Journal articles on the topic 'Stable heat load'
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1
Трушляков, Євген Іванович. "МЕТОДОЛОГИЧЕСКИЙ ПОДХОД К ЭНЕРГОСБЕРЕГАЮЩЕМУ ХЛАДОСНАБЖЕНИЮ СИСТЕМ КОНДИЦИОНИРОВАНИЯ ВОЗДУХА АДАПТАЦИЕЙ К ТЕКУЩИМ КЛИМАТИЧЕСКИМ УСЛОВИЯМ." Aerospace technic and technology, no. 4 (October 14, 2018): 58–62. http://dx.doi.org/10.32620/aktt.2018.4.08.
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The methodological approach was suggested to define a rational heat load of the air conditioning system (ACS) with taking into consideration the current climatic conditions of operation. The proposed approach is based on the hypothesis of sharing the current changeable heat load on the relatively stable share as the basic one for choosing installed (designed) refrigeration capacity of the refrigeration machine, operating with high energy efficiency in nominal or similar modes, and unstable heat load, corresponding to ambient air precooling at changeable current temperatures. To prove the methodological approach to defining a rational heat load of the ACS was carried out the analysis of current values of heat loads of the refrigeration machine ACS during cooling ambient air from its changeable current temperature to the temperature of 10, 15 and 20 ºС . It is shown that due to the different rates of annular refrigeration capacity production increment to cover the current heat loads with increasing the installed refrigeration capacity of the refrigeration machine, caused by the changes in heat load according to current climatic conditions during all the year round, it is necessary to choose a such heat load on the refrigeration machine of ACS (its installed refrigeration capacity), that provides a maximum or similar annular refrigeration capacity production at relatively high rates of its increment. Therein, the value of heat load for ambient air precooling is calculated according to remained principle as the difference between the rational total heat load and its basic relatively stable share. The proposed method is useful for defining a basic installed refrigeration capacity of the refrigeration machine of ACS with the accumulation of excessive (unapplied) refrigeration capacity at lowered current heat loads on ACS and its application for ambient air precooling, that is for covering unstable heat load share on ACS
2
Трушляков, Євген Іванович, Андрій Миколайович Радченко, Микола Іванович Радченко, Сергій Георгійович Фордуй, Сергій Анатолійович Кантор, and Богдан Сергійович Портной. "МЕТОДОЛОГІЧНІ ПІДХОДИ ДО ВИЗНАЧЕННЯ ХОЛОДОПРОДУКТИВНОСТІ СИСТЕМ КОНДИЦІЮВАННЯ ПОВІТРЯ ЗА ЗМІННИХ КЛІМАТИЧНИХ УМОВ." Aerospace technic and technology, no. 7 (August 31, 2019): 71–75. http://dx.doi.org/10.32620/aktt.2019.7.09.
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One of the most attractive reserves for improving the energy efficiency of air conditioning systems is to ensure the operation of refrigeration compressors in nominal or close to nominal modes by selecting a rational design heat load and distributing it within its design value according to the behavior of the current heat load under variable current climatic conditions to provide the maximum or close to maximum annual cooling capacity generation according to cooling duties of air conditioning. In the general case, the overall range of current thermal loads of any air conditioning system includes a range of unstable loads associated with the precooling of ambient air with significant fluctuations in cooling capacity according with current climatic conditions, and a relatively stable range of cooling capacity consumed to further reduce air temperature from a certain threshold temperature to the final outlet temperature. It is quite obvious that a stable range of heat load can be ensured within operating a conventional compressor in a mode close to the nominal mode while precooling the ambient air with significant fluctuations in heat load requires regulation of the cooling capacity through the use of a variable speed compressor. Thus, in response of the behavior of the change in current heat loads, any air conditioning system, whether the central air-conditioning system with its heat procession in a central air conditioner, or a combination thereof with a local recirculation system of indoor air, essentially consists of two subsystems: pre-cooling the ambient air and then cooling it to the set point temperature. The proposed method of distribution of design heat load depending on the behavior of the current heat load is useful for the rational design of central air conditioning systems and their combined versions with the local air conditioning system.
3
Cai, Bing, Weizhong Deng, Tong Wu, Tingting Wang, Zhengyuan Ma, Wei Liu, Lei Ma, and Zhichun Liu. "Experimental Study of a Loop Heat Pipe with Direct Pouring Porous Wick for Cooling Electronics." Processes 9, no. 8 (July 30, 2021): 1332. http://dx.doi.org/10.3390/pr9081332.
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A pouring silicate wick was manufactured to explore the influence of process and physical properties on the production and performance of loop heat pipes (LHP). This paper theoretically analyzed the advantages of pouring porous wick and introduced the technology of pouring silicate directly on evaporator. Based on this, the heat transfer performance of copper-methanol LHP system with pouring porous wick was tested under different positions. The results showed that with the input of multiple heat sources, the LHP could start up and maintain a stable temperature from 40 W to 160 W. When the vapor grooves were located above the compensation chamber, it was difficult to start up positively. By adding gravity assistance, the system could obtain more stable liquid supply and vapor flow, so as to realize start up. In the variable heat load test, the LHP showed good adaptability to the change of heat load. The thermal resistance of the system decreased with the increase of heat load. The thermal resistance of the evaporator almost unchanged and was always lower than 0.05 °C/W, which indicated that the pouring porous wick in the evaporator had good heat load matching.
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Jin, Yun Xue, Qiang Qiang Tong, Xiao Ya Wang, and Hong Mei Chen. "Effect of T6 Heat Treatment on Dry Sliding Frictional Wear Characteristics of Al-20Si-5Cu Alloy." Advanced Materials Research 750-752 (August 2013): 591–95. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.591.
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The effect of T6 heat treatment on dry sliding friction and wear characteristics of Al-20Si-5Cu under a fixed sliding speed of 200r/min and sliding time of 30mins was illustrated in this paper. The result reveals that T6 heat treatment can improve morphology of primary Si and Al2Cu particles, enhance the hardness of the matrix. Wear rate increased with increasing of applied load. T6 heat treated samples have high wear resistance which is related to the improvement of microstructure, particularly with their increased hardness of matrix. But friction coefficient varies with heat treatment processes and has no sensitivity to applied loads, which fluctuates in a small range, so the friction coefficient can be considered to be stable. The wear mechanisms of T6 heat treated samples are also changed with increasing of applied load, from oxidative wear to fatigue wear.
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Трушляков, Євген Іванович, Андрій Миколайович Радченко, Микола Іванович Радченко, Сергій Анатолійович Кантор, and Веніамін Сергійович Ткаченко. "ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ КОНДИЦІЮВАННЯ ЗОВНІШНЬОГО ПОВІТРЯ СИСТЕМИ КОМБІНОВАНОГО ТИПУ." Aerospace technic and technology, no. 4 (August 31, 2019): 9–14. http://dx.doi.org/10.32620/aktt.2019.4.02.
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One of the most attractive reserves of enhancing the energetic efficiency of air conditioning systems is to provide the operation of refrigeration compressors in nominal or close to nominal modes by choosing rational design cooling loads (cooling capacities) and their distribution according to a cooling load behaviour within the overall design (installed) cooling load band to match current changeable climatic conditions and provide close to maximum annual cooling capacity generation according to cooling duties. The direction of increasing the efficiency of outdoor air conditioning in combined central-local type systems by rationally distributing the heat load - cooling capacity of the central air conditioner into zones of variable heat load in accordance with current climatic conditions and its relatively stable value, i.e. cooling capacity required for further air cooling at the entrance to the indoor recirculation air conditioning system is justified. By comparing the values of the excessive production of cold and its deficit within every 3 days for a rational design heat load of the air conditioning system (cooling capacity of the installed refrigeration machine), which provides close to maximum annual production of cold, and the corresponding values of the excess and deficit of cooling capacity in accordance with current climatic conditions during July substantiated the feasibility of accumulating the excess of cooling capacity of a central air conditioner at low current loads and its use for covering cooling deficit at elevated heat loads through pre-cooling the outdoor air. It is developed a scheme of a combined central-local air conditioning system, which includes the subsystems for the outdoor air conditioning in a central air conditioner and the local indoor recirculated air conditioning.
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Kancherla, Prasada Rao, and Venkata Appa Rao Basava. "Experimental Investigation On Cylinder Vibration Analysis, Combustion, Emission and Performance Of An IDI Engine." International Journal of Manufacturing, Materials, and Mechanical Engineering 7, no. 1 (January 2017): 18–36. http://dx.doi.org/10.4018/ijmmme.2017010102.
