Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then

Answer: Option C

The overall heat transfer coefficient of a tube, denoted as U, decreases when dirt is deposited on either side of the tube. This is because the dirt layer adds thermal resistance, making heat transfer less efficient.

Initially, the tube has an overall heat transfer coefficient U1. After dirt deposition, the new coefficient is U2.

Since the dirt layer increases thermal resistance, it reduces the overall heat transfer coefficient:

U₁ > U₂

Therefore, the correct answer is Option C: U₁ > U₂.