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Aiming at solving the problem of high global warming potential of R134a, a new mixed refrigerant R13I1/R152a (molar fraction ratio of 35:65) with no ozone depletion potential and low global warming potential was proposed as a substitute for R134a in automotive air conditioning. The computational models for the thermodynamic properties of R13I1/R152a were established by using the PR equation of state combined with the vdW mixing rule. Based on these models, the cycle performance of this working fluid was calculated, which was also compared with that of R134a and R1234yf under the different operating conditions. The results show that R13I1/R152a is a near azeotropic refrigerant whose temperature glide is approximately 0, and the saturated vapor pressure curve of which is equivalent to that of R134a. Moreover, compared to R134a, R13I1/R152a has an average 5.7% improvement in coefficient of performance as well as similar volumetric cooling capacity. The average coefficient of performance and volumetric cooling capacity of R13I1/R152a are significantly higher than those of R1234yf by 13.8% and 12.0%, respectively. However, the average discharge temperature of R13I1/R152a is approximately 13.3 K higher than that of R134a, but it is also within reasonable limits. Hence, the application of the proposed refrigerant R13I1/R152a in automotive air conditioning system is technically feasible.

Adsorption refrigeration has more potential to become an attractive technology due to use of low-grade thermal energy and environmentally friendly refrigerants. Ammonia-activated charcoal pair based prototype of single bed adsorption cooling system was presented and tested. The most extreme measure of adsorption capacity of ammonia was found to be 0.22 kg/kg of activated charcoal, in shell and tube type adsorption bed respectively. This experimentation indicates that the cooling limit ranges from of 46.38 to 50.67 W, and thus the results show that it achieves a COP of 0.0971 during a 62-minute total working cycle time under the condition of the temperature of hot fluid 120 °C, cooling fluid provided at the temperature of 30 °C, adsorption bed temperature of 40 °C and working pressure range up to 16 bar. The results have been represented by graphical relations. This unit of adsorption cooling is environment-friendly and has zero ozone depletion potential. The result indicated that the adsorption refrigeration system works effectively and is a better alternative to replacement for traditional refrigeration systems and the concept of a waste heat driven adsorption cooling system can be applied in the small cold storages.

Series and parallel two-stage evaporative strategy for vapor compression refrigeration cycles characterized by temperature and humidity independent control were presented. The theoretical model was established to analyze the performance of parallel two-stage evaporative strategy regarding the coefficient of performance (COP), exergy loss, exergy efficiency in comparisons with series system. And refrigerants R290 and R600 with low global warming potential (GWP) and no ozone depletion potential (ODP) are proposed as alternative refrigerants for R134a in two systems. The results show that compared with R134a, the proposed R600 has better performance with higher specific refrigerating capacity and coefficient of performance, of which specific refrigerating capacity increase 102.72% than that of R134a on average. Series two-stage evaporative strategy for vapor compression refrigeration cycle with R600 had the optimal techno-economic performance, which COP and exergy efficiency are 7.8% and 11% higher than that of parallel two-stage evaporative strategy, respectively.

Implementation of Montreal Protocols-1987 enforced phase wise ban on production and application of ozone depleting chemicals (Halons). Since then, condensed aerosol-based fire extinguishing technology as an alternative to Halons has been a subject for numerous investigations for its research and applications worldwide. It has come up as the most efficient halon alternative technology in comparison to other alternatives such as water mist, dry powders, inert gases, hydro fluorocarbons, and carbon dioxide. Even it is three times more efficient than that of Halon 1301 on weight to volume basis. Over other Halon alternatives, it has many advantages, e.g., zero ozone depletion potential -atmospheric lifetime -global warming potential, modular structure, low space requirements, easy & cost-effective installation & maintenance, no requirement of piping & pressurized cylinders, no oxygen depression etc. Condensed aerosol based fire extinguishing systems (CAFES) have found versatile fire safety applications worldwide in many areas such as power generation, transportation, storage rooms, public buildings, heavy industries, battery storage systems, defence etc. This review mainly focuses on applications of CAFES for extinguishment of: class A fires in libraries, archives, storage rooms etc.; class B fires in machinery spaces, gas turbine enclosures, combat vehicles, chemical storage rooms; electrical fires occurring in control rooms, UPS rooms, electrical/power substations & panels. Various reports and case studies demonstrating its testing and implementation methodologies have also been covered. The future prospects of aerosol technology and potential research/applications areas are also discussed.