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An experimental study was conducted to evaluate the performance, emissions, combustion and heat release rate of an Indirect Diesel Injection (IDI) engine fuelled with Mahua methyl ester (MME) along with Methanol (M) additive blends. Smoke, NOx, CO, HC and CO2 emissions were recorded and various engine performance parameters were measured. A comparative study was conducted using diesel, MME and Methanol additive blends on an IDI engine. There is substantial improvement can be observed from the net heat and cumulative heat release rate plots in which the 3% additive blend reached the performance of diesel fuel and the corresponding cylinder vibration plots indicated smoother combustion. Five additive blends were tested, the blending ratios of 1/99, 2/98, 3/97, 4/96 and 5/95 (by vol.) and five discrete part load conditions viz. No Load, 0.77 kW, 1.54 kW, 2.31 kW, and 2.70 kW loads without gear box and clutch assembly ensuring stable engine operation. 57% HC, 20% CO, 14% NOx, 27% smoke reductions were observed at 3% additive at maximum opted load (2.70 kW and 1500 rpm) of the engine.
7
Трушляков, Євген Іванович, Микола Іванович Радченко, Андрій Миколайович Радченко, Сергій Георгійович Фордуй, Сергій Анатолійович Кантор, Веніамін Сергійович Ткаченко, and Богдан Сергійович Портной. "ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ СИСТЕМ КОНДИЦІЮВАННЯ ПОВІТРЯ ШЛЯХОМ РОЗПОДІЛУ ТЕПЛОВОГО НАВАНТАЖЕННЯ ЗА СТУПЕНЕВИМ ПРИНЦИПОМ." Aerospace technic and technology, no. 8 (August 31, 2019): 49–53. http://dx.doi.org/10.32620/aktt.2019.8.07.
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Maintaining the operation of refrigeration compressors in nominal or close modes by selecting a rational design thermal load and distributing it in response to the behavior of the current thermal load according to the current climatic conditions is one of the promising reserves for improving the energy efficiency of air conditioning systems, which implementation ensures maximum or close to it in the annual cooling production according to air conditioning duties. In general case, the total range of current thermal loads of any air-conditioning system includes a range of unstable loads caused by precooling of ambient air with significant fluctuations in the cooling capacity according to current climatic conditions, and a range of relatively stable cooling capacity expended for further lowering the air temperature from a certain threshold temperature to the final outlet temperature. If a range of stable thermal load can be provided within operating a conventional compressor in a mode close to nominal, then precooling the ambient air with significant fluctuations in thermal load requires adjusting the cooling capacity by using a variable speed compressor or using the excess of heat accumulated at reduced load. Such a stage principle of cooling ensures the operation of refrigerating machines matching the behavior of current thermal loads of any air-conditioning system, whether the central air conditioning system with ambient air procession in the central air conditioner or its combination with the local indoors recirculation air conditioning systems in the air-conditioning system. in essence, as combinations of subsystems – precooling of ambient air with the regulation of cooling capacity and subsequent cooling air to the mouth of the set point temperature under relatively stable thermal load.
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Komarov, V. A., E. A. Kishov, O. G. Laikova, and A. A. Pavlov. "Digital design of heat-resistant dimensionally stable carbon laminate (CFRP) structures." VESTNIK of Samara University. Aerospace and Mechanical Engineering 20, no. 1 (April 20, 2021): 75–86. http://dx.doi.org/10.18287/2541-7533-2021-20-1-75-86.
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Special features of designing heat-resistant dimensionally stable structures are considered. A new design procedure is proposed, in which finite elements are used as a language for describing the load-bearing structure of a construction and the distribution of material in it considering the possibility of setting the desired structure of a composite material. The design task is formulated in terms of nonlinear mathematical programming. A sequence of digital models is used for its approximate solution in the interactive mode. The specific features of finite element modeling of thin-walled structures made of laminated composite material are discussed. The technique is demonstrated using the example of the development of a large-size space telescope body.
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Radchenko, Mykola, Tadeusz Bohdal, Andrii Radchenko, Eugeniy Trushliakov, Veniamin Tkachenko, Oleksii Zielikov, and Felix Tzaran. "Alternative variable refrigerant flow (VRF) air conditioning systems with rational distribution of thermal load." E3S Web of Conferences 323 (2021): 00028. http://dx.doi.org/10.1051/e3sconf/202132300028.
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One of the most attractive reserves of enhancing the energetic efficiency of air conditioning systems (ACS) is to provide operation of compressors in closed to nominal modes by choosing the rational design refrigeration capacities and their distribution according to current thermal loading to provide closed to maximum annual refrigeration energy generation. Generally, the overall thermal load band of any ACS comprises the unstable load range, corresponding to ambient air precooling with significant load fluctuations, and a comparatively stable load part for further air conditioning from a threshold temperature to a target value. The stable thermal load range can be covered by operation of conventional compressor in closed to nominal mode, meantime ambient air precooling needs load modulation by applying a variable speed compressor. A proposed ACS enables a wide range of refrigerant flow variation without heat flux drop in air coolers and can be considered as advanced alternative to variable refrigerant flow systems.
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Wang, Xin Hua, Si Wei Zhang, and De Guo Wang. "Research on Friction and Wear Performance of Brake Disc Pair Materials for New Type of Drilling Rig." Key Engineering Materials 373-374 (March 2008): 438–41. http://dx.doi.org/10.4028/www.scientific.net/kem.373-374.438.
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Tribological performance of new brake pair is studied at different temperatures, load and speed by variable temperature friction and wear test. The research indicates that brake pair has better frictional characteristics at variable temperature as well as heat-fade resistance performance at high temperatures. Wear rate of brake block and brake disc increases with friction temperature rising, however wear-resisting performance of brake disc is comparatively stable. Load has less influence on frictional coefficient of brake pair. Wear rate of brake disc and brake block increases with load increasing, but brake block has comparatively stable wear-resisting performance. Frictional coefficient of brake pair increases and tends to stabilize gradually along with sliding speed increasing, and speed has less influence on wear rate of brake block and brake disc. Initial heat-fading occurs in brake block material along with frictional temperature rising, secondary solidification may happen when frictional temperature reaches a certain value. When temperature rises much higher, brake block begins to soften and plastic flow intensifies, in addition thermal decomposition occurs in organic substance and wear-resisting performance becomes poorer. Build-up welding material has strong age-hardening effect and stable thermal structure, which leaves surface hardness and structure performance of brake disc unchanged at high temperatures.
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Hoang, Anh T., Tuyen V. Nguyen, and Bao T. Nguyen. "The Experimental Evaluation of Energy Efficiency and Carbonic Emission Rates for All Stable Loads of Larger-Scale (+600 MW) Coal-Fired Power Generation Units in Vietnam." Energies 15, no. 6 (March 17, 2022): 2185. http://dx.doi.org/10.3390/en15062185.
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Performance guarantees and tests of thermal power plants are usually carried out at 100% rate output capacity. However, fossil-fired power plants have decreased full load hours, affecting energy efficiency, and are subjected to frequent load changes caused by variable renewable electricity and potential grid stability. Therefore, this study is conducted to calculate and draw the characteristic curves for all stable loads of coal-fired power units including the 60%, 75%, and 100% rate output. The study focuses on the corrected plant net heat rates—gross unit outputs, net standard coal consumption rates—throttle steam pressures, and corrected plant net efficiencies—carbonic emission rates. In addition, the experimental investigation for energy efficiency and carbonic emission of the latest larger-scale (+600 MW) coal-fired power generation units in Vietnam are also implemented using a performance guarantee calculation software called “PG_Cal” version 0.0, which is based on a mass and energy balance method by MATLAB programing language. From the results of this study, it is suggested that the performance guarantees and tests of new coal-fired units should be carried out at different stable loads, including minimum load. Vietnam should apply the ultra-supercritical technology for new units in order to increase their efficiency and decrease carbon dioxide emissions.
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Kim, Hongkyo, Yujin Nam, Sangmu Bae, Jae Sang Choi, and Sang Bum Kim. "A Study on the Effect of Performance Factor on GSHP System through Real-Scale Experiments in Korea." Energies 13, no. 3 (January 23, 2020): 554. http://dx.doi.org/10.3390/en13030554.
