scholarly journals Exergy of heat flows in exchanger consisting f gravity heat pipes

2012 ◽  
Vol 51 (No. 3) ◽  
pp. 73-78
Author(s):  
D. Adamovský ◽  
P. Neuberger ◽  
D. Herák ◽  
R. Adamovský
Keyword(s):  
Heat Flow ◽  
Air Temperature ◽  
Thermal Efficiency ◽  
Heat Pipes ◽  
Exergy Efficiency ◽  
Heat Flows ◽  
Heat Processes ◽  
The Impact

The paper deals with the analysis of the impact of inlet air temperature on the exergy efficiency and exergy of the losing heat flow and determination of the relation between the exergy and thermal efficiency in an exchanger consisting of gravity heat pipes. The assessment of heat processes quality and transformation of energy in the exchanger are also dealt with.

Optimum Flashing Pressure in Single and Double Flash Geothermal Power Plants

2008 ◽  
Author(s):  
Shahin Amiri ◽  
Hossein Shokouhmand ◽  
Ahmad Kahrobaian ◽  
Shayan Amiri
Keyword(s):  
Power Plant ◽  
Thermal Efficiency ◽  
Power Plants ◽  
Analytical Investigation ◽  
Exergy Efficiency ◽  
Maximum Efficiency ◽  
Single Flash ◽  
Geothermal Power ◽  
Double Flash

In this paper an analytical investigation has been reported on determination of the optimum flashing pressures to get maximum efficiency in flash geothermal power plants. Also, two different views on efficiency have been considered; thermal efficiency and exergy efficiency. Both views anticipate very close optimum flashing pressure and in this pressure, exergy efficiency is between 3 to 5.5 times more than thermal efficiency. It is observed that the optimum flashing pressure in a single flash power plant is between the optimum flashing pressures of two separators in a double flash power plant. Also both views predict an increase of 20–29 percent for the efficiency of double flash power plants than the efficiency of single flash power plants.

scholarly journals Visualization of heat transport in heat pipes using thermocamera

2010 ◽  
Vol 31 (4) ◽  
pp. 125-132 ◽  
Author(s):  
Patrik Nemec ◽  
Alexander Čaja ◽  
Richard Lenhard
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Fluid Transport ◽  
Heat Pipes ◽  
Working Fluid ◽  
Vertical Position ◽  
Change Of State ◽  
Heat Processes ◽  
High Level ◽  
The Impact

Visualization of heat transport in heat pipes using thermocamera Heat pipes, as passive elements show a high level of reliability when taking heat away and they can take away heat flows having a significantly higher density than systems with forced convection. A heat pipe is a hermetically closed duct, filled with working fluid. Transport of heat in heat pipes is procured by the change of state of the working fluid from liquid state to steam and vice versa and depends on the hydrodynamic and heat processes in the pipe. This study have been focused on observing the impact these processes have on the heat process, the transport of heat within the heat pipe with the help of thermovision. The experiment is oriented at scanning the changes in the surface temperatures of the basic structural types of capillary heat pipes in vertical position.

An Analysis of Heat Exchange Crisis in the Capillary Porous System for Cooling Parts of Heat and Power Units

2019 ◽  
pp. 21-35
Author(s):  
A.A. Genbach ◽  
D.Y. Bondartsev
Keyword(s):  
Heat Exchange ◽  
Heat Flow ◽  
Joint Action ◽  
Limit State ◽  
Bottom Layer ◽  
Heated Layer ◽  
Porous Coating ◽  
Porous System ◽  
Heat Flows ◽  
The Impact

A model of dynamics of the vapor bubbles that emerge on solid surfaces of porous structures and the steam generating wall (bottom layer) is presented in this work. The model was filmed and photographed by a high-speed camera SKS-1М. The discharge of high heat flows (up to 2·106 W/m2) was maintained by the joint action of capillary and mass forces with the help of intensifiers. An analytical model was developed based on the theory of thermoelasticity. The limit state of the porous coating with poor thermal conductivity and the metal bottom layer was determined. Heat flows were calculated from the spontaneous birth of the vapour nucleus (10–8) to the material destruction (102–103 s), thus the interval from the process of relaxation to the maximum process (destruction) was described. The size of the pullout particles determined in the model at the moment of porous coating destruction showed good congruence with the experimental data obtained at the optic stand. The destruction of coating under the compression forces occurs much earlier than the tension forces. It is probable that the destruction will happen under the impact of the compression and shear forces. The intervals of the heat flow when such destruction takes place are different for quartz and granite coating. Each thickness of the pullout particles under the impact of compression forces has its limit values of the heat flows, which are located within the mentioned intervals. As the specific heat flow in the heated layer increases and, therefore, the heating time decreases, the impact of the compression stresses increases as well. Despite the high resistance to compression, destruction from the compressive heat tension occurs in more favorable conditions immediately, and in diminutive volumes. Experimental testing units, test conditions, the outcome of the heat exchange crisis, the limit state of the surface and the calculation of critical heat flows are presented. The capillary porous system that works under the joint action of capillary and mass forces is studied. The system has advantages compared to pool boiling, thin-film evaporators and heat pipes.

