Spiral Walls vs. Straight Walls in Thermal Powerplants

generally spiral water walls used in once through boilers...because water is exposed with heat source more time...

can you provide any additional information.

I could give you the answer but first I need to know if this is a school assignment.

yes sir, iam working in a 660MW Thermal power plant (super critical boiler) as a trainee. I want to know deeply about thermal power plant construction and design aspects etc. Pls help me sir.

Ok. The simple answer is this:

Have you ever watched how the ocean hits the beach? It rolls in on waves. Water runs in spirals as does air. If you open an old air duct you will find that there will be dust,dirt and debris in the corners and a round(ish) hole in the middle. This is where the air flows with least resistance. Water flows the same way. in a square pipe you will have resistance. A round pipe will flow better and a spiral pipe,where the spiral flows with the turn of the water, will allow the flow of water with the least resistance.

There are a lot of numbers and theory behind it but this'll get you started.

Good luck.

Fluid dynamics is an interesting subject. As a fluid (or air) is forced around a turn, it rotates. In a river, water that was on top goes to the bottom, and water from down below is brought up. As water goes down a drain, it spins. In order to go down the drain, it had to go around a corner, so spin is applied.