Effect Of Ambient Air Temperature Research Articles

Data-driven modeling approach for performance analysis and optimal operation of a cooling tower

This paper proposes a data-driven adaptive modeling approach to investigate the performance and optimal operation of a cooling tower for energy conservation. To achieve this aim, the cooling tower process was first characterized by an adaptive model with nonnegative garrote (NNG) variable selection procedure, which ensured a compact and robust input–output relation. Owing to the high accuracy of the obtained model, implementing the optimal operation strategy for energy saving became readily practicable. Subsequently, on the basis of the statistical results of NNG variable selection, the effects of ambient air temperature and humidity on the cooling capacity of the tower were investigated by principal component analysis (PCA). Finally, the optimal strategy of fan operation was proposed and its implementation was virtually studied based on data from the actual operation of a cooling tower, which showed that there was considerable room for energy conservation. This is the first attempt to use the NNG variable selection method for developing model for cooling tower and to propose a model-based control scheme for operating a cooling tower.

Discrete model-based operation of cooling tower based on statistical analysis

This study is aimed to utilize the operation data to build a physical-meaningful and precise-enough model to assist the operation of a cooling tower. To do so, this work introduces a dimensionless index, which can describe the cooling capability of a cooling tower in terms of effective power utilization. In the first phase of this study, principal component analysis, one of factor analysis methods, is used to investigate effects of ambient air temperature and relative humidity on the cooling capability of a cooling tower. Based on the proposed cooling capability index, the operation data are partitioned into different groups by the fuzzy c-mean clustering algorithm. The resulted groups are distinctly categorized by the conditions of ambient air temperature and relative humidity. In the second phase of the study, data within the same mode of a set of fans are partitioned by the fuzzy c-mean clustering algorithm. The resulted groups of data are then modeled by linear regression. The acquired multiple models are highly accurate in predicting the output temperature of cooling water from the cooling tower. The acquired models assist the operator to accurately select the proper fan mode when process conditions, e.g., cooling loading, or environment conditions, e.g., ambient air temperature, change. It results in electricity saving. This study is concluded by the presentation of a discrete model-based approach to determine the fan mode. The application to a real cooling tower in an iron and steel plant is promising in saving electricity consumed by the fan set.

Reducing energy consumption of a raw mill in cement industry

Several grinding methods are available in cement industry depending upon the material to be ground. In cement production process, about 26% of the total electrical power is used in grinding the raw materials. During grinding process, the energy obtained from the rotary burner is consumed. In this study, the first and second law analysis of a raw mill is performed and certain measures are implemented in an existing raw mill in a cement factory in order to reduce the amount of energy consumption in grinding process. The first and second law efficiencies of the raw mill are determined to be 61.5% and 16.4%, respectively. The effects of ambient air temperature and moisture content of raw materials on the performance of the raw mill are investigated. The data collected over a 12-month period indicate that first and second law efficiencies of the raw mill increase as the ambient temperature increase and the moisture content of the raw materials decrease. The specific energy consumption for farine production is determined to be 24.75 kWh/ton farine. The use of an external hot gas supply provides 6.7% reduction in energy consumption corresponding to a saving of 1.66 kWh per ton of farine production.

Numerical simulation of buoyancy-driven turbulent ventilation in attic space under winter conditions

Attic design and construction have significant impacts on residential buildings’ energy performance. In order to understand how passive ventilation rates affect ridge-vent attic's performance, a two-dimensional steady-state finite volume model is employed to simulate the buoyancy-driven turbulent ventilation and heat transfer in a triangular attic space of a gable-roof residential building under winter conditions. The modeled attic has a pitch of 5/12 and a passive ventilation system, consisting of continuous ridge and soffit vents. The v2f model is used to analyze the turbulent air flow and natural convection heat transfer inside the attic. The effects of ambient air temperature, vent size, and ceiling insulation on heating load and ice dam formation are investigated. The thermal performance of the vented attic is compared with a sealed attic as well. The simulation results reveal that symmetrical air flow patterns exist in a vented attic, in contrast to the asymmetrical air flow patterns found in a sealed attic. In addition, it is suggested that increasing vent size results in higher ventilation air flow rate but barely affects the attic heating load, and that both sufficient ventilation and insulation are needed to ensure the proper functions of the attic and its energy efficiency.

