Diurnal temperature gradients in shallow water produced by populations of artificial aquatic macrophytes

1978 ◽  
Vol 56 (9) ◽  
pp. 1099-1106 ◽  
Author(s):  
H. M. Dale ◽  
T. J. Gillespie
Keyword(s):  
Temperature Gradient ◽  
Leaf Area ◽  
Aquatic Macrophytes ◽  
Time Of Day ◽  
Maximum Temperature ◽  
Water Evaporation ◽  
Vertical Temperature ◽  
Area Index ◽  
Leaf Arrangement ◽  
Maximum Temperature Gradient

Three artificial populations, with leaf area indices (L) of 4.4, 1.5, and 0.54 were submerged in identical tubs of 1-m3 capacity. Experiments showed that the maximum vertical temperature gradient of the water varied and was dependent on the ratio of solar radiation to wind speed, the leaf area index, and the arrangement of the leaves in the population. The time of day of the maximum temperature gradient was also dependent on L and leaf arrangement. The interception of the light energy by the leaf surface heated the water locally, while the shadow beneath caused the temperature to remain low. With fewer plants, water evaporation was slightly greater. Evaporation resulted in a marl deposit which was confined to the upper surface of the leaves.

scholarly journals Minimum maximum temperature gradient coil design

2012 ◽  
Vol 70 (2) ◽  
pp. 584-594 ◽  
Author(s):  
Peter T. While ◽  
Michael S. Poole ◽  
Larry K. Forbes ◽  
Stuart Crozier
Keyword(s):  
Temperature Gradient ◽  
Gradient Coil ◽  
Maximum Temperature ◽  
Coil Design ◽  
Gradient Coil Design ◽  
Maximum Temperature Gradient

scholarly journals Simulation of Photovoltaic Thermoelectric Battery Characteristics

2021 ◽  
Vol 64 (3) ◽  
pp. 250-258
Author(s):  
A. K. Esman ◽  
G L. Zykov ◽  
V. A. Potachits ◽  
V. K. Kuleshov
Keyword(s):  
Temperature Gradient ◽  
Solar Radiation ◽  
Power Density ◽  
Solar Spectrum ◽  
Electrical Energy ◽  
Time Of Day ◽  
Maximum Temperature ◽  
Back Side ◽  
Software Environment ◽  
Thermoelectric Converters

Solar radiation is an environmentally friendly and affordable energy source with high release of energy. The use of a photovoltaic thermoelectric battery makes it possible to increase the efficiency of converting solar and thermal radiation into electrical energy, both on serene and cloudy days. An original battery structure with photovoltaic and thermoelectric converters is proposed. The 3D model of the proposed photovoltaic thermoelectric battery was realized in the COMSOL Multiphysics software environment with the use of a heat transfer module. The simulation was performed for the geographical coordinates of Minsk and taking into account the diurnal and seasonal variations of both the ambient temperature and the power density of the concentrated AM1.5 solar spectrum, the maximum value of which being varied from 1 to 500 kW/m2. The dependences of the maximum temperature values of the photovoltaic thermoelectric battery and the thermoelectric converters as well as temperature gradient patterns in the thermoelectric converters have been calculated. The dependences of the maximum temperature gradient values inside the thermoelectric converters on the solar power density are obtained. The graphs of the temperature gradients inside the thermoelectric converters of the photovoltaic thermoelectric battery by concentrated solar radiation versus the time of day in the middle of July and January are provided. It is shown that the output voltage increases up to the maximum values of 635 and 780 mV, respectively, in January and in July were achieved due to the temperature stabilization of the back side of the external electrodes of the proposed device

scholarly journals Analysis of Sunshine Temperature Field of Steel Box Girder Based on Monitoring Data

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Hailin Lu ◽  
Jing Hao ◽  
Jiwei Zhong ◽  
Yafei Wang ◽  
Hongyin Yang
Keyword(s):  
Temperature Field ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Maximum Temperature ◽  
Temperature Model ◽  
Bridge Site ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Box Girder ◽  
Steel Box Girder

