scholarly journals Performance of low-pressure fans operating with hot air

2016 ◽  
Vol 20 (suppl. 5) ◽  
pp. 1435-1447
Author(s):  
Jasmina Bogdanovic-Jovanovic ◽  
Dragica Milenkovic ◽  
Zivan Spasic ◽  
Dragan Svrkota
Keyword(s):  
Air Temperature ◽  
Axial Flow ◽  
Low Pressure ◽  
Operating Conditions ◽  
Empirical Formulas ◽  
Hot Air ◽  
Air Temperatures ◽  
The Common ◽  
Law Of Similarity ◽  
Temperature And Pressure

Performance characteristics of fans are generally provided for the normal temperature and pressure conditions (tI = 20?C, pI = 101.325 kPa, ? I = 1.2 kg/m3). Very often, fans operate in different air conditions, occasionally at different air temperatures. In these cases, equations obtained by the law of similarity are usually used for recalculation of the fan operating parameters. Increasing the inlet air temperature causes a decrease in the characteristic of Reynolds number, and may lead to efficiency lowering of the fan. There are also some empirical formulas for recalculation of fan efficiency, when operating at different air temperatures. In this paper, the common way for obtaining fan performance for different operating conditions (air temperature changing) is presented. The results, obtained by recalculation of fan parameters using a law of similarity, are compared to numerical simulation results of the axial-flow fan operating with different air temperatures. These results are compared with results obtained by some recommended empirical formulas, as well. This paperwork is limited to low-pressure and mid-pressure fans, which represents the majority of all fans used in practice, for different purposes.

Effects of Air Temperature on Combustion Characteristics of LPG Diffusion Flame

2020 ◽  
Vol 1008 ◽  
pp. 128-138
Author(s):  
Ahmed M. Salman ◽  
Ibrahim A. Ibrahim ◽  
Hamada M. Gad ◽  
Tharwat M. Farag
Keyword(s):  
Air Temperature ◽  
Diffusion Flame ◽  
Nitrogen Addition ◽  
Flame Length ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Low Oxygen ◽  
Air Temperatures ◽  
Air Stream ◽  
Wide Range

In the present study, the combustion characteristics of LPG gaseous fuel diffusion flame at elevated air temperatures were experimentally investigated. An experimental test rig was manufactured to examine a wide range of operating conditions. The investigated parameters are the air temperatures of 300, 350, 400, 450, and 500 K with constant percentage of nitrogen addition in combustion air stream of 5 % to give low oxygen concentration of 18.3 % by mass at constant air swirl number, air to fuel mass ratio, and thermal load of 1.5, 30, and 23 kW, respectively. The gaseous combustion characteristics were represented as axial and radial temperatures distributions, temperatures gradient, visible flame length and species concentrations. The results indicated that as the air temperature increased, the chemical reaction rate increased and flame volume decreased, the combustion time reduced leading to a reduction in flame length. The NO concentration reaches its maximum values near the location of the maximum centerline axial temperature. Increasing the combustion air temperature by 200 K, the NO consequently O2 concentrations are increased by about % 355 and 20 % respectively, while CO2 and CO concentrations are decreased by about % 21 and 99 % respectively, at the combustor end.

scholarly journals Effects of Incomplete Premixing on NOx Formation at Temperature and Pressure Conditions of LP Combustion Turbines

1997 ◽  
Author(s):  
Teodora Rutar ◽  
Scott M. Martin ◽  
David G. Nicol ◽  
Philip C. Malte ◽  
David T. Pratt
Keyword(s):  
Air Temperature ◽  
Chemical Reactor ◽  
Nox Emissions ◽  
Reactor Model ◽  
Nox Formation ◽  
Air Temperatures ◽  
Primary Zone ◽  
Lean Premixed ◽  
Temperature And Pressure

A probability density function/chemical reactor model (PDF/CRM) is applied to study how NOx emissions vary with mean combustion temperature, inlet air temperature, and pressure for different degrees of premixing quality under lean-premixed (LP) gas turbine combustor conditions. Inlet air temperatures of 550, 650 and 750 K, and combustor pressures of 10, 14 and 30 atm are examined in different chemical reactor configurations. Primary results from this study are: incomplete premixing can either increase or decrease NOx emissions, depending on the primary zone stoichiometry; an Arrhenius-type plot of NOx emissions may have promise for assessing the premixer quality of lean-premixed combustors; and decreasing premixing quality enhances the influence of inlet air temperature and pressure on NOx emissions.