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A ground source heat pump system is one of the high-efficient technologies for space heating and cooling since it uses stable underground temperature. However, in actual application, many situations cannot be achieved due to the unsuitable design of operation. In particular, the design characteristics of buildings with different building load patterns are not reflected by the conventional design method. Moreover, the design capacity of the heat pump can be reduced by designing less capacity than the peak load through the introduction of the heat storage tank, but there is no related quantitative design method. Therefore, in this study, the effect of the ground source heat pump system design factors such as shape, length of the ground heat exchanger, and the capacity of the heat storage tank on the system performance was analyzed. To quantify the effect of such factors on system performance, an experimental plant was constructed and case studies were conducted for each design factor.
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Chesalkin, Artem, Petr Kacor, and Petr Moldrik. "Heat Transfer Optimization of NEXA Ballard Low-Temperature PEMFC." Energies 14, no. 8 (April 14, 2021): 2182. http://dx.doi.org/10.3390/en14082182.
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Hydrogen is one of the modern energy carriers, but its storage and practical use of the newest hydrogen technologies in real operation conditions still is a task of future investigations. This work describes the experimental hydrogen hybrid energy system (HHS). HHS is part of a laboratory off-grid system that stores electricity gained from photovoltaic panels (PVs). This system includes hydrogen production and storage units and NEXA Ballard low-temperature proton-exchange membrane fuel cell (PEMFC). Fuel cell (FC) loses a significant part of heat during converting chemical energy into electricity. The main purpose of the study was to explore the heat distribution phenomena across the FC NEXA Ballard stack during load with the next heat transfer optimization. The operation of the FC with insufficient cooling can lead to its overheating or even cell destruction. The cause of this undesirable state is studied with the help of infrared thermography and computational fluid dynamics (CFD) modeling with heat transfer simulation across the stack. The distribution of heat in the stack under various loads was studied, and local points of overheating were determined. Based on the obtained data of the cooling air streamlines and velocity profiles, few ways of the heat distribution optimization along the stack were proposed. This optimization was achieved by changing the original shape of the FC cooling duct. The stable condition of the FC stack at constant load was determined.
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Hiraki, Kazutoshi, Koshiro Mizobe, Takahiro Matsueda, Yuji Kashima, and Katsuyuki Kida. "Friction Coefficient and Wear of PEEK-PTFE Hybrid Radial Ball Bearings under Dry Conditions." Materials Science Forum 1020 (February 2021): 114–19. http://dx.doi.org/10.4028/www.scientific.net/msf.1020.114.
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In this paper, in order to investigate friction coefficient and wear of PEEK-PTFE hybrid radial bearings, rolling contact fatigue tests were performed under radial loads ranging from 93N to 387N at 600rpm in dry conditions. It was found that friction coefficients were 0.013 to 0.032 throughout the tests. Operation temperature followed the change in the friction coefficient, and PEEK-PTFE radial ball bearings exhibited stable performance even though the temperature locally approached 100 °C due to frictional heat. Moreover, wear loss of bearing components excluding alumina balls increased exponentially with increase of load.
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Yu, Jinghua, Kangxin Leng, Feifei Wang, Hong Ye, and Yongqiang Luo. "Simulation Study on Dynamic Thermal Performance of a New Ventilated Roof with Form-Stable PCM in Southern China." Sustainability 12, no. 22 (November 10, 2020): 9315. http://dx.doi.org/10.3390/su12229315.
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Latent heat storage in phase change material (PCM) is an efficient technology that can be applied in building envelopes. Installing PCM in building roof has been effective in altering space cooling loads. However, the heat absorbed by the PCM during the daytime will be released at night; the cooling load is shifted to the night. So, this study proposed a new ventilated roof with form-stable PCM (VRFP). The night cool air is used for ventilation during summer to remove the solidification heat of PCM and to store the cooling energy in the roof. Form-stable PCM is placed in the upper layer and ventilation duct is placed in the middle layer. The inner surface temperature of this roof is reduced sharply compared with the conventional PCM roof. The thermal performance of this PCM roof with night ventilation in Wuhan, a city in southern China, was studied by through Computation Fluid Dynamics (CFD) simulation. A three-dimensional dynamic numerical model of this roof was built. The effects of melting temperature range, thickness of Form-stable PCM layer and ventilation strategy on the thermal performance were analyzed. Results show that, in Wuhan city, the optimal melting temperature range is 35~38 °C, the appropriate thickness of PCM layer is 30~40 mm and the optimal ventilation speed is 2.4~2.5 m/s. This structure can effectively prevent the stored heat of PCM transferring from the exterior to the interior during the summer and reduce cooling energy consumption.
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Wang, Wei Zu, Liu Yi Wang, Zeng Xue Zhang, and Hai Bo Chen. "Boundary Lubrication Model under Square Surface Contact Condition." Applied Mechanics and Materials 29-32 (August 2010): 1396–401. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1396.
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The contact temperature of the frictional surfaces under boundary lubrication in square surface contact is calculated according to classic heat conduction theories. The friction coefficient of boundary lubrication is expressed with the friction coefficient of boundary film and direct contact. Then, a model is developed based on the relationship of adsorption heat, friction coefficient and contact temperature. The model is used to solve a sample question. The results illuminate that when the applied load is relatively small, the friction coefficient keeps at a stable small value with the variation of the sliding speed and the load. However, when the load reaches a certain value, the increase of the sliding speed or the normal load both leads to the increase of the friction coefficient. The friction coefficient is also increases with the increase of the contact temperature. The relative deficiency of oil, which indicates the proportion of the true contact area to mean contact area, has almost the same variation trend of the friction coefficient.
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Liang, Rui Jun, Wen Hua Ye, Qun Qiang Chen, and Xin Jie Zhao. "The Thermal Characteristics of the Ball Screw Feed System on a Gantry Machine Tool." Applied Mechanics and Materials 490-491 (January 2014): 1008–12. http://dx.doi.org/10.4028/www.scientific.net/amm.490-491.1008.
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With the increasing of machine tool feed speed, a large quantity of friction heat is generated on the ball screw system and will cause the temperature rising and thermal deformation along the ball screw that reduces the machining accuracy. The heat accumulated and dissipated are calculated to load to the established model of the Y feed system on a gantry machine tool. The stable temperature field at thermal equilibrium and the unstable temperature field before thermal equilibrium or with the variation of thermal load are gotten. From thermal structure analysis, the thermal deformation is derived. The FEM model is verified by the experiments carried out under the same condition with the simulation.
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Weng, Chien-Lun, and Lih-Jen Kau. "Design and Implementation of a Low-Energy-Consumption Air-Conditioning Control System for Smart Vehicle." Journal of Healthcare Engineering 2019 (August 27, 2019): 1–14. http://dx.doi.org/10.1155/2019/3858560.
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About 7% of people’s daily time is spent in taking vehicles between office and home. Besides, with the improvement of the living standard in today’s society, people’s requirements for a comfortable environment inside the car are constantly increasing and this must rely on an effective vehicle air conditioner to maintain the comfort of the cabin environment. In general, a vehicle air conditioner uses the air-mixing mode to regulate the temperature control system. In this mode of operation, the compressor needs to work continuously, which is extremely energy consuming. The vehicle’s air conditioner is greatly affected by the inner and outer heat load, which are generated therein. Furthermore, the heat load is instantly changeable. Therefore, only when the controller can adapt to the feature of heat load, then we can find the optimal control method, thus enabling the vehicle’s air conditioner to interact with the actual heat load to supply the balanced cooling capacity and, as a result, create the most comfortable environment inside the cabin with minimum energy consumption. For this purpose, we bring up in this paper a low-energy-consumption smart vehicle air-conditioning control system to detect total heat load, which can change the vehicle’s air-conditioning capacity mode to maintain the average temperature at 25.2°C∼26.2°C and the average humidity at 46.6%∼54.4% in the cabin. When the inner heat load is stable, the rest times of the compressor can reach 16∼23 times per hour, which attains a rate of fuel saving around 21%∼28%. With the proposed architecture, the purpose of the low-energy-consumption vehicle air-conditioning system can be achieved, which, at the same time, creates a comfortable environment inside the cabin.
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Li, Yongjun, Limin Jin, Wanqian Zhu, Song Xue, Min Zhang, and Shuai Wu. "Vacuum joints of CuCrZr alloy for high-heat-load photon absorber." Journal of Synchrotron Radiation 29, no. 2 (February 7, 2022): 363–68. http://dx.doi.org/10.1107/s160057752101273x.
