I have an endothermic gas generator which maintains a heat of 850 °C while not generating endothermic gas. The generator maintains it's temperature through a burner control system, however coolant still runs through a water jacket around the outlet pipe (which in this state has no gas running through it) the average flow out is 13.5 litres per minute. When the flow is stopped some heat is picked up from the generator and the coolant steadily increases temperature, however the temperature inside the generator does not appear to change due to the control system controlling the gas burner, however I presume that the coolant will carry some heat away from the generator. When full flow is resumed there is currently no difference in inlet and outlet coolant temperature (that is one I can measure with a standard thermometer). Can anyone think of an constitutive equation that will determine the required flow to maintain a specified cooling water temperature assuming say a pipe temperature of 200°C ?