How Do You Calculate UV Light Intensity Needed to Kill Germs on an AC Coil?

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SUMMARY

The calculation of UV light intensity necessary to eliminate germs on an AC coil involves determining the incident intensity at a distance of 24 inches from a tubular UV light source rated at 3.6 microwatts/sq.cm. per inch. To find the time required to achieve a UV dosage of 4500 microwatts.seconds, one must apply the inverse square law, which states that intensity decreases with the square of the distance from the source. By calculating the incident intensity on the target surface and dividing the required dosage by this intensity, the time in seconds can be accurately determined.

PREREQUISITES
  • Understanding of UV light intensity measurements (microwatts/sq.cm.)
  • Familiarity with the inverse square law in physics
  • Basic knowledge of germicidal UV dosage requirements
  • Ability to perform calculations involving intensity and dosage
NEXT STEPS
  • Research the application of the inverse square law in practical scenarios
  • Learn about UV light sources and their intensity ratings
  • Investigate the specific UV dosage levels required for different types of germs
  • Explore methods for measuring UV intensity at various distances
USEFUL FOR

This discussion is beneficial for HVAC technicians, microbiologists, and anyone involved in the design or maintenance of UV disinfection systems in air conditioning units.

mdd16
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Hello,

I need to calculate intensity of light at a distance of 24 inch from a tubular light source with a light intensity rating specified at 3.6 microwatts/sq.cm. per inch of lamp.

The light is a UV light which is to illuminating a cooling coil in air conditioning system. Supposedly there are germs on the surface of cooling coil which needs to be killed. There is a specified level of microwatts.seconds of UV dosage required to kill germs. (For this example we can assume it to be 4500). I want to calculate how long will it take to kill this germ.

Idea is to calculate incident intensity on target surface and then divide required dosage by incident intensity to get answer in seconds.

Can anyone help.

Thanks and regards
Mohan Dhingra
 
Engineering news on Phys.org
Your question is confusing. I don't see the geometry and I don't understand "3.6 microwatts/sq.cm. per inch of lamp."

But basically, just use the inverse square law. Draw a sphere around the source. Draw a sphere around the target. Intensity varies with the square of the radius.
 

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