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Heat Transfer and Reflectivity?

Heat Transfer and Reflectivity?

Heat Transfer and Reflectivity?

(OP)
Hi All,
I have an application, with mostly aluminum parts. I have a central block that is water cooled. I have exterior parts that are bolted to the central block. I do not want to impede the heat transfer from the outside block to the inside cooling block. However, I would like to plate the parts so that I can increase reflectivity. I want to reflect as much heat as possible. This is a welding head, so close proximity to the heat source. I was going to use an electroles Nickel coating for reflectivity but I haven't been able to find any info on thermal conductivity? I want to make sure I don't insulate the mating surfaces. I would have to mask the plating if the plating hurts the transfer. Any suggestions or comments appreciated.    

Thanks
Bill

RE: Heat Transfer and Reflectivity?

regular run of the mill aluminum has a 90% reflectivity. If you anodize the aluminum, the reflectivity drops to only 10%

RE: Heat Transfer and Reflectivity?

(OP)
The EN coating is not an anodize. I realize that anodize acts as an insulator and wouldn't be good for this application. EN coatings I believe are good at electrical conduction, and I believe heat transfer. I know some companies use EN on heat sinks and radiators (coils). I would like to find specific numbers on the heat transfer.  

Thanks
Bill

RE: Heat Transfer and Reflectivity?

(OP)
Thermal Conductivity
The thermal conductivity of an electroless nickel deposit containing 8 to 9 percent phosphorus is 0.0105 to 0.0135 cal/cm/sec/°C. Electrodeposited nickel has a value of 0.19 to 0.26 cal/cm/sec/°C.

I found the above on a website, converting 7954 W/mk = 0.19 cal/cm/sec/C. That must be wrong, higher than silver?  

Thanks
Bill

RE: Heat Transfer and Reflectivity?

Your conversion is off by a factor of 100: 79.55 W/m-K, which is consistent with 90.5 W/m-K for pure nickel.

However, when you look at the thermal conductance of a 5 micron thick layer of nickel, you get 16 MW/m^2-K, i.e., its conductance is absurdly large relative to the more pithy problem of contact resistance.

TTFN

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