References | Non-electrical | Very low | Low enthalpy | Moderate enthalpy | High enthalpy | Ultra-high |
|---|
Muffler (1979) | – | – | < 90 | 90–155 | > 150 | – |
Hochstein (1988) | – | – | < 125 | 125–225 | > 225 | – |
Haenel et al. (1988) | – | – | < 150 | – | > 150 | – |
Sanyal (2005) |  < 50–100 | 100–150 | 150–180 | 180–230 | 230–300 | > 300 |
