Indirect-fired heaters are used for well testing that use water or glycol mixtures as the transfer medium. These heaters can reheat the process fluid after it is cooled by the pressure drop expansion across the choke. It consists of a large, low-pressure tank that contains water or glycol heated by a gas or diesel burner in a tube. The fluid to be heated passes through high-pressure flow tubes or coils, which are installed in the tank and covered by water or glycol. The coils make multiple passes inside the tank to provide the largest amount of surface area possible for heat transfer. It prevents hydration and improves separation of oil/water emulsions & foaming oils by reducing surface tension and viscosity.

Indirect fired water heaters are used for low temperature types of supply water heating applications requiring temperatures up to 190F. These are also used for combination closed system/supply water heating applications. It is an industrial quality unit designed for economically heating large volumes of domestic or process water for commercial and industrial applications. The all bronze and copper heat transfer coil eliminates the possibility of rust throughout the water passages. The indirect principle of heating the process water with sealed-in primary water combined with controlled circulation minimizes the possibility of scaling within the heat transfer coil for low or high temperature applications.

Indirect Heat Exchanger means equipment in which heat from the combustion of fuel is transferred by conduction through a heat-conducting material to a substance being heated. An indirect heat-exchanger eliminates problems caused by the build-up of limescale and ensures that the panel cannot freeze in winter. An indirect heat exchangers are submerged in the water and in this way cold water circulated to a closed loop system is connected to mass produced fan coil units or other terminals. Indirect heat exchanger designed to transfer heat from combustion gas to the air stream added to the combustion zone.

Indirect rotary dryers are continuous, atmospheric contact dryers widely employed in industry for continuously processing large quantities of wet solids. It can handle very high throughputs. It is used when direct rotary dryers are unsuitable. This is because direct contact with hot combustion gases is not permissible for product quality reasons or because of the presence of fine particles, which can easily become entrained in the higher gas flows found in convective rotary dryers. It cannot handle liquids or slurries or adhesive solids. The most common design consists of a cylindrical shell inclined at a small angle to the horizontal. Wet feed is introduced into the upper end and dried product withdrawn at the lower end. Transportation of solids through the dryer is assisted by slowly rotating the shell.