scholarly journals The Evolution of Climate Changes in Portugal: Determination of Trend Series and Its Impact on Forest Development

Climate ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 78 ◽  
Author(s):  
Leonel J. R. Nunes ◽  
Catarina I. R. Meireles ◽  
Carlos J. Pinto Gomes ◽  
Nuno M. C. Almeida Ribeiro
Keyword(s):  
Rural Communities ◽  
Air Temperature ◽  
Critical Period ◽  
Large Scale ◽  
Climate Changes ◽  
Variable Precipitation ◽  
The Impact ◽  
The Relationship ◽  
Climatic Normal

Climate changes are a phenomenon that can affect the daily activities of rural communities, with particular emphasis on those directly dependent on the agricultural and forestry sectors. In this way, the present work intends to analyse the impact that climate changes have on forest risk assessment, namely on how the occurrence of rural fires are affecting the management of the forest areas and how the occurrence of these fires has evolved in the near past. Thus, a comparative analysis of the data provided by IPMA (Portuguese Institute of the Sea and the Atmosphere), was carried out for the period from 2001 to 2017 with the climatic normal for the period between 1971 to 2000, for the variables of the average air temperature, and for the precipitation. In this comparative study, the average monthly values were considered and the months in which anomalies occurred were determined. Anomalies were considered in the months in which the average air temperature varied by 1 °C than the value corresponding to the climatic norm, in at least 50% of the national territory. The same procedure was repeated for the variable precipitation, counting as anomaly the occurrence of a variation in precipitation of 50%, also in 50% of the national territory. Then the calculation of the moving averages for cycles of 3, 5 and 7 periods were applied, and the trend lines were projected. Subsequently, the relationship between the results obtained and the occurrence of rural fires as well as the spatial distribution of forest area, species and structure were analyzed. From the results obtained it was possible to confirm the existence of a tendency for the occurrence of climatic anomalies, highlighting the occurrence of an increasing number of months with temperatures higher by at least 1 °C. It was possible to foresee the relation between the occurrence of rural fires and the periods of anomaly and absence of precipitation. From the results obtained it is also possible to infer that, analyzing the tendency for these phenomena to occur, it can be necessary to change the “critical period of rural fires”, since it is verified that what is currently in use does not covers the entire period where anomalies occur and where large-scale rural fires potentially can happen.

Experimental Study of Exergy Analysis on Flat Plate Solar Photovoltaic Thermal (PV/T) Hybrid System

2015 ◽  
Vol 787 ◽  
pp. 82-87 ◽  
Author(s):  
B. Srimanickam ◽  
M.M. Vijayalakshmi ◽  
Elumalai Natarajan
Keyword(s):  
Flat Plate ◽  
Air Temperature ◽  
Hybrid System ◽  
Thermal Efficiency ◽  
Exergy Analysis ◽  
Ambient Air ◽  
Exergy Efficiency ◽  
Solar Photovoltaic ◽  
Electrical Efficiency ◽  
Energy And Exergy

The objective of present study is to conduct exergy analysis on flat plate solar photovoltaic thermal (PV/T) hybrid system. The solar insolation, current, voltage, inlet and outlet air temperature of the cooling duct, ambient air temperature, and solar panel surface temperature are the major parameters used to calculate the energy and exergy efficiency. An amended electrical efficiency is used to estimate the electrical output and performance of PV/T hybrid system. Further, an enriched equation for the exergy efficiency of a PV/T hybrid system has been used for exergy analysis. Finally, parametric studies have been carried out. An extensive energy and exergy analysis is carried out to calculate the electrical and thermal parameters. The experimental results are in good agreement with the earlier studies. In addition to that, the electrical efficiency, thermal efficiency, electrical thermal efficiency, overall energy efficiency and exergy efficiency of PV/T hybrid system is found to be about 9.78%, 24.22%, 27.17%, 44.84% and 11.23% respectively.

