According to the design boundaries specified in GB/T 151, the GCH-190 shell-and-tube heat exchanger has a design pressure of 1.6 MPa and a design temperature range of -20°C to 150°C. The design pressure and design temperature shall be used separately for strength calculation and material allowable stress verification: the former determines the wall thickness of the shell, channel, and flanges, while the latter is used to verify the allowable stress and thermal expansion of each component at that temperature. The two parameters are not interchangeable and shall both be submitted to the manufacturer for verification during model selection.
The tube bundle length and baffle spacing are usually not directly specified by experience but are back-calculated from the allowable pressure drops of the shell side and tube side. When the pressure drop budget is ample, the tube bundle may be appropriately lengthened and the baffle spacing enlarged to reduce the cost per unit area; when the pressure drop is limited, the tube bundle is shortened and the baffle spacing reduced to obtain a higher heat transfer coefficient. The back-calculated structural parameters must also be substituted back to verify flow velocity and vibration, and finalized after confirming no abnormalities.
The materials of the shell and tube bundle are selected according to the corrosiveness of the medium, and must simultaneously meet the allowable stress requirements within the range of -20°C to 150°C. At the low-temperature end, material toughness is of concern; at the high-temperature end, allowable stress reduction and expansion differential are of concern. When the temperature difference between the tube side and shell side is large, an expansion joint or a configuration other than a fixed tubesheet should be structurally provided, as determined by the calculated temperature difference.
When submitting parameters for design and model selection, it is recommended to include the names, flow rates, inlet and outlet temperatures, allowable pressure drops, corrosiveness descriptions, and installation space constraints of the media on both sides. Only when the above conditions are complete can the heat transfer area calculation and structural parameter back-calculation be completed. In the absence of allowable pressure drop data, the structural scheme often requires multiple rounds of adjustment.