To mitigate the rumen enteric methane (CH4) produced by ruminant livestock, Asparagopsis taxiformis is proposed as an additive to ruminant feed. During the cultivation of Asparagopsis taxiformis in the sea or in terrestrially based systems, this macroalgae, like most seaweeds and phytoplankton, produces a large amount of bromoform (CHBr3), which contributes to ozone depletion once released into the atmosphere. In this study, we focus on the impact of CHBr3 on the stratospheric ozone layer resulting from potential emissions from proposed Asparagopsis cultivation in Australia. The impact is assessed by weighting the emissions of CHBr3 with its ozone depletion potential (ODP), which is traditionally defined for long-lived halocarbons but has also been applied to very short-lived substances (VSLSs). An annual yield of ∼3.5 × 104 Mg dry weight is required to meet the needs of 50 % of the beef feedlot and dairy cattle in Australia. Our study shows that the intensity and impact of CHBr3 emissions vary, depending on location and cultivation scenarios. Of the proposed locations, tropical farms near the Darwin region are associated with the largest CHBr3 ODP values. However, farming of Asparagopsis using either ocean or terrestrial cultivation systems at any of the proposed locations does not have the potential to significantly impact the ozone layer. Even if all Asparagopsis farming were performed in Darwin, the CHBr3 emitted into the atmosphere would amount to less than 0.02 % of the global ODP-weighted emissions. The impact of remaining farming scenarios is also relatively small even if the intended annual yield in Darwin is scaled by a factor of 30 to meet the global requirements, which will increase the global ODP-weighted emissions up to ∼0.5 %.

HC-290 is one of the alternatives to HCFC22 in room air-conditioners. With the phase-down schedules in Kigali Amendment, it is imperative to use HC-290. However, there are concerns about its flammability in the event of a leak from the AC indoor unit (IDU). IEC 60335-2-40 has been revised to extend the capacity ranges for A2L refrigerants and is being further revised with a focus on A2 and A3 refrigerants. In real-life situations, furniture and occupants are present inside the room and these may positively or negatively influence the dispersion of any leaked HC-290. CFD simulation of dispersion of leaked HC-290 has been carried out for a variety of scenarios. The variables include leakage rates, IDU installation heights, IDU blower ON or OFF and types of furniture. Furniture, in general, appears to promote mixing, thereby reducing HC-290 stratification. The maximum concentration occurs on the side where the leak is directed by the momentum of the jet from IDU. There is no significant effect on the concentration distribution by the type and size of furniture with legs, although solid furniture has some marginal effect due to reduction of room free volume. The average concentration of HC-290 in the room is slightly more when the solid furniture like cupboards are placed some distance away from the IDU. The highest concentration at 30 cm above floor level, is 44% of LFL when the blower is ON, while it is 62% when the blower is OFF.

With the ever-increasing societal demands to control the climate change, various policy and regulatory actions are coming out to reduce or restrict refrigerants with non-zero ozone depletion potential (ODP) and high global warming potential (GWP). For low pressure centrifugal chiller applications, R123 with non-zero ODP and R245fa with high GWP, will be phased out. For the current study, the performance of R1233zd(E) and newly developed R1224yd(Z) were evaluated in view of replacement for R123 and R245fa for two-stage centrifugal chiller applications. The system-level thermal performance, component-level heat transfer performance/sizing, and life time environmental performance are investigated at a fixed cooling capacity of 500 t (1750 kW). Both fluids have an equivalent COP. R245fa and R1224yd(Z) can achieve a volume capacity 60% higher than that of R123, while that of R1233zd(E) is 40% higher. R245fa and R1233zd(E) can achieve a mass flow rate $$\sim 10$$ % lower than that of R123, and R1224yd(Z) displays a mass flow rate $$\sim 5$$ % higher than that of R123. R1233zd(E) and R1224yd(Z) demonstrate an evaporator shell side heat transfer coefficient 19% and 16% higher, respectively, as compared with R123. R1233zd(E) has a condenser shell side heat transfer performance 32% higher than that of R123, and those of R245fa and R1224yd(Z) are $$\sim 24$$ % higher. R1233zd(E) and R1224yd(Z) exhibit compressor impeller diameters 17.8% and 19.7% less, respectively, as compared with R123. Both R1233zd(E) and R1224yd(Z) can exhibit a $$\sim 10$$ % life cycle emission reduction as compared with R245fa. To sum up, R1233zd(E) and R1224yd(Z) can be good candidates to replace R123, and R1224yd suits better than R1233zd(E) to replace R245fa for centrifugal chiller systems, which is due to its heat transfer area close to that of R245fa and smaller compressor modifications. It is anticipated that the current study can be beneficial for the chiller community to maintain the maximum sustainability and economic benefits.

