Abstract

Cold plates are one of the most commonly used cooling methods in compact electronics circuits. This cooling system operates through conduction and forced convection heat transfer. To identify the optimum design of a cold plate that can dissipate up to 100 W/cm2 of heat generated from an electronic chip, three models are proposed and analyzed theoretically. Star CCM and EES program are used to conduct the simulation. In model 1 and 2, the cold plate material is Aluminum, while Copper is used in model 3. The use of thermal interface material (TIM) was also investigated and compare to a similar model without TIM. In addition, the effects of various design parameters on the junction temperature have been studied. The results show that using Copper as a cold plate material with a pipe diameter of 8 mm have resulted in 16.3 % reduction in junction temperature compared to model 1. The validation is performed by comparing results obtained from both software for model 1 without TIM, which showed a good agreement between them

Abstract

The redevelopment of the existing building stock is essential to reach sustainability goals, worldwide. The energy retrofit measure analyzed in the study is based on the installation of a double skin facade with the integration of transparent photovoltaic on a structural exoskeleton that has the function of providing the building with a higher level of structural and seismic safety. The examined building is an Italian typical building construction of the 60s and 70s, i.e., it represents an archetype building and not a real building. After carefully collecting the input data, the graphical software DesignBuilder® is used to model the building geometry and the HVAC systems, while EnergyPlus software is used for dynamic energy simulation. The model is validated against the energy need for the type of reference buildings. Initially, the effect related to the double skin façade is assessed, and then a gradual inclusion of the transparent photovoltaic is implemented. Therefore, the energy benefit, in terms of primary energy consumption, due to the combined use of the two technologies is evaluated. When PV panels cover the entire area of the external facade, a saving of 55% in primary energy consumption is achieved.

Abstract

Metal hydride based thermal energy storage system is regarded as a promising method due to its good reversibility, low cost, and no by-product. Multi-phase heat exchange has much higher heat transfer coefficient than single-phase fluid heat exchange, thus facilitating the steam generation. In this study, a two-dimensional model of the metal hydride reactor using multi-phase heat exchange is proposed to estimate the performance and its feasibility of application in the concentrated solar power system. The results show that the velocity of theheat transfer fluid should match well with the thermal conductivity of the metal hydride bed to maintain the heat flux at a relatively constant value. The match of thermal conductivity of 3 or 5 W/(m·K) and fluid velocity of 0.0050 m/s results in the heat flux up to about 19 kW/m2, which is increased by 3 orders of magnitude than single-phase heat exchange. This study helps to facilitate the widespread application of metal hydride based thermal energy storage system in the concentrated solar power system.

Abstract

For the remaining useful life prediction of lithium-ion batteries, the reliability of the features and the validity of the regression algorithm used to construct the prediction model are very important to the prediction results. For this reason, this paper proposes a prediction method based on AdaBoost-support vector regression. First, 9 features are extracted from the battery aging data, and the correlation between features and RUL is verified. Then, the random forest is used to select the extracted features to improve the reliability of the features. Finally, based on the selected features, the prediction model of RUL is established by using AdaBoost to optimize the support vector regression model. The validity of the proposed method is verified in NASA lithium battery data set.

Abstract

Improving the large-scale renewable energy accommodation plays an important role in accelerating energy transformation and optimizing energy consumption structure, which has outstanding economic significance and environmental benefits. China’s vast territory and the renewable resources are rich in the northwest, southwest, northeast, north China. This paper reviews the current accommodation status of renewable energy in China and its methods of improvement in power and thermal systems related in recent research. In latest years, the renewable energy curtailment problems have become more and more serious due to that the existing power systems are not able to absorb the renewable energy with intermittence and randomness. Hence, several methods are proposed to improve the flexibility of power systems, which is needed for the renewable energy up to the power grid. Some of researchers proposed methods in the field of power systems, such as electric storage, power-to-X, virtual power plants, power demand side management, etc. Some of others developed methods in the field of thermal systems, which is closely related to the power systems, such as by-pass auxiliary heating, active heat storage, passive storage, ice thermal storage, etc. Different approaches are compared comprehensively and it is found that only seeking methods within power systems is not enough. Thermal systems contain great flexibility which can be utilized in the power systems. Key issues of research lies in developing combined heat and power dispatch with fully consideration of the operation constraints and performance evaluation index for the power and thermal systems.

