417 research outputs found

    Recent research developments in polymer heat exchangers: a review

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    Due to their low cost, light weight and corrosive resistant features, polymer heat exchangers have been intensively studied by researchers with the aim to replace metallic heat exchangers in a wide range of applications. This paper reviews the development of polymer heat exchangers in the last decade, including cutting edge materials characteristics, heat transfer enhancement methods of polymer materials and a wide range of polymer heat exchanger applications. Theoretical modelling and experimental testing results have been reviewed and compared with literature. A recent development, the polymer micro-hollow fibre heat exchanger, is introduced and described. It is shown that polymer materials do hold promise for use in the construction of heat exchangers in many applications, but that a considerable amount of research is still required into material properties, thermal performance and life-time behaviour

    Evaluation of Suitability of a Parametrically Controlled Louvers for Various Orientations throughout a Year Comparing to an Existing Case

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    Nowadays, daylighting systems and shading devices are controlled automatically to achieve their optimum benefits. For more comprehensive accuracy, parametric control was recently used to manage complex parameters with more accuracy. Such a system was proposed and investigated in a previous research to provide steadier and more uniform daylight illuminance during the day and reduce more than 80% of the electricity consumption. This study is examining the daylighting performance by using the parametric system in different orientations and comparing with the conventional ones. Furthermore, the study will evaluate the suitability of the parametric system throughout the year during the working hours in a typical office room

    A feasibility study of a novel combined solar concentration/wind augmentation system

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    For deeper understanding of the formation of elite at enterprises, the article proposed to consider a hierarchy of an enterprise from the point of view of two main factors: social and organizational-occupational status.It was determined that the status of an individual in the structure of an enterprise is an integral characteristic, based on the synthesis of hierarchical aspects of organizational structure of an enterprise. It was noted that the current establishment at an enterprise is characterized by a position of an individual in the system of interpersonal relations, his/her rights, duties and privileges.As a social status, we suggested the amount of power, social perspective of the status and prestige of an individual. It was emphasized that the organizational-occupational status of the elite is characterized by different levels of management.It was noted that at enterprises each element serves to meet corresponding challenges to achieve a common goal. It was concluded that the structural-functional approach provides the possibility of further system analysis of the elite at enterprises.В статье рассмотрены проблемы становления элиты на современном предприятии с позиции социального и организационно-профессионального статуса. Определено, что статус индивида в структуре предприятия является интегральной характеристикой, основу которой составляет синтез иерархических аспектов организационной структуры предприятия. Отмечено, что современный истеблишмент на предприятии характеризуется позицией индивида в системе межличностных отношений, его прав, обязанностей и привилегий.У статті розглянуто проблеми становлення еліти на сучасному підприємстві з позиції соціального та організаційно-професійного статусу. Визначено, що статус індивіда в структурі підприємства є інтегральною характеристикою, основу якої складає синтез ієрархічних аспектів організаційної структури підприємства. Зазначено, що сучасний істеблішмент на підприємстві характеризується позицією індивіда у системі міжособистих відносин, його прав, обов’язків та привілеїв

    Effect of different carrier gases on productivity enhancement of a novel multi-effect vertical concentric tubular solar brackish water desalination device

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    A novel multi-effect vertical concentric tubular solar brackish water desalination device is introduced in present study. The device consists of four closely spaced concentric pipes, in which the feed water gets preheated by hot brine water to guarantee the evaporation efficiency. An experimental investigation and analytical analysis were carried out to signify the effect of carrier gas-water vapor mixture on productivity enhancement of the device. Different carrier gases were used in the performance evaluation: carbon dioxide, helium, nitrogen, oxygen, air and argon. The water yield and the top/bottom temperature values of condensation surface of the device with different carrier gases were tested. In addition, the present investigation is presented an approach to predict the theory yield based on the internal heat and mass transfer mechanism. The experimental results indicate that, when the heating temperature is 80 °C and the carrier gas is helium, the water productivity rate can reach to 1.19 kg/h. It is increased by 30.76% than the carrier gas of air. The numerical results had been calculated and a consistent agreement with the experimental results had been obtained of different operation temperatures. The Dv under different heating temperature were obtained according to the experimental results

    Thermodynamic and economic investigation of a screw expander-based direct steam generation solar cascade Rankine cycle system using water as thermal storage fluid

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    Solar electricity generation system (SEGS) which employs cascade steam-organic Rankine cycle (SORC) and steam screw expander (SE) is promising due to the high efficiency at moderate heat source temperature. This paper puts a special emphasis on heat storage and thermo-economic evaluation. Preferable operating temperature of the system is first clarified on the basis of SE characteristics. The temperature-dependent permissible stress of steam accumulator is modelled and the capital cost is investigated. Comparison between the direct steam generation (DSG) SEGS and an indirect one using thermal oil is made at a power capacity of 1 MW and storage of 6.5 h. The results indicate the DSG system has both thermodynamic and economic superiorities. The hot side temperature (THTH) of SORC generally does not exceed 250 °C to achieve an optimum solar thermal power efficiency. Given radiation of 750 W/m2, the maximum efficiency (ηT,mηT,m) is 14.3% with a corresponding THTH around 240 °C. The material cost of pressure vessels is 2.55 million RMB. For the indirect system, the optimal THTH is about 230 °C and ηT,mηT,m approximates to 13.2% and the estimated oil cost is 7.92 million RMB. It is recommended to adopt steam accumulators in the SE-driven SEGS

