1. Heat load of petrochemical heating furnace. That is, the ability of each petrochemical heating furnace to transfer heat to the medium in the tube per unit time indicates the production capacity of the petrochemical heating furnace.

2. Furnace temperature. The common name of the fire wall temperature refers to the temperature of the flue gas when it leaves the radiation chamber and enters the convection chamber. The higher the temperature, the greater the heat transfer of the radiant furnace tube and the greater the amount of heat entering the convection chamber. However, if the temperature is too high, the furnace tube and the middle tube frame are likely to be burnt.

3. Heat intensity of the furnace. That is, the total calorific value W/m² of fuel combustion in the furnace per unit time and unit volume. After the furnace size is fixed, burning more fuel will inevitably increase the heat intensity of the furnace. Correspondingly, the furnace temperature will also increase, and the heat of the furnace tube in the furnace will increase. The furnace heat intensity of the general tubular petrochemical heating furnace is 8.14~11.63W/m³( 7~10kcal/m³·h).

4. The surface heat of the furnace tube. The heat transferred per unit surface area and unit time of the furnace tube is called the surface heat intensity of the furnace tube. The higher the heat intensity of the furnace tube surface, the less furnace tube is required for a certain heat load, the furnace can be reduced, and the investment is reduced, but there is a limit to the improvement.

5. The thermal efficiency of the furnace. The percentage of the petrochemical heating furnace load to the total heat released when the fuel is burned is called the furnace thermal efficiency. The higher the thermal efficiency, the more fuel is saved. It indicates whether the furnace is superior.

6. Flow rate in the tube. The smaller the flow rate, the smaller the heat transfer coefficient, the longer the residence time of the medium in the furnace, the easier it is for the medium in the tube to coke, and the furnace tube is more likely to be damaged. The flow rate should be appropriate.