scholarly journals Impact of Changing the Surrounding Urban Context on Sustainable Design of Historic Buildings

2021 ◽  
Vol 318 ◽  
pp. 04010
Author(s):  
Hafedh Abed Yahya ◽  
Khalid J. Aluddin Ismail ◽  
Turki Hasan Ali
Keyword(s):  
Built Environment ◽  
Air Temperature ◽  
Thermal Efficiency ◽  
Building Materials ◽  
Conservation Strategy ◽  
Climatic Data ◽  
Historic Buildings ◽  
Urban Context ◽  
First Case ◽  
The Impact

Research aims are to explain the impact of the built environment on the efficiency of sustainability of historical buildings. The most vital factor of sustainability in hot and semi-dry climates is the thermal efficiency of inner spaces. The conventional building materials used in historic buildings in Mosul have high thermal efficiency, but it works with the surrounding built environment as an integrated thermal system. This surrounding built environment could be exposed to dramatic changes within the efforts of reconstruction of Mosul city. Al-Aghawat mosque was selected as a case study due to its surrounding urban context and original conventional building materials. This research adopts ENVImet analysis method. Physiologically Equivalent Temperature (PET) index was assumed to be the indicator for thermal comfort in hot and semi-dry weather. ENVI-met program applied for simulation of two cases at the hottest day in the summer of 2019-2020 through climatic data. The first case estimates the air temperature in the inner and open spaces of the mosque with its original surrounding context and then checks the air temperature of the same spaces after removing the surrounding context. The results reveal changes in thermal efficiency within the two cases. In order to conserve the thermal efficiency of the historic buildings, the researchers recommended adopting a conservation strategy of the surrounding context.

scholarly journals The distribution of air temperature and velocity in the selected boiler room

2018 ◽  
Vol 44 ◽  
pp. 00020 ◽  
Author(s):  
Robert Cichowicz ◽  
Artur Stelęgowski
Keyword(s):  
Air Temperature ◽  
Thermal Environment ◽  
Physical Factors ◽  
Limit Values ◽  
Air Supply ◽  
Industrial Buildings ◽  
Boiler Room ◽  
Environment Parameters ◽  
The Impact

The crucial impact on the indoor air quality in technological rooms, including boiler plant buildings, is made by operation of technological devices and ventilation systems. Therefore, the distribution of air temperature and velocity in these rooms mainly depends on location and heat gains generated by combustion devices, as well as emplacement of air supply and air exhaust elements. The temperature and airflow volume of supplied air is also an issue, because the indoor environment parameters are formed by the flow of air in the working area. Determination of the impact of physical factors on the thermal environment in a room is possible using an analysis of the air temperature and velocity. This issue is vital in terms of necessity to maintain the adequate heat conditions in the working area. Therefore, basing on the experimental measurements and numerical calculations (made in DesignBuilder software), the distribution of air temperature and velocity was analyzed in the selected industrial boiler room, located in the Lodz city, in Poland. The results obtained were compared with the recommended and limit values in the industrial buildings.

Assessment of sensitivity of the efficiency of regional tax spending towards investment attractiveness of the types of economic activity carried out by the residents of advanced development territory

2020 ◽  
pp. 98-110
Author(s):  
Evgeniya Mikhailovna Popova ◽  
Guzel Mukhtarovna Guseinova ◽  
Sergei Borisovich Milov
Keyword(s):  
Economic Activity ◽  
Socioeconomic Development ◽  
Federal District ◽  
Tax Incentives ◽  
Capital Investments ◽  
The Subject ◽  
Investment Process ◽  
The Impact ◽  
Advanced Development

The deficit of subnational budgets and deceleration capital investments in multiple Russian regions increase the relevance of research aimed at improvement of tax incentivizing practice of the regional investment process. The studies focused on determination of the impact of socioeconomic and institutional factors upon the efficiency of investment tax expenses obtained wide circulation within the foreign scientific literature. The subject of this article is the assessment of sensitivity of the efficiency of regional tax expanses towards investment attractiveness of the types of economic activity carried out by the residents of territories of advanced socioeconomic development, created in the subjects of Far Easter Federal District. The scientific novelty and practical values of this research consists in substantiation of the reasonableness of assessment of investment attractiveness of the types of economic activity that are stimulated by tax incentives. Methodology for assessing investment attractiveness is proposed and tested. The conclusion is made that in case of low investment attractiveness of the type of economic activity, which was planned to support by tax incentives, it is required to conduct and additional analysis to avoid unjustified tax expanses.

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