Heat Transfer (Q)

[hardtostop]

Two tubes : One is 0.38" diameter and the other is 0.505" diameter.

Q= hA (del T)

Small diameter tube has high "h" as velocity will be high (13.7 ft/s) and larger diameter tube will have low "h" as velocity is 9.37 ft/s. (h is directly proportional to sq root of Re)

Now the other part is smaller diameter tube has less urface area (A) where as larger diameter tube has more surface area (A). (More the area more the heat transfer)

In this case which one will have more impact on heat transfer (heat transfer coefficent or surface area)(Which heat exchanger tube will be better in heat transfer) (I am comparing 2 heat exchangers (fin and tube) One is having 39 tubes of 0.356" Inner dia and other is having 30 tubes of 0.481" inner diameter.... entering temperature is same, flow rate is same (flowrate divided by no. of tubes by assuming uniform flow through tubes)

I will appreciate your answer.

Thanks.

 

[rmw]

There is a lot that you have left out that will be necessary to offer a meaningful answer. One is the difference in area of the two Hx's in question, another is number of passes, tube metallurgy, fin spacing (and material if different, etc.

What you have presented here, while interesting, is not enough to be meaningful in completely evaluating your question. There are tons of variables here.

rmw

 

[25362]

Whatever the configuration the overall heat transfer coefficient will always be lower than the lowest "h".