The electrified cleaning agent requires a moderate volatilization rate, low ozone-depleting substances value, non-flammable, non-explosive and other characteristics. This study performed a whole life cycle assessment on a hydrocarbon-based electrified cleaning agent. The life cycle model is cradle-to-grave, and the background data sets include power grid, transportation, high-density polyethylene, chemicals, etc. The analysis shows that the global warming potential (GWP) of the life cycle of 1 kg of electrified cleaning agent is 2.08 kg CO2 eq, acidification potential (AP) is 9.49E-03 kg SO2 eq, eutrophication potential (EP) is 1.18E-03 kg PO43-eq, respirable inorganic matter (RI) is 2.13E- 03 kg PM2.5 eq, ozone depletion potential (ODP) is 4.91E-05 kg CFC-11 eq, photochemical ozone formation potential (POFP) is 2.89E-02 kg NMVOC eq, ionizing radiation-human health potential (IRP) is 3.16E-02 kg U235 eq, ecotoxicity (ET) is 2.69E-01 CTUe, human toxicity-carcinogenic (HT-cancer) is 4.32E-08 CTUh, and human toxicity-non-carcinogenic (HT-non cancer) is 2.31E-07 CTUh. The uncertainty of the results is between 3.46-9.95%. The four processes of tetrachloroethylene production, D40 solvent oil production, tetrachloroethylene environmental discharge during product use, and electricity usage during product disposal have substantial effects on each LCA indicator, so they are the focus of process improvement. Changes in power consumption during production and transportation distance of raw materials have little effect on total carbon emissions. Compared with the production process of single-solvent electrified cleaning agent tetrachloroethylene and n-bromopropane, the production of the electrified cleaning agent developed in this study has its own advantages in terms of carbon footprint and other environmental impact indicators. Carbon emissions mainly come from the power consumption of each process, natural gas production and combustion, and other energy materials for heating. It is recommended to use renewable raw materials instead of crude oil to obtain carbon credits based on geographical advantages, and try to use production processes with lower carbon emissions, while the exhaust gas from the traditional production process is strictly absorbed and purified before being discharged.

In this project an air conditioner was fabricated using R-410a as refrigerant and its COP is calculated. CFCs have been phased out, except for essential users, and HCFCs are to be eliminated by 2020, because of their ozone depletion potential.This generates a need for the investigation of zero ozone depletion potential (ODP) refrigerants or refrigerant blends.R410A is among newer brand of refrigerant blend, with zero ODP. The biggest difference to R22 is the pressure levels generated which are more than50% higher. The refrigerant R410A operates at higher pressure at the same saturated temperatures than R22, therefore system should be re designed. The overall COP of the system is 5 to 6% more than the R22. We also calculated the relative humidity of room air after it gets cooled, heat removed from the air by considering the input data from weather online which provides us the day to day climatic conditions. Present work provides us regarding performance of an self fabricated zeotropic air conditioner.