An iterative method for modelling the air-cooled organic Rankine cycle geothermal power plant

This work presents an iterative method for modelling the effect of ambient air temperature on the air-cooled organic Rankine cycle. The ambient temperature affects the condenser performance, and hence the performance of the whole cycle, in two ways. First, changing the equilibrium pressure inside the condenser, the turbine outlet pressure and the turbine pressure ratio vary. Since the turbine pressure ratio is a major parameter in determining the power generated by a turbine, the plant output is directly affected. Second, changing the condenser outlet temperature with ambient temperature, the pump inlet and outlet conditions are changed. Thus, the vapourizer equilibrium temperature and pressure are influenced. The developed method iteratively seeks the equilibrium conditions for both the condenser and vapourizer. Two case studies based on a real plant performance have been carried out to demonstrate the validity of the method. The developed method demonstrates robustness and converges regardless of the initial conditions allowed by the physical properties of the working fluid. This method is effective for cycles that use saturated vapour as well as superheated vapour under static or dynamic conditions with appropriate initial conditions and constraints. The developed method may be applied to any Rankine cycle with closed cycle operation. Copyright © 2010 John Wiley & Sons, Ltd.

Performance of a gas engine heat pump (GEHP) using R410A for heating and cooling applications

Abstract A gas engine heat pump (GEHP) represents one of the most practicable systems which improve the overall energy utilization efficiency and reduce the operating cost for heating and cooling applications. The present work aimed at evaluating the performance of a GEHP for air-conditioning and hot water supply. In order to achieve this objective, a test facility was developed and experiments were performed over a wide range of engine speed (1200 rpm–1750 rpm), ambient air temperature (24.1 °C–34.8 °C), evaporator water flow rate (1.99 m 3 /h–3.6 m 3 /h) and evaporator water inlet temperature (12.2 °C–23 °C). Performance characteristics of the GEHP were characterized by water outlet temperatures, cooling capacity, heating capacity and primary energy ratio (PER). The results showed that the effect of evaporator water inlet temperature on the system performance is more significant than the effects of ambient air temperature and evaporator water flow rate. PER of the considered system at evaporator water inlet temperature of 23 °C is higher than that one at evaporator water inlet temperature of 12.2 °C by about 22%. PER of the system decreases by 16% when engine speed changes from 1200 rpm to 1750 rpm.

Effects of Environmental Conditions on Performance of Vaginal Implant Transmitters

ABSTRACT Vaginal implant transmitters (VITs) are increasingly used to facilitate capture of neonatal ungulates. Environmental conditions potentially have a significant influence on performance of VITs; however, effects on VIT performance largely are unknown. We exposed VITs to conditions reflective of those present during white‐tailed deer fawning season in Alabama and examined effects of ambient air temperature and vegetative structure on their performance. Performance of VITs was inversely related to ambient air temperature, and VIT performance increased along with increasing amounts of shade provided by vegetation. Current devices likely will perform relatively well if expelled in areas where ambient air temperatures are below the user‐defined pulse switch point and habitat conditions provide shade. Performance of VITs will be severely compromised if expulsion occurs in areas where ambient air temperatures are above the user‐defined pulse switch point and devices are exposed to direct sun. Individuals interested in utilizing VITs should consider local climate and vegetative characteristics prior to initiating projects to evaluate if devices will meet performance requirements.

