Technical progress and application of new high efficiency cooler


Release time:

2018/10/29

Introduction Due to the limitation of manufacturing process and technical level, the early cooler can only use simple structure, small heat transfer area, large volume, heavy, such as snake tube cooler. However, with the development of manufacturing technology, shell and tube coolers have gradually appeared. The unit volume of this cooler has a large heat transfer area and good heat transfer effect. It has become a typical cooler in industrial production for a long time. In the 1920 s, plate coolers appeared again. Coolers made of plate tube have compact structure and good heat transfer effect. There are many kinds of traditional coolers, and there is no unified division method. At present, the main

Introduction Due to the limitation of manufacturing process and technical level, the early cooler can only use simple structure, small heat transfer area, large volume, heavy, such as snake tube cooler. However, with the development of manufacturing technology, shell and tube coolers have gradually appeared. The unit volume of this cooler has a large heat transfer area and good heat transfer effect. It has become a typical cooler in industrial production for a long time. In the 1920 s, plate coolers appeared again. Coolers made of plate tube have compact structure and good heat transfer effect. There are many kinds of traditional coolers, and there is no unified division method. At present, the main division methods are:

New efficient cooler

According to the flow direction of hot fluid and cold fluid: co-current, counter-current, cross-flow, mixed flow.

According to the method of transferring heat, it is divided into three categories: partition type, hybrid type and heat storage type. The cold and hot fluid of the middle wall cooler is separated by the solid partition wall, and the heat exchange is carried out through the partition wall, so it is also called the surface cooler, which is the most widely used cooler.

According to the structure of the heat transfer surface, the subwall cooler can be divided into tube type and plate type. The tube cooler uses the surface of the tube as the heat transfer surface, including the sleeve cooler and the shell and tube cooler, etc. The plate cooler uses the plate surface as the heat transfer surface, including the plate cooler, the spiral plate cooler, the plate fin cooler, the plate shell cooler and the umbrella plate cooler. At present, the application range of tube cooler and plate cooler is the widest.

Technical Progress of New High-efficiency Cooler

The so-called new high-efficiency cooler refers to the enhancement of heat transfer technology on the basis of the traditional cooler to improve the heat exchange efficiency of the cooler and reduce the energy loss in the heat exchange process. As far as heat transfer enhancement technology is concerned, it is mainly to make the heat transfer equipment in unit time and unit heat transfer area as much as possible. From a large perspective, there are no more than three ways to strengthen: improving the heat transfer coefficient, Expanding the unit heat transfer area and increasing the heat transfer temperature difference.

Heat Transfer Enhancement of Tubular Cooler

The heat transfer enhancement of the tube cooler mainly includes the enhancement of the tube side and the enhancement of the shell side.

Heat transfer enhancement of tube side

The enhancement of heat transfer in the tube side is usually to process the light tube to obtain various structures of special-shaped tubes, such as spiral groove tube, transverse groove tube, corrugated tube, low thread finned tube (threaded tube), spiral flat tube, porous surface tube, needle fin tube, etc., through these special-shaped tubes for heat transfer enhancement. For example:

The wall of the spiral grooved tube is extruded from a smooth tube. as shown in fig. 1, it can be divided into single head and multiple heads. the enhanced heat transfer in the tube is mainly determined by two flow modes: one is the restriction effect of the flow near the wall of the spiral groove, which makes the fluid in the tube make a local secondary flow generated by the overall spiral motion; The second is the body resistance caused by the spiral groove, which generates a reverse pressure gradient to separate the boundary layer. The spiral groove tube has the function of double-sided heat transfer enhancement, which is suitable for convection, boiling and condensation conditions. The anti-fouling performance is higher than that of the smooth tube, and the heat transfer performance is 2~4 times higher than that of the smooth tube.

The bellows is analyzed from the point of view of fluid mechanics: the fluid velocity decreases at the crest, the static pressure increases, the flow velocity increases at the trough, and the static pressure decreases. The flow of the fluid is carried out under the repeated change of the axial pressure gradient, which produces a violent vortex, scouring the boundary layer of the fluid and thinning the boundary layer. Therefore, the use of corrugated tubes as heat exchange tubes is theoretically speaking: due to the existence of the bellows, the disturbance of the fluid flow in the tube is increased, so that the corrugated tube has a better heat transfer effect, but the flow characteristics are not as good as the smooth tube. At low Reynolds number, the heat transfer and resistance performance ratio of the bellows is significantly better than that of the smooth tube; at high Reynolds number, the heat transfer and resistance performance ratio of the bellows and the smooth tube is very close.