What is fin tube heat exchanger
Fin tube heat exchanger is a kind of heat exchange equipment used in gas and liquid heat exchangers. It achieves the purpose of enhancing heat transfer by adding fins to the ordinary base tube.
The fin tube heat exchanger is one of the earliest and most successful discoveries in the process of improving tube heat transfer. This method is still the most widely used method among all tube heat transfer surface enhancement methods.
It is not only suitable for single-fin tube heat exchangers, which are widely used in power, chemical, petrochemical, air-conditioning engineering and refrigeration engineering.
Structure of fin tube heat exchanger
The basic heat transfer element of the fin tube heat exchanger is a finned tube, a finned tube mountain base tube and a fin combination. The base tube is usually a round tube, but there are also oval tubes and flat tubes. The surface structure of the fins includes flat fins, interrupted fins, corrugated fins and perforated fins.
The base pipe can be steel pipe; stainless steel pipe; copper pipe, etc. The fin can also be made of steel belt; stainless steel belt, copper belt, aluminum belt, etc. The fin tube heat exchanger is a device in which air is used as the heat exchange medium, and the temperature is transferred from one object to another.
There are two types of steam heat exchangers, heating air and cooling air. The heat exchange process is divided into two stages. First, the heating or cooling medium heats or cools the surrounding air under the action of the finned tube, and the heated or cooled air transfers the heat to other objects to achieve the purpose of heating and cooling.
Such as drying room drying and air cooling system. It is the main equipment in the hot air device. The heat medium used in the fin tube heat exchanger can be steam or hot water, or heat transfer oil. The working pressure of steam is generally not more than 0.8Mpa, and the temperature of hot air is below 150°C.
Classification of finned tubes in fin tube heat exchanger:
1. Classified by structure
From the structural type, the finned tube can be divided into two basic types: longitudinal and radial. Other types are the development and deformation of these two types. For example, the large spiral angle fin tube is close to the longitudinal direction, and the small spiral angle fin tube is close to the radial The shapes of the fins are round, rectangular and needle-shaped. In addition, the fin can be arranged outside the tube, called an outer finned tube; it can also be arranged inside the tube, called an inner fin tube or both.
2. Classified by manufacturing process
According to the manufacturing process, finned tubes can be classified into integral finned tubes, welded finned tubes, high-frequency welded finned tubes and mechanically connected finned tubes.
(1) The integral fin tube is made by casting, machining or rolling, and the fin and the tube are a whole.
(2) Welding finned tubes, using brazing or inert gas shielded welding and other processes to manufacture. Modern welding technology can connect fins of different materials together, and can make finned tubes simple and economical, with good heat transfer and mechanical properties, and has been widely used. Since the residue in the welding seam is not conducive to heat transfer and may even cause fracture, the quality of the welding process must be ensured when producing such finned tubes.
(3) High-frequency welding of finned tubes uses high-frequency electric induction generated by a high-frequency generator to generate high temperature at the contact point between the tube surface and the fins.
Melt the two in the left and right depth range, and then pressurize to connect the fin and the tube as a whole. No flux, no solder, simple manufacturing, high productivity, excellent heat transfer and mechanical properties. This is the most ideal type of finned tube, which is being recognized and adopted by the majority of users.
(4) The finned tubes are mechanically connected, usually in three types: winding type, inlaid type, sleeve type or string type. The winding fin tube is simple to manufacture. The metal band is fixed on one end of the tube by mechanical or welding method, and the metal belt is tightly wound on the outer wall of the tube by the tube rotation torque, and the other end is fixed to form a wound fin tube. The material of the winding sheet can be copper strip, steel strip or aluminum strip.
The basic equation of heat transfer calculation for fin tube heat exchanger is the same as that of other tube heat exchangers:
In the equation:
-Heat transfer, W;
–Total heat transfer coefficient based on the heat transfer area of the inner surface of the base pipe, W/(m2·℃);
–Total heat transfer coefficient based on the heat transfer area on the outer surface of the fin side, W/(m2·℃);
–The heat transfer area of the inner surface of the base pipe, m2;
– The heat transfer area of the outer surface of the fin side, m2;
– Logarithmic average temperature difference, ℃.
