The number of fins is not supposed to be the more the better or the higher the better. A couple of factors contribute to such a result.
1. Being experimented, when the contact area of fins is doubled, the heat exchange efficiency can not be doubled, and to converse, will be halved to 0.7 or 0.9. The higher fin will deteriorate the situation down to about 0.5.
2. The high density of fins will cause the problem of dusting and difficulty of cleaning.
3. The cost and difficulty of production will be enhanced when the fins are to close to each other, and over high.
Take the 1 m finned tube for instance, we mark the gross heat transfer area of finned tube as A, and mark the gross heat transfer are of unfinned pipe as A0. The ratio of A/A0 can point out the enlargement extent. So what kind of A/A0 value is the best, it all depends on the design and application purpose. Generally speaking, the finned pipe applied in the energy engineering industry has the A/A0 value ranging from 5 to 12, and the finned tube applied in the air conditioning industry has the A/A0 value ranging from 15 to 22.