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Unformatted text preview: ° (EAST) -50° 0° (DUE SOUTH) Solar Azimuth Angle, 50° 100° (WEST) Solar Azimuth Angle, South East line to sun (projected onto horizontal surface) West North Instantaneous Heat Balance for Sunlit Glazing Material (Adapted from ASHRAE Handbook of Fundamentals SI 2009, Chapter 15.) Outdoor Temperature, Incoming Solar Radiation Incident Angle, Indoor Temperature, Inward Heat Flow by Convection and Radiation Reflected Solar Radiation Transmitted Radiation Outward Heat Flow by Convection and Radiation Approximate Impact of “Angle of Incidence” on SHGC -- Single Sheet of Clear Architectural Glass (6 mm thickness) 0.90 incoming radiation 0.80 0.70 0.60 !"() 0.50 0.40 0.30 0.20 surface normal 0.10 0.00 0 10 20 30 40 50 60 70 Angle of Incidence, (degrees) 80 90 receiving surface Approximate Center-of-Glass Properties for Selected Glazing Systems Based on ASHRAE Handbook of Fundamentals 2009 SI (Chapter 145) 0.90 A 0.80 B 0.70 0.60 C 0.50 SHGC (θ) D 0.40 0.30 0.20 E 0.10 0.00 0 10 20 30 40 50 60 Incident Angle (degrees) 70 80 90 Glazings appearing on previous slide: G lazing System Description A Single glazed, clear glass B Double glazed, clear glass, 12.7 mm air space C Double glazed, clear glass, low-e = 0.2 on surface 3, 12.7 mm argon space D Double glazed, clear glass, low-e = 0.05 on surface 2, 12.7 mm argon space E Double glazed, gray tint outer pane, low-e = 0.05 on surface 2, 12.7 mm argon space C of G C of G Glazing U-value Visible System # W/m -K Transmitt. 0 40 50 60 70 80 90 Diffuse A 5.9 0.88 0.81 0.80 0.78 0.73 0.62 0.39 0.00 0.73 B 2.7 0.78 0.70 0.67 0.64 0.58 0.45 0.23 0.00 0.60 C 1.7 0.73 0.65 0.63 0.60 0.54 0.42 0.21 0.00 0.56 D 1.4 0.70 0.37 0.36 0.34 0.31 0.24 0.13 0.00 0.32 E 1.4 0.35 0.24 0.23 0.22 0.20 0.16 0.09 0.00 0.21 2 Center-of-Glazing SHGC Incidence Angle, (degrees) -- beam radiation Hemis. Components of Solar Radiant Heat Gain with Double-Pane Window, including both frame and glazing contributions (Adapted from ASHRAE Handbook of Fundamentals SI 2009, Chapter 15.) Incident Solar Inward flowing fraction of frame absorbed radiation Glazing Transmitted Radiation Inward flowing fraction of first glazing absorbed radiation Outer Lite Glass Coating Gas Fill Incident Solar Inward flowing fraction of second glazing absorbed radiation Inner Lite Inward flowing fraction of frame absorbed radiation Glazing Solar Energy Flux by Beam Radiation %& = '() ∙ cos ) ∙ !" () ( '() ∙ cos ) ( direct normal irradiance (W/m2) Glazing Solar Energy Flux by Beam Radiation %( = ('. +'0 ) ∙ !"( diffuse and reflected irradiance (W/m2) diffuse + reflected radiation Complex Glazing Systems % = '() ∙ cos ∙ !" ∙ 12" + ('. +'0 ) ∙ !"( ∙ 12"( translucent roller-blind venetian blind bug screen 12" = “indoor solar attenuation coefficient” fraction of heat flow that enters the room (accounting for shading devices) 1.25 m Outdoor Air: 30°C, 70% RH Indoor Air: 24°C, 60% RH Insolation Sun location: Due West Solar altitude: 30° Direct Normal: 700 W/m2 Diffuse & Reflected: 200 W/m2 2.5 m c 1.25 m 2.5 m Contributors to Heat Gain? (cooling load) Windows Glazing Type “D” No shades Other Heat Gains? ∙ Lights ∙ Occupants ∙ Equipment ∙ Ventilation ∙ Thermal Transmission ( ∙ ∆ … ? ) ∙ Lights Lighting Power Density = 12 W/m2 Floor Area = 16 m2 Lighting Power = 12 W/m2 x 16 m2 ≈ 192 W ∙ Occupants 1 occupant (moderately active) ≈ 140 W ∙ Equipment Computer tower (75 W) Monitor (40 W) Desktop printer (40 W) ≈ 155 W ∙ Ventilation Air 1 ACH (11 L/s) cooled + dehumidified from outdoor conditions (30°C, RH = 70%) to indoor conditions (24°C, RH = 60%) ≈ 0.011 m3 ≈ 0.882 m3/kga ℎ ≈ 79 kJ/kga ℎ ≈ 52 kJ/kga Psychrometric Calculation: = (ℎ − ℎ ) (neglect energy in condensate) ≈ 340 W ∙ Solar Gains through Windows Beam Radiation Flux through West Window (center-of-glass) = ∙ cos ) ∙ () ( = (700 W/m2) ∙ (cos 30°) ∙ (0.3625) = (606 W/m2) ∙ (0.3625) = 220 W/m2 approx glass area = 2.5 m2 Total heat gain due to beam radiation ≈ 220 x 2.5 = 550 W ∙ Solar Gains through Windows Diffuse and Reflected Radiation Flux through South and West Windows (center-of-glass) = (! +# ) ∙ = (200 W/m2) ∙ (0.32) = 64 W/m2 approx glass area = 5 m2 Total heat gain due to D&R radiation ≈ 64 x 5 = 320 W Total Solar Heat Gain = 550 + 320 = 870 W ∙ Thermal Transmission Not analyzed in this example – can be small or large contributor to overall heat gain depending on the situation… outdoors indoors heat gain $& $% Heat Gain Components? Component Thermal Transmission Lights Occupants Equipment Ventilation Solar (Windows) Total Heat Gain (W) (not calculated) 192 140 155 340 870 1697 Note: Window-to-wall ratio is 25%; glazing is type “D” Double the window area? (window-to-wall ratio = 50%) Component Solar (Windows) Total Heat Gain (W) 1740 2567 Double the window area and use clear glass? (window-to-wall ratio = 50%; glazing system B ) Component Solar (Windows) Total Heat Gain (W) 3260 4087 Building Energy Performance – Spring 2012 - Topic 11 - Energy Flow through Building Envelope (Part 6) Fenestration and Shading Devices in the Context of Building Energy...
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This note was uploaded on 10/04/2012 for the course ME 760 taught by Professor Davidmather during the Spring '12 term at Waterloo.

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