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A photon absorber, as a critical component of a synchrotron front-end, is mainly used to handle high-heat-load synchrotron radiation. It is mostly made of dispersion strengthened copper or CuCrZr which can retain high performance at elevated temperatures. Joining processes for vacuum, including tungsten inert gas welding (TIG) and electron beam welding (EBW), are novel ways to make a long photon absorber from two short ones and reduce power density. The mechanical properties of TIG joints and EBW joints of CuCrZr to the same material are obtained by tensile tests at 20°C, 100°C, 200°C, 300°C and 400°C. Testing results indicate that the tensile strength and yield strength of both vacuum joints decline as temperature increases. Compared with TIG joints, EBW joints have higher strength, better ductility and a more stable performance. An engineering conservative acceptance criteria of the vacuum joints is created by the polynomial fitting method. A novel welded photon absorber with a total length of 600 mm has been successfully designed and manufactured. Finite-element analysis by ANSYS shows that the maximum temperature, equivalent stress and strain are only 31.5%, 36.2% and 1.3%, respectively, of the corresponding thresholds. The welded photon absorbers with EBW joints will be applicable in the highest-heat-load front-end in the Shanghai Synchrotron Radiation Facility Phase-II beamline project.
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Amin, Muhammad, Bambang Ariantara, Nandy Putra, Adjie Fahrizal Sandi, and Nasruddin A. Abdullah. "Thermal Management of Electric Vehicle Batteries Using Heat Pipe and Phase Change Materials." E3S Web of Conferences 67 (2018): 03034. http://dx.doi.org/10.1051/e3sconf/20186703034.
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The performance of an electric vehicle depends on the battery used. While, in the operation of an electric vehicle, batteries experience a quick heating especially at the beginning of charging and could cause a fire. Therefore, the solution could be proposed is by employing heat pipe and Phase Change Material (PCM) for cooling of battery. The heat pipe serves to transfer the battery’s heat energy. In other hands, PCM functions as a heat sink when the battery runs, so its performance will stable and extend the lifespan. This study aimed to evaluate the performance of electric vehicle batteries at a temperature of 50°C using the combination of heat pipe and PCM. The ‘L’ type of heat pipe and beeswax PCM were assembled as cooling device. In addition, a battery simulator was employed as a test instrument by varying the heat load of 20, 30, 40, and 50 W. The experiments were successfully conducted, and the results showed that the addition of heat pipe and PCM could keep the surface temperature of battery below 50°C, at heat load of 20 - 50 W. Heat pipe and PCM for battery’s cooling system, can reduce the battery surface temperature significantly and can be proposed as an alternative system for cooling battery.
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Cekdin, Cekmas, Zainuddin Nawawi, and Muhammad Faizal. "An Effort to Reduce Voltage from DC to DC Converter with a Monolithic Circuit Based on IC LM 2596." Journal of Computational and Theoretical Nanoscience 16, no. 12 (December 1, 2019): 5162–65. http://dx.doi.org/10.1166/jctn.2019.8579.
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Step down regulator is a device that can reduce the more significant input voltage to a smaller output voltage. The output is stable and well regulated, although the voltage fluctuates in the recommended input voltage range. In the system using IC LM 2596, the input voltage is 40 Volt dc, and the output voltage is 30 Volt dc. The output current of 15 amperes is applied to charge a 100 Ampere hour (Ah) battery on an inverter system installed and integrated with other electronic devices. The step-down IC LM 2596 will be stable at the output current below 15 Ampere. It is especially stable at load currents from 13.2 Ampere to 14.57 Ampere. In order for the current not to shrink, a good cooling system must be designed to dispose of heat on the IC LM 2596. Because the high heat greatly affects the output current on the IC LM 2596.
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Koenig, Johannes, Stefanie Hoja, Thomas Tobie, Franz Hoffmann, and Karsten Stahl. "Increasing the load carrying capacity of highly loaded gears by nitriding." MATEC Web of Conferences 287 (2019): 02001. http://dx.doi.org/10.1051/matecconf/201928702001.
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Nitriding is a common heat treatment process for highly loaded gears. A very hard compound layer with a thickness of a few microns is produced at the surface of the gear. In the underlying material areas, a diffusion layer with nitride precipitations is formed. This publication summarizes the state of knowledge of nitrided gears and gives an overview of the current state of research in the field of nitrided gears. It can be concluded that a high load carrying capacity of nitrided gears is dependent on an adequate NHD and a stable compound layer. However, due to the increased surface roughness after nitriding, the risk of micropitting increases, too. Therefore, it may be favourable to grind the gears after nitriding. Ground gears also can provide a high load carrying capacity, but it must be taken into account that the wear performance will decrease significantly, since it is mainly influenced by the compound layer. In addition, nitrided gears usually show a high sensitivity against local load peaks. Beyond creating a stable compound the layer, the realization of a sufficient nitriding hardness depth with larger gear sizes is a focus in the current field of research.
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Li, Jinwang, Ningxiang Lu, and Tianshu Cong. "Experimental study on evaporation-capillary pumping flow in capillary wick and working fluid system." Thermal Science, no. 00 (2019): 413. http://dx.doi.org/10.2298/tsci180918413l.
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The evaporation-capillary pumping flow of the capillary wick and the working fluid system was experimentally studied in this paper. The capillary wick used in the experiment was fiber, and the working fluid contained water, ethanol and ethanol aqueous solution with water content of 25wt.%, 50wt.% and 75wt.%. The results show that the capillary pumping rate with ethanol as working fluid is between 210.0kg/m2sand 1812.5kg/m2swhen there is no heat load added. When the heating flux is 10616W/m2, 15924W/m2, 21231W/m2, 26539W/m2, the evaporation-capillary pumping rate is102.5kg/m2s, 247.5kg/m2s, 390.0kg/m2s and 530.0kg/m2s, respectively. The higher the heat load power, the greater the evaporation-capillary pumping rate and the higher the final stable temperature. With the increase of heat load power, the time required to reach temperature balance becomes shorter and the temperature fluctuations after reaching temperature equilibrium become larger. The obvious temperature fluctuation has occurred when the heat flux is 26539W/m2. The evaporation capillary pumping rate corresponding to the four different concentrations of ethanol solution in the experiment gradually decreases with the increase of water content. The temperature change processes and the final equilibrium temperatures of the four working fluids are nearly the same. The differences in boiling point of the working fluids do not have much influence here.
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Chen, Yuhui, Guoshuai Zhang, Ruolin Zhang, Timothy Gupta, and Ahmed Katayama. "Finite Element Study on the Wear Performance of Movable Jaw Plates of Jaw Crushers after a Symmetrical Laser Cladding Path." Symmetry 12, no. 7 (July 7, 2020): 1126. http://dx.doi.org/10.3390/sym12071126.
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At present, research on the influence of friction heat on the wear resistance of laser cladding layers is still lacking, and there is even less research on the temperature of laser cladding layers under different loads by a finite element program generator (FEPG). After a symmetrical laser cladding path, the wear performance of the moving jaw will change. The study of the temperature change of the moving jaw material in friction provides a theoretical basis for the surface modification of the moving jaw. The model of the column ring is built in a finite element program generator (FEPG). When the inner part of the column is WDB620 (material inside the cylinder) and the outer part is ceramic powder (moving jaw surface material), the relationship between the temperature and time of the contact surface is analyzed under the load between 100 and 600 N. At the same time, the stable temperature, wear amount, effective hardening layer thickness, strain thickness, and iron oxide content corresponding to different loads in a finite element program generator (FEPG) were analyzed. The results showed that when the load is 300 N, the temperature error between the finite element program generator (FEPG) and the movable jaw material is the largest, and the relative error is 4.3%. When the load increases, the stable temperature of the moving jaw plate increases after the symmetrical laser cladding path, and the wear amount first decreases and then increases. The minimum wear amount appears at a load of 400 N and a temperature of 340 °C; the strain thickness of the sample material increases gradually, and the effective hardening layer thickness increases. However, when the load reaches 400 N, the thickness of the effective hardening layer changes little; the content of Fe decreases gradually, and the content of FeO and Fe2O3 increases. The increase of the moving jaw increases in turn the temperature of the laser cladding layer of the test jaw material, which intensifies the oxidation reaction of the ceramic powder of the laser cladding layer.
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Zhao, Haoran, and Sen Guo. "Uncertain Interval Forecasting for Combined Electricity-Heat-Cooling-Gas Loads in the Integrated Energy System Based on Multi-Task Learning and Multi-Kernel Extreme Learning Machine." Mathematics 9, no. 14 (July 13, 2021): 1645. http://dx.doi.org/10.3390/math9141645.
