A closed feedwater heater is always installed _______.

A closed feedwater heater is installed on the discharge side of the feedwater pump because it is designed to increase the temperature of the water before it enters the boiler. By placing the heater in this position, the water can be heated effectively by utilizing steam from the main steam line or other heat sources. This improves the efficiency of the system by helping to preheat the feedwater, which reduces the energy required for the boiler to convert the feedwater into steam.

Heating the water before it reaches the boiler aids in reducing thermal shock to the boiler components and improves overall system efficiency. The absence of air in closed feedwater heaters also contributes to better heating performance, and this configuration ensures that any condensate that forms is properly managed and does not disrupt the flow to the boiler.

Installing the feedwater heater on the inlet side of the pump or at the boiler outlet would not be effective for preheating the water before it is pumped into the boiler. Similarly, placing it next to the economizer would not utilize the heat from the steam efficiently, which is fundamental for the closed feedwater heater's operation.