In steam-heated air applications, operators often find that the tube-side outlet temperature cannot reach the setpoint. During troubleshooting, if the match between shell-side baffle spacing and flow velocity is overlooked, even ample heat transfer area cannot make up for the heat load. During the design and selection stage, parameters must be determined one by one from the following dimensions.
The GCH-320 shell and tube heat exchanger is suitable for heat exchange conditions such as liquid-liquid, steam-liquid, and oil-water. The design pressure is 1.6 MPa, and the design temperature range is -20~200°C. When the tube side carries fouling-prone media, a removable channel head structure can be selected; when the shell side carries corrosive media, the shell material should preferably be stainless steel clad plate. The heat exchange tube specification is Φ19×2, arranged in a triangular pattern, with a tube pitch of 25 mm.
It is recommended to record the secondary-side outlet temperature once a week. When the deviation exceeds the design value by ±5°C, the cause must be investigated. Common factors include a decrease in heat transfer coefficient caused by fouling, mismatch between baffle notch orientation and flow velocity, and bypass leakage. After cleaning, the pressure difference must be re-measured to confirm that it has returned to the design range; if the pressure difference has not decreased, it is recommended to use a borescope to spot-check the inner wall of the tube side and observe whether hard scale remains or the tube bundle is deformed.
The heat transfer area must be calculated according to the heat load and then a margin of 10%~15% should be reserved to avoid increased pressure drop caused by undersized selection. The design pressure determines the wall thickness grade of the shell and tube bundle, and the design temperature affects material selection and expansion calculation—when the temperature difference exceeds 60°C, an expansion joint should be provided for a fixed tubesheet structure. The inlet and outlet pipe diameters affect flow velocity and pressure drop. The shell-side flow velocity should preferably be controlled at 0.3~0.8 m/s, and the tube-side flow velocity should preferably be 0.8~1.5 m/s.
For a secondary-side heat exchange station in central heating, the GCH-320 shell and tube heat exchanger should preferably be selected, with high-temperature water on the shell side and heating return water on the tube side; for cooling circulation of chemical reactors, this model can be selected, with cooling water on the tube side and reaction materials on the shell side; in waste heat recovery systems, if the flue gas side has a high dust content, a dust removal device must be installed before the tube bundle.