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The accurate prediction of electricity-heat-cooling-gas loads on the demand side in the integrated energy system (IES) can provide significant reference for multiple energy planning and stable operation of the IES. This paper combines the multi-task learning (MTL) method, the Bootstrap method, the improved Salp Swarm Algorithm (ISSA) and the multi-kernel extreme learning machine (MKELM) method to establish the uncertain interval prediction model of electricity-heat-cooling-gas loads. The ISSA introduces the dynamic inertia weight and chaotic local searching mechanism into the basic SSA to improve the searching speed and avoid falling into local optimum. The MKELM model is established by combining the RBF kernel function and the Poly kernel function to integrate the superior learning ability and generalization ability of the two functions. Based on the established model, weather, calendar information, social–economic factors, and historical load are selected as the input variables. Through empirical analysis and comparison discussion, we can obtain: (1) the prediction results of workday are better than those on holiday. (2) The Bootstrap-ISSA-MKELM based on the MTL method has superior performance than that based on the STL method. (3) Through comparing discussion, we discover the established uncertain interval prediction model has the superior performance in combined electricity-heat-cooling-gas loads prediction.
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Zhu, Yuewei, Tao Zhang, Qingsong Ma, and Hiroatsu Fukuda. "Thermal Performance and Optimizing of Composite Trombe Wall with Temperature-Controlled DC Fan in Winter." Sustainability 14, no. 5 (March 7, 2022): 3080. http://dx.doi.org/10.3390/su14053080.
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This paper discusses an improved approach to the Trombe wall: an insulated panel is installed on the inner side, and vents are installed at the top and bottom to connect the outer and inner air layer with the interior. Direct current (DC) fans are installed in the upper vents for stable control of the air circulation. The study first analyzed the thermal performance of this composite Trombe wall, for which the heat load was 27.3% less compared to the classic Trombe wall and 32.1% less compared to the case without the Trombe wall. However, its efficiency for heating the room temperature was not high without heating. Then, we optimized the ventilation efficiency, the proportion of the Trombe wall in the room, and the type of glazing. The highest heat load savings could be achieved when the ventilation openings used high ventilation with temperature-controlled fans and the Trombe wall about 3% of the house floor area. With the use of Low-e double-glazing, we were able to save nearly 41.3% of the heat load than that with the regular single-glazing. For the composite Trombe wall, after taking into account the optimization factors, the room temperature was significantly higher, and could save nearly 52.3% of energy compared to the pre-optimization period.
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Yatim, Ardiyansyah, Gatot Prayogo, Ahmad Karayan, Hendra Novi, Wildan Hamdani, Sahrudin Tambunan, and Rahmat Burhanuddin. "Integrity Analysis of a Vessel Subject to Weld Repair and Post-Weld Heat Treatment: Thermal Stress Distribution Using Numerical Approach." Materials Science Forum 1000 (July 2020): 348–55. http://dx.doi.org/10.4028/www.scientific.net/msf.1000.348.
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Here, we present a numerical approach to analyze the integrity of a vessel that was subject to a weld repair. A Post-Weld Heat Treatment (PWHT) process was implemented to a vessel undergone weld repair due to leakage. Due to the thick wall of the welded bottom head, this welding process must be followed by the PWHT to relieve the residual stress, as well as to improve the material properties. PWHT process was performed by heating the welded area to reach 675 °C temperature. A numerical approach using finite element analysis (FEA) method was performed to analyze the integrity of the vessel. Based on the analysis, the structure is still stable within the applied load. PWHT process does not lead to buckling on the main structure and the load is still lower than the load required for the occurrence of buckling. A sensitivity analysis was also performed with reduced temperatures to 630 °C or reduction of PWHT area width. These changes were found to have negligible effects in reducing the stress and strains in the vessel. After PWHT is completed, the structure is still considered to be safe to be operated, as indicated by its strain that is still below the allowable strain and only relatively small deflection was occurred.
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Szczęśniak, Sylwia, and Juliusz Walaszczyk. "Estimation of sensible and latent heat based on measurements for non-typical large room." E3S Web of Conferences 116 (2019): 00085. http://dx.doi.org/10.1051/e3sconf/201911600085.
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The knowledge about dynamic changing heating and cooling load in existing building is essential for proper energy management. Whenever existing building is analyzed or ventilation system is going optimized, it’s essential to estimate temporary sensible and latent heat based on historical data. The basic conditions for heat calculations are quasi-stable thermal conditions. If supply air temperature significantly varies in short time, what happens very often, the calculations can give untrue results. The procedure described in this article improves usability of measured data affected by rapid supply air temperature changing. Therefore real sensible and latent heat can be calculated, what it is important for future optimization process. Specified, on the basis of varying supply and exhaust air temperatures, thermal loads range from -55.8 kW to 40.7 kW was substitute to more authentic range from -14.1 kW to 51.2 kW received from the conducted simulations. In addition, the data obtained from the simulation showed that latent heat gains were associated with the air temperature in the room, and not with the operation mode of the ventilation unit (day/night) as observed on the basis of historical data.
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Wu, Xiang Dong, and Ze Hua Liu. "The Analysis on Energy-Saving Reconstruction on Condensing Heat Recovery System of Air-Conditioning System." Applied Mechanics and Materials 865 (June 2017): 212–16. http://dx.doi.org/10.4028/www.scientific.net/amm.865.212.
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Combining with the energy consumption of air-conditioning system and the characteristics of the cooling and heating load in the hotel, the authors analyse the energy-saving property and necessity of adopting condensing heat recovery from water chillers. Taking the air-conditioning system of a star-hotel as an example, the optimization design for condensing heat recovery system from chillers on raising the temperature difference between supply and return water, the hot-water tanks in series and the water temperature stratification effectively realizes cascade and sequential utilization of hot-water, which keeps the water temperature stable and becomes more energy-saving.
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Beloglazova, T. N., and T. N. Romanova. "DIRECTIONS OF TRANSFORMATION OF ENERGY SUPPLY SYSTEMS TAKING INTO ACCOUNT THE PROSPECTIVE DEVELOPMENT OF TERRITORIES." Construction and Geotechnics 12, no. 4 (December 15, 2021): 68–82. http://dx.doi.org/10.15593/2224-9826/2021.4.05.
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Modern cities have a multi-level structure of technological systems that functionally and organizationally meet the needs of consumers. The development of urban areas requires an integrated approach. Heat and gas supply systems are the main element of energy systems. In accordance with the economic, social and technological conditions, heat and gas supply systems undergo organizational and structural transformations. The purpose of the study is to develop promising schemes of heat and gas supply systems for territories based on mutual influence. Methods. Based on the analysis of the functional and planning zoning of urban areas, the calculation method provides options for the development of heat and gas supply schemes. The implementation of modern standards of heat supply is possible due to multivariate approaches. The reliability of the research results is ensured by the use of proven calculation methods. Residential neighborhoods with a load on heat supply and household consumption are considered as the main consumers. Small industrial and municipal facilities are taken into account when planning the use of energy resources in the considered territory. Industrial consumption, as a rule, has an independent system of heat and gas supply. The method for determining loads is based on specific normative indicators. When developing the gas distribution scheme for urban areas, the possibility of spreading the load on the heat supply is taken into account. Results. On the one hand, the developed variants of heat and gas supply schemes were considered as alternative ones. Both the scheme of the main heat supply networks and the gas distribution scheme will be able to perform functional tasks to provide subscribers with resources for the considered design area independently. On the other hand, at different stages of system development, alternative options can complement each other, according to the periods of phased development, taking into account the criteria of reliability and cost-effectiveness. Conclusions. The variants of heat and gas supply systems allowed us to identify the main linear parameters for different building densities. The general material criterion for heat and gas supply systems is the material characteristic. The development of heat and gas supply schemes, taking into account the mutual influence, ensures a stable and economical development of the territory.
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McCue, B. M., R. L. Greenwell, M. I. Laurence, B. J. Blalock, S. K. Islam, and L. M. Tolbert. "SOI Based Voltage Regulator for High-Temperature Applications." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, HITEC (January 1, 2012): 000207–13. http://dx.doi.org/10.4071/hitec-2012-wp12.
