This study investigates the thermal modeling of heaters at the city gate stations (CGS) in Iran with a focus on efficient heat transfer and fuel consumption. Gas heaters are basic equipment with applications in various industries, especially CGS sites. Research on gas heaters and their optimal and efficient performance has been a challenging subject in the engineering world. This study aimed to change the heaters' thermal functionality from free to forced convection and examine the effect of such alteration on the heaters' efficiency while reducing their energy consumption. To make forced convection in the heater, a pump is required to be installed on it. This pump causes fluid circulation inside the heater and by creating movement in the fluid, it increases the heat transfer coefficient and changes the heat transfer mechanism of the system from free convection to forced convection. Using the first law of thermodynamics, the net energy these heaters emit into the environment consists of multiple components. These include the energy expended as follows: in the chimney, to warm up the gas, and the part dissipated away from the heater's body. The heat transfer coefficient is determined after calculating the energy loss for each of the components. Changes in the required energy for the total heat transfer coefficient for both free and forced convection may be analyzed. The results of this research indicate that forced convection heat transfer causes more heat loss from the heater's body than that transferred to the gas stream in the heater coils. This energy transfer ultimately reduces the heater's efficiency concerning the net generated heat. Thus, a reduction in the efficiency occurs and the initial efficiency (32%) of the free convection declines to a lower coefficient value for the forced convection.