Trifluoroethene (HFO-1123) has a very low global warming potential (GWP) and ozone depletion potential (ODP); thus, it has been proposed as a next-generation refrigerant. However, a short circuit in a motor under high temperature and pressure conditions may cause a disproportionation reaction of HFO-1123. Therefore, to commercialize a split air conditioner using HFO-1123, it is necessary to develop a technology to suppress this disproportionation reaction. In this study, disproportionation experiments were conducted under various temperature and pressure conditions. Variations in pressure, temperature, and input energy were recorded. Using a discharge method, we experimentally determined the threshold pressure of the disproportionation reaction. The disproportionation reaction was photographed using two high-speed cameras, and the flame temperature was measured using the two-color temperature radiometry method. The experiment was conducted using R32 and trifluoroiodomethane (R13I1) as the disproportionation reaction inhibitors, and the suppression effect of the disproportionation reaction was evaluated.

Made available in DSpace on 2021-06-25T10:20:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-01 Purpose: Currently, there are no life cycle impact data available on the construction of road infrastructure in Brazil. This study aimed to determine several environmental impacts associated with the construction of an asphalt-paved highway in Brazil using the life cycle assessment approach and road construction data available from two Brazilian highways. The results from this study can potentially raise awareness to the importance of life cycle thinking in road construction in Brazil. Methods: The processes considered within the asphalt road pavement product system were extraction and processing of sand, gravel, and pitch; transportation of these inputs; and machinery use and operation, including direct and indirect emissions, raw materials, and electricity/fuel. Inventories available in Ecoinvent were used, and processes relevant to the Brazilian scenario were selected, with modifications made when necessary. The ReCiPe method was used to calculate the impacts, and for each category a second method was used to verify the results. The impact categories analyzed were global warming potential (GWP), terrestrial acidification potential (TAP), ozone depletion potential (ODP), freshwater eutrophication (FWEP), marine eutrophication (MEP), and freshwater ecotoxicity (FWECP). In addition, an alternative scenario was considered by substituting diesel with biodiesel in the transportation trucks. Results and discussion: Gravel production was the main contributor to TAP (56% based on ReCiPe) and MEP (62%) categories. It was also a significant contributor to the GWP (16%), FWEP (25%), and FWECP (33%) categories. Transport of raw materials was the most impactful process in the GWP (58%), FWEP (55%), and FWECP (52%) categories. Pitch production was the major contributor to the ODP category (57%). The impact from sand production was negligible for all categories. Machinery operation had a small contribution in all impact categories (less than 14%). The different assessment methods used for each category indicated similar percent contributions for all processes considered (gravel, sand, pitch, transport, and machinery). Substitution of diesel with biodiesel caused an increase in the total impact for all categories, except for ODP. Conclusions and recommendations: Gravel and pitch production, as well as raw material transport, were the most impactful processes in road construction. Therefore, strategies to reduce the impacts of road construction projects should focus on these three processes. In particular, investigation of the environmental impact, using a life cycle approach, of substituting gravel and pitch with alternative or recycled materials should be carried out for the Brazilian context. Department of Production Engineering UNESP – Universidade Estadual Paulista Department of Chemical Engineering UFSCar – Universidade Federal de São Carlos Department of Civil and Environmental Engineering UNESP – Universidade Estadual Paulista Department of Production Engineering UNESP – Universidade Estadual Paulista Department of Civil and Environmental Engineering UNESP – Universidade Estadual Paulista

Life cycle thinking analysis (LCT) was conducted on the production of vanillin via bamboo wet air oxidation compared to vanillin production from crude oil or Kraft lignin. Synthetic vanillin has been produced from crude oil and paper pulping process “waste” for nearly a century. Bamboo is quick growing, lignin rich biomass with the potential for the generation of aromatic products including vanillin. Wet air oxidation experiments were performed, using CuSO4 and Fe2O3 catalysts in alkaline environments, on raw bamboo with the purpose of determining the aromatic compound yields in order to investigate bamboo as a potential source of fine chemical products. From the LCT approach, production of vanillin from Kraft Lignin compared to crude oil has a lower environmental impact across all categories per kg produced of vanillin. Kraft lignin production of vanillin is shown to reduce smog formation and CO2 emissions from non energy sources to negligible levels while decrease acidification potential by 38 times, toxic inhalation by 18 times and toxic inhalation potential by 346 times compared to crude oil. The proposed bamboo oxidation route has the potential to have the least environmental impact with negligible impact on smog formation potential and ozone depletion potential if a green polar extractive solvent can be utilised in future while also decreasing toxicity by inhalation by a further 10 fold and ingestion by 198 fold. This work has the potential to contribute to the United Nation Sustainable Development Goal for Responsible Consumption and Production, Goal 12

