Although org babel works exactly as you would expect it, sometimes you might
forget. Here is a simple, simple examply so you can see it and believe it:

* A
  :PROPERTIES:
  :noweb-ref: a-block
  :END:

#+begin_src emacs-lisp
;; A
;; A
;; A
#+end_src

* B
  :PROPERTIES:
  :noweb-ref: b-block
  :END:

#+begin_src emacs-lisp
;; B
;; B
;; B
#+end_src

* C
  :PROPERTIES:
  :noweb-ref: c-block
  :END:

#+begin_src emacs-lisp
;; C_a
;; C_a
;; C_a
<<a-block>>
<<b-block>>
;; C_z
;; C_z
;; C_z
#+end_src

* D

#+begin_src emacs-lisp :tangle ~/tmp/tmp.el :noweb tangle
;; D_a
;; D_a
;; D_a
<<c-block>>
;; D_z
;; D_z
;; D_z
#+end_src

* Tangled result

#+begin_src emacs-lisp
;; D_a
;; D_a
;; D_a
;; C_a
;; C_a
;; C_a
;; A
;; A
;; A
;; B
;; B
;; B
;; C_z
;; C_z
;; C_z
;; D_z
;; D_z
;; D_z
#+end_src

The source is here: