How to design a finned tube heat exchanger?

- Aug 21, 2018-

How to design a finned tube heat exchanger?

Finned tube heat exchanger optimized design, finned tube heat exchanger is suitable for heating and cooling air (or other gases), because the efficiency of finned tube heat exchanger products, so far, has not been more mature and superior A high efficiency heat exchanger can replace it. Therefore, the optimized design of the finned tube heat exchanger is very important in the product design. By improving the heat exchange efficiency, not only can the product heat exchange effect be improved, but also the cost can be saved and the product volume can be reduced. Research on finned tube heat exchangers has been done by many professionals, both by modeling calculations, by computer simulations, and even by experimental tests, summarizing and accumulating a lot of valuable theoretical and practical experience.

The basic calculation formula for the heat exchanger is: Q=KxFxΔtm

Q—The amount of heat transferred through the heat transfer surface per unit time, W

K—heat transfer coefficient, W/m2.C

F—heat transfer area, m2

Δt—the average heat transfer temperature difference between hot and cold fluids, C

Δt=(Δtmax-Δtmin)/ln(Δtmax/Δtmin)

Δtmax—the value of the temperature difference between the hot and cold fluids at both ends of the heat exchanger, C

Δtmin--a small value of the temperature difference between the hot and cold fluids at both ends of the heat exchanger, C

It can be seen from the above formula that the finned tube heat exchanger can only obtain the above three aspects by obtaining a large amount of heat exchange:

(1) K, heat transfer coefficient, which reflects the efficiency of heat exchange, such as enhancing the disturbance of the wind flow can improve the heat exchange efficiency;

(2) F, heat transfer area, the size of the heat exchanger structure it reacts to, such as the use of internally threaded tubes, can increase the heat exchange area, and also enhance the refrigerant disturbance and improve the heat exchange efficiency;

(3) Δtm, the heat transfer temperature difference, which reacts to the temperature difference between the heat exchange fluids, and selects the appropriate flow direction to make the heat transfer temperature difference as large as possible.

These three parameters are not independent. They interact with each other and cannot only pursue the increase of a single value. Instead, they should be considered together to find the balance point between the parameters, so that the heat transfer of the fin-tube heat exchanger can be achieved. value.

Under normal circumstances, the heat exchange area A of the fin-and-tube heat exchanger should be reduced as small as possible to meet the process conditions, which can improve the cost performance of the equipment. In the process technology, the parameters of the hot and cold fluid are fixed, and the range that can be changed is small. Of course, as far as possible, the countercurrent or crossflow will also have a certain influence on the logarithmic mean temperature difference. The heat transfer coefficient K value is very important in the design. It is possible to increase the velocity of the fluid inside and outside the pipe by using appropriate materials, while taking into account flow loss and operating costs.

The design optimization of finned tube heat exchanger is a professional discipline. The textbooks of heat exchanger equipment at home and abroad have relatively few descriptions and materials in this field. Most of them only involve air conditioning and air conditioning, and optimize the design in process technology. It is even less, and requires relevant manufacturers for further research and design optimization.