Celsius, Fahrenheit and Kelvin; absolute zero is 0 K.
Kelvin is absolute (0 K = -273.15 °C); T(K)=T(°C)+273.15; °F=1.8°C+32. Thermodynamic equations require absolute temperature. The ITS-90 defines practical scale fixed points such as the triple point of water at 273.16 K.
Room temperature 20 °C is 293.15 K.
Absolute temperature is needed in the gas laws and efficiency formulas, so using Celsius in those equations gives wrong answers.
Celsius, Fahrenheit and Kelvin; absolute zero is 0 K.
Absolute temperature is needed in the gas laws and efficiency formulas, so using Celsius in those equations gives wrong answers.
Ratios of temperatures in efficiency and gas law formulas only make sense on an absolute scale that starts at zero.
Add 273.15 to the Celsius value, so 25 degrees Celsius is 298.15 K.
Typical applications include converting a boiler outlet temperature to kelvin for an efficiency calculation, checking the temperature in the ideal gas law and comparing the temperatures of two heat sources in a Carnot calculation.
Study "Temperature and zeroth law" first (topic 4 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
Temperature differences same in K and °C. Rankine for °F absolute. Use K in ideal gas law.
Room temperature 20 °C is 293.15 K.
The next topic is "Pressure", which builds directly on this one.
It is classed as Beginner in Thermodynamics & Fluids (topic 5 of 105). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
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