    An Investigation into the Potential of Hosting Capacity and the Frequency Stability of a Regional Grid with Increasing Penetration Level of Large-Scale PV Systems

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    It is widely believed that the incorporation of renewable energy to the current power grid is the way forward in achieving sustainable power generation. Currently, with the reduction of PV prices, many countries have started connecting PV systems into their grid network, hence leading to a sharp increase of the penetration levels of renewable electricity production. This will bring significant change in the load pattern and the ramping requirements of the grid’s conventional generation system due to the varying nature of the renewable energy generation. This significant change affects the stability of the grid frequency because it becomes more challenging for the system operators to maintain the equilibrium between the generation and load. Additionally, this significant change affects the PV system potential hosting capacity of the traditional grid because of the PV system’s curtailment in order to comply with the constraints of the grid’s conventional generation system. In this paper, the net load, grid frequency stability, and grid potential hosting capacity are evaluated in the situation of increasing the penetration level of large-scale PV systems generation into the grid. The results show that the grid operators will face increasingly variable net load patterns and steeper ramping events as the PV system penetration level increases. Additionally, the results show the requirement of having flexibility measures that target each grid constraint as the PV system penetration level increases

    Identification of Potential Barriers to Electric Vehicle Adoption in Oil-Producing Nations—The Case of Saudi Arabia

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    Electric vehicles (EVs) are important elements in the global strategy to tackle climate change; however, research often fails to sufficiently identify the range of barriers which affect their adoption. Taking Saudi Arabia as a case study, this paper analyses responses from 698 potential drivers in order to identify and rank the infrastructure, performance, financial, social, and policy barriers to EV adoption in a major oil-producing nation with a hot climate and a desert terrain. According to this study’s findings, the most important barriers in this context are the lack of charging infrastructure and the additional load placed on the national grid, while others include the safety and effectiveness of batteries at high temperatures, and the ability of EVs to perform in desert conditions. Common themes also include concerns that EVs may damage Saudi’s oil-based economy, cost of purchase and maintenance, low resale value, and the absence of awareness about EVs. The study concludes that EV manufacturers must demonstrate that their vehicles are suitable for the Saudi climate. Governments should also provide subsidies, or other incentives, to promote adoption of EVs as the study also found that variations in the cost of different EV models in Saudi Arabia, for example, the Tesla Model 3, is up to 40% more expensive to own than a Toyota Camry, mean that owning EVs can cost significantly more than small sized internal combustion engine-based vehicles (ICEVs). This paper identifies and ranks the barriers to EV ownership in a desert nation which is a leading petroleum producer and compares the relative costs of EVs and ICEVs in the country. As such, it has immediate relevance in countries with similar economic, geographic, and climatic conditions

    The study of a seasonal solar cchp system based on evacuated flat-plate collectors and organic rankine cycle

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    The demands of cooling, heating and electricity in residential buildings are varied with seasons. This article presented a seasonal solar combined cooling heating and power (CCHP) system based on evacuated flat-plate collectors and organic Rankine cycle. The heat collected by evacuated flat-plate collectors is used to drive the organic Rankine cycle unit in spring, autumn and winter, and drive the double-effect lithium bromide absorption chiller in summer. The organic Rankine cycle condensation heat is used to yield hot water in spring and autumn, whereas supply heating in winter. The system thermodynamic performance was analyzed. The results show that the system thermal efficiency in spring, autumn and winter, ηsys, I, increases as organic Rankine cycle evaporation temperature, T6, and evacuated flat-plate collectors outlet temperature, T2, decrease. The maximum ηsys, I of 67.0% is achieved when T6 = 80 °C and T2 =100 °C. In summer, the system thermal efficiency, ηsys, II, increases first and then decreases with the increment of T2. The maximum ηsys, II of 69.9% is obtained at T2 =136 °C. The system output performance in Beijing and Lanzhou is better than that in Hefei. The average output power, heating capacity, hot water and cooling capacity are 50-72 kWh per day, 989-1514 kWh per day, 49-57 ton per day and 1812-2311 kWh per day, respectively. The system exergy efficiency increases from 17.8-40.8% after integrating the organic Rankine cycle unit

    Numerical and lab experiment study of a novel concentrating PV with uniform flux distribution

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    The uniform illumination profile that falls on the PV cell is good for PV output and lifespan, however the flux distribution of the concentrating PV appears to be non-uniform in most cases which is harmful for the overall performance of the concentrating photovoltaic. In order to overcome this disadvantage, a novel asymmetric compound parabolic concentrator concentrating PV with uniform flux distribution is proposed in this paper. A two-dimensional finite element model is built for electrical performance simulation of the concentrating photovoltaic module. The prototype of the concentrating photovoltaic module is manufactured and assembled to conduct the indoor lab experiment under Standard Test Condition to verify the feasibility and reliability of the model. The outdoor experiments are conducted to show the electrical performance of the concentrating photovoltaic module under the real weather condition. Then the model is used to analyze the electrical performance of the PV cell under the flux distribution created by the proposed concentrator. The results show that the electrical performance of the proposed concentrating photovoltaic module is close to that under the uniform flux distribution with the same total radiation level, which confirms that the proposed concentrator is beneficial for the PV output under concentrating illumination due to uniform flux distribution
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