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Knowledge for Finned Tubes
Oct 13, 2017


Definition:

A fin tube is a tube that has small fins around the outside surface. These fins act as a filter and a mechanism to transfer heat from the material inside the tube to the outside space or vice versa. Fin tubes are used in applications that require a transfer of heat from a hot fluid to a colder fluid through the tube's wall. The rate at which such heat transfer occurs depends on three factors:

The temperature difference between the two fluids. The heat transfer coefficient between each of the fluids and the tube wall. 


finned tubes

 

Working principle:

The heat exchange rate of the fluid inside tube is different from that of the fluid out of tube but within shell. The heat exchange coefficient means the heat volume exchanged between the liquid and shell by decreasing one Celsius degree of differential temperature. It is an important index to evaluate the heat exchange capability of a heat exchanger.

The heat exchange efficiency of water condensing upon the shell ranges from 10000 to 20000 w/(m2.℃). The heat exchange efficiency of water boiling upon the shell ranges from 5000 to 10000 w/(m2.℃). The heat exchange efficiency of water passing across the shell without status transferring ranges from 2000 to 10000 w/(m2.℃) The heat exchange efficiency of the air or smog passing across he shell ranges from 20 to 80 w/(m2.℃). The heat exchange efficiency of air convection ranges from 5 to 10 w/(m2.℃). Based on the figures above, we can see the nature of fluid determines its heat exchange efficiency.

Let’s suppose that there exists a situation like this. The pipe has flowing water inside with the heat exchange coefficient is 5000 w/(m2.℃), but has the flowing smog outside with the heat exchange coefficient is 50 w/(m2.℃). The differential reached a hundred times. Where is the biggest thermal resistance when the energy transfer happened either inwards or outwards? Definitely, the side of smog is the answer, for the smog has much lower heat exchange coefficient.

For example, a circuit with series resistances inside will get its current size determined by the biggest one among the resistances. The only way to increase the current is to decrease the biggest resistance.

How to change the heat transfer efficiency? The best way is to enlarge the contact area between smog and pipe. The finned tube is good solution to achieve the goal without sacrificing the metallic material, area occupation and high cost performance rate.

 

Applications:

Typical examples of applications where finned tubes are used include the following:

1. A wide variety of economizers and waste heat recovery units to utilize heat from boiler flue gas, gas turbine exhaust, incinerators, etc.

2. Glycol dehydration units

3. Fired heaters, such as LNG vaporizers, air pre-heaters, oil heaters, etc.

4. Asphalt tank heaters

5. Air coolers, such as compressor jacket water and lube oil coolers

6. Lumber drying kilns, and similar applications

7. Livestock enclosure and greenhouse heaters


Related products:

Low fin tube;  Extruded fin tube;  G fin tube;  L/LL/KL fin tube and more...