In this study, based on the recorded meteorological data of the bridge site, a spatial-temporal temperature model of a 3-span steel box girder is developed through applying the thermal analysis software TAITHERM. Firstly, the rationality and dependability of the proposed spatial-temporal temperature model are adequately verified by means of implementing the comparison with the measurement data. Then the temperature distribution of the steel box girder is analyzed and discussed in detail. The analytical results show that the time of the bottom of pavement reaching the daily maximum temperature lags behind the top of pavement by 2 or 3 hours due to the thermal insulation effect of pavement, and the maximum vertical temperature gradient of the structure exceeds the existing standards. Moreover, with the help of the analytical model, a parametric study of comprehensively meteorological factors is also performed. The results of the sensitivity analysis indicate that solar radiation is the most significant factor affecting the maximum vertical temperature gradient of the steel box girder, followed by air temperature and wind speed. After that, with the representative values of the extreme meteorological parameters during 100-year return period in Wuhan City in China being considered as the thermal boundary conditions, the temperature distribution of the steel box girder is further studied for investigation purpose. The results demonstrate that the heat conduction process of the steel box girder has distinct “box-room effect,” and it is of great necessity to consider both the actual weather conditions at the bridge site and the “box-room effect” of steel box girder when calculating thermal behaviors of bridge structures. Finally, it is related that the particular method proposed in this paper possesses a satisfactory application prospect for temperature field analysis upon various types of bridges in different regions.

Effects of Averaging the Heat Transfer Coefficient on Predicted Material Temperature and Its Gradient

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Chien-Shing Lee ◽  
Tom I-P. Shih ◽  
Kenneth Mark Bryden
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Gradient ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Biot Number ◽  
Maximum Temperature ◽  
Gradual Transition ◽  
The Heat Transfer Coefficient ◽  
Maximum Temperature Gradient

The heat transfer coefficient (HTC) is often averaged spatially when designing heat exchangers. Since the HTC could vary appreciably about a heat transfer enhancement feature such as a pin fin or a rib, it is of interest to understand the effects of averaging the HTC on design. This computational study examines those effects via a unit problem—a flat plate of thickness H and length L, where L represents the distance between pin-fins or ribs. This flat plate is heated on one side, and cooled on the other. Variable HTC is imposed on the cooled side—a higher HTC (hH) over LH and a lower HTC (hL) over LL = L − LH. For this unit problem, the following parameters were studied: abrupt versus gradual transition between hH and hL, hH/hL, LH/L, and H/L. Results obtained show that if the averaged HTC is used, then the maximum temperature in the plate and the maximum temperature gradient in the plate can be severely underpredicted. The maximum temperature and the maximum temperature gradient can be underpredicted by as much as 36.3% and 542%, respectively, if the Biot number is less than 0.1 and as much as 13.0% and 570% if the Biot number is between 0.25 and 0.4. A reduced-order model was developed to estimate the underpredicted maximum temperature.

ATMOSPHERIC REFRACTION AND TEMPERATURE GRADIENT

1962 ◽  
Vol 16 (1) ◽  
pp. 24-31 ◽  
Author(s):  
P.V. Angus-Leppan
Keyword(s):  
Temperature Gradient ◽  
Solar Radiation ◽  
Radiation Intensity ◽  
Time Of Day ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Atmospheric Refraction ◽  
Intensity Measurements ◽  
Solar Radiation Intensity

The coefficient of refraction is far from constant. It varies chiefly because of changes in the vertical temperature gradient of the atmosphere. From measurements of vertical angles between points of known heights, observed angles of refraction can be deduced. By the use of simultaneous meteorological measurements, various methods of calculating refraction are developed. It is necessary to derive a formula representing temperature as a function of height and time of day. Calculated refraction compares accurately with observed, especially when solar radiation intensity measurements are used.

