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Heat conduction process of finned tube heat exchanger

Finned tube heat exchangers are usually composed of baffles, fins, seals, and deflectors. Place fins, deflectors and seals between two adjacent baffles to form an interlayer, called a channel. Stack these interlayers according to different fluids and braze them into a whole to form a plate bundle. The plate bundle is a fin The core of the finned tube heat exchanger is equipped with necessary heads, tubes, supports, etc. to form a finned tube heat exchanger.


From the perspective of heat transfer mechanism, the finned tube heat exchanger still belongs to the shoulder arm heat exchanger. Its main feature is that it has an extended secondary heat transfer surface (fins), so the heat transfer process is not only performed on the primary heat transfer surface (separator), but also on the secondary heat transfer surface. The heat of the medium on the high temperature side is transferred into the medium on the low temperature side once, and part of the heat is transferred along the height direction of the fin surface, that is, along the height direction of the fin, there is a baffle into the heat, and then the heat is transferred to the low temperature side by convection medium.


Since the height of the fin greatly exceeds the thickness of the fin, the heat conduction process along the height direction of the fin is similar to the heat conduction of the homogeneous elongated guide rod. At this time, the thermal resistance of the fin cannot be ignored. The maximum temperature at both ends of the fin is equal to the temperature of the baffle. With the convection of the fin and the medium, the temperature continues to decrease until the medium temperature in the middle of the fin.


Finned tube heat exchanger


1. High heat transfer efficiency.Because the fins disturb the fluid, the boundary layer is constantly broken, so it has a large heat transfer coefficient; at the same time, because the separator and the fins are thin and have high thermal conductivity, the fin tube heat transfer The device can achieve high efficiency.


2. Compact.As the finned tube heat exchanger has an expanded secondary surface, its specific surface area can reach 1000㎡/m3.


3. Lightweight.The reason is compact and mostly made of aluminum alloy. Now steel, copper and composite materials have been mass produced.


4. Strong adaptability.The finned tube heat exchanger can be applied to: heat exchange between gas-gas, gas-liquid, liquid-liquid, various fluids, and phase-change heat in which the state change occurs. Through the arrangement and combination of flow channels, it can adapt to different heat exchange conditions such as countercurrent, crossflow, multi-stream and multi-pass flow. Through the combination of series, parallel and series-parallel between units can meet the heat exchange needs of large equipment. In the industry, it can be shaped and mass-produced to reduce costs and expand interchangeability through building block combination.


5. Strict manufacturing process requirements.The process is complex. It is easy to block, not resistant to corrosion, and difficult to clean and repair, so it can only be used in occasions where the heat transfer medium is clean, non-corrosive, not easy to scale, not easy to deposit, and not easy to block.