scholarly journals DETERMINATION OF LOAD DURATION CURVE (ROSSANDER GRAPH) FOR THE REGIONS OF UKRAINE

2018 ◽  
Vol 40 (4) ◽  
pp. 41-49
Author(s):  
V.G. Kramar
Keyword(s):  
Thermal Load ◽  
Energy Production ◽  
Ambient Air ◽  
Heat Energy ◽  
Climatic Data ◽  
Load Duration ◽  
Ambient Temperatures ◽  
Load Duration Curve ◽  
Air Temperatures ◽  
Regional Centers

The purpose of this work is to determine the duration of the ambient air temperatures of different gradations during heating periods in different regions of Ukraine, based on the climatic data for 2005-2018 and the construction of load duration curves for the respective regions. The load duration curve (Rossander graph) is used to determine the number of maximum thermal load using hours, as well as in cases where the thermal load is provided by several sources - to determine their level of participation in the total annual heat energy production. It is important for a more accurate technical and economic evaluation of implementation results for some thermal energy sources. The climatic data of meteorological stations located in the regional centers of Ukraine and the capital of Autonomous Republic of Crimea, or as close as possible to them, were used for the study. The climatic data of heating periods from the autumn of 2005 to 2018 were considered. As the result of study, the duration of various degrees of ambient air temperature in the heating period was determined for all the regional centers of Ukraine. Taking into account the significant climatic differences in the regions of Ukraine, the results were analyzed separately for two groups of regions, for which, according to averaged data, load duration curves were determined. The examples of using of obtained results for calculations are given. On the basis of obtained data regarding duration of ambient temperatures higher than +8°C during the heating season, the energy saving potential of implementation of weather-dependent regulation of heat energy production for heating purposes in different regions was theoretically estimated, which is, on average, 8.4% for the first temperature zone (north, center) and 13% for the second zone (south).

scholarly journals Numerical Simulation of Thermal-Hydrodynamic Behavior within Solar Air Collector

2018 ◽  
Vol 24 (3) ◽  
pp. 29
Author(s):  
Mustafa T. Mustafa ◽  
Ayad T. Mustafa
Keyword(s):  
Three Dimensional ◽  
Ambient Air ◽  
Heat Energy ◽  
Air Velocity ◽  
Hydrodynamic Behavior ◽  
Ansys Fluent ◽  
Velocity Increase ◽  
Air Temperatures ◽  
Solar Air Collector ◽  
Simulation Results

Solar collectors, in general, are utilized to convert the solar energy into heat energy, where it is employed to generate electricity. The non-concentrating solar collector with a circular shape was adopted in the present study. Ambient air is heated under a translucent roof where buoyant air is drawn from outside periphery towards the collector center (tower base). The present study is aimed to predict and visualize the thermal-hydrodynamic behavior for airflow under inclined roof of the solar air collector, SAC. Three-dimensional of the SAC model using the re-normalization group, RNG, k−ε turbulence viscus model is simulated. The simulation was carried out by using ANSYS-FLUENT 14.5. The simulation results demonstrated that at same insolation; airflow, ground and air temperatures increase when the collector radius decreases towards the collector center. The ground temperature and air velocity increase, while airflow temperature decreases when the inclination angle increases from 0° to 20° due to changing in airflow movement. More decreasing in airflow temperature has been occurred when the inlet height increases from 0.1m to 0.25m. The simulation results were validated by comparing with the experimental data. In conclusions, the obtained results showed the capability of producing warm airflow to generate electricity in Baghdad city.    

Investigating Thermal Performance of PCM Plates for Free Cooling Applications in South Africa

2017 ◽  
Author(s):  
Daniel M. Madyira ◽  
Ranwedzi P. Mukhodobwane ◽  
Tien C. Jen
Keyword(s):  
South Africa ◽  
Thermal Comfort ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Air Flow Rate ◽  
Storage Medium ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Free Cooling ◽  
Change Material

Free cooling involves using a thermal energy storage medium such as a phase change material (PCM) in order to store the ambient “cold” during the night when ambient air temperatures are lower compared to the indoor building temperatures and release this stored “cold” by using a heat transfer fluid (i.e. air) into the building during the day when higher ambient temperatures are experienced especially during the summer months. This paper assesses the free cooling potential in South Africa by using a set of Rubitherm RT25HC PCM plates. The performance of these PCM plates is assessed by benchmarking the ambient air cooled by the PCM plates during the day against the defined thermal comfort temperatures requirements. The influence of varying the air flow rate on the availability of thermal comfort temperatures at the PCM rig outlet is also studied. The results clearly show the potential of using PCM’s as a means of cooling higher ambient air temperature which is experienced in hot summer months to within thermal comfort temperatures for human occupancy in a building.