Simplify the above formula to get
Heat transfer characteristics of fin tube heat exchanger
From the perspective of heat transfer mechanism, the fin tube heat exchanger is still a 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 (baffle), but also on the secondary heat transfer surface.
The heat of the medium on the high temperature side is poured into the medium on the low temperature side once on the surface, and part of the heat is also transferred along the height of the fin surface, that is, along the height of the fin, there is a partition to pour the heat, and then the heat is transferred to the low temperature side medium.
Since the height of the fin greatly exceeds the thickness of the fin, the heat conduction process along the height of the fin is similar to that of a homogeneous elongated guide rod. At this time, the thermal resistance of the fin cannot be ignored.
The temperature at both ends of the fin is at most equal to the temperature of the partition. With the convection and heat release of the fin and the medium, the temperature continues to decrease until the temperature of the medium in the middle of the fin.
1. High heat transfer efficiency. Due to the continuous rupture of the boundary layer due to the disturbance of the fins to the fluid, it has a large heat transfer coefficient; at the same time, because the partitions and fins are very thin and have high thermal conductivity, plate-fin heat transfer is made The device can achieve high efficiency.
2. Compact Because the plate-fin heat exchanger has an extended secondary surface, its specific surface area can reach 1000㎡/m3.
3. Lightweight The reason is that it is compact and mostly made of aluminum alloy. Now steel, copper, composite materials, etc. have also been mass-produced.
4. Strong adaptability The fin tube heat exchanger can be applied to: heat exchange between gas-gas, gas-liquid, liquid-liquid, various fluids, and phase-change heat that undergoes concentration changes. Through the arrangement and combination of runners, it can be adapted to different heat exchange conditions such as counter-flow, cross-flow, multi-stream, multi-pass flow. The combination of series, parallel, series and parallel between the units can meet the heat exchange needs of large equipment. Industrially, it can be finalized and mass-produced to reduce costs, and interchangeability can be expanded through modular combination.
Selection parameters of fin tube heat exchanger
How to choose a fin tube heat exchanger is indeed a question that consumers need to think about.
Some focus on thermal efficiency and care about whether they can obtain obvious results in a short time; some focus on corrosion resistance due to environmental factors; and whether the shape is beautiful in accidents. Such all kinds. So which ones are the most basic and cannot be ignored?
First: The working pressure of the finned tube radiator should meet the working pressure of the system and comply with the current national product standards;
Second: Industrial buildings with high requirements for dust emission or dust prevention should use finned tube radiators that are easy to clean;
Third: Corrosion-resistant finned tube radiators should be used in industrial buildings with corrosive gases or in environments with high relative humidity;
Fourth: When using steel finned tube radiators, a closed system should be adopted and meet the product’s water quality requirements.
Fifth: When using aluminum finned tube radiators, internal anti-corrosion aluminum finned tube radiators should be used, and meet the product’s water quality requirements;
Sixth: Choose a regular finned tube radiator manufacturer, with better after-sales guidance, installation, and technical support. Our company specializes in manufacturing various radiator equipment, heat exchangers, oil coolers, surface air coolers, and radiators. , Finned tube.
Application of fin tube heat exchanger
Fin tube heat exchangers are widely used in power, chemical, petrochemical, air conditioning engineering and refrigeration engineering, such as surface air coolers, air heaters, and fan coils used in air conditioning engineering.
The air cooler evaporator and frost-free refrigerator evaporator used in refrigeration engineering are not only suitable for the flow of single-phase fluid, but also have great value for phase change heat.
Most of the fin-tube heat exchangers used for clean gas use a new and efficient fin surface structure, which has achieved a significant heat transfer enhancement effect.For more information, contact us!