Thermodynamics for spaceheaters

code/game/machinery/spaceheater.dm

@@ -178,16 +178,25 @@
 
 						if(removed)
 
-							var/heat_capacity = removed.heat_capacity()
-							//world << "heating ([heat_capacity])"
-							if(heat_capacity) // Added check to avoid divide by zero (oshi-) runtime errors -- TLE
-								if(removed.temperature < set_temperature + T0C)
-									removed.temperature = min(removed.temperature + heating_power/heat_capacity, 1000) // Added min() check to try and avoid wacky superheating issues in low gas scenarios -- TLE
-								else
-									removed.temperature = max(removed.temperature - heating_power/heat_capacity, TCMB)
-								cell.use(heating_power/20000)
-
-							//world << "now at [removed.temperature]"
+							if(removed.temperature < set_temperature + T0C)	//heating air
+								// Added min(set_temperature + T0C, 1000) check to try and avoid wacky superheating issues in low gas scenarios
+								var/energy_used = min( removed.get_thermal_energy_change(min(set_temperature + T0C, 1000)) , heating_power )
+								
+								removed.add_thermal_energy(energy_used)
+								cell.use(energy_used*CELLRATE)
+							else	//cooling air
+								var/heat_transfer = min(abs(removed.get_thermal_energy_change(target_temperature)), heating_power)
+								
+								//Assume the heat is being pumped into the hull which is fixed at 20 C
+								//none of this is really proper thermodynamics but whatever
+								
+								var/cop = removed.temperature/T20C	//coefficient of performance -> power used = heat_transfer/cop
+								
+								heat_transfer = min(heat_transfer, cop * heating_power)	//this ensures that we don't use more than MAX_ENERGY_CHANGE amount of power - the machine can only do so much cooling
+								
+								heat_transfer = -removed.add_thermal_energy(-heat_transfer)	//get the actual heat transfer
+								
+								cell.use(heat_transfer/cop*CELLRATE)
 
 						env.merge(removed)