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Developments in automotive (particularly hybrid-electric vehicles), aerospace, and energy production industries have led to expanding research interest in integrated circuit (IC) design toward high-temperature applications. A high-voltage, high-temperature silicon-on-insulator (SOI) process allows for circuit design to expand into these extreme environment applications. Nearly all electronic devices require a reliable supply voltage capable of operating under various supply voltages and load currents. These supply voltages and load currents can be either DC or time-varying signals. In this work, a stable supply voltage for embedded circuits is generated on chip via a voltage regulator producing a stable 5-V output voltage. Although applications of this voltage regulator are not limited to gate driver circuits, this regulator has been developed to meet the demands of a gate driver IC. The voltage regulator must be able to provide reliable output voltage over an input range from 10 V to 30 V, a temperature range of −25°C to 200°C, and output loads from 0 mA to 200 mA. Additionally, low power stand-by operation is provided to help reduce heat generation resulting in lower operating junction temperature. The designed voltage regulator has been successfully tested from −50°C to 200°C while demonstrating an output voltage variation of less than 10 mV under the full range of input voltage. Additionally, line regulation tests from 10 V to 30 V show a 12-ppm/V supply sensitivity. Full temperature and input voltage range tests reveal that the no-load supply current draw is within 17 mA while still providing in excess of 200-mA load current upon demand. Modifications to the existing design or off-chip biasing can widen the range of attainable output voltages and drive capabilities.
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Liu, Jianan, Hao Yu, Haoran Ji, Kunpeng Zhao, Chaoxian Lv, and Peng Li. "Optimal Operation Strategy of a Community Integrated Energy System Constrained by the Seasonal Balance of Ground Source Heat Pumps." Sustainability 12, no. 11 (June 5, 2020): 4627. http://dx.doi.org/10.3390/su12114627.
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Ground source heat pumps (GSHPs) are now widely used in community integrated energy systems (CIES) because of their high efficiency in energy conversion. However, the coefficient of performance (COP) of GSHPs is unstable if the soil temperature changes with seasonal imbalanced cooling and heating loads, thus downgrading the overall performance of CIES. In this paper, an annual optimization model for CIES that considers the seasonal balance of GSHPs is established. Then, a day-ahead operation strategy based on the pre-allocated load of the GSHP in the yearly balance is proposed while considering the uncertainties in daily conditions. The proposed strategy is validated on a practical CIES in China and assessed on a year-round time scale. The results show that the operation of CIES can be stable, economical and sustainable while ensuring the seasonal balance of the GSHP.
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Zhang, Shu, and Mao Yu Zheng. "Sustainability Study on GCHP Heating System in Severe Cold Area of China." Applied Mechanics and Materials 411-414 (September 2013): 3084–87. http://dx.doi.org/10.4028/www.scientific.net/amm.411-414.3084.
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In this paper, the mathematical models of a GCHP system and a Ground-couple heat pump system with air-soil thermal storage (GCHPASTS) were developed, and the 20-year performances of the two systems were simulated in severe cold area of china, respectively. The results show that the soil temperature declines gradually during the operation of a GCHP system, which leads to the decrease of the coefficient of performance (COP) and the heating effect of the heat pump year after year. On the contrary, the balance of ground thermal load can be realized during the operation of a GCHPASTS system, and the heating performance of heat pump is stable and efficient for long time. So, it can be proved that a GCHP system cant be used for heating alone, while a GCHPASTS system is feasibility.
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Martinez, Leticia, Den Palessonga, Philippe Roquefort, Alexis Chevalier, Azar Maalouf, Julien Ville, and Vincent Laur. "Development of a high temperature printable composite for microwave absorption applications." AIMS Materials Science 8, no. 5 (2021): 739–47. http://dx.doi.org/10.3934/matersci.2021044.
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<abstract> <p>This study deals with the development of a printable composite material based on a polyphenylene sulfide (PPS) matrix and carbonyl iron (Fe) particles, with controlled electromagnetic performance. More specifically, materials were simultaneous melt mixed and shaped under the form of filament with a diameter suitable for Fused Deposition Modeling. After reminding the potentialities of the printable PPS matrix, especially in terms of temperature resistance, microwave characterizations were performed on toroidal samples. The measured electromagnetic properties were compatible with absorption applications and compared to those of a commercial iron-filled PolyLactic Acid (PLA). Rectangular waveguide microwave loads were designed and fabricated by Fused Deposition Modeling with both materials. The PPS-Fe load has a volume that is 7 times lower than the PLA-Fe load due to a higher permittivity-permeability product and losses. Heat treatments demonstrated that no degradation is observed for the PPS-Fe load up to 180 ℃ while the PLA-Fe load is totally melted at 150 ℃. In the same time, it was observed that the maximum power supported by the PPS-Fe load is three times higher than the one supported by the PLA-Fe load. Finally, the temperature stability of the electromagnetic response of the PPS-Fe composite was demonstrated by measurements in the −70 ℃ to 140 ℃ temperature range. This new high temperature printable composite paves the way to the development of efficient, low-cost, low-weight, power and temperature stable absorbers for microwave applications.</p> </abstract>
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Ahlhelm, Matthias, Sergio H. Latorre, Hermann O. Mayr, Christiane Storch, Christian Freytag, David Werner, Eric Schwarzer-Fischer, and Michael Seidenstücker. "Mechanically Stable β-TCP Structural Hybrid Scaffolds for Potential Bone Replacement." Journal of Composites Science 5, no. 10 (October 17, 2021): 281. http://dx.doi.org/10.3390/jcs5100281.
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The authors report on the manufacturing of mechanically stable β-tricalcium phosphate (β-TCP) structural hybrid scaffolds via the combination of additive manufacturing (CerAM VPP) and Freeze Foaming for engineering a potential bone replacement. In the first step, load bearing support structures were designed via FE simulation and 3D printed by CerAM VPP. In the second step, structures were foamed-in with a porous and degradable calcium phosphate (CaP) ceramic that mimics porous spongiosa. For this purpose, Fraunhofer IKTS used a process known as Freeze Foaming, which allows the foaming of any powdery material and the foaming-in into near-net-shape structures. Using a joint heat treatment, both structural components fused to form a structural hybrid. This bone construct had a 25-fold increased compressive strength compared to the pure CaP Freeze Foam and excellent biocompatibility with human osteoblastic MG-63 cells when compared to a bone grafting Curasan material for benchmark.
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Guo, Kun Ya, Wen You Zhang, Peng Jin, Jiang Tao Li, Yong Jia Chen, Shu Han Wang, and Si Cong Wu. "Simulation Research on Solutions to 66kV Vertical SVC Switching Overvoltage and the Implementation." Applied Mechanics and Materials 602-605 (August 2014): 2974–77. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.2974.
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The dry hollow reactor has the features of good inductance linearity and heat dissipation and is not easy to produce ferromagnetic resonance with capacitive load in the system. Therefore, the phase controlled reactor in TCR-type SVC is usually a dry hollow reactor. According to years’ actual operating condition, the phase controlled reactor in 35kV SVC or SVC at a lower level operates stably while tree discharge or breakdown failure frequently happens to the phase controlled reactor in the 66kV vertical SVC, which seriously affects the stable operation of the equipment. This paper puts forward a method of installing arrester on the phase controlled reactors to relieve the SVC switching overvoltage impulse and protect the phase controlled reactors. Besides, it uses PSCAD to conduct a simulation and verifies the feasibility of this method.
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Ukai, Makiko, Masaya Okumiya, and Hideki Tanaka. "Energy Performance Evaluation of a Desiccant Air Handling System to Maximize Solar Thermal Energy Use in a Hot and Humid Climate." Sustainability 12, no. 5 (March 3, 2020): 1921. http://dx.doi.org/10.3390/su12051921.
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A desiccant air handling unit is one of the major types of dehumidification handling systems and requires hot water or hot air to regenerate sorption materials. If solar thermal energy is used as the heat source for regeneration, in general, a backup electrical heater, backup boiler, or combined heat and power (CHP) is installed in order to maintain a stable hot water supply. In this study, effective control is proposed for a desiccant air handling system that uses solar thermal energy (flexible control), and its energy performance is compared to that of a traditional control (the fixed control) through a system simulation. The diurnal behavior shows that the system with a fixed control without a backup boiler cannot process the latent load properly (28 GJ of unprocessed latent load for July and August). On the other hand, the system with a flexible control without a backup boiler is able to process required latent heat load. Based on the fact that the fixed control needs a backup boiler to process the latent load, the system with a fixed control with a backup boiler is considered for the energy performance comparison. The simulation results show that the primary energy-based coefficient of performance (hereafter, COP) of the system with a flexible control without a backup boiler reaches 1.56. On the other hand, the primary energy-based COP of the system with a fixed control with a backup boiler reaches only 1.43. This proves that the flexible control contributes to the higher energy performance of the system and maximizes the use of solar thermal energy more than the fixed control.
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Lombardo, Luca, Giorgia Toni, Filippo Stefanoni, Francesco Mollica, Maria Paola Guarneri, and Giuseppe Siciliani. "The effect of temperature on the mechanical behavior of nickel-titanium orthodontic initial archwires." Angle Orthodontist 83, no. 2 (August 22, 2012): 298–305. http://dx.doi.org/10.2319/040612-287.1.