Effect of encased concrete on section temperature gradient of corrugated steel web box girder

2021 ◽  
pp. 136943322199249
Author(s):  
Feng Zhang ◽  
Jia Shen ◽  
Jinyi Liu
Keyword(s):  
Temperature Gradient ◽  
Solar Radiation ◽  
Maximum Temperature ◽  
Daily Maximum ◽  
Box Girder ◽  
Structural Temperature ◽  
Corrugated Steel Web ◽  
Maximum Temperature Gradient ◽  
Lateral Temperature ◽  
Concrete Section

Thirty-two temperature sensors, a solar radiation sensor, wind speed, and direction sensor were installed on the bridge for the field monitoring of structural temperature, solar radiation, and wind. The frequency was set at 60 min for 211 days. Empirical equations were used to predict the maximum vertical and lateral temperature gradients, and the daily maximum and minimum mean temperatures of the corrugated steel web box girder. The results showed that the temperature gradient of the corrugated steel web box girder was closely related to the temperature gradient of air. The vertical maximum temperature gradient occurred at 4 pm. The height of the box girder had a significant effect on the accuracy of the predicted vertical maximum temperature gradient. Compared with the section without encased concrete, the maximum temperature gradient of the encased concrete section was reduced by 10.48%. Encased concrete showed minimal effect on both the vertical and lateral temperature gradient of the top plate part, however, the effect on the vertical temperature gradient of the haunch reduced by 17.19%. The maximum temperature gradient of corrugated steel with a composite encased concrete section was 4.12°C, which was less than that of the section without encased concrete at 5.06°C. The encased concrete had a significant effect on the maximum temperature gradient of corrugated steel web with a 26.99% deviation.

scholarly journals Further Results on Studies of Temperature-Gradient Metamorphism

1982 ◽  
Vol 28 (98) ◽  
pp. 205-210 ◽  
Author(s):  
E. E. Adams ◽  
R.L. Brown
Keyword(s):  
Temperature Gradient ◽  
Maximum Temperature ◽  
Material Strength ◽  
Snow Pack ◽  
Laboratory Studies ◽  
Thermodynamic Process ◽  
Temperature Variations ◽  
Field Investigations ◽  
Maximum Temperature Gradient

AbstractA correlation between temperature gradient in snow–pack and material strength is found to exist in laboratory studies on temperature gradient metamorphism of snow. These results are in agreement with earlier field investigations and eliminate diurnal solar and temperature variations as reasons for the existence of the maximum temperature gradient in the zone of minimum strength. Also the laboratory studies have indicated that locally dense layers such as ice crusts tend to enhance weakness directly below the crust due to local alteration of the thermal regimen. Further studies are continuing to describe the thermodynamic process of temperature gradient metamorphism more exactly.

Analysis on the Loading Stress, Thermal Stress and Coupling Stress in PCC-AC Composite Pavement

2011 ◽  
Vol 383-390 ◽  
pp. 2700-2704
Author(s):  
Bin Yang ◽  
Tai Qin Yang ◽  
Gao Dian Peng
Keyword(s):  
Thermal Stress ◽  
Temperature Gradient ◽  
Crack Initiation ◽  
Maximum Temperature ◽  
Dowel Bar ◽  
Maximum Temperature Gradient ◽  
Reflection Crack

PCC-AC composite pavement has the advantages of high carrying capability and excellent comfort. The maximum temperature gradient formula of PCC-AC composite pavement in Guangxi region is fitted. The loading stress, thermal stress and coupling stress in AC layer of with dowel bar can significantly reduced. All kinds of stresses are also decreased with the narrow dowel bar space. Therefore, the Shrinking joints of composite pavement with dowel bars can greatly reduce the probability of reflection crack initiation. As the thickness of AC layer, there is greater influence on thermal stress and coupling stress than on loading stress, The loading stress, thermal stress and coupling stress in PCC layer decreases with the thickness increasing of AC layer, their relationship is linear. The loading stress and coupling stress of PCC layer reduce significantly with increasing the PCC thickness. AC layer also plays a role in reducing the loading stress and coupling stress of PCC layer.

