Heat Exchange Tubes

Heat exchange tubes are the core components of heat exchangers, located inside the shell and used for heat exchange between two media. They possess high thermal conductivity and isothermal properties. They are referred to as heat transfer superconductors, with a thermal conductivity thousands of times greater than that of copper, enabling rapid heat transfer with virtually no heat loss. Common materials include carbon steel, low-alloy steel, stainless steel, and copper-nickel alloys. Besides plain tubes, enhanced heat transfer tubes such as finned tubes and threaded tubes are also used. The tube diameter is generally between Φ19mm and Φ38mm, typically using seamless steel or stainless steel tubes, and the tube bundle arrangement is primarily in a triangular pattern.

Common materials include carbon steel, low-alloy steel, stainless steel, copper, copper-nickel alloys, aluminum alloys, and titanium. In addition, there are some non-metallic materials such as graphite, ceramics, and polytetrafluoroethylene. The appropriate material should be selected based on working pressure, temperature, and the corrosiveness of the medium during the design process.

Isostatic Pressing Process:
1. Initial stage: At low forming pressure, the powder particles migrate and rearrange.
2. Intermediate stage: As the pressure increases, local flow and fragmentation of the powder occur.
3. Final stage: At maximum pressure, the powder volume is compressed, pores are eliminated, and densification is achieved.
The isostatic pressing process consists of the following steps: A fluid medium (gas or liquid) is pumped into a high-pressure steel sealed container using a high-pressure pump (as shown in the figure). The hydrostatic pressure of the high-pressure fluid acts directly on the powder within the elastic mold. The powder body is subjected to uniform pressure in all directions simultaneously, resulting in a compact with uniform density distribution and high strength.

Process Flow: