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This work proposes a novel fluid-thermal-electric multiphysics numerical model to predict the performance of thermoelectric generator systems applied to fluid waste heat recovery, with the consideration of multiphysics coupling effects of fluid, thermal, and electric fields. The comprehensive numerical simulations of the thermoelectric generator system are performed via COMSOL coupled solver. Besides, the effect of the neglect of parasitic heat on the output performance is investigated through the comparison with numerical results predicted by ANSYS and COMSOL separate solver, wherein the fluid-thermal field is computed first, then the thermal-electric field. The results show that the output power predicted by COMSOL separate solver is 8.52% lower than that predicted by COMSOL coupled solver at the inlet air temperature of 550 K and inlet air velocity of 30 m/s due to the neglect of parasitic heat. The output performance of the TEG system predicted by ANSYS is less affected by inlet air boundary conditions than that predicted by COMSOL. Finally, the experimental results show that the fluid-thermal-electric multiphysics model solved by the COMSOL coupled solver shows the lowest output power deviation of 2.81%. The proposed model can guide the numerical modeling of the thermoelectric generator system applied to fluid waste heat recovery.

Abstract Currently, electric vehicle (EV) are facing unprecedented development opportunities under the support of national policy guidelines and local governments. There is a great potential to substitute EV for internal combustion engine vehicles in the future. However, the practical applications are facing with some essential issues need to be break through, such as battery performance deterioration in some extreme climate areas and driving conditions, heat pump (HP) lower efficiency and defrosting problems under cold temperature region, and vehicle-mounted energy complementation, etc. Therefore, investigations of electric vehicle thermal management (VTM) have gaining increasing attentions in China and other countries. This paper reviewed the status of electric vehicle thermal management worldwide, meanwhile, the basic proposal for further development in the field was presented. From battery thermal management (BTM) to heating ventilation air conditioning (HVAC), a coming work should aim at more research on basic problems, such as exploration of efficient and compact liquid heat exchanger, precise and synergy control of BTM, cold and hot impact phenomena and improving method, mechanism of thermal runaway, ignition and explosion and relative inhibition method, establishment of electric vehicle integrated thermal management system, low energy consumption and frosting inhibition of HP, reutilization of vehicle-mounted energy by PCM thermal storage, and experimental and simulation analysis method system. These explorations will strengthen theoretical and practical understanding and accelerate more extensive application of EV in different regional environment.

PDMS–MWCNTs/TiO2 microparticles made by microfluidics can achieve 85% removal efficiency of RhB pollutant in wastewater via synergetic treatment.

Abstract In recent years, thermoelectric (TE) devices have emerged as promising alternative environmental friendly applications for heat pumps and power generators since the environmental issues such as the global warming and the limitations of energy resources gradually drew worldwide attentions. Due to the green feature and distinct advantages, the thermoelectric technology have been applied to different areas in an effort of designing simple, compact and environmental friendly systems. The applied areas are extended from the earliest application on kerosene lamp to aerospace applications, transportation tools, industrial utilities, medical services, electronic devices and temperature detecting and measuring facilities. The application potentials of TE in directly conversing thermal energy into electrical power have been identified, especially for where the cost of thermal energy input need not to be considered, such as waste heat utilization, in the light of the present low efficiency of thermoelectric conversion. The capability of TE in producing thermal energy (in terms of cooling or heating) with the use of electrical power is also well identified. This paper reviews the status of the material development and thermoelectric applications in different areas and discusses the difficulties in terms of the commercialisations of advanced materials. Other than this, the main purpose of this paper is to present the great potential of achieving both environmental and economic benefits by exclusively utilizing thermoelectric applications in different areas. It also comes to the conclusion that the thermoelectric applications with the current conversion efficiency are economically and technically practical for micro/small applications. However, it would be transformed to a more significant green energy solution for improving the current environment and energy issues by using medium/large scale thermoelectric applications when the thermoelectric materials with a figure-of-merit over 2 come into commercial practice.

Transport represents over a quarter of Europe's greenhouse gas emissions and is the leading cause of air pollution in cities. It has not seen the same gradual decline in emissions as other sectors. Recently, the thermoelectric power generation (TEG) technology emerges as an alternative solution to the emission reduction challenge in this area. In this paper, we present an innovative pathway to an improved heat supply into the concentric shape-adapted TEG modules, integrating the heat pipe technologies. It relies on a phase changing approach which enhances the heat flux through the TEG surface. In order to improve the heat transfer for higher efficiency, in our work, the heat pipes are configured in the radial direction of the exhaust streams. The analysis shows that the power output is adequate for the limited space under the chassis of the passenger car. Much effort can also be applied to obtain enhanced convective heat transfer by adjusting the heat pipes at the dual sides of the concentric TEG modules. Heat enhancement at the hot side of the TEG has an effective impact on the total power out of the TEG modules. However, such improvements can be offset by the adjustment made from the coolant side. Predictably, the whole temperature profile of TEG system is subject to the durability and operational limitations of each component. Furthermore, the results highlight the importance of heat transfer versus the TEG power generation under two possible configurations in the passenger car. The highest power output per repeat unit is achieved at 29.8 W per 0.45 L with a ZT value 0.87 for a Bi2Te3-based thermoelectric material in our studies. The study provides an insight into a structurally achievable heat exchanger system for other high-temperature thermoelectric materials.