TEMPERATURE MODIFICATION BY BAGS OF THE BAGWORM THYRIDOPTERYX EPHEMERAEFORMIS (LEPIDOPTERA: PSYCHIDAE)

1983 ◽  
Vol 115 (7) ◽  
pp. 855-858 ◽  
Author(s):  
P. Barbosa ◽  
M. G. Waldvogel ◽  
N. L. Breisch
Keyword(s):  
Tree Species ◽  
Internal Surface ◽  
Ambient Air ◽  
Host Tree ◽  
Ambient Temperatures ◽  
Surface Temperatures ◽  
Temperature Modification ◽  
Air Temperatures ◽  
Host Tree Species ◽  
Sun And Shade

AbstractSurface and internal temperatures of bags made by Thyridopteryx ephemeraeformis (Haworth) as well as ambient temperatures were recorded in sun and shade. Temperatures of bags in both shaded and exposed areas of the tree were significantly higher than ambient air temperatures. Bag surface temperatures were not significantly different from internal bag temperatures. Differences between internal, surface, and ambient temperatures could not be attributed to host tree species. Finally, there were no significant differences in temperature between bags with and without larvae.

scholarly journals A New Submersion Detection Sensor Using Two Resistance Temperature Detectors Operating on the Thermal Equilibrium Principle

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4310 ◽  
Author(s):  
Youngjun Lee ◽  
Young Sam Lee
Keyword(s):  
Temperature Difference ◽  
Thermal Equilibrium ◽  
Dynamic Performance ◽  
Convective Heat Transfer Coefficient ◽  
Ambient Air ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Static Performance ◽  
Signal Conditioning Circuit ◽  
Reference Sensor

In this study, a new submersion detection sensor with improved reliability and stability is proposed. The new sensor uses two Resistance Temperature Detectors (RTDs) and operates on the thermal equilibrium principle. The submersion detection sensor controls two RTDs that maintain a constant temperature difference between them in the surrounding environment. The first RTD is used as a reference sensor to measure ambient temperature and the second RTD is supplied with higher current than the reference sensor for self-heating. When submerged, because the thermal conductivity and convective heat transfer coefficient of water are higher than that of air, the temperature difference between the two RTDs is lower in water than in air based on the thermal equilibrium principle. Under these conditions, a submersion detector with a signal conditioning circuit detects these temperature differences. The static performance of the proposed sensor was evaluated by checking whether malfunctions occurred at varying ambient temperatures, differing humidities, and when there was rainfall. In addition, the dynamic performance was evaluated using the response time at varying ambient air temperatures before submersion and with changing water temperatures after submersion, as a metric. The proposed submersion detection sensor is expected to find useful application in aircrafts, ships, and various other industrial fields.

Method for Redesign of District Heating Networks within Transition from the 2nd to the 3rd Generation

2014 ◽  
Vol 657 ◽  
pp. 689-693
Author(s):  
Răzvan Corneliu Lefter ◽  
Daniela Popescu ◽  
Alexandrina Untăroiu
Keyword(s):  
District Heating ◽  
Design Stage ◽  
Heating Systems ◽  
Load Duration ◽  
Load Duration Curve ◽  
District Heating Systems ◽  
Consumption Rates ◽  
Heat Loads ◽  
Heating Networks

Important investmentsare made lately in the area of district heating, as a technology capable ofhelping countries to reach sustainability goals. In Romania, European fundswere spent for transition from the 2nd to the 3rdgeneration of district heating systems. The lack of appropriate monitoringsystems in old district heating systems makes optimisation nowadays very difficult,especially because nominal values used in the first design stage areoverestimated. Realistic nominal heat loads are necessary to make goodestimations of hydraulic parameters to be used for redesign. This studyproposes a method that uses the heat load duration curve theory to identify theappropriate nominal heat loads to be used for redesign. Comparison betweenresults obtained by applying the nominal heat loads of each consumer, as theywere established in the first design stage, and the ones identified by theproposed method are analyzed in a case study. The results show that errors arein the +/- 3% band, between the metered heat consumption rates and the proposedrates. The new method can be used for the sizing of pumps and district heatingnetworks after retrofit, in order to get better adjustments of the circulationpumps and increase of the energy efficiency.

