scholarly journals Influence of Prescribed Burning on a Pinus nigra subsp. Laricio Forest: Heat Transfer and Tree Vitality

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 915
Author(s):  
Lila Ferrat ◽  
Frédéric Morandini ◽  
Gauthier Lapa
Keyword(s):  
Heat Transfer ◽  
Prescribed Burning ◽  
High Efficiency ◽  
Low Cost ◽  
Fire Spread ◽  
Pinus Nigra ◽  
Critical Threshold ◽  
Long Term Effects ◽  
Tree Vitality ◽  
The Impact

Surface fuel removal is crucial to facilitate the mitigation of severe fires in forests. Prescribed burning is often used by forest managers, thanks to its low cost and high efficiency in hard-to-reach areas. The determination of heat transfer between fires and trees has rarely been carried out on living species and consequently, their long-term effects on tree physiology are still not fully understood. In this study, a multidisciplinary approach was conducted to evaluate the impact of a late spring (June) prescribed burning on a Mediterranean pine forest (Pinus nigra subsp. laricio). The surface fuels consisted of a 656 g m−² needle litter, mixed with a few scattered living herbaceous strata. During the fire spread, measurements of the inner and outer trunk temperatures were made at the base of 12 trees with an average bark thickness of 19.4 ± 7.0 mm. The fireline intensity and flame residence time were in the range of 110–160 kW m−1 and 220–468 s, respectively. Despite a maximum heating rate at the cambial area of 4.37 °C min−1, the temperature of these tissues remained below 60 °C, a critical threshold above which thermal damage will occur. In addition, prior- and post-fire physiological monitoring was performed over a long time period (2.5 years) on 24 trees, using sap flow, chlorophyll fluorescence and gas exchange measurements. All parameters remain highly correlated and indicate that the burned trees did not suffer physiological damage. Moreover, drought resistance strategies were not altered by the prescribed burning. The thermal insulation capability of the bark allowed the functional tissues to experience low heat stress that did not affect tree vitality.

scholarly journals The Impact and Empirical Analysis of the Development Level of E-commerce Industry on China’s Export Trade

2021 ◽  
Vol 235 ◽  
pp. 02046
Author(s):  
Chun Feng ◽  
Fei Lei ◽  
Zhijun Luo
Keyword(s):  
High Efficiency ◽  
Positive Impact ◽  
Low Cost ◽  
Status Quo ◽  
Export Trade ◽  
Empirical Methods ◽  
Existing Problems ◽  
Development Level ◽  
The Status ◽  
The Impact

With its advantages of low cost and high efficiency, e-commerce is not only favored by ordinary consumers, but also effectively promotes SMEs to find business opportunities and win the market. This article starts with the development scale of China’s e-commerce industry and the status quo of export trade, and measures the overall index of China’s e-commerce industry development level from 2008 to 2018 through empirical methods to analyze its impact on China’s export trade. The results show that the development level of the e-commerce industry has a significant positive impact on China’s export trade. Finally, it analyzes the existing problems in the development of China’s e-commerce industry.

Conjugate heat transfer simulation of turbine blade high efficiency cooling method with mist injection

2014 ◽  
Vol 228 (15) ◽  
pp. 2738-2749 ◽  
Author(s):  
Yuting Jiang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
Ping Dong ◽  
Jie Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Turbulence Models ◽  
Operating Conditions ◽  
Cooling Performance ◽  
Convective Cooling ◽  
Mist Cooling ◽  
The Impact

The idea of utilizing a finely dispersed water-in-air mixture has been proven to be a feasible technique to produce very high cooling rates. The accuracy of numerical simulation program for conjugate heat transfer methodology is verified with the Mark II transonic high pressure turbine stator which is cooled by internal convection through radial round pipes, and different turbulence models and transition models are employed to analyze the influence on results. On the basis of it, the mist cooling is simulated under typical gas turbine operating conditions for internal convective cooling to discuss the improvement of cooling performance. Though the results indicate that mist cooling can decrease the temperature of boundary layer without impact on the temperature of the mainstream and the thickness of boundary layer, the cooling capacity is limited by inadequate evaporation of mist. Considering the distribution of thermal stress and mist evaporation, a compound cooling blade of film cooling with trailing edge ejection is acquired which is modified from the blade of Mark II internal convective cooling; the effects of various parameters including mist concentration and mist diameter on the improvement of cooling performance are investigated, meanwhile the impact of curvature on cooling efficiency and mist trajectory is analyzed finally.

