scholarly journals Fenestration peak solar heat gain: A review of the cloudless day condition as conservative hypothesis

2011 ◽  
Vol 15 (1) ◽  
pp. 223-234 ◽  
Author(s):  
Lucia Fontana ◽  
Alessandro Quintino
Keyword(s):  
Horizontal Surface ◽  
Total Radiation ◽  
Clearness Index ◽  
Heat Gain ◽  
Solar Heat ◽  
The North ◽  
Conservative Condition ◽  
Solar Heat Gain

Peak solar heat gain through fenestration, particularly for clear and cloudy day conditions, was estimated, using an approach based on the ASHRAE methodology and considering the correlation between hourly clearness index kT and diffuse ratio of the total radiation. Hourly SHGCLEAR and SHGCLOUDY values for surfaces facing the basic cardinal orientations and the horizontal surface, at different latitudes, on the 21st day of each month, have been computed and compared. Results show that in many cases solar heat gain for cloudy day may exceed that for clear day. For wall exposures near the North the clear day condition could not be the most conservative condition for the peak SHG evaluation.

Reducing Roof Solar Heat Gain by Using Double-Skin Ventilated Roofs

2020 ◽  
Vol 38 (3A) ◽  
pp. 402-411
Author(s):  
Mohannad R. Ghanim ◽  
Sabah T. Ahmed
Keyword(s):  
Inclination Angle ◽  
Convection Heat Transfer ◽  
Ventilation Rate ◽  
Channel Length ◽  
Air Gap ◽  
Galvanized Steel ◽  
Heat Gain ◽  
Solar Heat ◽  
Double Skin ◽  
Solar Heat Gain

Double skin ventilated roof is one of the important passive cooling techniques to reduce solar heat gain through roofs. In this research, an experimental study was performed to investigate the thermal behaviour of a double skin roof model. The model was made of two parallel galvanized steel plates. Galvanized steel has been used in the roof construction of industrial buildings and storehouses in Iraq. The effect of inclination angle (ϴ) from the horizontal and the spacing (S) between the plates was investigated at different radiation intensities. It is found that using a double skin roof arrangement with a sufficient air gap (S) can reduce the heat gain significantly. The higher the inclination angle (ϴ) the higher the ventilation rate, the lower the heat gain through the roof. In this study, increasing the air gap from 2 cm to 4 cm reduced the heat gain significantly but when the gap was further increased to 6 cm, the reduction in the heat flux was insignificant. A dimensionless correlation was also reduced between Nusselt number () and the single parameter  where L is the channel length. This correlation can be handily utilized for designing of engineering applications dealing with high temperature difference natural convection heat transfer.

scholarly journals VEGETATION INSULATION SCREEN AS A PASSIVE COOLING SYSTEM IN HOT HUMID CLIMATE: HEAT AND MASS EXCHANGES

2021 ◽  
Vol 9 (10) ◽  
pp. 1368-1378
Author(s):  
Hodo-Abalo Samah ◽  
◽  
Magolmeena Banna ◽  
Belkacem Zeghmati ◽  
◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Cooling System ◽  
Gain Factor ◽  
Passive Cooling ◽  
Humid Climate ◽  
Heat Gain ◽  
Area Index ◽  
Solar Heat ◽  
Solar Heat Gain

Planted roofs are passive cooling techniques that reduce the thermal load of buildings. In this paper, a Dynamic mathematical model based ontime average Navier-Stokes equationsfor a plantedroof in hothumidclimates has beendeveloped for evaluating the cooling potential.Transfer equations are solved using a finite difference scheme and Thomas algorithm. The model was applied for the simulation of a planted roof in Togolese climate conditions. Results showed that, evapotranspiration and Solar Heat gain Factor are functions of the Leaf Area Index LAI which is the most important parameter when considering the foliage material. For LAI equal to 6, latent heat peak value reaches 900 W.m-2while that of sensible heat is around 350 W.m-2. Solar heat gain factor can bereducedto 15% fortheplantedroofagainst 45% forbareroof. It is clearly proved that the foliage density and hence the vegetation canopy type selection greatly influence the thermal efficiency of the bioclimatic insulation screen. A larger Leaf Area Index reduces the solar flux penetration and increases evapotranspiration which is an important parameter when considering surrounding microclimate formation.

Effects of solar radiation and wind speed on metabolic heat production by two mammals with contrasting coat colours.

1995 ◽  
Vol 198 (7) ◽  
pp. 1499-1507 ◽  
Author(s):  
G E Walsberg ◽  
B O Wolf
Keyword(s):  
Wind Speed ◽  
Solar Radiation ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Heat Gain ◽  
Solar Heat ◽  
Wind Speeds ◽  
Convective Heat Loss ◽  
Metabolic Heat ◽  
Solar Heat Gain

We report the first empirical data describing the interactive effects of simultaneous changes in irradiance and convection on energy expenditure by live mammals. Whole-animal rates of solar heat gain and convective heat loss were measured for representatives of two ground squirrel species, Spermophilus lateralis and Spermophilus saturatus, that contrast in coloration. Radiative heat gain was quantified as the decrease in metabolic heat production caused by the animal's exposure to simulated solar radiation. Changes in convective heat loss were quantified as the variation in metabolic heat production caused by changes in wind speed. For both species, exposure to 780 W m-2 of simulated solar radiation significantly reduced metabolic heat production at all wind speeds measured. Reductions were greatest at lower wind speeds, reaching 42% in S. lateralis and 29% in S. saturatus. Solar heat gain, expressed per unit body surface area, did not differ significantly between the two species. This heat gain equalled 14-21% of the radiant energy intercepted by S. lateralis and 18-22% of that intercepted by S. saturatus. Body resistance, an index of animal insulation, declined by only 10% in S. saturatus and 13% in S. lateralis as wind speed increased from 0.5 to 4.0 ms-1. These data demonstrate that solar heat gain can be essentially constant, despite marked differences in animal coloration, and that variable exposure to wind and sunlight can have important consequences for both thermoregulatory stress experienced by animals and their patterns of energy allocation.

Analysis of Selecting Cooling Load Coefficient Methods

2014 ◽  
Vol 501-504 ◽  
pp. 2311-2314
Author(s):  
Jian Chen ◽  
Wen Wen Xie
Keyword(s):  
Heat Source ◽  
Cooling Load ◽  
Heat Gain ◽  
Solar Heat ◽  
Correct Calculation ◽  
Solar Heat Gain

This paper analyses the method of how to select the coefficient of cooling load caused by indoor heat source (including equipment, lighting and personnel) and solar heat gain, which provides a basis for the correct calculation of air condition cooling load.

Sign in / Sign up

Export Citation Format

Share Document