scholarly journals STATIC CALCULATION OF FILM ROOF OF CULTIVATION STRUCTURE

2020 ◽  
Vol 5 (10) ◽  
pp. 17-22
Author(s):  
A. Blazhnov
Keyword(s):  
Wind Load ◽  
Operating Conditions ◽  
Wind Pressure ◽  
Small Scale ◽  
Roof Material ◽  
Construction Design ◽  
Static Calculation ◽  
Spring And Autumn Period ◽  
Building Standards ◽  
Circular Outline

Membrane roofing greenhouses and small-scale farms are used in the spring and autumn period for growing various crops. The main load for such structures is wind. Norms of construction design of greenhouses do not contain provisions for calculating the membrane roof of cultivation structures for this type of load. For arched greenhouses with a circular outline of the coating, an approximate method for determining the forces from the wind load in a membrane stabilized by wind ropes is proposed. The membrane roof is considered as a soft cover under the influence of negative wind load. The calculated dependences for estimating the stress-strain state of the roof material are derived analytically. The calculation scheme of the roof deformed by wind pressure, corresponding to the actual operating conditions of the structure, is used to derive the dependencies. The roof of the structure is considered from the polyethylene membrane recommended by the building standards for the design of greenhouses, the physical and mechanical characteristics of which are standardized. Dependences are derived for determining the longitudinal and annular stresses in the roof material, the rational pitch of wind ropes and the maximum possible force in them. The proposed method of static calculation of the membrane roof can be used for cultivation structures with the outline of the coating close to circular

Wind Pressure and Wind-Induced Vibration of Heliostat

2008 ◽  
Vol 400-402 ◽  
pp. 935-940 ◽  
Author(s):  
Ying Ge Wang ◽  
Zheng Nong Li ◽  
Bo Gong ◽  
Qiu Sheng Li
Keyword(s):  
Dynamic Response ◽  
Wind Direction ◽  
Wind Load ◽  
Wind Pressure ◽  
Induced Response ◽  
Vertical Angle ◽  
Lateral Direction ◽  
Direction Angle ◽  
Wind Pressures ◽  
Fluctuating Wind

Heliostat is the key part of Solar Tower power station, which requires extremely high accuracy in use. But it’s sensitive to gust because of its light structure, so effect of wind load should be taken into account in design. Since structure of heliostat is unusual and different from common ones, experimental investigation on rigid heliostat model using technology of surface pressure mensuration to test 3-dimensional wind loads in wind tunnel was conducted. The paper illustrates distribution and characteristics of reflector’s mean and fluctuating wind pressure while wind direction angle varied from 0° to 180° and vertical angle varied from 0° to 90°. Moreover, a finite element model was constructed to perform calculation on wind-induced dynamic response. The results show that the wind load power spectral change rulers are influenced by longitudinal wind turbulence and vortex and are related with Strouhal number; the fluctuating wind pressures between face and back mainly appear positive correlation, and the correlation coefficients at longitudinal wind direction are smaller than those at lateral direction; the fluctuating wind pressures preferably agree with Gaussian distribution at smaller vertical angle and wind direction angle. The wind-induced response and its spectrums reveal that: when vertical angle is small, the background responsive values of reflector’s different parts are approximately similar; in addition, multi-phased resonant response occurring at the bottom. With the increase of , airflow separates at the near side and reunites at the other, as produces vortex which enhances dynamic response at the upper part.

Gas Cooling and Humidification: Design of Packed Towers from Small-Scale Tests

1950 ◽  
Vol 163 (1) ◽  
pp. 41-53 ◽  
Author(s):  
W. F. Carey ◽  
G. J. Williamson
Keyword(s):  
Operating Conditions ◽  
Total Heat ◽  
Small Scale ◽  
Water Cooling ◽  
Packed Tower ◽  
Simple Method ◽  
Worked Example ◽  
Gas Cooling ◽  
Heat Method ◽  
Working Out

