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

ANS:A - U₁ = U₂

When dirt is deposited on either side of a tube, it typically reduces the overall heat transfer coefficient. Therefore: U2​<U1​ Explanation:

• The overall heat transfer coefficient (U) represents the combined resistance to heat transfer on both the fluid side and the tube side of the heat exchanger.
• When dirt accumulates on the tube surface, it creates an additional layer of thermal resistance, reducing the overall heat transfer coefficient.
• The presence of dirt increases the thermal resistance, making it more difficult for heat to transfer through the tube wall and between the fluid and the tube surface.
• As a result, the overall heat transfer coefficient U2​ with dirt deposited on the tube is lower than the original coefficient U1​.