According to recent Kigali amendment in 2016, ODS (ozone depleting substances) and high GWP (global warming potential) refrigerants must be phased out. There is need to find an alternative refrigerant for air conditioning applications. This article presents the performance comparison for selected low GWP refrigerants commonly used by different air conditioner manufacturers. A baseline test was conducted on a 5.2 kW air conditioner originally designed for HCFC-22 in psychrometric lab as per Indian standard IS 1391 part 1. Simulation tool was tuned and validated against the experimental results within ± 5% accuracy. Parametric analysis was done using IMST-ART tool for the best suitable configuration of compressor capacity, capillary tube, heat exchangers etc. for maximum energy efficiency. Simulation study concluded that the HFC-161 is an energy efficient and climate friendly alternative since it has zero ODP (ozone depletion potential) and ultra-low GWP of 12 except its flammability issue. European standard EN 378, specifies the limit of about 15 g/m3 for charging HFC-161 in the AC system. For HFC-161, the highest cooling capacity of 5.3 kW is achieved in case 4. The HFC-161 gave 27.2% higher EER compared to HCFC-22 system due to 26.47% lowered power consumption. Discharge temperature of HFC-161 is also lowered in the range of 70 °C to 82 °C compared to selected refrigerants. The required charge for HFC-161 was only 55% of HCFC-22.

In refrigeration technology, there is a need for alternative refrigerants that need to fulfill several requirements, such as low (or no) global warming potential, flammability, ozone depletion potential, and toxicity. While there are many substances available that could potentially be used as refrigerants, only relatively few meet all of the requirements. Pure alternative refrigerants have been studied quite extensively in the past. However, mixtures (blends) of refrigerants are not that well-studied. One of the reasons for this is that the prerequisite for an extensive screening of refrigerant mixtures is the availability of reliable predictive mixture models. In this work, we investigate typically used mixture models for a simple refrigeration cycle (split air conditioner with internal heat exchanger) and compare their predictive performance with the results of reference multi-fluid mixture models for three binary mixtures with different mixing behavior, i.e., R-410a, R-421a, and R-507a. We found that regarding coefficient of performance (COP), heat exchanger performance parameter, and volumetric cooling capacity, the largest differences between the models have been observed in the prediction of the heat exchanger performance parameter. For the studied systems, the COP and heat exchanger performance parameter are mostly influenced by the pure fluid equations of state used, while the volumetric cooling capacity depends more on the choice of the mixture model. Furthermore, some models yield results for some of the studied performance parameters that are in very good agreement with the reference model, although the prediction of thermophysical properties deviates significantly from the reference model.

The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable alternatives to replace conventional R134a, which can be beneficial for climate change. Most of the experimental and numerical investigations have been conducted to explore supercritical water, carbon dioxide and R134a as heat transfer working fluids. Hydrofluoroolefin (HFO) and refrigerants blends have been considered the most environment-friendly refrigerants to replace Chlorofluorocarbons (CFCs), Hydrochlorofluoro-carbons (HCFCs) and Hydrofluorocarbons (HFCs). Their main advantage of zero Ozone Depletion Potential (ODP) and comparatively lower Global Warming Potential (GWP) have attracted growing amount of attention to mitigate environmental issues. This work adopts the computational method and takes the environmentally friendly refrigerants to investigate the heat transfer characteristics under widely used shear-stress transport (SST) model. A comprehensive comparison was performed at reduced pressure of 1.10 for supercritical fluids R515A, R1234ze(E) and R134a. The peaks of heat transfer coefficient occurred in the vicinity of pseudo critical temperature for all of these considered fluids; however, R134a resulted in higher heat transfer coefficient, Reynolds number and Prandtl number in comparison with R515A and R1234ze(E). The higher heat transfer coefficient of supercritical fluid R134a is owing to its thermophysical properties and the specific heat plays crucial role in the heat transfer of supercritical fluids. Owing to environmental issues, R515A can be a considerable replacement of R134a. R1234ze(E) is also promising alternative to R134a; however, safety issues should thoroughly concern its mild flammable characteristics.

