Bug get_density() function for gas commodity

[tolga-akan]

A bug has been identified in get_density() function in asset_tocomponent_base.py. Ideally, condition (elif NetworkSettings.NETWORK_TYPE_GAS in carrier.name:) should use a case‑insensitive comparison to detect the commodity name: str(NetworkSettings.NETWORK_TYPE_GAS).upper() in str(carrier.name).upper(). However, updating the condition causes the unit test test_gas_network_pipe_split_head_loss in test_head_loss.py to fail. The reason is that in the test ESDL, the commodity name is defined as "gas", whereas NetworkSettings.NETWORK_TYPE_GAS returns "Gas". With a case‑insensitive comparison, this elif condition no longer matches, causing the code to use the default density from the else branch (6.2). That value makes the test pass. This indicates a potential underlying bug in the head‑loss calculation logic.

[KobusVanRooyen]

After a quick look into this, the following issues were identified (test_gas_network_pipe_split_head_loss):

• The test fails due to the upper bound of the gas producer and the gas demand
• The upper bounds originate from the component setup in esdl_heat_model.py:
  • max_mass_flow_g_per_s uses specific_energy via get_energy_content(). This latter function calculates density for gas at 8bar since there is not upper case check on the carrier type (via carrier name gas/Gas/...). When upper case check is added then in get density, then the energy_content_j_kg changes, which changes the upper limit of the gas producer/demand