scholarly journals Experimental investigation of occupants’ thermal sensation under a personalized ventilation system

2021 ◽  
Vol 2069 (1) ◽  
pp. 012167
Author(s):  
P Ebrahimi Naghani ◽  
S A Zolfaghari ◽  
M Maerefat ◽  
J Toftum ◽  
S M Hooshmand ◽  
...  
Keyword(s):  
Air Temperature ◽  
Cooling System ◽  
Thermal Sensation ◽  
Ventilation System ◽  
Body Part ◽  
Whole Body ◽  
Energy Costs ◽  
Air Temperatures ◽  
The Common ◽  
Personalized Ventilation

Abstract By considering the importance of providing proper indoor environment conditions for occupants and also due to energy costs, one of the solutions for indoor local air-conditioning is Personalized Ventilation System (PVS). In this paper, the occupants’ thermal sensation was experimentally studied for body segments that are mostly affected by the PVS. The local sensation of head, chest, arm, and hand at two supply air temperatures of 16 and 32°C were investigated. Eight volunteer subjects participated in this survey. The subjects reported the most thermal satisfaction on their hands. Also, the arms were the segments with the coolest thermal sensation (-1.28, between slightly cool and cold). Results indicate that the head’s thermal sensation at both supply air temperatures was neutral and the hand was the only body part that experienced warm thermal sensation during the test. Also, by increasing the supply air temperature to 32°C whole body thermal sensation changed from -0.46 to -0.09 on the seven-point scale, which means that the cooling system worked properly for occupants’ cooling. In this system, cooling occurred at 32°C instead of the common 16°C supply air temperature, which results in energy-saving and decreases annual running costs.

scholarly journals Temperate Air Breathing Increases Cycling Performance in Hot and Humid Climate Environment

Life ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 911
Author(s):  
Clovis Chabert ◽  
Aurélie Collado ◽  
Olivier Hue
Keyword(s):  
Air Temperature ◽  
Cycling Performance ◽  
Humid Climate ◽  
Constant Intensity ◽  
Male Athletes ◽  
Perceived Effort ◽  
Sports Events ◽  
Hot Air ◽  
Air Temperatures ◽  
Hot And Humid Climate

Practicing physical activity in a hot and humid climate (HHC) is becoming increasingly common due to anthropogenic climate change and the growing number of international sports events held in warm countries. The aim of this study was to understand the physiological and psychological effects of breathing two air temperatures during cycling exercise in HHC. Ten male athletes performed two sessions of exercise in HHC (T°: 32.0 ± 0.5 °C, relative humidity: 78.6 ± 0.7%) during which they breathed hot air (HA, 33.2 ± 0.06 °C) or temperate air (TA, 22.6 ± 0.1 °C). Each session was composed of 30 min of pre-fatigue cycling at constant intensity, followed by a 10 min self-regulated performance. During pre-fatigue, TA induced a better feeling score and a lower rating of perceived effort (respectively, +0.9 ± 0.2, p < 0.05; 1.13 ± 0.21; p < 0.05) with no changes in physiological parameters. During performance, oxygen consumption and mechanical workload were increased by TA (respectively, +0.23 ± 0.1 L min−1, p < 0.05 and +19.2 ± 6.1 W, p < 0.01), whereas no significant differences were observed for psychological parameters. Reducing the breathed air temperature decreased the discomfort induced by HHC during exercise and increased the performance capacity during self-regulated exercise. Thus, breathed air temperature perception is linked to the hardship of training sessions and directly contributes to the performance decrease in HHC.

Flame Propagation Following the Autoignition of Axisymmetric Hydrogen, Acetylene, and Normal-Heptane Plumes in Turbulent Coflows of Hot Air

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Christos N. Markides ◽  
Epaminondas Mastorakos
Keyword(s):  
Flame Propagation ◽  
Air Temperature ◽  
High Speed ◽  
High Speed Camera ◽  
Stoichiometric Mixture ◽  
Air Velocity ◽  
Flame Propagation Velocity ◽  
Hot Air ◽  
Air Temperatures ◽  
Continuous Injection