Physical fitness and thermoregulatory reactions in a cold environment in men

1988 ◽  
Vol 65 (5) ◽  
pp. 1984-1989 ◽  
Author(s):  
J. H. Bittel ◽  
C. Nonotte-Varly ◽  
G. H. Livecchi-Gonnot ◽  
G. L. Savourey ◽  
A. M. Hanniquet
Keyword(s):  
Physical Fitness ◽  
Cold Stress ◽  
Heat Production ◽  
Ambient Air ◽  
Metabolic Heat Production ◽  
Adult Males ◽  
Fitness Level ◽  
Metabolic Heat ◽  
Air Temperatures ◽  
Thermoregulatory Reactions

The relationship between the physical fitness level (maximal O2 consumption, VO2max) and thermoregulatory reactions was studied in 17 adult males submitted to an acute cold exposure. Standard cold tests were performed in nude subjects, lying for 2 h in a climatic chamber at three ambient air temperatures (10, 5, and 1 degrees C). The level of physical fitness conditioned the intensity of thermoregulatory reactions to cold. For all subjects, there was a direct relationship between physical fitness and 1) metabolic heat production, 2) level of mean skin temperature (Tsk), 3) level of skin conductance, and 4) level of Tsk at the onset of shivering. The predominance of thermogenic or insulative reactions depended on the intensity of the cold stress: insulative reactions were preferential at 10 degrees C, or even at 5 degrees C, whereas colder ambient temperature (1 degree C) triggered metabolic heat production abilities, which were closely related to the subject's physical fitness level. Fit subjects have more efficient thermoregulatory abilities against cold stress than unfit subjects, certainly because of an improved sensitivity of the thermoregulatory system.

scholarly journals Direct Calculation of Thermodynamic Wet-Bulb Temperature as a Function of Pressure and Elevation

2013 ◽  
Vol 30 (8) ◽  
pp. 1757-1765 ◽  
Author(s):  
Sayed-Hossein Sadeghi ◽  
Troy R. Peters ◽  
Douglas R. Cobos ◽  
Henry W. Loescher ◽  
Colin S. Campbell
Keyword(s):  
Air Temperature ◽  
Mean Absolute Error ◽  
Direct Calculation ◽  
Ambient Air ◽  
Absolute Error ◽  
Mean Square ◽  
Air Temperatures ◽  
Order Polynomial ◽  
The Mean ◽  
Very High

Abstract A simple analytical method was developed for directly calculating the thermodynamic wet-bulb temperature from air temperature and the vapor pressure (or relative humidity) at elevations up to 4500 m above MSL was developed. This methodology was based on the fact that the wet-bulb temperature can be closely approximated by a second-order polynomial in both the positive and negative ranges in ambient air temperature. The method in this study builds upon this understanding and provides results for the negative range of air temperatures (−17° to 0°C), so that the maximum observed error in this area is equal to or smaller than −0.17°C. For temperatures ≥0°C, wet-bulb temperature accuracy was ±0.65°C, and larger errors corresponded to very high temperatures (Ta ≥ 39°C) and/or very high or low relative humidities (5% < RH < 10% or RH > 98%). The mean absolute error and the root-mean-square error were 0.15° and 0.2°C, respectively.

EFFECTS OF LOW FLUCTUATING TEMPERATURES ON FARM ANIMALS.: III. INFLUENCE OF AMBIENT AIR TEMPERATURE ON FEED INTAKE OF LACTATING HOLSTEIN-FRIESIAN COWS

1958 ◽  
Vol 38 (2) ◽  
pp. 148-159 ◽  
Author(s):  
M. A. MacDonald ◽  
J. M. Bell
Keyword(s):  
Milk Production ◽  
Air Temperature ◽  
Low Temperatures ◽  
Ambient Air ◽  
Feed Consumption ◽  
Ambient Temperatures ◽  
Ambient Air Temperature ◽  
Holstein Friesian ◽  
Cent Level ◽  
Friesian Cows

