventional heat pump cycle using a suction gas cooled compressor with and without an additional superheater. The third configuration uses an internal heat exchanger. The heat pump prototype is described and the experimental results are presented in this paper. The results showed that at a heat source inlet temperature of 60 °C and a heat sink outlet temperature of 110 °C a COP of 3.5 is possible.
DOI: 10.18462/iir.gl.2018.1270
title: Vapor pressure measurement of liquid dessicants at low temperatures by a novel technique.

description: Due to non-condensable gas under conditions of vacuum and low temperatures, it becomes difficult to obtain precise vapor pressures of typical liquid desiccants by an experiment. Usually, non-condensable gas is removed by a traditional degassing method (degassing after prepared solutions - DPS), in which prepared liquid desiccants are circularly frozen and non-condensable gas is pumped out. However, the solvent of liquid desiccants could greatly evaporate during traditional degassing processes. Concentrations of the prepared liquid desiccants could be greatly deviated from those of the prepared liquid desiccants. Accordingly, measured vapor pressures usually greatly deviate from those corresponding to the concentrations of the prepared liquid desiccants. Moreover, it becomes very difficult to determine new concentrations of the prepared liquid desiccants after degassing, precisely. To overcome the challenges for precise measurements of typical liquid desiccants, a novel technique is developed in this context. The new method is called DSSPS (degassing solvents and solutes before preparing solutions - DSSPS), in which degassed solvent and solute is weighted respectively, and then, is mixed as measured solutions. Thus, concentrations of the measured solutions could be determined easily and precisely. Vapor pressures of LiCl-H2O desiccants are measured by the new method at a range from 218K to 258K and with the mass fractions of solutions from 5% to 20%. Totally, 35 sets of vapor pressure are measured. Then, the data is correlated based on Antoine equation.The ARD% (Absolute Relative Deviation - ARD) of equation is from 0.04% to 3.21% and AARD% (Average Absolute Relative Deviation - AARD) is 1.73%. So, the new method could be used to measure vapor pressure of aqueous solutions at vacuum and low temperatures precisely. The average error between experimental data and the results calculated by EES (Engineering Equation Solver - EES) is within 15.2%, and its maximum error is 35.46%. Vapor pressure data in this context also provides important reference for development of a precise calculation model.
DOI: 10.18462/iir.gl.2018.1347
title: Preliminary design of a low-temperature refrigeration system with natural refrigerants for a psychrometric chamber.

description: The sectors of refrigeration and air-conditioning have always been affected by great changes and innovations. Today's revolution seeks to find low-GWP solutions that maintain high efficiency without increasing the risks for people: this is a major challenge to which the industry has to respond. One of these important sectors is the refrigeration of psychrometric chambers. These chambers are used in many industrial applications for various purposes, so there are many refrigeration technologies used to ensure the required indoor conditions. Even for this type of equipment, innovative solutions and technologies will be needed according to the environmental requirements. In this context, an analysis was carried out to develop the preliminary design of a refrigeration system using natural fluids able to reach the indoor temperature of -80 °C for a psychrometric chamber used for laboratory tests. The project involved sizing of the main components, market analysis and the application of the safety requirements (EN 378:2016).
DOI: 10.18462/iir.gl.2018.1382
title: Large-capacity propane heat pumps for DHW production in residential buildings.

description: Paper published in poster form during the conference. Using heat pump technology to provide Space Heating (SH) and to produce Domestic Hot Water (DHW) for residential buildings has been widely applied during past decades. In this study, two scenarios adopting large-capacity propane heat pumps are defined and evaluated. These two scenarios, which are named after Scenario A and Scenario B respectively, provide SH and DHW either separately by two units or integrally by one unit. The COP1s of two scenarios are compared based on the simulation results from experimentally validated models. The results show that two scenarios have almost equal efficiency; the relative difference is within 6%. In the optimization analysis of Scenario B, varying DHW heating capacity produced by the desuperheater in the heat pump is modelled. The DHW demand ratio varies from approximately 9% to 20% with no detectable influences on the COP1. The corresponding COP1s and temperature profiles in the heat exchangers are demonstrated. The simulation results indicate that increasing DHW capacity in Scenario B can narrow down the temperature approach in the condenser and insignificantly improves the overall COP1s.
DOI: 10.17632/npx9dybxrx.1
title: Data for: Responses of sub-Saharan smallholders to climate change: strategies and drivers of adaptation

description: Data from the CCAFS survey used in this study.
DOI: 10.18462/iir.gl.2018.1268
title: Optimization of the intermediate pressure for two-stage cycles with vapor-injection for subcritical and transcritical cycles.