Through Flow Calculations for Convective Cooling Turbines

2014 ◽  
Author(s):  
Li Haibo ◽  
Chunwei Gu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Calculation Method ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Thermodynamic Efficiency ◽  
Inlet Temperature ◽  
Flow Calculation ◽  
Through Flow ◽  
The Impact

Conjugate heat transfer is a key feature of modern gas turbine, as cooling technology is widely applied to improve the turbine inlet temperature for high efficiency. Impact of conjugate heat transfer on heat loads and thermodynamic efficiency is a key issue in gas turbine design. This paper presented a through flow calculation method to predict the impact of heat transfer on the design process of a convective cooled turbine. A cooling model was applied in the through flow calculations to predict the coolant requirements, as well as a one-dimensional mixing model to evaluate some key parameters such as pressure losses, deviation angles and velocity triangles because of the injection cooling air. Numerical simulations were performed for verification of the method and investigation on conjugate heat transfer within the blades. By comparing these two calculations, it is shown that the through flow calculation method is a useful tool for the blade design of convective cooled turbines because of its simplicity and flexibility.

scholarly journals Economics of an Additive Manufactured Heat Exchanger for Concentrating Solar Power

2022 ◽  
Author(s):  
Tracey Ziev ◽  
Erfan Rasouli ◽  
Ines Noelly-Tano ◽  
Ziheng Wu ◽  
Srujana Yarasi Rao ◽  
...  
Keyword(s):  
High Efficiency ◽  
Solar Power ◽  
Cost Model ◽  
Low Cost ◽  
Operating Conditions ◽  
Concentrated Solar Power ◽  
Future Technologies ◽  
The Cost ◽  
Alternative Current ◽  
The Impact

Developing low cost, high efficiency heat exchangers (HX) for application in concentrated solar power (CSP) is critical to reducing CSP costs. However, the extreme operating conditions in CSP systems present a challenge for typical high efficiency HX manufacturing processes. We describe a process-based cost model (PBCM) to estimate the cost of fabricating an HX for this application using additive manufacturing (AM). The PBCM is designed to assess the effectiveness of different designs, processes choices, and manufacturing innovations to reduce HX cost. We describe HX design and AM process modifications that reduce HX cost from a baseline of$780/kW-thto$570/kW-th. We further evaluate the impact of alternative current and potential future technologies on HX cost, and identify a pathway to further reduce HX cost to$270/kW-th.

scholarly journals High Performance of Solar Cooker by Heat Transfer Mode Condition System Using Fuzzy Logic Controller Applications

2018 ◽  
Vol 7 (4.10) ◽  
pp. 278 ◽  
Author(s):  
Bhavani S ◽  
Shanmugan. S ◽  
Selvaraju P
Keyword(s):  
Heat Transfer ◽  
Fuzzy Logic ◽  
Thermal Performance ◽  
System Performance ◽  
High Performance ◽  
Fuzzy Logic Controller ◽  
High Efficiency ◽  
Low Cost ◽  
Heat Transfer Mode ◽  
Transfer Mode

In this work has been made to predict the effect of several parameters on the productivity to a system by expending fuzzy set technique. A solar cooker has been developed low cost and critically high efficiency produce in Vel Tech Multitech Engineering College at Chennai, Tamilnadu, India. Dissects in thermal performance of cooking system have been produced heat transfer follow in fuzzy logic techniques (Low, Medium, and High). The thermal effect of factor should be developed in fuzzy logic for the system. They should have groups of heat transfer produced in fuzzy logic controller for solar cooker system which had been implemented of system performance discussed. It is to study have induced to give the shortly time for the enhancement of the box solar cooker production.  