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ABSTRACT Objectives: To investigate and compare the characteristics of commonly used types of traditional and heat-activated initial archwires at different temperatures by plotting their load/deflection graphs and quantifying three parameters describing the discharge plateau phase. Materials and Methods: Forty-eight archwires of cross-sectional diameters ranging from 0.010 inches to 0.016 inches were obtained from seven different manufacturers. A modified three-point wire-bending test was performed on three analogous samples of each type of archwire at 55°C and 5°C, simulating an inserted archwire that is subjected to cold or hot drinks during a meal. For each resulting load/deflection curve the plateau section was isolated and the mean value of each parameter for each type of wire was obtained. Results: Permanent strain was exhibited by all wires tested at 55°C. Statistically significant differences were found between almost all wires for the three considered parameters when tested at 55°C and 5°C. Loads were greater at 55°C than at 5°C. Differences were also found between traditional and heat-activated archwires, the latter of which generated longer plateaus at 55°C, shorter plateaus at 5°C, and lighter mean forces at both temperatures. The increase in average force seen with increasing diameter tended to be rather stable at both temperatures. Conclusions: All nickel-titanium wires tested showed a significant change related to temperature in terms of behavior and force for both traditional and heat-activated wires. Stress under high temperatures can induce permanent strain, whereas the residual strain detected at low temperatures can be recovered from as temperature increases.
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Tahir, Furqan, Abdelnasser Mabrouk, and Muammer Koç. "CFD Analysis of Falling Film Hydrodynamics for a Lithium Bromide (LiBr) Solution over a Horizontal Tube." Energies 13, no. 2 (January 8, 2020): 307. http://dx.doi.org/10.3390/en13020307.
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Falling film evaporators are used in applications where high heat transfer coefficients are required for low liquid load and temperature difference. One such application is the lithium bromide (LiBr)-based absorber and generator. The concentration of the aqueous LiBr solution changes within the absorber and generator because of evaporation and vapor absorption. This causes the thermophysical properties to differ and affects the film distribution, heat, and mass transfer mechanisms. For thermal performance improvement of LiBr-based falling film evaporators, in-depth analysis at the micro level is required for film distribution and hydrodynamics. In this work, a 2D numerical model was constructed using the commercial CFD software Ansys Fluent v18.0. The influence of the liquid load corresponding to droplet and jet mode, and the concentration, on film hydrodynamics was examined. It was found that the jet mode was more stable at a higher concentration of 0.65 with ±0.5% variation compared to lower concentrations. The recirculation was stronger at a low concentration of 0.45 and existed until the angular position (θ) = 10°, whereas at 0.65 concentration it diminished after θ = 5°. The improved heat transfer is expected at lower concentrations due to lower film thickness and thermal resistance, more recirculation, and a higher velocity field.
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Dekterev, A. A., V. A. Kuznetsov, and E. S. Tepfer. "Calculation analysis of heat transfer in a four-vortex furnace of a pulverized coal boiler when operating at various loads." Journal of Physics: Conference Series 2119, no. 1 (December 1, 2021): 012149. http://dx.doi.org/10.1088/1742-6596/2119/1/012149.
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Abstract The work is devoted to the mathematical modeling of heat and mass transfer processes during flare combustion of coal dust in a four-vortex combustion chamber. For modeling, a set of interrelated models is used that describes the gas movement, thermal and radiant energy transfer, the processes of destruction and burnout of coal particles, and the formation of NOx. The simulation results showed that in a wide range of changes in the boiler load in the furnace, a stable four-vortex flow structure is formed with a fairly uniform temperature distribution in the furnace volume and a low level of NOx formation.
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Zhao, Yichen, Haiquan Bi, and Honglin Wang. "Air conditioning predictive control for rail transit vehicles based on load prediction." E3S Web of Conferences 165 (2020): 04071. http://dx.doi.org/10.1051/e3sconf/202016504071.
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This paper proposes a predictive control method for rail vehicle air-conditioning systems. Due to heat transfer and diffusion, the air-conditioning system is a long-time-delay system. However, most air-conditioning systems use feedback control, which has problems such as long transition time, system shock, and mismatch between air cooling capacity and load, resulting in the waste of energy. Combined with feedforward and feedback control, a predictive control method with dynamic correction is proposed to solve this problem. Based on the load prediction, the real-time indoor temperature feedback link is added to send the cold air into the room in advance, which makes the room temperature stable, and the energy-saving effect significant. In the study, variance analysis of environmental factors is performed to improve the accuracy of the load prediction system, and the mean relative error (MRE) of the prediction reached 0.0112. By comparing the simulation results of predictive control and feedback control, it is proved that the predictive control with correction has a smoother room temperature curve. The energy-saving rate is about 25.2%.
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Kerekes, A., and A. Zöld. "The fiancée is unduly beautiful." International Review of Applied Sciences and Engineering 6, no. 1 (June 2015): 55–62. http://dx.doi.org/10.1556/1848.2015.6.1.8.
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According to the Energy Performance of Buildings Directive, a significant share of the energy consumption of nearly zero energy buildings is covered from renewable energy. Biomass is considered as one of the most important renewable sources. It is promising since most of the Member states apply very low primary energy conversion factors for it. Nevertheless, the primary energy need is not as favourable as the conversion factors suggest, due to the efficiency of the biomass boilers for all over the year which depends on the changing load. Heating systems supplied with biomass boilers need buffer storage tanks which further decrease the efficiency of the system. The nearly zero energy buildings, especially those of residential use exhibit more stable load due to the lower heat loss and the overwhelming share of the net energy need of domestic hot water supply.
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Praisner, T. J., and C. R. Smith. "The Dynamics of the Horseshoe Vortex and Associated Endwall Heat Transfer—Part II: Time-Mean Results." Journal of Turbomachinery 128, no. 4 (February 1, 2005): 755–62. http://dx.doi.org/10.1115/1.2185677.
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Time-mean endwall heat transfer and flow-field data in the endwall region are presented for a turbulent juncture flow formed with a symmetric bluff body. The experimental technique employed allowed the simultaneous recording of instantaneous particle image velocimetry flow field data, and thermochromic liquid-crystal-based endwall heat transfer data. The time-mean flow field on the symmetry plane is characterized by the presence of primary (horseshoe), secondary, tertiary, and corner vortices. On the symmetry plane the time-mean horseshoe vortex displays a bimodal vorticity distribution and a stable-focus streamline topology indicative of vortex stretching. Off the symmetry plane, the horseshoe vortex grows in scale, and ultimately experiences a bursting, or breakdown, upon experiencing an adverse pressure gradient. The time-mean endwall heat transfer is dominated by two bands of high heat transfer, which circumscribe the leading edge of the bluff body. The band of highest heat transfer occurs in the corner region of the juncture, reflecting a 350% increase over the impinging turbulent boundary layer. A secondary high heat-transfer band develops upstream of the primary band, reflecting a 250% heat transfer increase, and is characterized by high levels of fluctuating heat load. The mean upstream position of the horseshoe vortex is coincident with a region of relatively low heat transfer that separates the two bands of high heat transfer.
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Song, H. H., A. Padmanabhan, N. B. Kaahaaina, and C. F. Edwards. "Experimental study of recompression reaction for low-load operation in direct-injection homogeneous charge compression ignition engines with n-heptane and i-octane fuels." International Journal of Engine Research 10, no. 4 (June 12, 2009): 215–29. http://dx.doi.org/10.1243/14680874jer03309.
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Experiments have been reported in the literature in which the low-load limit of a retention-mode HCCI engine operating on gasoline has been significantly extended by pre-processing of the fuel during negative valve overlap. This paper presents experimental studies in which this low-load-limit extension is demonstrated and characterized using simple, single-component hydrocarbon fuels with relatively well-known chemical kinetics. The model fuels were n-heptane and i-octane and this choice was made both because of the extensive work that has been undertaken to develop their chemical kinetic mechanisms and because these fuels span the range of ignitability that is likely to be of interest for HCCI engines. The experimental results reported here show that both fuels exhibit load extension to as low as 1 bar net indicated mean effective pressure when operated at high residual mass fractions, low equivalence ratios, and an appropriate choice of compression ratio (13 for n-heptane, 18 for i-octane). Near the low-load limit, combustion is stable, exhibits slightly advanced timing, has relatively low unburned hydrocarbon emissions, negligible (< 5 ppm) NO emissions, and slightly increased CO emissions (compared to higher load conditions). The indicated efficiency of low-load operation with recompression reaction is somewhat reduced, mainly due to increased heat transfer and decreased combustion efficiency.