description: In this paper, the optimum intermediate pressure of two-stage cycles is presented taking into account the fact that the heat sink does not have infinite capacity (constant temperature). The refrigerants R-290 and others (R-152a, R-22, R-32, R-410A, R-134a, and R-1234yf) were considered for the subcritical cycle optimization and the CO2 for the transcritical cycle optimization. In both cases, the intermediate pressure optimization was performed for two-cycle configurations (flash tank and economizer) considering a wide range of operating conditions and secondary fluid conditions. Based on the optimization results, correlations are proposed in order to estimate the optimum intermediate pressure for the two kinds of cycles. In the subcritical cycles, the subcooling is taken into account in the correlation, besides the evaporating and condensing temperatures. In supercritical cycles, the optimal rejection pressure of the gas cooler and the refrigerant outlet temperature of the gas cooler are taken into account in the correlation. Finally, the proposed correlations are used to calculate the optimum intermediate pressure of a sanitary hot water application using an air to water heat pump with R-290 (subcritical) and CO2 as a refrigerant (transcritical).
DOI: 10.18462/iir.gl.2018.1278
title: Experimental study of flow boiling of propane in a 6mm internal diameter horizontal tube.

description: This paper provides new experimental data on flow boiling of propane in a stainless steel horizontal tube, whose heated length is 193.7 mm and its internal diameter is 6.0 mm. Heat transfer coefficient and pressure drop data were collected over the whole range of vapor qualities for saturation temperatures from 25 to 35°C, by varying also the imposed heat flux from 2.5 to 40 kW/m2 and using mass velocity from 150 to 300 kg/m2s. The pressure gradient and local heat transfer coefficient data are finally compared with correlations taken from scientific literature, evaluating the mean and absolute deviations as statistical parameters.
DOI: 10.18462/iir.gl.2018.1295
title: A simplified ammonia water absorption cycle without distillation column in small temperature lift applications.

description: Paper published in poster form during the conference. The water content in the refrigerant may undermine the cooling effect in ammonia water absorption refrigeration systems. A distillation column is normally implemented. The use of distillation column, however, may increase complexity especially in the practical operation. In fact, the distillation column can be eliminated under particular operating conditions. A simplified cycle is proposed, in which the distillation column is replaced by two separators and one heater, the resulting vapor is nearly pure with ammonia mass fraction of 0.998. The heat integration modifications are carried out for boosting the thermal performance, at working condition TCOND=21°C, TEVAP=5°C and TH=80°C, the simulated Coefficient of Performance (COP) is 0.863. The results are also compared with the Generator-Absorber heat eXchange absorption cycle (GAX) and lithium-bromide and water absorption cycle. It is demonstrated that the proposed cycle delivers roughly the same COP, but the simpler configuration makes it attractive under certain working conditions.
DOI: 10.18462/iir.gl.2018.1357
title: Efficient R744 technology for supermarket heating, cooling and refrigeration - a theoretical assessment of energy advantages in various Spanish cities.

