DrDrreeeaaa
Electrical
- Apr 25, 2008
- 266
Hi All
Part of my job is to calculate the size and number of fans which are required to keep the inside of outdoor electrical enclosures at a suitable temperatures.
It's a fairly standard approach of quantifying the heat load produced by the equipment in the panel, the solar heat load, and the amount of heat which is dissipated from inside to outside by the panel surface. The balance of the heat load represents the amount which must be dissipated by the fans.
A fairly common approach for outdoor panels is to fit sunshields to the exterior faces. These shields are made of the same material as the panel and are placed so that there is an inch or two gap between the panel and the shield. The idea is that the sun hits the shield and not the panel and this is supposed to reduce the overall temperature inside.
My problem is how do I represent this in the calculations? It doesn't seem correct to assume that the sun shield results in zero solar load on the panel, as the air between the panel and the sunshield would be heated by the sun.
One idea that I have is to calculate the resulting air temperature between the sunshield and the panel, and use this to recalculate the amount of heat that the panel surface itself can dissipate. I could then only include a small portion of the solar heat load (i.e. area of the panel not covered by heat shields).This would be conservative as it would assume that the space between the panel and the sun shield would be enclosed while natural air movement would occur.
Does anyone have some feedback on this? how do you quantify the affect of sunshields yourself? What do you think of my proposed method above?
Thanks
Regards, Michael.
Part of my job is to calculate the size and number of fans which are required to keep the inside of outdoor electrical enclosures at a suitable temperatures.
It's a fairly standard approach of quantifying the heat load produced by the equipment in the panel, the solar heat load, and the amount of heat which is dissipated from inside to outside by the panel surface. The balance of the heat load represents the amount which must be dissipated by the fans.
A fairly common approach for outdoor panels is to fit sunshields to the exterior faces. These shields are made of the same material as the panel and are placed so that there is an inch or two gap between the panel and the shield. The idea is that the sun hits the shield and not the panel and this is supposed to reduce the overall temperature inside.
My problem is how do I represent this in the calculations? It doesn't seem correct to assume that the sun shield results in zero solar load on the panel, as the air between the panel and the sunshield would be heated by the sun.
One idea that I have is to calculate the resulting air temperature between the sunshield and the panel, and use this to recalculate the amount of heat that the panel surface itself can dissipate. I could then only include a small portion of the solar heat load (i.e. area of the panel not covered by heat shields).This would be conservative as it would assume that the space between the panel and the sun shield would be enclosed while natural air movement would occur.
Does anyone have some feedback on this? how do you quantify the affect of sunshields yourself? What do you think of my proposed method above?
Thanks
Regards, Michael.
