High-frequency welding finned tube defects
1, due process limitations fin spacing, minimum spacing 4mm 55mm fin height maximum is generally cooler 2.3mm aluminum fins fin spacing, 57mm fin height so, wing of the ratio is low, Max is only 13 or so, the normal flaking or swelling film is 23, meaning that the same base pipe area, finned aluminum fins of the small size of only about 55% z effect of heat transfer is limited.
2, the fins of steel or stainless steel sheet, thick sheet, the thinnest 0.8mm, and the aluminum is about 0.3-0.45mm, fin heat efficiency is poor, if the stainless steel fins, stainless steel heat exchanger efficiency worse as (pass Thermal efficiency is only 65% of aluminum), the low heat transfer efficiency.
3, high-frequency welding finned, although the contact resistance is small, but the fin area is limited, poor heat transfer fin thickness, therefore, the overall thermal efficiency of the finned tube is not high. Except for some special process, in general, use less. Applications Based on the above description, high frequency welding finned tubes in the air cooler is inappropriate unless the temperature is higher than 500 ℃ situation. But based on their corrosion better, such as stainless steel fin - stainless steel base tube, evaporative cooling in methanol synthesis applications can be used, however, the heat transfer efficiency is greatly reduced, and only about 45% of aluminum (area of only aluminum 60% of tablets, aluminum heat exchanger efficiency is only 70%, the overall effect is 0.6 × 0.7 = 0.45), so its water-saving effect is poor.
Integral finned tube has the following six advantages
1.Integral finned tubes can Extended heat exchange effect (area and heat transfer coefficient). In the case of the same base tube (for example in the base tube is φ32X4 fin height 12 fin spacing 12), one meter is equivalent to 4 m or 2.6 m fluorescent membrane structure spacing 62X3, 30X3 or 1.5 m steel flat wound welded wings piece tube steel 12X3.
2 Integral finned tube wear. As the overall finned tubes finned tube is integrally formed with the base, the same crystal structure, stable performance, besides the shape of the fins were sand dunes, and the temperature gradient shape when heated match, the outer surface of the fin when heated consistent temperature, thermal stress homogeneous, no focus, it will not have strength weak points, mainly due to the high wear point σ should be low, in addition, the fins having a diversion effect of the gas, while the diversion, the tobacco gas indicators, temperature, flow rate, ash more uniform, does not produce smoke drift, it will not cause gas concentration scour a region or a particular area. Therefore, more wear-resistant.
3 Integral finned tube stiffness greatly enhanced. Size depends on the size of the stiffness moment of inertia, moment of inertia of the whole finned tubes is 4.76 times the corresponding fluorescent tubes. φ32X4 moment of inertia 35168mm2, and finned tubes inertia 167613mm2, light pipe bracket spacing is 2.71m (3.55m old REGULATORY), finned tube 5.28 m (6.91m old pipe gauge), if the calculation of the wall temperature reaches 460 ° close bracket spacing will be reduced, so some economizer tubes in two rows on the middle bracket break phenomenon. This phenomenon is occurring fracture neat. The material and found no problems.
4 Integral finned tubes not fouling. The reason is that fouling caused by Karman vortex gas flow through the tube, the tube will form a negative pressure zone on the back, in this region, the flue gas flow or return to zero, the accumulation of gas in this, the ash attached to the the pipe surface. The thermal resistance is relatively large ash, ash piled thick, thermal resistance increases, less and less heat transfer increases the exhaust gas temperature, boiler efficiency also decreases. The finned tubes for gas diversion to overcome the Karman vortex, but also combing the ash distribution, so that in the flue gas distribution.
5 heat transfer performance and stability. A body structure as the heating surface, in the years without blowing operation, the boiler flue gas temperature fluctuations changed little, no economizer tube pipe explosion occurred.
6 long life. Coal under the same operating conditions, temperature, heating surface position, finned tube fluorescent tubes guarantee life of more than 2 times. Under normal circumstances the light tube life of 3 to 4 years, the finned tube life of at least 7 to 8 years.
Key Words: Finned Tube, Fin Tubes, Extruded Fin Tubes, Embedded Fin Tube, L Fin tube, Tubos Aletados