Experiments on the transition from the steady to the oscillatory marangoni convection of a floating-zone under various cold wall temperatures and various ambient air temperature effects

The transition from the steady to the oscillatory Marangoni convection of a floating-zone under various cold wall temperatures and various ambient air temperature effects have been investigated experimentally by heating the sample from above (opposite direction of Marangoni convection and buoyant forces). The heat transfer takes place mainly through conduction as well as the natural convection of the air around the cylindrical liquid bridge. The ambient airflow in the present work is varied by varying the cold wall temperature and ambient air temperature. In this study, the transition from the steady to the oscillatory Marangoni convection flow of a high Prandtl number fluid in a floating half-zone is visualized by means of the already proven method of the “light-cut-technique”. The test fluid zone is held in ambient air at +4 °C, +10 °C, +16 °C, +23 °C, and +28 °C. The onset of oscillations, the oscillation level, and oscillation pattern are investigated under various conditions. It is found that the critical temperature difference (ΔTCr) varies substantially when the cold wall temperature and the ambient air temperature are varied.

The effect of ambient air temperature on whole-body bioelectrical impedance

It has previously been shown that extreme changes in ambient air temperature can affect whole-body bioelectrical impedance. The purpose of this study was to determine if more moderate changes in ambient air temperature, such as those experienced in most laboratory settings, would also affect bioelectric impedance analysis (BIA). In addition, to elucidate the mechanism responsible for changes in BIA with ambient air temperature, both skin blood flow (SBF) and the electrode–skin interface temperature were independently manipulated to determine their effect on BIA. During the first part of the study, nine healthy volunteers had their BIA measured in five different ambient air temperatures (15, 20, 25, 30 and 35 °C). Mean BIA was 513 Ω under the 15 °C condition and decreased significantly (p < 0.05) to 486 Ω in the 35 °C trial. However, no significant change was found in mean BIA between the 20 and 25 °C trials, which is the temperature range seen in most laboratories. Thus, moderate changes in ambient air temperature have only minor effects on BIA. In the second and third parts of the study, the electrode–skin interface temperature and SBF were independently manipulated using ice packs and electric heating pads placed over the four BIA electrodes. The results showed that BIA was inversely related to SBF (r = −0.95), and strongly suggest that changes in SBF, not electrode–skin interface temperature, are responsible for the changes seen in BIA.

Snow Removal and Ambient Air Temperature Effects of Forest Soil Temperatures in Northern Vermont

Soil Science Society of America JournalVolume 67, Issue 5 p. 1629-1629 Erratum Snow Removal and Ambient Air Temperature Effects of Forest Soil Temperatures in Northern Vermont K.L.M. Decker, K.L.M. DeckerSearch for more papers by this authorD. Wang, D. WangSearch for more papers by this authorC. Waite, C. WaiteSearch for more papers by this authorT. Scherbatskoy, T. ScherbatskoySearch for more papers by this author K.L.M. Decker, K.L.M. DeckerSearch for more papers by this authorD. Wang, D. WangSearch for more papers by this authorC. Waite, C. WaiteSearch for more papers by this authorT. Scherbatskoy, T. ScherbatskoySearch for more papers by this author First published: 01 September 2003 https://doi.org/10.2136/sssaj2003.1629Citations: 3Read the full textAbout ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume67, Issue5September 2003Pages 1629-1629 RelatedInformation

Snow Removal and Ambient Air Temperature Effects on Forest Soil Temperatures in Northern Vermont

We measured deciduous forest soil temperatures under control (unmanipulated) and snow-free (where snow is manually removed) conditions for four winters (at three soil depths) to determine effects of a snow cover reduction such as may occur as a result of climate change on Vermont forest soils. The four winters we studied were characterized as: ‘cold and snowy’, ‘warm with low snow’, ‘cold with low snow’, and ‘cool with low snow’. Snow-free soils were colder than controls at 5- and 15-cm depth for all years, and at all depths in the two cold winters. Soil thermal variability generally decreased with both increased snow cover and soil depth. The effect of snow cover on soil freeze-thaw events was highly dependent on both the depth of snow and the soil temperature. Snow kept the soil warm and reduced soil temperature variability, but often this caused soil to remain near 0°C, resulting in more freeze–thaw events under snow at one or more soil depths. During the ‘cold snowy’ winter, soils under snow had daily averages consistently >0°C, whereas snow-free soil temperatures commonly dropped below −3°C. During the ‘warm’ year, temperatures of soil under snow were often lower than those of snow-free soils. The warmer winter resulted in less snow cover to insulate soil from freezing in the biologically active top 30 cm. The possible consequences of increased soil freezing include more root mortality and nutrient loss, which would potentially alter ecosystem dynamics, decrease productivity of some tree species, and increase sugar maple (Acer saccharum Marshall) mortality in northern hardwood forests.