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CHO, SUNG-HWAN, SEONG-KI HONG, SANG-HO CHOI, and M. ZAHEERUDDIN. "MEASURED ENERGY CONSUMPTION ANALYSIS OF A DISTRICT HEATING SYSTEM UNDER DIFFERENT TEMPERATURE CONTROL STRATEGIES." International Journal of Air-Conditioning and Refrigeration 22, no. 02 (April 29, 2014): 1450008. http://dx.doi.org/10.1142/s2010132514500084.
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In this study, the secondary side measured energy consumption of a district heating system (DHS) with different hot water supply temperature control methods was compared. Two control methods were evaluated: an outdoor temperature reset control (OTRC) and an outdoor temperature predictive control (OTPC). While the OTRC strategy has been widely used for energy savings in DHS, the results show that the OTPC strategy resulted in higher energy savings. In general, the OTPC strategy maintained lower supply water temperature, and thereby reduced standby losses and increased overall heat transfer rate to the heated spaces due to higher water mass flow rate to the spaces. During the actual energy consumption monitoring, the OTPC strategy saved about 6.6% more energy compared to that of OTRC strategy. Also, it was found that under partial load conditions, such as during the daytime, the fluctuations in hot water supply temperature with OTRC were more severe than OTPC strategy. Overall, the results showed that the OTPC strategy gave better control and was more stable under full load and partial load conditions.
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Zeng, Guang, Sen Lin Zhao, Lai Wei, Run Ze Huang, and Modiri Badirwang. "Experimental Study on Technical Difficulties of Botswana First Circulating Fluidized Bed Boiler during Loading Process." Advanced Materials Research 721 (July 2013): 357–62. http://dx.doi.org/10.4028/www.scientific.net/amr.721.357.
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For study of technical difficulties that make Botswana first CFB (Circulating Fluidized Bed) boiler can’t reach full load at beginning of loading process, first experiments were carried out as awful experimental cases to analyze influencing factors; Second experiments were carried out as tentative experimental cases to select useful solutions; Third experiments were carried out as targeted experimental cases to execute chose solutions. Results indicate that one prominent difficulty during CFB boiler reaching full load is that boiler operation bed temperature was too high which was a comprehensive effect with some other influencing factors. CFB boiler bed temperature MFT (Main Fuel Trip) set point slight increasing, grain size changing of both start-up material and feeding coal, limestone injecting, fluidizing air of seal pot and FBHE appropriate controlling and FBHE (Fluid Bed Heat Exchanger) gradually start working are taken simultaneously, all these effective solutions solve the technical difficulties and accelerate the boiler reach full load, but attentions still need to be paid for the boiler stable operation permanently in future.
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Joshy, Sam, Jayadevan K.R., Ramesh A., and Mahipal D. "Influence of loading conditions on wear behaviour of H11 tool steel." World Journal of Engineering 16, no. 5 (October 7, 2019): 614–24. http://dx.doi.org/10.1108/wje-12-2018-0434.
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Purpose In hot forging, a significant amount of forging force is used for overcoming frictional force at the die-billet interface. The high frictional force along with thermomechanical stress lead to wear, plastic deformation, mechanical fatigue and cracks, which reduce the service life of hot forging dies. Of all these different types of issues, wear is the predominant mode of failure in hot forging dies. This paper aims to describe mechanisms of wear transition in different loads at near forging temperature, occurring during sliding of chromium-based H11 tool steel specimens. Design/methodology/approach High temperature pin-on-disc tests are performed with pin specimens machined from bars of X38CrMoV5 steel, heat treated to surface hardness of 40-42 HRc. The disc is made of EN 31 steel with hardness of 60-62 HRc. Tests are performed at constant temperature of 500°C, and the normal load was varied from 20 to 70 N. Findings Scanning electron microscopy investigations on worn surface have revealed that wear is primarily due to abrasion and plastic deformation. The test results show an increasing trend in wear rate with increase in load up to 30 N, followed by a reversal in trend until 50 N. This transition in wear rate is caused by development of wear resistant layers, which are formed by compaction of wear debris particles on to the worn surfaces. These compact layers are found to be stable during load range from 40 and 50 N. However, with further increase in load, abrasive wear tracks are observed without any evidence of protective layers. As a result, there is an increase in wear rate with increase in loads above 50 N. In addition, plastic shearing was dominant over abrasive wear at this load regime. Originality/value The study on wear behaviour of H11 hot forging steel at 20 to 70 N will be an input to the research in hot forming industries.
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Shin, Ji-Hyun, Yoon-Bok Seong, Yong-In Kim, and Young-Hum Cho. "Development of Changeover Operating Method Based on Performance Prediction of Hybrid Geothermal Heat Pump Systems through Field Test and Numerical Analysis." Energies 13, no. 20 (October 13, 2020): 5333. http://dx.doi.org/10.3390/en13205333.
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The installation and operation of geothermal systems increased due to the expectation of good cooling and heating performance due to stable heat source temperatures. In actual geothermal system operations, heat source temperature rises or falls due to an imbalance of heating and cooling energy usage. Problems of source side temperature result in reduced geothermal system performance. The purpose of this study is to develop hybrid geothermal system operation technology to stabilize temperature and improve system performance by utilizing auxiliary heat source system. The auxiliary heat source system is operated by comparing the performance when operating the geothermal heat pump system alone and the performance when operating the hybrid geothermal heat pump system. The performance of a hybrid geothermal system is determined by the circulating water temperature of the geothermal system and the circulating water temperature of the auxiliary heat source system. Hybrid geothermal heat pump system performance is predicted through numerical analysis and collection of hybrid geothermal system performance data at various temperature ranges through field test. An operating method was developed using the predicted performance as the changeover operating point of the hybrid geothermal heat pump system. When applying the development and operation technology, it handled about 11% more load than the existing geothermal system operation. The addition of an auxiliary heat source increases the initial investment cost compared to the existing geothermal system, but decreases energy consumption, confirming that the initial investment cost of 15.3 years is recovered.
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Tan, Zhi Hai, Qiang Guo, Xia Li, and Zheng Ping Zhao. "The Tribological Behaviour of Precipitation-Hardening Stainless Steel 0Cr17Ni4Cu4Nb against 30CrMnSiA Steel under Sliding Condition." Advanced Materials Research 479-481 (February 2012): 1102–9. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.1102.
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The tribological behaviour of precipitation-hardening stainless steel 0Cr17Ni4Cu4Nb against 30CrMnSiA steel under sliding condition was tested using the M2000A model wear tester. The surface roughness, hardness and load under the dry or grease lubricated conditions were studied. It indicated that the volume wear, mass wear, wear rate and friction coefficient were all large, and the main wear mechanism was the adhesive wear under the dry friction. The grease lubrication can effectively reduce the volume wear and friction coefficient, and enhance the wear resistance properties of 0Cr17Ni4Cu4Nb. The tribological properties were the best when the surface roughness was 0.8μm under the grease lubricated friction. Meanwhile the volume wear was also small when its hardness was low. The hardness was higher and the friction coefficient was more stable after the heat treatment on 0Cr17Ni4Cu4Nb. The volume wear and friction coefficient were both increased with the increasing of the loads under the grease lubricated friction.
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Xu, Ye, Na Meng, Xu Wang, Junyuan Tan, and Wei Li. "A Multiobjective Fractional Programming for a CHP System Operation Optimization Based on Energy Intensity." Energies 15, no. 6 (March 8, 2022): 1965. http://dx.doi.org/10.3390/en15061965.
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The objective of this research is to establish a multiobjective fractional programming (MOFP) model for supporting the operational management of a combined heat and power (CHP) system. Compared with the traditional operational optimization model of the CHP system, the importance of the energy intensity (i.e., the ratio of energy consumption and energy production) was emphasized in the MOFP model, which is considered as the system objective for replacing the common objective of minimizing the economic cost. This innovative transformation effectively reduces excessive energy consumption, accompanied by improvement in the system revenue. The CHP system of an industrial park in the City of Jinan, China, was used as a study case for demonstration. The obtained results reflected that the combination of two gas turbines (GTs) ensured safe, efficient, and stable output for meeting daily power requirements in various seasons. As for the steam load, during the summer, two heat recovery steam generators (HRSGs) play a major role, where the insufficient part is supplemented by two gas-fired boilers (SBs); conversely, the steam load in winter is mainly satisfied by the aid of two SBs. The successful application of the MOFP model in the park could provide a good demonstration for CHP management in many other districts and cities.