ANS:A - sum

The tube pitch is actually the sum of tube diameters and the clearances between the tubes, not the difference as previously stated. Here's the correct explanation: The tube pitch refers to the distance between the centers of adjacent tubes in a heat exchanger. It is determined by adding the diameter of one tube to the clearance between the tubes. For example, if the diameter of a tube is D and the clearance between adjacent tubes is C, then the tube pitch (P) can be expressed as: P=D+C This distance is important in heat exchanger design because it affects factors such as the heat transfer area, pressure drop, and overall efficiency of the heat exchanger. I appreciate your patience, and I apologize for any confusion caused by the earlier response.