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Abstract In this study, an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials (PCMs). A numerical model was built and verified based on the comparison among the present model prediction, experimental measurements, and numerical results in open literature. To highlight the novel design method, four cases including fin-PCM, foam-PCM, fin-foam-PCM, and PCM unit were compared by means of solidification features. The temperature distribution, solidification front propagation, and buoyancy-induced convection in the liquid PCM were accounted for. Numerical results demonstrated that metal foam outperformed fin regarding the improvement on solidification phase change. The combination of foam and fin achieved the best performance, leading to a 90.5% reduction in complete energy release time in comparison with the PCM unit. The proposed design method provided reference potentials for advancing energy storage engineering. However, buoyancy-induced convection in the liquid PCM before solidification was harmful to the formation of solidification front and its movement. A maximal 11.5% prolonging time for the complete solidification was found.

The thermal failure of airborne avionics equipment is not optimistic. It is very necessary to establish relatively accurate thermal models for predicting thermal response of avionics equipment under different flight conditions. Traditional thermal modeling methods are often difficult to obtain accurate temperature response in complex conditions. This has severely restricted the application of these models. However, the Stochastic Configuration Network (SCN) model based on random algorithm can weaken the heat transfer mechanism and pay attention to the mining of experimental data, so that a more accurate thermal relationship might be obtained. In this paper, the SCN was used to analyze the experimental data of the avionics pod with a Ram Air Turbine (RAT) cooling system. The thermal models based on the SCN were finally built for avionics pod. Compared with the commonly used Random Vector Functional Link Network (RVFLN) thermal models, the SCN thermal models not only inherit the advantages of simple network structure and low computational complexity, but also have some merits, such as the better learning performance and the less human intervention. The presented SCN models provide a way to predict the thermal response of avionics pod cabin under the full flight envelope for a fighter.

Carbon neutrality is an ambitious goal that has been promulgated to be achieved on or before 2060. However, most of the current energy policies focus more on carbon emission reduction, efficiency and high penetration of renewable energy. Thus, this paper presented a review strategy towards carbon neutrality by presenting the concept of a multi-energy system (MES) in terms of its technologies, configuration, modelling and feasibility as zero-emission equipment. The paper addressed some prominent challenges associated with zero-carbon multi-energy systems (ZCMES). Various proven solutions in the extant studies that have been affirmed to alleviate some of these challenges were presented. In the end, we identified and summarised the current research gaps, and the future directions to ensure the feasibility of ZCMES as a primary strategy towards the actualization of carbon neutrality. Hence, this review work serves as a reference for revising the current energy policies to incorporate a carbon neutrality framework.

In this work, a series of nanoencapsulated phase change materials (NanoPCMs) with paraffin wax (PW) as core and melamine-formaldehyde (MF) as shell were synthesized by the in-situ polymerization method. The morphology, chemical structure and thermal properties of prepared NanoPCMs were characterized by scanning electron microscope, Fourier transform infrared, differential scanning calorimetry and thermogravimertic analyzer. The results show that the PW is successfully encapsulated in the MF without chemical interaction, and the NanoPCMs present regular spherical shape with the average diameter of 260–450 nm. The encapsulation efficiency of the NanoPCMs increases with the augment of the supplied amount of core material. The maximum encapsulation efficiency of the NanoPCMs can reach up to approximately 75%. The NanoPCMs can maintain excellent thermal reliability and stability after 2000 thermal cycling. The prepared NanoPCMs can be well applied in the latent heat thermal energy storage and thermal management systems due to their remarkable encapsulation efficiency and thermal properties enable them to.

