A heat balance is the primary tool for indicating the thermal efficiency of a process. Many Industrial Heating articles over the past several years have pointed out the benefits of decreasing the heat loss, controlling the combustion air to get closer to stoichiometric, enriching the air with oxygen and preheating the combustion air. Here, we show how to account for the heat flow into and out of a process, the amount of heat generated by fuel combustion and (by difference) the heat loss. Once you have a heat balance, you can calculate the effect of changing process variables on thermal efficiency. Our example is the same one used in last month’s article – the heating of aluminum ingots – where we demonstrated how to make a material balance. We’ll also need data from previous “Combustion Concepts” articles.