description: Various appealing expedients aimed at enhancing the energy efficiency of transcritical CO2 (R744) supermarket refrigerating systems have been recently developed. The concurrent adoption of these could lead such hydrofluorocarbon (HFC)-free technologies to become standard even in the South of Europe. Consequently, these solutions have drawn an enormous interest in the Spanish food retail industry as this features very severe regulations with the purpose of substantially mitigating ongoing climate change. In this theoretical work the performance of a state-of-the-art transcritical R744 supermarket refrigerating system, i.e. a solution including medium (MT) and low temperature (LT) overfed evaporators, parallel (or auxiliary) compression and “all-in-one” (or fully integrated) concept, was exhaustively investigated. This was compared to that of a baseline (i.e. “old” solution relying on R404A-based units to satisfy the refrigeration loads and a R410A reversible heat pumping unit) and to that of another alternative complying with the environmental legislative acts in force (i.e. solution based on a R134a/R744 cascade arrangement to provide the refrigeration demands and a R1234ze(E) reversible heat pump unit). The study was carried out by considering an average-size food retail store located in the Spanish climate context. The outcomes obtained revealed that the fully integrated R744 refrigeration plant offers total energy conservations between 1% (in Tenerife) and 33% (in Burgos) over conventional separated HFC-based units. In addition, the investigated transcritical R744 system brought the total annual electricity consumption down by at least 39% compared to HFC-based arrangements in heating mode.
DOI: 10.18462/iir.gl.2018.1365
title: Experimental measurements on the effect of a modulating ejector in a transcritical CO2 system.

description: The success of CO2 as a refrigerant in commercial refrigeration is due to several factors, including the technological evolution of carbon dioxide refrigeration systems. One of the most recent developments is the use of an ejector in on/off and modulating versions. The present paper studies a refrigeration unit equipped with double technology: modulating ejector and traditional booster system. Experimental tests were carried out to measure and analyze the effect of the modulating ejector in the transcritical CO2 booster compressor rack. The tests were performed by measuring the external conditions, the main thermodynamic parameters of the unit and the power absorbed by the unit. The main objective of the investigation is the study of the energy efficiency comparison between the standard transcritical operation mode with parallel compression and the ejector operation mode. Measurements of the energy consumption for the two technologies were performed for more than five months. An estimation of the annual energy saving was calculated based on measured data. A theoretical model was developed to simulate the cycles with and without ejector.
DOI: 10.18462/iir.gl.2018.1395
title: Bubble-point measurement of CO2 + HC refrigerant mixtures at low temperatures below 230K.

description: In order to extend vapor-liquid coexistance range of CO2 to lower temperatures below 216.59 K, binary mixture with isobutane was studied.Bubble-point pressures of CO2-rich composition were measured at temperatures below 225 K. Originaly designed cryogenic vapor-pressure measurement system was used. By controling a Stirling-cooler module, the system temperature can be well controled even at 200 K. Thus measured bubblepoints agreed with an available mixture equation of state. At lower temperatures below 213 K, solid-vapor equilibrium was observed. As a result of the present measurements, triple-point temperature of the mixture where the mole fraction of CO2 being 0.94 was determined.
DOI: 10.20393/8b82e6e3-69f0-4ebb-8ff2-2af0dad04b8a
title: Midnight surface water temperatures from the Mill Race, Furnace, Newport, Co. Mayo

description: The Mill Race links upstream Lough Feeagh with Downstream Lough Furnace. The channel is short (200 metres) and shallow (&lt;1 metre generally) and water temperatures measured here are very close to those measured on the surface waters of Lough Feeagh. This record has therefore, historically been used as a proxy for Lough Feeagh surface water temperature.   Between 1960-2004, a Negretti paper chart recorder was used, and data were extracted for midnight each day. The chart recorder was checked sporadically against a mercury thermometer. From 2004 to 2009, a StowAway TidbiT temperature data logger from Onset (TBI32-05+37) was used (https://www.onsetcomp.com/products/data-loggers/tbi32-0537 ), and data extracted for time step nearest midnight. Between 2010 and 2017, temperature was recorded using an Orpheus mini water level recorder (https://www.ott.com/products/water-level-1/ott-orpheus-mini-water-level-logger-3/  ) and data extracted for time step before midnight.
DOI: 10.18462/iir.gl.2018.1106
title: Kinetics of water freezing in mesopores of silica gel.

description: The research presented in the manuscript aims at the determination of the kinetic model of water freezing in mesopores using differential scanning calorimetry. The microstructure of the silica gels under investigation have one dominant pore diameter, which equals 15 nm. Additionally, their microstructure is investigated using the nitrogen adsorption/desorption techniques before and after freezing cycles. We test four cooling rates: 2.5 °C/min; 5.0 °C/min; 7.5 °C/min and 10.0 °C/min. The relation between ice content and temperature is determined for each cooling rate. We find that the process rate depends only on the temperature and the extent of conversion. The activation energy is determined by differential Friedman’s method. Three algorithms for the determination of model parameters are compared: Málek method, the method proposed by Perez-Maqueda et al., and the one introduced by Arshad and Maaroufi. The Šesták-Berggren model gives the best approximation of the conversion function.
DOI: 10.18462/iir.gl.2018.1168
title: Diesel explosion of propane at pump-down of air conditioner.

