What is the cooling source for the inline desuperheater?

The cooling source for an inline desuperheater is indeed feedwater. In the context of steam systems, a desuperheater functions to reduce the temperature of superheated steam. It does so by injecting cooler water into the steam flow. This cooler water is typically feedwater, which is the water that is already treated and prepared to be converted into steam in the boiler. The feedwater absorbs heat from the steam, effectively lowering its temperature to a more desirable level for subsequent processes or for re-entering the steam system.

Using feedwater is effective because it ensures that the water a system relies on for its operation is utilized efficiently, and this practice avoids introducing any foreign substances that could adversely affect system performance or integrity. Other options such as chilled water or cooling oil do not serve this function within the context of steam systems. Chilled water is meant for cooling in air conditioning systems, while cooling oil would typically be used for lubrication rather than heat exchange in high-temperature steam applications.