Refrigeration and air-conditioning play an important role in our life and industrial applications. They have great impact on our life. They have also contributed to the world’s major environmental issues like ozone layer depletion and global warming. Common refrigerants such as CFCs and HCFCs which are working as fluid in refrigeration cycles have unfavorable environmental impacts and this has brought about concerns and regulations prohibiting their production and use as refrigerants by the year 2030. The development of different refrigerants over time took place based on safety and environmental impact issues. This paper, presents the selection of optimal working fluids for Vapor-Compression Refrigeration Cycle (VCRs) based on computer aided molecular design (CAMD) and process optimization techniques. The resulting methodology utilizes from CAMD for the generation of optimum working fluid candidates. Candidates were evaluated as alternative refrigerants for the R134a refrigerating system through simulation using Aspen Hysys V8.0, with restricted by priority coefficient of performance COP, environmental and safety criteria. Ethyl trifluoromethyl ether 1,1,1-TrifluoroButane (new refrigerant) shows a good environmental and toxicity data also have high COP, 4.5, 2.7 respectively and were favored amongst the studied refrigerants as the choice alternative refrigerants to replace R134a. The methodology systematically identified conventional molecular structures that enable optimum VCRs process performance.

Hydrogen is considered an important energy carrier and fuel within the context of sustainable energy technologies. However, finding the ways to produce hydrogen in a more nature-friendly manner is vital while increasing the use of hydrogen in energy applications. In the current study, environmental impacts of five different hydrogen production options via nuclear energy are comparatively assessed through a life cycle assessment (LCA) technique in five impact categories; abiotic depletion potential (ADP), acidification potential (AP), global warming potential (GWP), ozone depletion potential (ODP), and human toxicity potential (HTP). Required thermal and electrical energy for production processes are supplied from nuclear power plants (NPPs). Energy and material inputs for production processes are defined. For the extensive LCA calculations, a powerful software is employed. According to the LCA study results, the GWPs of employed hydrogen production methods, namely high temperature electrolysis (HTE), conventional electrolysis (CE), 3-,4-, and 5-step Cu–Cl cycles, are 0.4768, 0.7071, 1.320, 1.201, and 1.346 kg CO2 eq per kg of hydrogen respectively.

The aim of this study is to quantify and compare the environmental impact from cradle-to-gate of different systems for building floor rehabilitation. The Life Cycle Assessment (LCA) method was used for the evaluation of the potential environmental impact of the production of each floor system in eight categories and a monetisation method was used for the weighting of the results and for their expression into one single indicator. Five functionally equivalent (from a structural standpoint) systems were assessed, including: (i) traditional solutions, such as timber floors and reinforced concrete (RC) slabs; (ii) less conventional solutions, such as beam-and-block and steel–concrete composite slab systems; and (iii) an innovative glass fibre reinforced polymer (GFRP) sandwich panel system. The environmental impacts of these systems are compared in this paper for the first time. It was found out that timber is the most environmentally friendly solution, since it presents the lowest total values in all environmental impact categories (under 1% of the impact of the solution with highest impact in each category, RC or GFRP), except for primary renewable energy consumption, for which the RC solution presents the least consumption. On the other hand, it was found out that: the steel–concrete composite floor is the least environmentally friendly solution in abiotic resource depletion; the RC solution is the least performing option in terms of global warming potential and ozone depletion potential; and the GFRP system presents the worst behaviour in five environmental impact categories – non-renewable energy consumption, photochemical ozone formation potential, acidification potential, eutrophication potential and Eco-costs. However, if the most important inefficiencies identified during the production of the latter floor system are at least partly amended, its impacts would be substantially reduced, particularly regarding the Eco-costs indicator, which considers four environmental categories at once – in that case, the RC solution would become the worst solution and GFRP sandwich panels would have an aggregated result of 80% of the RC. The final part of the paper presents a qualitative assessment of the gate-to-grave performance of the different solutions.

Difluoromethane (R32) as a refrigerant with zero ozone depletion potential and low global warming potential has received extensive attention in the refrigeration industry. The phase behavior of ref...

