Hello
I am using six 500W-Halogen lamps to heat up the surface of an HDPE plate in order to get a thermal gradient over its thickness required for IR Thermography (IRT). I am using IRT to detect subsurface defects. For this purpose, I heated up the HDPE plate with the six halogen lamps for 180 s and after removing the heat source I started monitoring the target. I wanted to use the Furriers equation to calculate the temperature at the location of each subsurface defect. My problem is how to calculate (Q) in Furrier's equation? (I think I am wrong if I calculate the "Q" like this: 6*500*180 because it gave me unrealistic values for the temperature at the defect location).
Dear Amir
Really you are wrong if you calculate Q as 6*500*180
because not all consumed energy transferred to heat
You must know how many percentage of consumed energy was transferred to heat
you can use one lamp to heat a certain amount of water and measure the water temperature increase and then you can calculate the heat dissipated from one lamp and then multiply by 6
500W is energy consumption of Halogen lamp. To know actual heat transferred to HDPE plate, you need heat flux sensor. With that you can measure heat flux incidents on plate, this is Q/A (W/m2). Then you need to know the absorptivity (or from emissivity) of plate surface. Product of these two will give you actual heat (ignoring other heat falls) transferred to plate.
IN fact, you should know the absorption coefficient of your plate for the whole halogen spectrum, since the energy transferred to the plate is the radiation falling onto the plate multiplied by the absorption coefficient.
You should also know which part of the radiation emmitted by the lamp falls onto your plate. Maybe some of this radiation misses it if the lamps dont have a mirror.
@ Palani Nainar
To ensure that the heat flux sensor measures the correct heat flow density from the lamps, it sould have the same absorption coefficient for the radiations coming from the lamps. One method is to embed the heat flow meter under the surface of your plate.
Another proposal is to glue a thin temperature sensor (e.g. a thermocouple) ohn one or more locations on your suface, so you will know the temperature at these locations, and calibrate your IRT picture on these points.
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