Advanced Fluid Information. The Effect of Temperature on the Minimum Fluidization Velocity Calculated by Distinct Element Method.

The effect of ambient air temperature on the minimum fluidization velocity U mf of glass beads is investigated by Distinct Element Method (DEM). Under different ambient air temperatures, the pressure drop curves are calculated by DEM to determine U mf . The mean kinetic energy E of particles is defined to judge whether the particles move or not. The fluidization characteristics of fluidized bed are investigated in details. The calculated U mf is compared with empirical data. The different behavior of Geldart B and D particles against temperature is reproduced numerically. U mf decreases with increasing ambient temperature for Geldart B particles, while it increases for Geldart D particles.

Energy balance analysis of nighttime leaf temperatures and frost formation in a subalpine environment

Nocturnal leaf temperatures depend primarily on convective heat exchange with the air and longwave radiation exchange with the surroundings. Consequently, the leaf boundary layer and upper hemisphere infrared radiation dominate the energy balance of a leaf. Longwave radiation from the night sky may be particularly low in the subalpine environment because of the decreased atmospheric density, as well as the low moisture content of the atmosphere. The sky infrared radiation input during the growing season was often as low as 230 W m −2 in the subalpine, equating to a blackbody equivalent sky temperature of less than −20°C. Leaf temperatures predicted from energy balance equations were compared with field measurements of leaf temperatures for Erigeron peregrinus, a perennial herb common to subalpine meadows with a characteristic leaf dimension of approximately 2 cm. Differences between predicted and measured temperatures generated a root-mean-square error of 0.9°C, while the root-mean-square deviation between the air and leaf temperature observations was 3.9°C ( n = 461). Leaf temperatures were modelled in simulations addressing the effects of ambient air temperature, wind speed, sky infrared radiation, and sky exposure characteristic of this high elevation environment. Leaf temperature responses to air temperature and sky infrared radiation were linear, while the sensitivity of the leaf temperature response to wind speed increased substantially under calm conditions (less than 0.4 m s −1). Low wind in combination with clear, cold nights generated simulated leaf temperature depressions of over 6°C below air temperature, frequently resulting in frost episodes during the entire growing season.

Energy and water management in evaporitive cooling systems in Saudi Arabia

A mathematical model was developed to estimate water evaporation rate, airflow rate and cooling effect in an evaporative cooling system for farm structures. The model was only applied to evaporative cooling systems for greenhouses. The effect of ambient air temperature, solar radiation and system efficiency on water evaporation rate, airflow rate and the resulting cooling effect were studied. Generally, water flow rate and air flow rate are adjusted based on daily maximum temperature. However, a substantial saving in energy and water consumption in the cooling system would be achieved by regulating water flow rate and air flow rate to follow the diurnal variation on temperature. Improving the cooling efficiency and covering the roof of the greenhouse with an external shading would save an appreciable amount of energy and water consumption. The model could also be applied to other farm structures such as animal shelters.