Within the context of the HVAC sector decarbonization, the market of solar driven heating and cooling systems has expanded significantly over the last years. The ZEOSOL system has as its key principle the coupling of a 12.5 kWc hybrid zeolite-water adsorption chiller with a 40 m2 solar field of vacuum tube collectors. The impact assessment has been conducted using ReCiPe 2016 method, using as reference system a conventional reversible heat pump of equal cooling capacity. The analysis indicated that the ZEOSOL system has a smaller environmental footprint in terms of impact categories such as global warming and ozone depletion potential, with a 51.2% and a 37.4% decrease of the equivalent emissions in comparison with the reference respectively. This is mainly due to the significant reduction in electricity consumption, given its high solar fraction, in contrast with the grid driven conventional system. On the other hand, the examined system performs worse in impact categories such as eco-toxicity and mineral resources scarcity, as a result of the use of large masses of copper based materials, mainly for pipelines and the solar field. On the contrary, the conventional system uses significantly less materials and therefore has better performance in the influenced categories.

Since the 1987 Montreal Protocol, chlorinated refrigerants (CFCs and HCFCs) have been pointed out as responsible for the destruction of the ozone layer. The chemical industry has realized suitable replacement for CFC-12 and for HCFC-22 e.g. HFC-134a, HFC-404A, HFC-410A, HFC-507. This generation of refrigerants developed by the chemical industry can be characterized by the no ozone depleting potential and long atmospheric lifetime resulting in global warming potential. The contribution of the HFCs to the global warming brings up to discussion whether the HFCs should be considered as a transitional substance. Historically the use of natural and ecologically safe refrigerants was a strategy to eliminate environmental problems and avoid uncertainties with synthetic replacement fluids. Since ammonia is toxic, carbon dioxide provide high pressure, and the hydrocarbons are flammable, the general conclusion is often drawn that natural fluids gave safety problems. This paper will describe the possibilities of application as working fluids in low-temperature engineering refrigeration, heat pumping and organic Rankine cycles of the hydrofluoroolefins (HFOs) as third generation of synthetic working fluids.

A power generation scheme based on biomass integrated gasification combined cycle (BIGCC) has emerged as a potentially high-efficiency and environmentally friendly power system. However, a life cycle assessment (LCA) of BIGCC systems with different technology options has not been performed to date. This study provides LCA of eight BIGCC systems, which examines technical alternatives of biomass gasification, syngas combustion, and CO2 emission control. This study uses OpenLCA software according to the CML (Center of Environmental Science of Leiden University) 2015 impact assessment method. Results show BIGCC systems’ global warming potential (GWP) is lower than 240 kg CO2-eq/MWh, which is negative when BIGCC systems integrate with CO2 capture and storage technology. Furthermore, the external syngas combustion method has lower GWP, human toxicity potential, and ozone depletion potential than the internal syngas combustion technology, and the Selexol CO2 capture process is cleaner than the MEA CO2 capture method. Moreover, sensitivity analysis illustrates plant construction and energy efficiency have larger impacts on the environmental indicators of BIGCC plants than other parameters. Finally, uncertainty analysis indicates that BIGCC systems have a high potential to reduce the emissions from the mixed electricity grid of European Union of 27 Member States (EU27).

The air source heat pump water heater (ASHPWH) is an efficient and environmentally friendly system that is widely used in China. In this study, a refrigerant mixture R290/R600a/R13I1 with low global warming potential (GWP) and no ozone depletion potential (ODP) is proposed as drop-in replacement for R134a in ASHPWH. A theoretical model for an ASHPWH is developed based on MABLAB linking with REFPROP. The cycle performances of the proposed mixture, a contrast mixture, and R134a are analyzed under different working conditions, to investigate the feasibility of substitution. The annual performances of the ASHPWH that uses different refrigerants are also studied for comparison. The results show that compared with R134a, the proposed mixture has better performance with lower condensing pressure and compression ratio, and higher specific heating capacity and coefficient of performance (COP). The discharge temperature is also reasonable. Therefore, it is feasible to replace R134a with the proposed mixture. The ASHPWH using the proposed mixture has obvious advantages when the ambient temperature is very low. The annual average COP with the proposed mixture is 4.65, which is about 6.2% higher than with R134a, and the total equivalent warming impact (TEWI) can be reduced by 18.99%.

