and pressure gases to the steam section of the engine does not present difficulties because the cheng cycle system is open non condensable gases are vented through the counterflow heat exchanger exhaust 54 this eliminates the undesirable accumulation of non condensable gases in the economizer 64 and evaporator 12 sections of the counterflow heat exchanger the improved cold start up procedure differs from the conventional 34 blow down 34 method because the steam injector control valve 18 is open during cold start up the process steam control valve 30 is closed during cold start up the other steps in the procedure are essentially the same as in the conventional start up procedure described above by leaving the steam injector control valve 18 open during start up the liquid level control in the water storage drum 16 is simplified by the introduction of non condensable gases into the drum 16 these non condensable gases flow from the air compressor 40 back through the steam injection line 34 through the superheater 20 through the valve 18 to the drum 16 these non condensable gases in the drum 16 are directly in contact with the air compressor 40 discharge thus the pressure in the water storage drum 16 substantially equivalent to the compressor discharge pressure exceeds the vapor pressure of the water in the drum 16 preventing the increase in liquid volume known as boiler swelling with the premature boiling of liquid in the water storage drum 16 minimized there is a greatly reduced possibility of liquid carryover into the superheater.