description: Propane (R290) is a potential alternative refrigerant for reducing greenhouse gas emissions from refrigeration and air conditioning equipment; it is necessary to carry out an adequate safety assessment because of its high flammability. This study focuses on compressor explosion accidents at pump-down of split air conditioners. Pump-down is an operation used to gather an entire refrigerant into an outdoor unit by closing the outlet valve of the outdoor unit and forcefully driving the compressor. If the entrance of air into the tube for the refrigerant occurs owing to an error during operation, the lubricating oil in the compressor may cause a self-ignition and a diesel explosion. Experiments were conducted to reproduce the diesel explosion, and its characteristics were examined. A mixture of air, a refrigerant, and lubricating oil was compressed by a compressor and an explosion occurs under certain conditions. R290 was used as the refrigerant, and its safety was evaluated in comparison with conventional fluorocarbon refrigerants.
DOI: 10.18462/iir.gl.2018.1203
title: OpenFOAM implementation of algebraic frosting model and its applications on heat pump evaporators.

description: This paper presents the implementation of an algebraic frosting model into a general-purpose Navier-Stokes computational fluid dynamics (CFD) solver. The selected frosting model, derived from the energy and mass conservation equations, is used to predict the growth of the frost zone in space and time, and the resulting modification of the local flow characteristics within the non-frosted part of the domain. This implementation is used for a CFD analysis of the frosting behavior of a heat pump evaporator (represented through all relevant geometrical features) under realistic operating conditions. The obtained simulation results are compared with the findings of the experimental investigation of the fin-and-tube heat exchanger frosting, coming from the air-to-water heat pump measurements.
DOI: 10.18462/iir.gl.2018.1234
title: Design performance of CO2 refrigeration systems for ice production in snow making generators at ambient temperatures above 0 °C.

description: Paper published in poster form during the conference. Flake ice systems (sub-critical and trans-critical) with a production capacity of 50 and 100 tons day-1 was modelled in EES, to investigate the thermodynamic performance at different ambient temperatures. Optimization of trans-critical system was made with respect to pressure in gas-cooler and type of heat exchanger. Flake ice machine was modelled in COMSOL for design optimization. The increasing of flake ice machine capacity can be achieved by varying boiling temperature and ice thickness. The 200 pipes were sufficient to provide to provide effective freezing. One stage sub-critical system showed the best COP at low ambient temperatures. Two stage trans-critical can be preferable, when there is a demand in hot tap-water production or heating. The trans-critical two stage system was more energy demanding, when producing ice (up to 33.65 kWh m-3). Application of coaxial gas-cooler was beneficial due to increasing of total COP of the system and heat recovery.
DOI: 10.18462/iir.gl.2018.1243
title: A concept of performance improvements for R744 two-phase ejector with bypass duct.

description: A concept of the two-phase ejector with a bypass duct for CO2 applications is proposed in this study. A geometry and bypass positioning, idea of regulation as well as integration with suction nozzle duct was designed and described. Preliminary numerical analysis of the proposed bypass geometry was performed. Computational platform ejectorPL integrated with well validated mathematical model of transcritical R744 two-phase flow were used. Gas cooler and evaporator conditions characteristic for large systems such as supermarket refrigeration units were examined. Separation pressure of 32 bar in liquid receivers were simulated for the bypass variants with two duct shapes and six attachment positions. The perspective results were obtained for this low pressure conditions. Namely, the suction mass flow rate increment was of 36.9% for the bypass angle of 19°. Hence, the bypass implementation resulted in the efficiency improvement from 22.2% to 30.4%. Significant influence of the bypass geometry into the overall ejector efficiency was reported. Finally, a possible shape optimisation of bypass duct as well as further analysis focused on the regulation and control strategy were given.