Application areas of finned heat exchangers and the role of fins

Application areas of finned heat exchangers and the role of fins

Fin heat exchangers are industrial general-purpose heat transfer equipment with various types of finned tubes as heat transfer elements. This type of heat exchanger has a large range of operating pressures in the tube range and is suitable for liquid-gas heat exchange, steam-gas heat exchange and gas-gas heat exchange occasions. Today, we will tell you about the role of fins and the application areas of finned heat exchangers.

The role of fins

   1、Fin spacing

   The row spacing is 31.75mm in the case of 14 kinds of flat finned coils. Test results obtained: 4 rows of tubes, heat transfer performance and fin spacing has nothing to do; each row of pressure drop of the tube also has nothing to do with the number of rows of tubes. For 1 or 2 rows of tubes, however, the pattern is different; for ReDc > 5000, the effect of eddy currents occupies an important position and the effect of fin spacing can be ignored.

   When ReDc < 5000, the heat exchange performance increases with decreasing fin spacing. It is found that higher air flow rates and larger tube rows lead to the creation of vortex areas, therefore, the effect of fin spacing on the heat exchange coefficient can both be ignored.

   2. Number of tube rows

   For flat fins: the influence of the number of rows on the heat transfer characteristics is only significant when the number of rows is large, the fin spacing is small and the Reynolds number is low.

   When ReDc < 3000, the heat transfer factor decreases with increasing number of rows due to the influence of the boundary layer; the influence of the number of rows on the frictional resistance factor is relatively small. However, when ReDc > 3000, the effect of the number of rows on the heat transfer decreases.

   For corrugated fins: at low Reynolds numbers, the number of tube rows has no significant effect on the heat transfer coefficient and friction coefficient; at high Reynolds numbers, the heat transfer coefficient increases with the number of tube rows.

   For open slit fins: at low Reynolds numbers, the number of rows has a significant effect on the heat transfer coefficient, and the heat transfer factor decreases sharply as the number of rows increases; the number of rows has a relatively small effect on the friction factor.

   3、Tube-diameter

   For flat fins, the larger the tube diameter, the larger the invalid area after the tube is caused. The heat transfer coefficient increases slightly with the reduction in the diameter of the heat pipe of the home decoration effect buckling machine press machine. For example, for single-row and double-row tubes, the heat transfer coefficient at Dc=8.51mm is slightly higher than that at Dc=10.23mm; however, the pressure drop at Dc=10.23mm is 10%-15% greater than that at Dc=8.51mm.

   For other fin types (corrugated fins, slit fins, louvered fins), a small tube diameter can also reduce the dragging effect of the tube row, thus increasing the heat transfer coefficient outside the tube; and can reduce the pressure drop loss. For example: for louvered fins, when the wind speed Vfr < 1.5m / s, the use of small tube diameter of the multi-row tube structure is conducive to improving the heat transfer performance of the heat exchanger, and can reduce the pressure drop loss of 10%.

Application areas of finned heat exchangers

   Commercial air conditioning: fan coils, air conditioning treatment units, air-cooled condensers, dehumidifiers

   Commercial refrigeration: display cabinets, ice machines, beverage machines, vending machines, chillers

   Transport: refrigerated trucks, refrigerated containers, buses/trucks/subways/ships

   Others: industrial drying equipment, environmental laboratories, oil coolers, power, tobacco, metallurgy, steel, textiles, wood, paper, food, pharmaceuticals, minerals, etc.