In light of the adverse environmental impact of the R134a refrigerant, replacing it with a more environmentally friendly refrigerant has become imperative than ever. This study presents an experimental investigation into the utilization of R152a and R134a refrigerants in a vapor compression refrigeration system employing a variable displacement oil-free linear compressor. The potential for the replacement of R134a with R152a was examined based on energy, environmental, and economic performance analyses. The outcomes indicated that R152a exhibited a higher coefficient of performance (COP) in comparison to R134a under identical operating conditions. Specifically, when the pressure ratio was 2.0 and the piston stroke was 11 mm, R152a's COP was 13.0% higher than R134a. It was also discovered that reducing the operating stroke and increasing the pressure ratio could effectively lower CO2 emissions and total costs. Under the 2.0 pressure ratio and 9-mm piston stroke, R134a produced 1082.4 kg more CO2 emissions than R152a, representing a 209% increase. In addition, the R152a and R134a total cost was reduced by 8.3% with the 2.5 pressure ratio and 11-mm piston stroke. Notably, the results of the current study demonstrated that R152a outperformed R134a in energy consumption, environmental friendliness, and economy in oil-free linear compressor refrigeration systems. R152a used less electric power, generated fewer CO2 emissions, and naturally reduced predicted running costs in order to maintain the same COP.
Driven by the need for solutions to address the global issue of waste accumulation from human activities and industries, this study investigates the thermal behaviors of empty fruit bunch (EFB), tyre waste (TW), and their blends during co-pyrolysis, exploring a potential method to convert waste into useable products. The kinetics mechanism and thermodynamics properties of EFB and TW co-pyrolysis were analysed through thermogravimetric analysis (TGA). The rate of mass loss for the blend of EFB:TW at a 1:3 mass ratio shows an increase of around 20% due to synergism. However, the blend's average activation energy is higher (298.64 kJ/mol) when compared with single feedstock pyrolysis (EFB = 257.29 kJ/mol and TW = 252.92 kJ/mol). The combination of EFB:TW at a 3:1 ratio does not result in synergistic effects on mass loss. However, a lower activation energy is reported, indicating the decomposition process can be initiated at a lower energy requirement. The reaction model that best describes the pyrolysis of EFB, TW and their blends can be categorised into the diffusion and power model categories. An equal mixture of EFB and TW was the preferred combination for co-management because of the synergistic effect, which significantly impacts the co-pyrolysis process. The mass loss rate experiences an inhibitive effect at an earlier stage (320 °C), followed by a promotional impact at the later stage (380 °C). The activation energy needed for a balanced mixture is the least compared to all tested feedstocks, even lower than the pyrolysis of a single feedstock. The study revealed the potential for increasing decomposition rates using lower energy input through the co-pyrolysis of both feedstocks. These findings evidenced that co-pyrolysis is a promising waste management and valorisation pathway to deal with overwhelming waste accumulation. Future works can be conducted at a larger scale to affirm the feasibility of EFB and TW co-management.
This paper presents the landscape of research on airborne microplastics and nanoplastics (MPs/NPs) according to the bibliometric analysis of 147 documents issued between 2015 and 2021, extracted from the Web of Science database. The publications on airborne MPs/NPs have increased rapidly from 2015 onwards, which is largely due to the existence of funding support. Science of the Total Environment is one of the prominent journals in publishing related papers. China, England, the USA, and European Countries have produced a significant output of airborne MP/NP research works, which is associated with the availability of funding agencies regionally or nationally. The research hotspot on the topic ranges from the transport of airborne MPs/NPs to their deposition in the terrestrial or aquatic environments, along with the contamination of samples by indoor MPs/NPs. Most of the publications are either research or review papers related to MPs/NPs. It is crucial to share the understanding of global plastic pollution and its unfavorable effects on humankind by promoting awareness of the existence and impact of MPs/NPs. Funding agencies are vital in boosting the research development of airborne MPs/NPs. Some countries that are lacking funding support were able to publish research findings related to the field of interest, however, with lesser research output. Without sufficient fundings, some impactful publications may not be able to carry a substantial impact in sharing the findings and discoveries with the mass public.