Axisymmetric plumes of hydrogen, acetylene, or n-heptane were formed by the continuous injection of (pure or nitrogen-diluted) fuel into confined turbulent coflows of hot air. Autoignition and subsequent flame propagation was visualized with an intensified high-speed camera. The resulting phenomena that were observed include the statistically steady “random spots” regime and the “flashback” regime. It was found that with higher velocities and smaller injector diameters, the boundary between random spots and flashback shifted to higher air temperatures. In the random spots regime the autoignition regions moved closer to the injector with increasing air temperature and/or decreasing air velocity. After a localized explosive autoignition event, flames propagated into the unburnt mixture in all directions and eventually extinguished, giving rise to autoignition spots of mean radii of 2–5mm for hydrogen and 6–10mm for the hydrocarbons. The average flame propagation velocity in both the axial and radial directions varied between 0.5 and 1.2 times the laminar burning speed of the stoichiometric mixture, increasing as the autoigniting regions shifted upstream.

Flame Propagation Following the Autoignition of Axisymmetric Hydrogen, Acetylene and Normal-Heptane Plumes in Turbulent Co-Flows of Hot Air

2006 ◽  
Author(s):  
Christos N. Markides ◽  
Epaminondas Mastorakos
Keyword(s):  
Flame Propagation ◽  
Air Temperature ◽  
High Speed ◽  
Stoichiometric Mixture ◽  
Air Velocity ◽  
Flame Propagation Velocity ◽  
Hot Air ◽  
Air Temperatures ◽  
Intensified Camera ◽  
Continuous Injection

Axisymmetric plumes of hydrogen, acetylene or n-heptane were formed by the continuous injection of (pure or nitrogen-diluted) fuel into turbulent co-flows of hot air. Autoignition and subsequent flame propagation was visualized with a high-speed intensified camera. The resulting phenomena include the statistically steady ‘Random Spots’ and the ‘Flashback’ regimes. It was found that with higher velocities and smaller injector diameters, the boundary between Flashback and Random Spots shifted to higher air temperatures. In the Random Spots regime, the autoignition regions moved closer to the injector with increasing air temperature and/or decreasing air velocity. After a localized explosive autoignition event, flames propagated into the unburnt mixture in all directions and eventually extinguished, giving rise to autoignition ‘spots’ of mean radius 2–5mm for hydrogen and 6–10mm for the hydrocarbons. The average flame propagation velocity in both the axial and radial directions varied between 0.5 and 1.2 times the laminar burning speed of the stoichiometric mixture, increasing as the autoigniting regions shifted upstream.

Temperature Regulation by Respiratory Evaporation in Grasshoppers

1990 ◽  
Vol 154 (1) ◽  
pp. 463-474 ◽  
Author(s):  
HENRY D. PRANGE
Keyword(s):  
Air Temperature ◽  
Locusta Migratoria ◽  
Evaporative Cooling ◽  
Internal Temperature ◽  
Common Assumption ◽  
Cuticular Transpiration ◽  
Air Temperatures ◽  
The Common ◽  
Rate Of Evaporation ◽  
Respiratory Evaporation

Grasshoppers of the species Schistocerca nitens (Thünberg), Locusta migratoria (L.) and Tmethis pulchripennis (Bolivar) are able to withstand air temperatures higher than lethal internal temperature (48 °C) for more than an hour, during which time they maintain an internal temperature as much as 8°C below air temperature. Rates of evaporation at high air temperatures are much greater than those observed for cuticular transpiration alone. The rate of evaporation and the ventilation frequency remain relatively constant at temperatures of up to about 45°C, above which they both increase markedly. The depression of internal temperature thus appears to be caused by increased tracheal ventilation for evaporative cooling. This finding contradicts the common assumption that evaporative cooling is of little adaptive advantage for thermoregulation in insects. In L. migratoria, the increase in ventilation appears to be achieved almost entirely by an increase in frequency of ventilation, although other species may alter tidal volume as well.

scholarly journals Thermo-Economic Assessment of a Gas Microturbine-Absorption Chiller Trigeneration System under Different Compressor Inlet Air Temperatures

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4643 ◽  
Author(s):  
Guillermo Valencia Ochoa ◽  
Carlos Acevedo Peñaloza ◽  
Jorge Duarte Forero
Keyword(s):  
Air Temperature ◽  
Economic Assessment ◽  
Economic Factor ◽  
Operating Conditions ◽  
Exergy Destruction ◽  
Absorption Refrigeration ◽  
Steam Generation ◽  
Cost Difference ◽  
Air Temperatures ◽  
Compressor Inlet

