Physics Help Forum heating on glass

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Nov 8th 2016, 01:13 AM #1 Junior Member   Join Date: Nov 2016 Posts: 3 heating on glass Hi, i need some help to determine heating on glass for the glass door freezer with inner cabinet temperature -25°C needed to avoid condensation by calculation and let say the dewpoint temperature that i want is 31°C. Test was run without any heating and the glass temperature that i get is 27°C at ambient 35°C/75%RH. Should i consider both convection and conduction heat for the calculation to determine amount of heat or Joule/s needed to heat up the glass until it achieved the dewpoint temperature? Please advise. Thanks.
 Nov 8th 2016, 08:50 AM #2 Physics Team     Join Date: Jun 2010 Location: Naperville, IL USA Posts: 2,271 I would think you'd consider heat conduction through the glass and convection into air at the outside surface of the glass.
 Nov 8th 2016, 05:48 PM #3 Junior Member   Join Date: Nov 2016 Posts: 3 Hi, okay...i have calculated the convection heat for both temperature @27°C(actual measurement) and @32°C(dewpoint). To get the amount of heat or Joule/s that i need to add as heating on the glass, am i correct to substract the convection heat @32°C with convection heat @27°C? Does it applied the same method for the conduction heat?
 Nov 9th 2016, 05:47 AM #4 Physics Team     Join Date: Jun 2010 Location: Naperville, IL USA Posts: 2,271 I would simply determine the heat flow in through the glass that would be caused by a 4 degree increase in temp of the outside surface, That would be equal to the heat you need to add to the outside surface of the glass in order to get it to to rise from 27 to 31 degrees.
 Nov 9th 2016, 08:20 AM #5 Junior Member   Join Date: Nov 2016 Posts: 3 Hi, Do you mean that the prior is to calculate the conduction heat? If make comparison, convection heat will generate more compare to conduction heat. Furthermore, after done with the calculation i continue the test by add the heating to the glass surface and it seems like to be more equal to the convection heat.

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