Due to being solid-state, noiseless and maintenance free, thermoelectric devices have found wide applications in different areas since they were discovered over 180 years ago. The applications are concerned with environment-friendly refrigeration and power generation in transportation tools, industrial utilities, military devices, medical services and space applications. It is utilisation of waste heat in varying applications that make the modules particularly attractive. Nevertheless, despite a few academic papers, there has not been extensive use in the domestic sector. A concept of thermoelectric cogeneration system (‘TCS’) is proposed to highlight the direction for enhancing the sustainability by improving the energy efficiency in domestic sector. Compared to the thermoelectric systems used in other areas which only uses the part of converted energy but wastes the unconverted part by dissipating it into the environment, the system presented here maximally recover the available heat by generating electrical power and producing hot water simultaneously. The viability of this system concept is evaluated on a bench-scale experimental prototype. The outputs of electrical power and hot water have been investigated at different temperature difference. The cost saving potential and cost recovery period have been estimated using the available heat sources in domestic sector. The results intend to provide reference for developing the real-scale domestic thermoelectric cogeneration system and show the potential benefits.

Ground source heat pump (GSHP) facilitates the efficient utilization of renewable energy sources and energy conservation, and it is expected to be more prevalent in the future for the great potential to substitute the use of renewable energy for burning of fossil fuels. As we all know, groundwater heat pump (GWHP) and aquifer thermal energy storage (ATES) are typical forms in the area of GSHP and underground thermal energy storage (UTES) respectively. The effect of energy conservation plays an important role in the national energy strategy, but the groundwater environment has been affected and even damaged to some extent because of over-exploitation and unreasonable utilization. This paper reviewed the development from GWHP to ATES worldwide, especially in China and surveyed the situation of groundwater utilization from GWHP. It shows that lack of cognitive ability, scientific constraints and reasonable utilization may bring catastrophic damage to the groundwater resource. Future work should aim at more research on basic problems during the demonstration of applications, such as thermal interaction between pumping and injecting wells, energy transport in the field of well, groundwater contamination, etc. In fact, the characteristics and performance of unsteady and transient heat transfer in the complex underground environment of multi-wells, and their control strategies of the GWHP and ATES systems have been also the most pressing problems. Their explorations and studies will strengthen the theoretical and practical understanding, and guide an orderly, healthy and sustainable development from GWHP to ATES technologies. (C) 2014 Elsevier Ltd. All rights reserved.

Energy storage technologies (EST) facilitate the efficient utilization of renewable energy sources and energy conservation, and they are expected to be more prevalent in the future. There is a great potential to substitute the use of EST for burning of fossil fuels by using stored heat that would otherwise be wasted and using renewable generation resources. These energy sources can be used more effectively through the addition of short- or long-term energy storage, even to the seasonal thermal energy storage. Underground thermal energy storage (UTES) is one form of EST, and perhaps the most frequently used storage technology in North America and Europe. Gradually it is growing as the application of ground source heat pump (GSHP) with UTES in China. But UTES systems involve complicated unsteady processes that include energy rejection, accumulation, preservation and extraction. This paper reviewed the progress of UTES companioning with GSHP worldwide, and surveyed the development of GSHP and the origination of UTES, especially as to soil/rock UTES. Meanwhile, the basic proposal for development in the future to supply a gap in the field of UTES in China was presented. A coming work should aim to more researching basic problems during the demonstration application, such as investigation of mechanisms, characteristics and performance of the unsteady and transient heat transfer in a complex underground environment, and control strategies of the UTES system. These problems will strengthen theoretical and practical understanding and facilitate more extensive application of UTES in China.

The automotive thermoelectric generator system is a promising technology of exhaust waste heat recovery, but reasonable theoretical models to predict its dynamic performance are lacking. In this work, a transient fluid-thermal-electric multiphysics coupling field numerical model is proposed for the first time, and the model is used to evaluate the dynamic performance of a simplified automotive thermoelectric generator system under vehicle driving cycles. The transient numerical model, which takes into account the dynamic characteristics, fluid-thermal-electric multiphysics field coupling effects, and material temperature dependence, is thus far the most complete model ever. Numerical results reveal that there is a delay in output response with the change of exhaust temperature, and the change of output voltage and output power is often accompanied by the change of exhaust mass flow rate. The small and short-term fluctuation of exhaust gases has a slight influence on output performance. With the transient variation of exhaust characteristics, the output voltage and output power show more stable changes and slower responses, but the situation is the opposite for conversion efficiency. The output power predicted by steady-state numerical simulation is 12.6% higher than that of transient numerical simulation. Moreover, the proposed transient numerical model is recommended to investigate the dynamic performance of automotive thermoelectric generator systems.