Energy Exchanges And Related Temperatures Of An Earth-Tube Heat Exchanger In The Heating Mode

An instrumented earth-tube heat exchanger was designed, installed, and operated as a single-pass heat exchanger to investigate its potential as an alternate energy source. Energy exchange magnitudes were determined and related to concurrent temperatures of operation. The system consisted of 64 m (210 ft) of 15-cm (6-in.) diameter metal pipe buried 1.8 m (6 ft) deep in red clay soil with risers provided at the inlet and outlet and at 15-m (50-ft) intervals. The system was equipped with a high pressure, direct-drive industrial type blower with radial blade wheels. Air temperatures and the peripheral soil temperatures were obtained at both the inlet and outlet ends of the tube, and the outlet air was exhausted to the atmosphere. The system was operated on a 24-hour daily schedule, and this article reports results selected from winter periods of two separate years. Energy exchanges are presented including the effects of ambient air temperature and daily weather types. Also, data related to both lateral and longitudinal gradients of soil, tube wall, and airflow temperatures are presented. The results provided a descriptive and encouraging overview of earth-tube energy exchange performance and related temperatures of operation.

Use of vegetation indices to estimate indices to estimate intercepted solar radiation and net carbon dioxide exchange of a grass canopy

Photosynthesis, respiration, and decomposition in terrestrial plant communities consume and produce large amounts of carbon dioxide (CO 2) and play an important role in the global cycle of carbon. Recent studies have suggested that satellite remote sensing may be useful in providing the extensive data sets needed to quantify these processes over large areas, but many of the factors which potentially limit the accuracy of the analysis in natural vegetation have not been examined experimentally. We have conducted field experiments relating spectral reflectance to intercepted photosynthetically active radiation (PAR) and net CO 2 exchange in a natural canopy composed of the tidal wetland grass Spartina alterniflora (marsh cordgrass). Reflectance measurements made by a hand-held radiometer with Landsat Thematic Mapper spectral wavebands were used to compute remote sensing indices such as the normalized difference vegetation index (NDVI). Net CO 2 exchange was measured in a clear, climate-controlled chamber placed over square meter plots of the canopy. The NDVI was near-linearly related to the proportion of solar PAR intercepted by green plant material. The relationship was not as strong as has been reported for growing agricultural canopies, but the regression model form persisted throughout the growing season (March through October) and was applicable to a wide variety of growth forms exhibiting different proportions of green foliage. NDVI was also near-linearly related to net CO 2 exchange rates throughout the growing season and in plots subjected to varying levels of chronic stress. However, significant uncertainty in the relationship was produced by changes in photosynthetic efficiency in response to varying environmental conditions. Estimates of CO 2 exchange based on NDVI were improved if the effect of ambient air temperature on net photosynthesis was assessment of photosynthesis and net gas exchange in natural vegetation is feasible, particularly if the analysis incorporates information on biological responses to environmental variables.

Single COM Droplet Combustion by Forced-Ignition

Combustion behaviour and characteristics of a COM (Coal-Oil Mixture) droplet by forced ignition were investigated experimentally, considering time change of droplet diameter, droplet temperature and effect of ambient air temperature on the combustion rate coefficient.The results were compared with those reported in the previous paper regarding self-ignited COM droplet. The results showed that the combustion behaviour of COM droplets were successive two process combustion, gasification combustion was followed by solid combustion of residual carbon as same as in the case of spontaneous (self-) ignition. During the gasification combustion period, it was observed that droplets swelled and deflated alternatively in consequence of the polymerisation reaction proceeding simultaneously with the thermal cracking of oil and coal. The gasification combustion rate coefficient of COM droplets was increased linearly with increasing of ambient air temperature and it's value was smaller than those of spontaneous ignition. It is confirmed that the solid combustion rate coefficient of residual carbon could be predicted roughly by the modified Essenhigh's equation. The reac-tion on the surface of solid residual carbon can be considered both C+1/2 O2→CO and C+O2→CO2 are proceeding competively.Furthermore, overall combustion rate coefficient of COM droplets were about 1/2-1/4 comparing with that of base oil. It may be explained with the longer solid combustion period of COM droplets and this period are covering considerable part of overall combustion period.

Effect of Temperature and Exercise on Energy Intake and Body Weight of the White-Throated Sparrow Zonotrichia albicollis

Effect of Temperature and Exercise on Energy Intake and Body Weight of the White-Throated Sparrow Zonotrichia albicollis