Skip to main content

The importance of finned tube heat exchanger in specification selection



The importance of finned tube heat exchanger in specification selection

The role of the fins of the finned tube heat exchanger is to enhance heat transfer. When selecting finned tube specifications, the focus should be on enhancing heat transfer. For the enhanced heat transfer of heat exchangers, many theoretical and practical results have already been achieved. For example, by changing the fin material, improving the fin processing technology, increasing the fin ratio, improving the flow state and increasing the turbulence, etc., the height and thickness of the fin are affected by the manufacturing level and process and are limited to a certain Within the scale.
The heat transfer inside and outside the tube is single-phase convective heat transfer and the heat transfer coefficient increases in proportion to the power exponent of the fluid velocity. Fluid flow is divided into the laminar flow and turbulent flow. The main mechanism of laminar and turbulent flow enhancement is to use the increase of the secondary heat transfer surface to destroy the original unenhanced fluid velocity and temperature distribution field. The heat transfer coefficient of laminar flow is relatively low, and the heat transfer coefficient of turbulent flow is relatively high. Usually, a more economical enhancement measure is to change the flow state of laminar flow to turbulent flow. You can reduce the pipe diameter and add disturbances. To achieve this by tapping or increasing the flow speed of the medium, the most economical way in the current process is to use small-diameter heat exchange tubes, such as copper tubes for air conditioning, mostly in sizes of 9.52mm, 12.7mm and 15.88mm.

When the flow state inside and outside the tube is turbulent, a reasonable fin ratio should be used as much as possible. The heat transfer coefficient can be obtained by calculating the heat transfer coefficient of the inner film of the tube, the heat transfer coefficient of the outer film of the tube, and the thermal resistance of the tube wall. For bottlenecks, increase the density of fins and increase the height of the fins on the weaker heat transfer capacity. For the occasion of heat exchange with the air, if the air outside the tube has no phase change, the higher the fin ratio, the better. The commonly used steel-aluminum composite fin tube on the air cooler is 25*2-57/2.3/0.3. The best example is that due to the limitation of the processing technology, the density and height of the fins cannot be increased, otherwise, there is still potential to be tapped.
Conversely, for the air outside the tube with condensation and phase change, the existence of the water film can increase the heat transfer capacity on the airside, and the difference in heat transfer coefficients inside and outside the tube is not that big. At this time, the focus is on how to remove the condensate generated in time. The condensate stagnating in the middle of the fins will cause a drag on the heat transfer of the fin tubes. It is equivalent to the high temperature and stagnant water outside the tube, which cannot exchange heat with the air. At this time, a larger sheet distance should be used to reduce the tension on the waterside, and the selection of fin tube specifications is also particularly important.

The selection of finned tube specifications must also consider the adaptation of the material to temperature. Such as high-temperature flue gas heat exchange, high-frequency welding fins should be used, and the temperature resistance of aluminum rolled fins is not suitable.

Of course, anti-corrosion, service life, contact thermal resistance, and heat exchange effect are all important points in the selection of specifications for finned tube heat exchangers.


Comments

Popular posts from this blog

What are railway rail fasteners?

What are railway rail fasteners? Railway rail fasteners Railway rail fasteners are a kind of railway accessories. The parts used to combine rails and sleepers (or other types of under-rail foundations) on the track are also called central joint parts. Its function is to fix the steel rail on the sleeper, maintain the gauge and prevent the longitudinal and lateral movement of the rail relative to the sleeper. The railway rail fastener system is divided into the shrapnel fastener system, gusset fastener system, and elastic strip fastener system. The gusset-type fastener is composed of a gusset plate, a threaded spike, a spring washer, an iron seat, and a buffer pad. The threaded spike is anchored in the reserved hole of the concrete sleeper bearing platform with sulfur cement mortar, and then bolts are used to fasten the buckle. Plate fastened. There are elastic strips I, II, and III types of clip fasteners. Type I elastic strip is composed of ω elastic strip,  screw spike , gauge b...

30 LB RAIL FOR SALE

  30 LB RAIL FOR SALE What is a 30 lb rail? A 30 lb rail refers to a rail weighing 30 lb in meters, which is an ASCE 30 model rail produced according to ASTM A1. As a common light track, it is mainly used for laying mining track lines. Therefore, it is widely used in the South American market. The dimensions of the 30 lb rail are as follows: Head width: 42.9mm Track height: 79.4mm Track bottom width: 79.4mm Waist thickness: 8.4mm GloryRail is an important  mining rail  supplier in China. Engaged in rail supply for more than 20 years. Rail products are exported to many countries and regions around the world. Trusted and supported by many mining customers. We maintain long-term cooperative relationships with many important customers in Peru, Colombia, Panama, and Venezuela in South America BUY 30 LB RAIL FROM CHINA As the world’s most important rail tracks production base. There are six major steel mills in China producing rails with an annual output of millions of tons. G...
  What are seamless rails? seamless rails Continuous seamless rails, also known as a welded long rail line, is a line that welds ordinary rails without leaving rail seams. meters or longer. The long rails are laid and fixed on the sleepers within the specified temperature range. There are rail slits at the end of the long rail, and the middle part cannot expand or contract with the temperature rise and fall. Therefore, the middle section of the steel rail will generate a large temperature pressure in summer and a large temperature tension in winter. The large pressure and tensile force in the rail can be calculated according to the annual high and low temperature of the place where the rail is laid. The large pressure on the rail should not cause the rail to buckle, and the large tensile force should not cause the rail to break. The seamless rails line greatly reduces the  rail joints , reduces the impact on the rails when the wheels pass through the joints, is conducive to s...