scholarly journals Numerical Analysis on Erosion and Optimization of a Blast Furnace Main Trough

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4851
Author(s):  
Hao Yao ◽  
Huiting Chen ◽  
Yao Ge ◽  
Han Wei ◽  
Ying Li ◽  
...  
Keyword(s):  
Blast Furnace ◽  
High Efficiency ◽  
Low Cost ◽  
Continuous Production ◽  
Hot Metal ◽  
Main Trough ◽  
Impact Position ◽  
Refractory Life ◽  
Volume Method ◽  
The Impact

The main trough of a blast furnace (BF) is a main passage for hot metal and molten slag transportation from the taphole to the torpedo and the slag handling. Its appropriate working status and controlled erosion ensure a safe, stable, high-efficiency and low-cost continuous production of hot metal. In this work, the tapping process of a main trough of a BF in the east of China was numerically studied with the help of a CFD library written in C++, called OpenFOAM, based on the use of the Finite Volume Method (FVM). The results show that turbulence intensity downstream of the hot metal impact position becomes weaker and the turbulence area becomes larger in the main trough. During the tapping, thermal stress of wall refractory reaches the maximum value of 1.7 × 107 Pa at the 4 m position in the main trough. Furthermore, baffles in the main trough placed between 5.8 m and 6.2 m were found to control and reduce the impact of the turbulence on the refractory life. The metal flowrate upstream of the baffles can be decreased by 6%, and the flow velocity on the upper sidewall and bottom wall decrease by 9% and 7%, respectively, compared with the base model. By using baffles, the minimum fatigue life of the refractory in the main trough increases by 15 tappings compared with the base model, so the period between the maintenance stops can be prolonged by about 2 days.

scholarly journals Iterative Learning Method for In-Flight Auto-Tuning of UAV Controllers Based on Basic Sensory Information

2019 ◽  
Vol 9 (4) ◽  
pp. 648 ◽  
Author(s):  
Wojciech Giernacki
Keyword(s):  
Control Systems ◽  
Performance Index ◽  
High Efficiency ◽  
Search Algorithm ◽  
Low Cost ◽  
Sensory Information ◽  
Learning Method ◽  
Comprehensive Description ◽  
Auto Tuning ◽  
The Impact

With an increasing number of multirotor unmanned aerial vehicles (UAVs), solutions supporting the improvement in their precision of operation and safety of autonomous flights are gaining importance. They are particularly crucial in transportation tasks, where control systems are required to provide a stable and controllable flight in various environmental conditions, especially after changing the total mass of the UAV (by adding extra load). In the paper, the problem of using only available basic sensory information for fast, locally best, iterative real-time auto-tuning of parameters of fixed-gain altitude controllers is considered. The machine learning method proposed for this purpose is based on a modified zero-order optimization algorithm (golden-search algorithm) and bootstrapping technique. It has been validated in numerous simulations and real-world experiments in terms of its effectiveness in such aspects as: the impact of environmental disturbances (wind gusts); flight with change in mass; and change of sensory information sources in the auto-tuning procedure. The main advantage of the proposed method is that for the trajectory primitives repeatedly followed by an UAV (for programmed controller gains), the method effectively minimizes the selected performance index (cost function). Such a performance index might, e.g., express indirect requirements about tracking quality and energy expenditure. In the paper, a comprehensive description of the method, as well as a wide discussion of the results obtained from experiments conducted in the AeroLab for a low-cost UAV (Bebop 2), are included. The results have confirmed high efficiency of the method at the expected, low computational complexity.

scholarly journals Updating the Role of Reduced Graphene Oxide Ink on Field Emission Devices in Synergy with Charge Transfer Materials

