Heating the water in a Nordic bath

[player8fr]

Hello
I am currently working on the creation of a "home" Nordic bath (around 1100 l)
I wonder about the most appropriate method to heat the water knowing that I do not wish to have an internal stove to optimize the place in the bath
After consulting a multitude of sites, images and videos on the subject, I am moving towards a "turbo" stove (also called a workshop stove ") of the THECA type around which I think to pass a copper tube to heat water I really like the principle of the rocket stove but I have doubts about the autonomy of this type of stove (my idea being to be able to light the stove a few hours before enjoying the benefits of the hot bath). The advantage of the turbo stove in my opinion being to be able to put more wood in it and to let it heat for hours without needing to recharge.
My main question now is whether I run the copper tube around the stove (as in this picture: https://i.pinimg.com/originals/ce/17/26 ... ef8005.jpg) or if I put it squarely inside (like in this picture: https://encrypted-tbn0.gstatic.com/imag ... L&usqp=CAU).
Thank you for your opinion and advice