Why do solar hot water panels have a shiny silver inner surface?
by admin on Wednesday, December 9th, 2009 | 2 Comments
Will the silver surface not reflect the heat absorbed by the matt black outer surface before it reaches the pipes to heat the water?
The pipes are black to absorb the heat.
The inner surface is reflective to focus the suns rays that miss the black pipes on the way in back on to the pipe.
A similar but opposite arrangement is seen on sunbeds where the light from the tube is reflected outwards onto the body of the person on the sunbed
If objects appear white (reflective in the visual spectrum), they are not necessarily equally reflective (and thus non-emissive) in the thermal infrared; e. g. most household radiators are painted white despite the fact that they have to be good thermal radiators. Acrylic and urethane based white paints have 93% blackbody radiation efficiency at room temperature (meaning the term "black body" does not always correspond to the visually perceived color of an object).
References :
http://en.wikipedia.org/wiki/Thermal_radiation
The pipes are black to absorb the heat.
The inner surface is reflective to focus the suns rays that miss the black pipes on the way in back on to the pipe.
A similar but opposite arrangement is seen on sunbeds where the light from the tube is reflected outwards onto the body of the person on the sunbed
References :