This manuscript presents a thermo-economic analysis for a trigeneration system integrated by an absorption refrigeration chiller, a gas microturbine, and the heat recovery steam generation subsystem. The effect of the compressor inlet air temperature on the thermo-economic performance of the trigeneration system was studied and analyzed in detail based on a validated model. Then, we determined the critical operating conditions for which the trigeneration system presents the greatest exergy destruction, producing an increase in the costs associated with loss of exergy, relative costs, and operation and maintenance costs. The results also show that the combustion chamber of the gas microturbine is the component with the greatest exergy destruction (29.24%), followed by the generator of the absorption refrigeration chiller (26.25%). In addition, the compressor inlet air temperature increases from 305.15 K to 315.15 K, causing a decrease in the relative cost difference of the evaporator (21.63%). Likewise, the exergo-economic factor in the heat exchanger and generator presented an increase of 6.53% and 2.84%, respectively.

scholarly journals Relationship between climate trends and grassland yield across contrasting European locations

2018 ◽  
Vol 13 (1) ◽  
pp. 589-598 ◽  
Author(s):  
Piotr Goliński ◽  
Marek Czerwiński ◽  
Marit Jørgensen ◽  
Jørgen A.B. Mølmann ◽  
Barbara Golińska ◽  
...  
Keyword(s):  
Air Temperature ◽  
Dry Matter ◽  
Meteorological Variables ◽  
Climate Trends ◽  
Degree Days ◽  
Climatic Trends ◽  
June July August ◽  
Air Temperatures ◽  
The Common ◽  
June July

AbstractWe investigated climatic trends in two contrasting locations in Europe at a regional level and at two specific sites, and we analysed how these trends are associated with the dry matter yield (DMY) of agriculturally improved grasslands. Trends of different meteorological variables were evaluated for Wielkopolska province, central Poland (1985-2014) and Troms county, northern Norway (1989-2015), as well as for two research stations located in these regions. Significant trends of increased mean air temperatures annually, and in April, June, July, August and November were identified both at the regional and site levels in Wielkopolska. In addition, growing degree days were increasing in Wielkopolska. In Troms, the common trends for the region and site studied were increase in mean air temperature in May and decrease in January. Grassland DMY was subsequently regressed against those meteorological variables for which significant trends were detected. In the Wielkopolska region, yields were negatively associated with the increase in air temperature in June, August, and the annual air temperature. The last relationship was also detected at the site level. We did not find any significant effects of climate trends on grassland DMY in the Norwegian study site or region.

On the dynamics of distribution of the American White Butterfly, Hyphantria cunea Drury, 1973 (Lepidoptera, Arctiidae), in Ukraine regarding the annual minimal air temperatures

2018 ◽  
Vol 14 (1) ◽  
pp. 44-57
Author(s):  
S. N. Shumov
Keyword(s):  
Air Temperature ◽  
Annual Reports ◽  
Complete Elimination ◽  
Hyphantria Cunea ◽  
White American ◽  
Gis Technologies ◽  
Data Analyses ◽  
Air Temperatures ◽  
Negative Temperatures

The spatial analysis of distribution and quantity of Hyphantria cunea Drury, 1973 across Ukraine since 1952 till 2016 regarding the values of annual absolute temperatures of ground air is performed using the Gis-technologies. The long-term pest dissemination data (Annual reports…, 1951–1985; Surveys of the distribution of quarantine pests ..., 1986–2017) and meteorological information (Meteorological Yearbooks of air temperature the surface layer of the atmosphere in Ukraine for the period 1951-2016; Branch State of the Hydrometeorological Service at the Central Geophysical Observatory of the Ministry for Emergencies) were used in the present research. The values of boundary negative temperatures of winter diapause of Hyphantria cunea, that unable the development of species’ subsequent generation, are received. Data analyses suggests almost complete elimination of winter diapausing individuals of White American Butterfly (especially pupae) under the air temperature of −32°С. Because of arising questions on the time of action of absolute minimal air temperatures, it is necessary to ascertain the boundary negative temperatures of winter diapause for White American Butterfly. It is also necessary to perform the more detailed research of a corresponding biological material with application to the freezing technics, giving temperature up to −50°С, with the subsequent analysis of the received results by the punched-analysis.

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