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Spiral Tube Heat Exchanger
Helix pattern flow inside the tubes
The flexible spiral wound tube bundle is acting as a spring , expanding or shrinking during the start-up or shut down phases . This allows for a differential expansion between the bundle and the pressure vessel required to ensure its mechanical integrity . This expansion is guided axially by the centre pipe . In fact , there are no mechanical limitations in temperature rise and fall , making this technology highly reliable under process fluctuations . It allows for very low constraints on start-up / shutdown procedures and emergency situations . This patented design gives :
• Resilience under upset conditions .
• Resistance to thermal and pressure shock .
• No limit for cooling and heating rates during start-up , shutdown and upset conditions within the design pressures and temperatures .
Just one exchanger can replace multiple horizontal or vertical exchangers , saving on installation and capital cost for both new units or revamping projects . Compared to traditional shell & tube exchanger , the spiral tubes exchanger has a smaller volume and weight due to its high heat transfer efficiency . It can offer a heat exchange up to 30,000 m ² for reforming and aromatic processes , and up to 10,000 m ² for hydroprocessing units in a single piece .
On the tube side The Helix-pattern flow in the tubes creates , thanks to the centrifugal forces , a secondary flow consisting of a pair of vortices enhancing the heat transfer coefficient at the peripheral of the tubes . In order to limit the mechanical constraints , the spiral tubes are coiled layer by layer in opposite directions to ensure a homogeneous heat transfer and temperature gradient all along the exchanger , from the cold to section with higher temperatures .
On the shell side The high turbulence flow on the shell side is created by the design of the tube coils . The variation of the fluid velocity between the tubes and the layers creates a pulse-surge collision flow regime , subsequently increasing the heat exchange coefficient outside the tubes . The possibility of fouling is greatly limited by the non-baffle design and the absence of a stagnant zone , the turbulence of the fluid and the very low surface roughness of the tubes .
Performances With the spiral tube design , the heat transfer efficiency is 2 to 3 times higher than conventional shell and tube heat exchangers . It allows for an achievable hot approach temperature as low as 10 ° C for feed / effluent exchanger on the reactor loop of the hydroprocessing units , for example . With this very high heat recovery , the charge heater can even be used only during the start-up and then shut-down during the normal operation ; the temperature of the process being controlled by a by-pass line . The minimum temperature difference between the two fluids ( pinch point ) can be as low as 2 ° C . The minimum pressure drop on shell side is 2 to 3 kPa , and the operating ranges up to 650 ° C for the temperatures and 26 MPa for the pressures . There is no limitation on reverse pressure between the shell and the tube sides .
Fabrication ZPJE is using a class 100,000 dust-free clean workshop to fabricate its exchangers . It provides an exceptional manufacturing environment usually only used in semi-conductor or photovoltaic industries .
Bundle temperature gradient
Applications
Crude Oil Refineries : Hydrotreating , hydrocracking Reforming Crude distillation unit Solvant deasphalting Others Process gas heater Overhead condenser Low-grade heat recovery
Petrochemicals Aromatics Propane dehydrogenation Poly propylene EOEG Olefins catalytic cracking Fertiliser Rectisol Methaniser www . heat-exchanger-world . com Heat Exchanger World November 2022
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