On plants in which gases are processed, the gases are often brought into direct contact with water—usually in packed towers. The purpose may be to cool a hot gas, to increase the humidity of a gas, or, in the well-known special case of water-cooling towers, to cool water by contact with atmospheric air. These processes involve simultaneous transfers of sensible heat and water vapour, and existing methods of analysis are complex and laborious, except for the cooling of water, for which Merkel's total-heat method has long been available. Merkel's approximate solution offers the engineer a simple method of working out, for any operating conditions, the amount of heat transferred and the “driving force” available for transferring it. The present paper generalizes the total-heat method and, with a permissible sacrifice in accuracy, preserves the essential simplicity of the water-cooling treatment for gas-cooling and humidification processes. To complete the design of a packed tower, a knowledge is required of the characteristics of the packing. Information obtained in small towers is given for a number of packings, and a worked example shows how to apply the method of treatment, and the packing data presented, to the design of a large plant tower.

scholarly journals Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Load Capacity ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Fluid Film ◽  
Small Scale ◽  
Vapor Compression ◽  
Density Profiles ◽  
Film Pressure

Abstract High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles is investigated for two one-dimensional bearing geometries (parabolic and Rayleigh step) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting of a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggests the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

scholarly journals Examination of physical properties of final product and drying properties of combined (convective pre-drying and freeze finish-drying) dehydration method

2014 ◽  
pp. 5-12
Author(s):  
Tamás Antal
Keyword(s):  
Freeze Drying ◽  
Operating Conditions ◽  
Small Scale ◽  
Case Hardening ◽  
Degree Polynomial ◽  
Hot Air Drying ◽  
Drying Time ◽  
Drying Characteristics ◽  
Hot Air ◽  
Drying Properties

In this study, the effects of freeze drying (FD), hot-air drying (HAD) and combined drying (HAD-FD) on drying characteristics, energy uptake, texture, rehydration and color of carrot were investigated. Results showed that HAD-FD significantly improved the drying time compared with FD under the same operating conditions, and the HAD-FD can reduce the total cost of dehydration. The drying kinetics was described by the Henderson-Pabis and the third degree polynomial models in the case of HAD, FD and HAD-FD. The HAD carrot samples were exhibited shrinkage, case hardening, poor rehydration and brown surface. The FD carrot cubes appeared porous structure, excellent rehydration, soft texture and loose color. The HAD-FD samples were superior to HAD products and was nearer in quality to FD products with respect to appearance, rehydration and surface resistance (texture). Finally, it is concluded that HAD-FD is effective in improving the FD drying rate. However, the combined drying has a small-scale adverse effect on product quality.

scholarly journals A Novel Hybrid Technique of Frequency Control for Distributed Energy Resources

2021 ◽  
Vol 40 (1) ◽  
pp. 180-204
Author(s):  
Hasham Khan
Keyword(s):  
Power Distribution ◽  
Distribution System ◽  
Energy Demand ◽  
Frequency Control ◽  
Industrial Sector ◽  
Operating Conditions ◽  
Small Scale ◽  
Hybrid Technique ◽  
Operating Characteristics ◽  
Power Distribution System

The rapid increase in the population and fastest development in the industrial sector has increased the energy demand throughout the world. Frequent outages and load shedding has seriously deteriorated the efficiency of the electrical power distribution system. Under such circumstances, the implementation of Distributed Generation (DG) is increasing. Small hydel generators are considered as the most-clean and economical for generating electrical energy. These are very complex nonlinear generators which usually exhibits low frequency electromechanical oscillations due to insufficient damping caused by severe operating conditions. These DGs are not connected to the utility in many cases because, under varying load, they cannot maintain the frequency to the permissible value. This work presents detailed analysis of operating characteristics and proposes a hybrid frequency control strategy of the small hydel systems. The simulation and testing is performed in MATLAB, the results verified the improved performance with the recommended method. The proposed method conserves half of the power consumption. The control scheme regulates the dump load by connecting and disconnecting it affectively. The application of presented methodology is convenient in the deregulated environment, especially under the severe shortage of energy. The proposed model keeps the frequency of system at desired level. It reduces the noise, thereby improving the response time of the designed controller as compared to conventional controllers. The innovative scheme also provides power for small scale industrial, agricultural and other domestic application of far-off areas where the supply of utility main grid is difficult to provide. The recommended scheme is environmental friendly and easy to implement wherever small hydel resources are available.