Abstract

Raceway ponds with paddlewheels are widely used in mass algae cultivation. Algae sedimentation in the long straight part of the pond is a challenge due to poor vertical mixing of water flow in this section. In order to enhance vertical mixing, a novel algae pond with serpentine path was proposed previously as an alternative design to the paddlewheel raceways. However, the water mixing characteristics in the novel pond have not been thoroughly investigated and need to be quantitatively evaluated. Moreover, the important key design parameters including the dam number, dam length, and baffles should be optimized to enhance vertical water mixing and reduce dead zone area. The present study developed a 3D numerical model of water flow in the pond and studied the effects of dam number and dam length on the dead zone area, retention time and light/dark cycles.

Abstract

In this study, with a rectifier grid upstream of ammonia injection grid (AIG), a three-dimensional CFD model was established to optimize the flow field. The effect of the installation height, rectifier grid spacing and plate height on the flow field were investigated. The results show that the uniformity of flow field is improved as the distance between rectifier grid and AIG upstream section decreases. Reducing the grid spacing at high-velocity region is also a valid way to improve the flow field. In addition, the plate height of 200 mm is selected for better performance in optimizing the flow field. Besides adding curved plates at the corner, a suitable rectifier grid arranged upstream of AIG can effectively improve the flow field as well.

Abstract

The electric bus (EB) has been widely recognized by the public in recent years because of low noise, high driving stability and zero emission. However, EB still has short driving range due to the on-board battery technology. In such condition, the drivers has the driving range anxiety and they dare not turn on the air conditioner (AC) during the operation. To solve this problem, a model is developed to optimize the AC usage of each trip for a given EB. The impact of environmental temperature and AC usage on the coach temperature is quantified. The energy consumption of each trip is estimated based on filed collected data. A chance constrained programming model is then developed considering the stochastic travel times. Maximizing total travel time of the trips that can provide comfortable temperature for passengers is taken as the objective function. Finally, a real bus route is used to validate the proposed method. Results show that the method can provide reliable AC usage scheme under the impacts of stochastic travel times.

Abstract

This paper focuses on the parameter optimization and economic performance comparison of single-pressure steam cycle (SRC), dual-pressure steam cycle (SDC) and steam flash cycle (SFC) based on the waste heat source with initial temperature of 400-700℃ and mass flow rate of 40kg/s. We take the heat exchanger area per unit power output (APR) as the economic evaluation index and use genetic algorithm (GA) for optimization. The derivation of the formulas shows that as the pinch point temperature difference between the flue gas and working fluid increases, the APRs of SRC, SFC and SDC decrease accordingly. The APRs of SFC and SDC are higher than that of SRC, which is due to the fact that the effect of the increase of total heat exchanger area caused by the SDC and SFC is greater than that of the increase of net power output. With the increase of the initial temperature of flue gas, the optimum APRs of SRC, SFC and SDC decrease accordingly and the degree of decline gradually decreases. When the initial temperature of flue gas reaches 700℃, the optimum APRs of SRC and SFC increase slightly.

Abstract

The microstructure of the catalyst layer has a great influence on the performance of the fuel cell. Industrial camera and optical microscope are used to observe the drying process and deposition of catalyst inks, and electrochemical tests are performed by linear sweep voltammetry. The focus is on the drying kinetics of the catalyst ink with different isopropyl alcohol (IPA) contents in the solvent and the effect on the formation of the microstructure. Experiments have found that the deposition height is symmetrical in the diameter direction. A coffee ring is formed at the edge of the deposition, and the slender aggregates are arranged in the shape of petals inside the edge. As the IPA content decreases, the deposition becomes more uneven, the circulatory flow is gradually activated, and a large number of particles run from the edge of the droplet to the center.