how to calculate maximum temperature of wattage on wire?
I found a definition of the &quot;Celsius heat unit&quot; but I have no idea if it is true or correct:

The Celsius heat unit is the energy required to increase the temperature of one pound of water by one degree Celsius (or 1.8 degrees Fahrenheit) at a constant pressure of one atmosphere. One Celsius heat unit is equal to 1.8 British thermal units. Source: Conversion Website

The definition seems to be a confused mess of metric and imperial units and you will find it far better to work in SI (metric) units.

The Celsius scale measures temperature.
Use watts (W) to measure power.
Use joules (J) to measure energy.


if i have 144 watts, converting it to Celsius heat units (IT) per hour would be 272 degrees Celsius. But i still  don't know, if that is the hottest it will get.

The temperature will stabilise when the heat lost to the surroundings of the wire is equal to the electrical power input to the wire. To calculate this you would need to know the length, surface area and emissivity of the wire to calculate radiated energy and the temperature and flow rate of the surrounding fluid (e.g., air) for convective losses. You might be able to ignore conduction losses depending on the geometry of the setup.
Forget about &quot;Celsius heat units (IT) per hour&quot;. It's not used in general or electrical engineering.