Study on Conjugate Thermal Performance of a Steam-Cooled Ribbed Channel with Thick Metallic Walls

2021 ◽  
Author(s):  
Lei Xi ◽  
Liang Xu ◽  
Jianmin Gao ◽  
Zhen Zhao
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Thermal Performance ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Performance ◽  
Thick Wall ◽  
Maximum Temperature ◽  
Transfer Performance ◽  
Ribbed Channel ◽  
Maximum Temperature Gradient

Abstract In this work, a conjugate heat transfer model was established to numerically investigate the conjugate thermal performance of a steam-cooled ribbed channel with thick metallic walls. By employing the software of ANSYS CFX, the flow field in the channel and the temperature field in the solid channel were calculated. The flow behavior, heat transfer performance and temperature gradient distributions of ribbed channels with wall thickness (δ) of 1–5 mm, rib height-to-hydraulic diameter (e/D) of 0.047–0.188, rib pitch-to-height ratio (P/e) of 5–15 and rib angle-of-attack (α) of 30°–90° were compared and analyzed. The optimum structure parameters of thick-wall ribbed channel with higher heat transfer performance and lower maximum temperature gradient were obtained. The results show that the SST k-ω turbulence model is more suitable for the conjugate heat transfer problem of steam in the thick-wall ribbed channels. The friction factor reduces gradually with the increase of Re, increases greatly with the increase of e/D and α, and first increases then decreases with the increase of P/e. The average Nusselt number increases up to 8.81 times, while the maximum temperature gradient decreases about 45.35% when Reynolds number varies from 10,000 to 70,000. The rib angle of about 45°–60°, e/D of 0.188, and P/e of 10 are suitable to obtain the optimum thermal performance of steam flow in the ribbed channel. The influence of δ on the flow and heat transfer characteristics is non-significant.

Quantifying genetic effects of ground cover on soil water evaporation using digital imaging

2010 ◽  
Vol 37 (8) ◽  
pp. 703 ◽  
Author(s):  
Daniel J. Mullan ◽  
Matthew P. Reynolds
Keyword(s):  
Soil Water ◽  
Leaf Area ◽  
Rapid Development ◽  
Ground Cover ◽  
Genetic Differences ◽  
Soil Evaporation ◽  
Water Evaporation ◽  
Analysis Tool ◽  
Area Index ◽  
Normalised Difference Vegetation Index

Rapid development of leaf area and/or aboveground biomass has the potential to improve water harvest of rain fed wheat in Mediterranean-type environments through reduced soil evaporation. However, quantitative relationships between genetic differences in early ground cover and soil water evaporation have not been established. Furthermore, accurate phenotyping of ground cover and early vigour have typically been achieved via destructive sampling methods, which are too time-consuming to undertake within breeding programs. Digital image analysis has previously been identified as an alternative indirect method of analysis, whereby computer analysis is ued to determine percentage ground cover. This study uses a digital ground cover (DGC) analysis tool for high throughput screening of four large wheat populations. The DGC methodology was validated via comparisons with alternative measures of canopy cover, such as normalised difference vegetation index (NDVI) (r2 = 0.69), biomass (r2 = 0.63), leaf area index (r2 = 0.80) and light penetration through the canopy (r2 = 0.70). The wheat populations were utilised to estimate the potential variation in soil evaporation associated with genetic differences in early ground cover, which was validated using established models. Estimates of genetic differences in soil evaporation within the four populations (6.90–24.8 mm) suggest that there is sufficient genetic variation to increase water harvest through targeting faster ground cover. Implications for improved wheat yields and breeding are discussed.

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