The aim of this study is to investigate the effect of low global warming potential refrigerants on the optimum intermediate pressure (POPT,int) and performance (COP) values of a refrigeration system with flash intercooling. For realize, the optimum operating parameters of system were determined in low temperature applications through a theoretical analysis according to the different refrigerants (R290, R404A, R407C, R507A, and R22). The theoretical modelling of system is done by optimizing the intermediate pressure at given evaporation (TE) and condensation (TC) temperatures for selected refrigerants. After optimization, the maximized values of COP and Second law efficiency are computed from the predicted values of POPT,int . The linear regression method is then used to derive three correlations of POPT,int , maximum values of COP and Second law efficiency according to TE and TC. Hence, the POPT,int values maximizing the system performance are found from various TE and TC values for each refrigerant. Due to calculations, increasing TE and TC cause the increase in POPT,int in low temperature applications. The R507A system has the highest POPT,int values and R22 system has the lowest POPT?int values. Although R22 system has slightly more efficient than R290 system, it is being phased out world?wide because of the risk of ozone depletion potential and global warming potential considerations. Therefore, it is important to evaluate the R22 replacement options. The R290 was discovered to have better performance than the R404A, R407C and R507A systems in terms of COPmax (1.81), global warming potential (11), and ozone depletion potential (0) when TE and TC are -35?C and 40?C.

The boiling heat transfer of refrigerants on these surfaces generates more active nucleation sites and it depends on the properties of refrigerants and surface materials. Heat improvement consequence within the boiling heat transfer mainly depends on thermo-physical features of material & the working fluid, modification of surface techniques, thin-film (nano-scale, micro-scale, macro-scale surfaces, and hybrid scale), coating method, working fluid (water or refrigerants) and additives for fluids. This paper describes the current investigations on hydrofluoroolefin (HFO) refrigerants in pool boiling heat transfer. In boiling heat transfer process, a heat enhancement depends on the solid surfaces materials (surface design, surface geometry, surface material, surface finish condition), working fluid (water and refrigerants) and fluid additives, etc. Heat transfer enhancement improves the system performance of the thermal system and reduces the size of heating applications parts. In recent years, refrigerant emissions have become a serious concern as it is responsible for depleting the ozone layer. Under this circumstance, HFO refrigerants are considered as an alternative of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Hydrofluoroolefin (HFO) refrigerants have some excellent properties such as zero ozone depletion potential (ODP), low global warming potentials (GWP), low toxicity, mild flammability (manageable) and same system performance as HFCs for any surface tested. Based on the literature review, this paper proposed a brief future study to identify existing shortcomings.

This study carried out the “cradle to the gate” Life Cycle Assessment (LCA) of two Polyethylene Terephthalate (PET) bottle recycling routes in a Brazilian context: 1) production of Post-Consumer Recycled PET (PET-PCR) by the bottle-to-bottle (B2B) process; 2) production of Recycled Polyester Fiber by the bottle-to-fiber (B2F) process. Primary data are all real data from a recycling unit in Minas Gerais State, Brazil – a highlight of this work; secondary data were given from the literature and LCA databases. The environmental impact indicators evaluated were: Global Warming Potential (GWP), Abiotic Resource Depletion (ARD), Terrestrial Acidification, Water Scarcity, Ozone Depletion Potential and Freshwater Ecotoxicity. Methodologies recommended for the Brazilian context were used for the impact assessment. A comparison between B2B and B2F was done: in five of the seven categories evaluated, B2F had a greater environmental potential impact; however, both show a lower impact than virgin PET. Related to similar products, results were compared with those of studies for other regions, for GWP and ARD, fossil, transportation characteristics such as average distance and load, resulting in impacts of the same order except when only transportation is analyzed. Environmental hotspots were related to diesel consumption in bottle logistics, and to the consumption of natural gas and electricity in industrial recycling processes. Improvement opportunities were identified, and proposals were discussed. The impact on changing bottle logistics was achieved by resizing PET-bottle bales, using more appropriate vehicles, and adopting transport distances compatible with international practice.