This report presents effects of low temperatures on the feed consumption and efficiency of milk production of six mature, lactating, Holstein-Friesian cows that were confined in stanchions for three fortnightly experimental periods during which ambient temperatures measured in degree-hours per day (d-h/day) ranged from 110 to 1152 and daily minimum ambient air temperature (DMAAT) varied from 0° to 38°F. Applying results obtained, it was calculated that as temperatures decreased, i.e., d-h/day increased from 100 to 1200 and DMAAT decreased from 40° to 0°F, average daily intakes of total dry matter, hay, and gross and digestible Calories increased approximately 6.4 lb., 5.3 lb., 13 Therms and 9 Therms, respectively. Each of these increases was statistically significant at the 1 per cent level. Reductions in temperature also decreased gross and net caloric efficiencies of milk production approximately 10 and 8.5 per cent, respectively. These decreases were significant at the 2 per cent level. No correlation was evident between crude protein utilization and temperature.Results indicated that thermal stress was not overcome adequately by supplementary hay intake alone and that appetite stimulation by low temperatures had a carry-over effect continuing at least 24 hours. For continued efficient milk production during winters where low ambient temperatures are prevalent these results suggest it is necessary to provide some form of building insulation, ambient heat and/or provide a high energy supplement to otherwise adequate production rations.

scholarly journals Performance Evaluation of a CO2 Refrigeration System Enhanced with a Dew Point Cooler

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1079 ◽  
Author(s):  
Martin Belusko ◽  
Raymond Liddle ◽  
Alemu Alemu ◽  
Edward Halawa ◽  
Frank Bruno
Keyword(s):  
Weather Conditions ◽  
Dew Point ◽  
Coefficient Of Performance ◽  
Experimental Program ◽  
Refrigeration System ◽  
Conventional System ◽  
Ambient Temperatures ◽  
Air Temperatures ◽  
Condenser Temperature

Dew point cooling (DPC) is a novel indirect evaporative cooling concept capable of delivering air temperatures approaching the dew point. Coupling this technology with CO2 refrigeration is well suited to minimising transcritical operation when the coefficient of performance (COP) is dramatically reduced in hot climates. A substantial experimental program was conducted to characterise this combination by testing a 20 kW CO2 refrigeration system subject to ambient temperatures above 40 °C. It was demonstrated that DPC operation not only avoided transcritical operation during such weather conditions, but also increased the COP by up to 140% compared to the conventional system. The combination of these technologies was successfully mathematically modelled, from which the optimum condenser inlet air temperature was identified for each condenser temperature. Using this optimum condition, it was possible to maximise the COP for a range of conditions applicable to the psychometric chart. An annual case study for Adelaide, Australia was conducted which demonstrated that optimally coupling DPC with CO2 refrigeration can reduce the annual energy consumption and peak demand by 16% and 47%, respectively, compared to a conventional CO2 booster system. Furthermore, the number of hours of transcritical operation was reduced from 3278 to 27.

scholarly journals Measurement report: Chemical characteristics of PM<sub>2.5</sub> during typical biomass burning season at an agricultural site of the North China Plain

2021 ◽  
Vol 21 (4) ◽  
pp. 3181-3192
Author(s):  
Linlin Liang ◽  
Guenter Engling ◽  
Chang Liu ◽  
Wanyun Xu ◽  
Xuyan Liu ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Inorganic Ions ◽  
Northern China ◽  
Ambient Air ◽  
Rural Site ◽  
Biomass Combustion ◽  
Chemical Components ◽  
The North ◽  
Air Temperatures ◽  
Agricultural Site

Abstract. Biomass burning activities are ubiquitous in China, especially in northern China, where there is a large rural population and winter heating custom. Biomass burning tracers (i.e., levoglucosan, mannosan and potassium (K+)), as well as other chemical components, were quantified at a rural site (Gucheng, GC) in northern China from 15 October to 30 November, during a transition heating season, when the field burning of agricultural residue was becoming intense. The measured daily average concentrations of levoglucosan, mannosan and K+ in PM2.5 (particulate matter with aerodynamic diameters less than 2.5 µm) during this study were 0.79 ± 0.75, 0.03 ± 0.03 and 1.52 ± 0.62 µg m−3, respectively. Carbonaceous components and biomass burning tracers showed higher levels during nighttime than daytime, while secondary inorganic ions were enhanced during daytime. An episode with high levels of biomass burning tracers was encountered at the end of October 2016, with high levoglucosan at 4.37 µg m−3. Based on the comparison of chemical components during different biomass burning pollution periods, it appeared that biomass combustion can obviously elevate carbonaceous component levels, whereas there was essentially no effect on secondary inorganic aerosols in the ambient air. Moreover, the levoglucosan / mannosan ratios during different biomass burning pollution periods remained at high values (in the range of 18.3–24.9); however, the levoglucosan / K+ ratio was significantly elevated during the intensive biomass burning pollution period (1.67) when air temperatures were decreasing, which was substantially higher than in other biomass burning periods (averaged at 0.47).

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