Or, evaporative cooling for spacewalks. Water heat of evaporation at 25°C is 678 Wh/kg, so 200W of heat is about 0.3 kg per hour. Quite manageable!
EDIT: Apparently the Apollo suits did this. An interesting detail is that they used sublimation (evaporating ice directly to vapor), because I suppose that's a lot more practical to exchange the heat.
EDIT: Apparently the Apollo suits did this. An interesting detail is that they used sublimation (evaporating ice directly to vapor), because I suppose that's a lot more practical to exchange the heat.