Tube parameters: Design of fluid channels

The tube diameter refers to the diameter of the heat exchange tube. Commonly used tube diameters include Φ9.52×0.35mm, Φ10×0.5mm, etc. The selection of the tube diameter needs to consider heat transfer efficiency, pressure drop, and material cost. Smaller tube diameters can increase the heat transfer area and improve heat transfer efficiency but may also lead to a higher pressure drop. Larger tube diameters can reduce the pressure drop but may decrease the heat transfer area. During design, the tube diameter should be reasonably selected based on the fluid's physical properties and heat transfer requirements. For example, for the new refrigerant R410a, condenser tube diameters such as Φ7.94 or Φ7.0×0.35mm can be chosen to enhance heat transfer efficiency.

Tube length refers to the length of the heat exchange tube, typically around 0.65 meters. The selection of tube length needs to consider the heat exchange area and equipment size. Longer tubes can increase the heat exchange area and improve efficiency, but they also increase equipment size and material costs. Shorter tubes can reduce equipment size but may decrease the heat exchange area. During design, the appropriate tube length should be chosen based on specific working conditions and requirements. For example, in refrigeration systems, the tube length of evaporators is generally 0.6–0.8 meters, while that of condensers is 0.7–0.9 meters.

The number of tube rows refers to the arrangement of heat exchange tubes in a heat exchanger, typically ranging from 1 to 8 rows. The selection of the number of tube rows needs to consider both the heat exchange area and the air flow resistance. A higher number of tube rows can increase the heat exchange area and improve heat transfer efficiency, but it also increases air flow resistance. Conversely, fewer tube rows reduce air flow resistance but may decrease the heat exchange area. During design, the appropriate number of tube rows should be chosen based on specific operating conditions and requirements. For example, in refrigeration systems, evaporators usually have 2 to 4 tube rows, while condensers typically have 3 to 6 tube rows.