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 137 ◽  
Author(s):  
Minas Stylianakis ◽  
George Viskadouros ◽  
Christos Polyzoidis ◽  
George Veisakis ◽  
George Kenanakis ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Field Emission ◽  
Large Scale ◽  
High Efficiency ◽  
Low Cost ◽  
Field Enhancement ◽  
Field Emitter ◽  
Reduced Graphene ◽  
The Impact

Hydroiodic acid (HI)-treated reduced graphene oxide (rGO) ink/conductive polymeric composites are considered as promising cold cathodes in terms of high geometrical aspect ratio and low field emission (FE) threshold devices. In this study, four simple, cost-effective, solution-processed approaches for rGO-based field effect emitters were developed, optimized, and compared; rGO layers were coated on (a) n+ doped Si substrate, (b) n+-Si/P3HT:rGO, (c) n+-Si/PCDTBT:rGO, and (d) n+-Si/PCDTBT:PC71BM:rGO composites, respectively. The fabricated emitters were optimized by tailoring the concentration ratios of their preparation and field emission characteristics. In a critical composite ratio, FE performance was remarkably improved compared to the pristine Si, as well as n+-Si/rGO field emitter. In this context, the impact of various materials, such as polymers, fullerene derivatives, as well as different solvents on rGO function reinforcement and consequently on FE performance upon rGO-based composites preparation was investigated. The field emitter consisted of n+-Si/PCDTBT:PC71BM(80%):rGO(20%)/rGO displayed a field enhancement factor of ~2850, with remarkable stability over 20 h and low turn-on field in 0.6 V/μm. High-efficiency graphene-based FE devices realization paves the way towards low-cost, large-scale electron sources development. Finally, the contribution of this hierarchical, composite film morphology was evaluated and discussed.

Operational Experience With High Efficiency Cyclones: Comparison Between Boiler A and B in the Zeran Power Plant — Warsaw, Poland

2003 ◽  
Author(s):  
Ireneusz Lalak ◽  
Joachim Seeber ◽  
Frank Kluger ◽  
Stanislaw Krupka
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
High Efficiency ◽  
Operational Experience ◽  
Significant Positive Effect ◽  
Internal Circulation ◽  
Technological Developments ◽  
The Impact ◽  
Positive Effect ◽  
Operational Data

The two 450t/h CFB units of the Zeran heat and power plant in Warsaw, Poland, are nearly identical in design, except for the cyclones. While the first CFB unit Zeran A which was commissioned in 1995 had cyclones of a prior design, the second unit Zeran B, which went into operation in late 2001, was equipped with high efficiency cyclones with the latest technological developments. The impact of the cyclone design is clearly visible in the operational data. Due to the high cyclone efficiency, the internal circulation became much higher and the fineness of the circulating particles was shifted to finer particles. As a result, the heat transfer in the furnace was boosted and the temperature profile became more even. This had a significant positive effect on the emissions, especially NOx and on the limestone consumption, which was considerably reduced.

Laminar Flow Theory as a Guide to Compact Recuperator Design

2003 ◽  
Author(s):  
William I. Chapman
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
High Efficiency ◽  
Low Cost ◽  
Flow Theory ◽  
Heat Transfer Surface ◽  
Flow Volume ◽  
Flow Length ◽  
Typical Design ◽  
Simple Flow

A small gas turbine needs a good recuperator to achieve high efficiency. It is desirable that this recuperator be small in size, light in weight, and low cost. Laminar flow theory is used to show the effect of heat transfer surface selection, passage size, and flow length. A comparative study was then made of counterflow recuperators using heat transfer test data from published sources to show how these variables apply to a typical design. One group of surfaces with simple flow passages, smooth, straight, and constant cross-section, followed laminar flow theory quite closely. A second group of more complicated surfaces deviated considerably from laminar flow theory. For a given performance, both groups show that as flow length is reduced, along with the corresponding passage size, the flow volume and surface area decreases. The corresponding material weight and cost also decrease. There are practical limitations on how far this can go.

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