No abstract

Li-ion batteries (LIBs) are being used extensively in a wide range of applications owing to the facile preparation technology as well as a high energy density, which exceeds those of other commercial batteries. However, LIBs alone cannot satisfy the burgeoning energy demand due to Li-resource constraints.Recently, K-ion batteries (KIBs) have garnered the interest of the scientific community as promising alternatives for LIBs due to the abundance of K resources, the affordability of K, and its superior electrochemical properties. However, the development of KIBs is hindered by the slow development of appropriate anode materials that can accommodate the repeated intercalation/ deintercalation of large K ions without sustaining significant structural damage. Thus, the development of appropriate anode materials is crucial for the realization of practically viable KIBs. Carbon nanomaterials are promising anode materials due to their remarkable potassiation/depotassiation ability, structural stability, and structural evolution from zero to three dimensions. It is anticipated that an evaluation of the recent advances in carbon and their composites anode materials for KIBs can facilitate the development of practically viable KIBs. This review comprehensively discusses recent developments in carbonaceous and their composites as anode materials for KIBs and provides a prospective for the next research step.

No abstract

In the present work, the freezing and melting characteristics of water seeded with chemically functionalized graphene nanoplatelets in a vertical cylindrical capsule were experimentally studied. The volume percentage of functionalized graphene nanoplatelets varied from 0.1% to 0.5% with an interval of 0.1%. The stability of the synthesized samples was measured using zeta potential analyzer. The thermal conductivity of the nanocomposite samples was experimentally measured using the transient hot wire method. A ~24% (maximum) increase in the thermal conductivity was observed for the 0.5% volume percentage in the liquid state, while a ~53% enhancement was observed in the solid state. The freezing and melting behavior of water dispersed with graphene nanoplatelets was assessed using a cylindrical stainless steel capsule in a constant temperature bath. The bath temperatures considered for studying the freezing characteristics were −6 °C and −10 °C, while to study the melting characteristics the bath temperature was set as 31 °C and 36 °C. The freezing and melting time decreased for all the test conditions when the volume percentage of GnP increased. The freezing rate was enhanced by ~43% and ~32% for the bath temperatures of −6 °C and −10 °C, respectively, at 0.5 vol % of graphene loading. The melting rate was enhanced by ~42% and ~63% for the bath temperatures of 31 °C and 36 °C, respectively, at 0.5 vol % of graphene loading.

In this work, the experimental investigation on the performance and exergy analysis of mobile air conditioning system with suction line heat exchanger using environmental friendly HFO-1234yf was carried out under varied evaporator air flow rates. The performance was compared with existing HFC-134a results. The performance analysis showed that the cooling capacity and the coefficient of performance of the system with HFO-1234yf were lower than that of the HFC-134a by upto 2–11%. The power consumption and the volumetric efficiency of the compressor with HFO-1234yf were found to be 14.02% and 11.2% higher than that of HFC-134a. From the exergy analysis, it was observed that the major exergy destruction occurred in the compressor, followed by the condenser, evaporator, thermostatic expansion valve, and suction line heat exchanger for both refrigerants. The exergy efficiency of the system with HFO-1234yf was 2.4–12.6% lower than that of HFC-134a. From this study, it was observed that the losses experienced in the compressor, thermostatic expansion valve and evaporator lead to poor performance with HFO-1234yf.