Question

In a heat exchanger, the primary controlled variable is often:

• A. Outlet temperature
• B. Inlet pressure
• C. Pump speed
• D. Pipe diameter

Hint:

In heat exchanger systems, always think of the outlet temperature as the key measure of heat transfer performance — it's the main variable being controlled.

Answer 1

The Correct Option is A

In a heat exchanger, the fundamental objective is to transfer heat from one fluid to another in a controlled manner. The most important variable that determines how well this process is being carried out is the outlet temperature of the process fluid.
The outlet temperature reflects the effectiveness of the heat transfer and is typically what needs to be regulated to meet process requirements.
Let’s examine why the other options are incorrect:
- Inlet pressure is often a disturbance variable rather than a controlled one.
- Pump speed is generally a manipulated variable, not a controlled variable — it is adjusted to achieve the desired temperature.
- Pipe diameter is a fixed mechanical property and not controllable during operation.
Therefore, in heat exchanger applications, outlet temperature is the primary controlled variable because it reflects the end goal of maintaining a desired heat transfer output.