Typical leakage values Martin Karlstedt 02.11.13 1 Estimating leakage dX A = Area ΔT = temperature difference H λ dX = thickness of box B L λ = material insulation property h = convection factor A*ΔT _______ ___ dX + __ 1 λ h 2 Leakage in W/K Leakage in a steel cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,002 [m] λ = 46 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h A*ΔT _______ 0,200043 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 25W/K 50W/K 75W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 50W/K 100W/K 150W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 100W/K 200W/K 300W/K For h we normally calculate between 5-20. 5 = low convection, 20 = high convection 3 Leakage in a aluminum-alloy cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,002 [m] λ = 190 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h A*ΔT _______ 0,200011 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 25W/K 50W/K 75W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 50W/K 100W/K 150W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 100W/K 200W/K 300W/K For h we normally calculate between 5-20. 5 = low convection, 20 = high convection We realize that for high λ’s the difference is very small or none for leakage values 4 Leakage in a plexi-glass cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,002 [m] λ = 1,9 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h A*ΔT _______ 0,201053 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 25W/K 50W/K 75W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 50W/K 100W/K 150W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 100W/K 200W/K 300W/K Still the λ’s are high why the difference is very small or none for leakage values 5 Leakage in a 10mm LDPE insulated cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,01 [m] λ = 0,04 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h 6 A*ΔT _______ 0,45 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 11W/K 22W/K 33W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 22W/K 44W/K 66W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 44W/K 88W/K 133W/K Leakage in a 20mm LDPE insulated cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,02 [m] λ = 0,04 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h 7 A*ΔT _______ 0,45 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 7W/K 14W/K 21W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 14W/K 28W/K 43W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 28W/K 57W/K 86W/K Leakage in a 10mm PUR insulated cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,01 [m] λ = 0,025 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h 8 A*ΔT _______ 0,6 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 8,3W/K 16,7W/K 25W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 16,7W/K 33,3W/K 50W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 33,3W/K 66,7W/K 100W/K Leakage in a 20mm PUR insulated cabinet A = area [m^2] ΔT = temperature difference [-] dX = 0,02 [m] λ = 0,025 [W/mK] h = 5 [W/m^2K] A*ΔT _______ ___ dX + __ 1 λ h 9 A*ΔT _______ 1 Box 0,5m2 , ΔT=10°C Box 0,5m2 , ΔT=20°C Box 0,5m2 , ΔT=30°C 5W/K 10W/K 15W/K Box 1m2 , ΔT=10°C Box 1m2 , ΔT=20°C Box 1m2 , ΔT=30°C 10W/K 20W/K 30W/K Box 2m2 , ΔT=10°C Box 2m2 , ΔT=20°C Box 2m2 , ΔT=30°C 20W/K 40W/K 60W/K Conclusions • At high λ’s (above at least 2) the leakage factor is almost not affected • Insulation is key to get a good function of an installation • Convection factor h has a big influence for poorly insulated cabinets 10 Martin Karlstedt [email protected] 11