Heres another idea.
By combining nitrogen and carbon dioxide
you create an exotic new chemical that happens to be
ENDOTHERMIC.
Ammonia is the most well known endothermic chemical
that was used in refrigerators.
So couldn't a chem-system be installed inside a Venera that would combine CO2 and N2 inside to create that exotic heat-absorbing
chemical, which itself would be dumped under pressure outside,
taking all those kilocalories of heat energy with it?