scholarly journals A Research of Construction Mechanism of Vassal State’s City Group during Spring and Autumn Period Based on the Analyzation of Geographic Image – Take south region of Shandong as example

2015 ◽  
Vol XL-5/W7 ◽  
pp. 151-157
Author(s):  
X. Gao ◽  
B. Li ◽  
X. Zhou
Keyword(s):  
Geographical Location ◽  
Small Scale ◽  
Topographic Map ◽  
Autumn Period ◽  
Economic Support ◽  
Independent Unit ◽  
Spring And Autumn Period ◽  
Space Layout ◽  
The One ◽  
Agricultural Areas

Spring and Autumn period, the vassal states began to carry out country defense construction actively, brought changes to building the ideological. At that time, the south region of Shandong, as an independent unit of geography, seldom affected by external factors, and had striking cultural characteristics. Vassal states there constructed their capital mainly to defense the neighboring countries and cope with small scale mergers war, not involving the nationwide military deployment. Therefore, the region reflect the construction thought changes during the Spring and Autumn Period, and consistent with the research purpose. Based on this judgment, the author analyzed each capital’s location and terrain feature by topographic map. In brief, the Spring and Autumn Period, feudal states acted of one's own free will, the relationship between cities contained the one within and between vassal states. Within vassal state relationships included economic support, entrenching each other and protecting the country together. Meanwhile, strategic defensing, scrambling for resources and geographical location comprised of the competition between vassal states. In the agrarian age, the political centers and agricultural areas were interdependent, giving priority to the development of political cities. Transformation of capitals’ space layout was actually the process of carving up farming plains, the powerful states occupy favorable geographical position, and the small countries would be encroached and annexed gradually.

Conduction Roaster for Accelerated Roasting of Peanut

2021 ◽  
Vol 58 (02) ◽  
pp. 112-123
Author(s):  
Rakesh Kumar Raigar ◽  
Hari Niwas Mishra
Keyword(s):  
Energy Consumption ◽  
Specific Energy ◽  
Rotational Speed ◽  
Specific Energy Consumption ◽  
Quality Parameters ◽  
Operating Conditions ◽  
Moisture Loss ◽  
Optimum Operating ◽  
Small Scale ◽  
Roasting Temperature

Roasting is one of the thermo-mechanical operation in cereals and oilseeds processing. Low-capacity machine for mechanisation of roasting is necessary for small-scale processing. A conduction-type motorised rotary roaster (8 kg per batch) was designed and developed for roasting of peanuts. Performance of the roaster was evaluated in terms of moisture loss, scorched kernels, and specific energy consumption for accelerated roasting of peanut. The effects of different roasting conditions were studied to determine the optimum operating conditions of the roaster. Quality indices of peanuts as moisture loss (kg.kg-1), scorched kernel (%), and specific energy consumption (kWh.kg-1) were dependent on the operating conditions. The optimum value of moisture loss (0.041± 0.003 kg.kg-1), scorched kernel (0.93± 0.0.004 % ), and specific energy consumption (0.185 ± 0.005 kWh.kg-1) were obtained at roasting temperature of 170°C, roasting time of 15 min, and rotational speed of 20 rpm for roasting peanut. The roasting characteristics of peanut decreased linearly with increase in the temperature and time; and decrease in the rotational speed. The inferior quality parameters were observed at higher temperatures, speed and medium time of roasting. The study indicated optimum roasting temperature of peanut to be 170°C, and further increase in the process temperature had undesirable effects on roasted peanut quality due to high loss of moisture.

Can Water Dilution Avoid Flashback on a Hydrogen Enriched Micro Gas Turbine Combustion? A Large Eddy Simulations Study

2020 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre Bénard ◽  
Ward De Paepe
Keyword(s):  
Gas Turbines ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Reference Case ◽  
Large Eddy ◽  
Pure Methane ◽  
Water Dilution ◽  
Air Humidification

