Rename alpha_w_per_m2k to u_w_per_m2k

[dad616610]

This PR completes the renaming of the heat transfer coefficient parameter from alpha_w_per_m2k to u_w_per_m2k to align with standard thermodynamic notation (U = overall heat transfer coefficient). The changes include:

• Parameter renaming and description updates
• branch index synchronization (ALPHA to U)
• Documentation fixes
• Selective test updates (preserving deprecation tests)

Key changes

Parameter updates

• Renamed alpha_w_per_m2k to u_w_per_m2k throughout codebase
• Updated parameter description from "heat transfer coefficient" to "overall heat transfer coefficient"
• Changed branch index from ALPHA to U

Documentation:

• Updated all references in docs to reflect u_w_per_m2k and new description

Test Updates:

• Modified tests that used alpha_w_per_m2k syntax to use u_w_per_m2k (modified test_heat_consumer.py)
• Preserved tests checking deprecation path for alpha_w_per_m2k (unchanged)

[EPrade]

Looks good, thank you! Could you also add a changelog entry?

[dad616610]

Done!

[EPrade]

Could you solve the merge conflicts please? Then we would merge the PR. Thanks!

[dad616610]

Apologies for expanding the scope right before merge - I noticed the variable naming inconsistency during rebase and felt it was worth addressing now for consistency.

I've rebased to resolve conflicts and:

• Renamed alpha (heat transfer context) to u_overall in:
  • src/pandapipes/converter/stanet/table_creation.py
  • src/pandapipes/pf/derivative_calculation.py
• Updated CSV field names in src/pandapipes/test/data/Temperature_*

Open questions:

1. Network files (src/pandapipes/networks/network_files/* with alpha_w_per_m2k):
   Rename to u_w_per_m2k?
2. Legacy tests (src/pandapipes/test/api/old_versions/*):
   Preserve alpha_w_per_m2k for compatibility?

[SimonRubenDrauz]

Thanks for your contribution. Regarding your two questions see my answers below:

1. Agree! Renaming would make sense!
2. Legacy tests should keep alpha_w_per_m2k, as this structure is expected in older versions. Therefore, preserve the structure!

[dad616610]

Done! I've renamed the network files as suggested. Please let me know if it looks good!