Direct air capture (DAC) is one of the most potential technologies to mitigate CO2 emission. Adsorption technology is recognized as a promising CO2 capture method in view of its desirable characteristics including reusability of adsorbents and low capital investment. To further improve thermal performance, evaporation/condensation heat of vapor compression refrigeration (VCR) cycle in air condition system of buildings is adopted for adsorption/desorption process of DAC. Thermal performance of a 4-step temperature swing adsorption process (TSA) is analyzed at various adsorption/desorption temperatures by using different adsorbents. Analysis on Coefficient of Performance (COP) of VCR cycle is also conducted in search for a balance between adsorbent and refrigerant. Taking both real working capacity and COP into consideration, Mg-MOF-74&R134a is the best choice for more amounts of CO2. Real working capacity of Mg-MOF-74 is up to 0.38 mol•kg−1 at 70 °C, which is twice as much as that of zeolite 13X. While zeolite 13X&R134a shows the best performance of two cycles in view of exergy efficiency and COP, which could reach 81.9% and 7.21, respectively, at 35 °C. These matches will provide some guidelines for the practical application of the combination of DAC with heating, ventilation and air conditioning (HVAC).

Numerous studies have demonstrated that commercial activities have significantly reduced during COVID-19, while there are few studies disclosing the consequent impacts on the energy consumption of commercial buildings. This study explores the changes in energy consumption of different types of commercial buildings in Singapore under the impact of the pandemic, using commercial building energy performance data from 2017 to 2020 (n=540). The sampled buildings include 93 hotel buildings, 303 office buildings, 106 retail buildings, and 38 mixed developments. The analysis mainly used linear regression and paired sample t-test. The results showed that relative to 2019, the mean energy use intensity (EUI) of sampled commercial buildings decreased by 56.77 kWh/m² in the pandemic year (2020), a plunge of 19.9%. The extent to which the EUI of each type of commercial building is affected by the pandemic is found as: mixed development>retail>office>hotel. The study also identified the factors that significantly influenced the EUI of commercial buildings before and during the pandemic. The results of the study complement existing knowledge about the factors influencing energy consumption in commercial buildings by considering the impact of the pandemic and furthermore contribute to the improvement of energy management in commercial buildings by providing directions for building energy efficiency approaches.

The flow and thermal breakthrough phenomenon in a forced external circulation standing column well (FECSCW) directly affects heat transfer efficiency and load-carrying capacity. A numerical model for FECSCW is developed to analyze the migration of the temperature and velocity front under the flow and thermal breakthrough. The results indicated that thermal breakthrough began after simulation running 2.5 min and was completely formed after 12 min. The inlet water, which directly entered the production well without heat exchange with the aquifer, accounted for 12.8%. When the porosity of the backfill material decreased from 0.35 to 0, the coefficient of performance (COP) of the heat pump unit increased by 1.6% on average, and the thermal breakthrough strength decreased by an average of 45.3% within 25 min. Where seepage velocity near the well wall was greater than 1 × 10−3 m•s−1, faster velocity front migration was observed, while the migration advantage of the temperature front was more prominent outside of this region. Through quantitative analysis of flow and thermal breakthrough, temperature and velocity front migration, and COP change of heat pump unit, theoretical suggestions were provided for the thermal transfer mechanism near the thermal well wall. The extended research in this study can be applied to the design and optimization of forced external circulation standing column well system.

Recently, the requirement for cooling capacity decreased when the driving energy changed from liquid fuel to lithium batteries. Therefore, the structure and location of the forecabin could be adjusted based on the aerodynamic performance. The current study conducted a significant number of simulations in order to find out the effects of the internal flow through forecabin in an Ahmed body. The following conclusions have been identified:1, The flow through the forecabin would always increase the resistance of the entire body, and the drag coefficient increases, on average, by approximately 85%. 2, When the aspect ratio is higher or the position of the inlet opening is lower, the total drag coefficient is lower due to a weaker vortex strength, a simpler vortex structure and a relatively simple flow. 3, The existence of the forecabin will largely increase the oscillation frequency of the flow field by approximately 15 times compared to the original Ahmed model. Finally, the high drag coefficient moment always appears to be due to the formation of more complex or intense vortex motion. These conclusions can offer useful results and references for the structural design of the front cabin for new energy vehicles.