Indirect Heaters

When the gas pressure drops suddenly, the temperature decreases, which is called the Jules Thomson effect. In natural gas pressure reduction stations, the gas temperature is also reduced due to the reduction of gas pressure in the regulators For this purpose, at natural gas pressure reduction stations, there is a need to heat the incoming gas into the regulators to a certain temperature to prevent hydrate formation. Indirect heaters are designed to heat the gas without any need to use pressure vessels. In these heaters, gas flows in a submerged tube in a hot water bath and is therefore referred to as indirect heaters. This bath is heated by a combustion chamber equipped with a burner. Indirect heaters are supplied as a complete package with a gas supply system, control and safety systems, electric or pneumatic type. The control and safety system can detect all operational failures and can control the unit under any working conditions to adjust the temperature of the outlet gas to the set point. The field of application of this type of heater may vary, but it is specifically used to heat the gas to prevent hydrate formation. Indirect heaters are divided into two categories natural convection (natural draft) and forced convection (forced draft). 

Indirect heaters (natural draft):

Indirect heaters are designed to heat gases without the need to use pressure vessels. These heaters are called indirect because of the gas flow in a submerged tube in a hot water bath. The bath is heated by a combustion chamber equipped with a burner. The field of application of this type of heaters may vary, but it is specifically used to heat the gas to prevent hydrate formation.

Forced draft heaters:

In this type of heaters, the burner is equipped with an electric blower that delivers combustion products to the firetube at high speed. Sometimes, when the burner is in shut down mode, the gas control valve of the entering fuel does not work properly, and the gas leaks into the firetube and accumulates there. Therefore, in burners in forced draft heaters, the fan works for a few seconds before combustion to exhaust any accumulated gas in the firetube. This is very important for the operators’ safety. In addition, due to the speed of combustion products in the fire tube, the heat transfer coefficient increases and the required heat transfer area decreases, hence