Temperature and heat

Associations:         0°C = 273,15 K = 32°F

Difference in temperature:  Δ 1°C = 1K = 1,8°F

  Kelvin [K] ° Celsius [C] ° Fahrenheit (F)
Kelvin = 1 K - 273,15 K · 1,8 − 459,67
° Celsius = 273,15 + °C 1 1,8 x °C + 32
° Fahrenheit = (°F + 459,67) x 0,5555555 (°F - 23) x 0,5555555 1

 

Heat

SI Units joule [J] kilojoule [kJ] megajoule [MJ] wattseconds [Ws] kilowatt hour [kWh] calorie [cal]
1 joule = 1 0,001 1,0000·10-6 1 2,7778·10-7 0,2388
1 kilojoule = 1.000 1 0,001 1.000 0,0002778 238,85
1 megajoule = 1.000.000 1000 1 1.000.000 0,2778 238.846
1 wattsesond = 1 0,001 1,0000·10-6 1 2,7778·10-7 0,2388
1 kilowatt hour = 3.600.000 3.600 3,6 3.600.000 1 859.845
1 calorie = 4,1868 0,004187 4,1868·10-6 4,1868 1,1630·10-6 1

 

Heat quantity

Heat quantity= specific heat capacity  x  mass  x  difference in temperature


Q = c x m x Δt  [J]                 unit of specific heat capacity [J / kg K]

  • The amount of heat necessary for heating a body is proportionate to the mass of the body and difference in temperature that is to be achieved
  • c is not constant but depending on temperature
  • By cooling down Δt becomes negative, amount of heat becomes negative which means that it must not be added but dissipated
     

Specific heat capacity of textile raw materials

Unit glass wool
 cotton
viscose		 wool
silk		 polyamide (PA) polyester (PES) polyethen (PE) PVC
kJ / kg K 0,657 1,325.... 1,356 1,356 / 1,386 1,85 1,3 2,50 1,3 - 2,1

 

 Specific heat capacity for substances in textile finishing

Unit iron steel stone/fireclay water at 
20°C		 air air (steam)
100% humidity
kJ / kg K 0,439 0,477 - 0,5 0,75 - 0,84 4,182 1,005 1,030

 

Enthalpy

  • Enthalpy is the heat energy based on 0°C that a material possesses at a certain temperature.
  • SI-unit of enthalpy: Q1 = [J]
  • For temperatures t > 0°C enthalpy is positive
  • For temperatures t < 0°C enthalpy is negative
  • For temperatures t = 0°C enthalpy is zero

Heat values

Heat value H is the proportion of the amount of heat to be released from combustion and the mass of the burned material.  

released amount of heat (Q) = mass (m) x heat value (H)

  heat value (H)
Brown coal
 18 MJ/kg
Black coal, coke 28 MJ/kg
Petroleum/heating oil/fuel  41 MJ/kg
Diesel 38 - 41 MJ/kg

Source: SI-Systeme