Abstract Considering the growing interest in Power-to-Fuel, i.e. production of H2 using electrolysis to store excess renewable electricity, combustion-based technologies still have a role to play in the future of power generation. Especially in a decentralized production with small-scale cogeneration, micro Gas Turbines (mGTs) offer great advantages related to their high adaptability and flexibility, in terms of operation and fuel. Hydrogen (or hydrogen enriched methane) combustion is well-known to lead to flame and combustion instabilities. The high temperatures and reaction rates reached in the combustor can potentially lead to flashback. In the past, combustion air humidification (i.e. water addition) has proven effective to reduce temperatures and reaction rates, leading to significant NOx emission reductions. Therefore, combustion air humidification can open a path to stabilize hydrogen combustion in a classical mGT combustor. However accurate data assessing the impact of humidification on the combustion is still missing for real mGT combustor geometries and operating conditions. In this framework, this paper presents a comparison between pure methane and hydrogen enriched methane/air combustions, with and without combustion air humidification, in a typical mGT combustion chamber (Turbec T100) using Large Eddy Simulations (LES) analysis. In a first step, the necessary minimal water dilution, to reach stable and low emissions combustion with hydrogen, was assessed using a 1D approach. The one-dimensional unstretched laminar flame is computed for both pure methane (reference case) and hydrogen enriched methane/air combustion cases. The results of this comparison show that, for the hydrogen enriched combustion, the same level of flame speed as in the reference case can be reached by adding 10% (in mass fraction) of water. In a second step, the feasibility and flexibility of humidified hydrogen enriched methane/air combustion in an industrial mGT combustor have been demonstrated by performing high fidelity LES on a 3D geometry. Results show that steam dilution helped to lower the reactivity of hydrogen, and thus prevents flashback, enabling the use of hydrogen blends in the mGT at similar CO levels, compared to the reference case. These results will help to design future combustor towards more stability.

Determination of Basic Wind Velocity for Wind Load-Governed Limit State

2019 ◽  
Author(s):  
Ji Hyeon Kim ◽  
Hae-Sung Lee
Keyword(s):  
Wind Velocity ◽  
Reliability Index ◽  
General Procedure ◽  
Limit State ◽  
Wind Load ◽  
Wind Pressure ◽  
Load Factor ◽  
Load Effect ◽  
Design Life ◽  
Target Reliability Index

<p>This paper proposes a general procedure for evaluating a nominal value of wind velocity for a wind load- governed limit state to secure a target reliability index during the design life of a structure. The nominal value of wind velocity, referred to as a basic wind velocity, and wind load factor should be determined so that the factored wind load effect secures a target reliability index for a wind load-governed limit state. In this study, the analytical form of the return period of the basic wind velocity is expressed as a function of the target reliability index, wind load factor, and statistical parameters of wind pressure, which are derived as linear functions of the coefficient of wind velocity. The proposed approach is applied to the Korean Highway Bridge Design Code-Cable supported Bridge, which specifies the design life of a structure as 100- and 200-year.</p>

INTERNAL FORCES IN THE FRAME OF BUILDING OF PRISMATIC FORM UNDER DIFFERENT DISTRIBUTION OF WIND PRESSURE

2021 ◽  
Vol 97 (5) ◽  
pp. 31-39
Author(s):  
V.S. KUZNETSOV ◽  
◽  
A.A. SHURUSHKIN ◽  
Keyword(s):  
Russian Federation ◽  
Research Method ◽  
Relevant Information ◽  
Wind Load ◽  
Building Codes ◽  
Wind Pressure ◽  
Regulatory Documents ◽  
Internal Forces ◽  
The Russian Federation ◽  
Graphic Interpretation

The features of the effect of wind on a prismatic-type building with different methods of determining the coefficient of wind pressure along the height are considered. The study was carried out on the basis of studying the main provisions of regulatory documents governing design and development activities in the Russian Federation, as well as current publications of domestic and foreign scientists, corresponding to research in this area. The research method is structural and analytical analysis using the correlation dependences of the factors under study. Analytical dependencies for determining the wind forces for various methods of assigning the wind load coefficient along the height of the building and their graphic interpretation are given. The work is based on the provisions of domestic building codes and relevant information contained in other domestic and foreign sources. For prismatic buildings with a height of up to 80 meters, there are areas where the forces from the main wind load significantly depend on the method of its determination. The conducted research indicates the ambiguity used in the practice of designing the parameters of the wind load, allowing the possibility of excess or underloading of structures or individual elements.

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