This is a proposal for a "thermostat" type part to transfer heat in and out of the part it's attached to in order to maintain an internal temp that approximates habitable conditions. Refer to detailed forum post here:

http://forum.kerbalspaceprogram.com/index.php?/topic/112027-130-heat-control-more-radiators-updated-june-19/&do=findComment&comment=3110161

Closed per forum response on 4 July 2017.