all these in shell and tube heat exchanger

1. When do you think it’s necessary to insulate the shell?Should we insulate the
shell for the design in hand?
2. Why the shell is not part of TEMA standards?
3. What is more economic and why; a large diameter shell withsmaller length,
or a smaller diameter shell with longer length?
4. What is the recommended range of velocity in the tubeside andwhy?
5. What is the recommended range of velocity in the shellside andwhy?
6. When is it convenient to employ shells in parallel?
7. When is it convenient to employ shells in series?
8. How to estimate graphically the number of shells in series toachieve
temperature cross with non-pure counterflow heat exchanger?