Material tables on specific
heat and storage
Refractory Cast iron
Table description and reading guide
To understand the storage capacity well, we must observe four major values.
1.Density (p) in kg/liter
It describes the mass of the body: the weight of the volume. The accumulation depends on
the mass of the body. The more mass a body has, the more it can accumulate heat. So
the higher this value, the better the accumulation.
2. calore specifico (cp) in Wh / kg K
It describes how much energy (Wh, watt/hour) is needed to heat 1 kg of mass of a body to
raise its temperature (K) by 1°. The energy stored later is available to be released into the
environment.
Table description and reading guide
3. Thermal conductivity ( λ )
It describes the property of a material to accumulate, transmit and conduct heat. The higher
the value, the more the conduction property develops and subsequently the creation of the
"convective transmission" (hot air). The lower this value, the higher the capacity to
accumulate heat through radiation (it heats like a sun).
formula: W / mK
4. Thermal diffusion (A)
It describes and includes the dimension of time ("s" as a second). The lower this value, the
slower the material is in heat transmission. In the case of accumulation and radiation, the
energy accumulated in the mass of the stove body is emitted over a long time (8-12 hours). The
higher this value and the faster the heat is transmitted, the charged energy (specific heat) is
released with higher temperatures.
-6 formula: 10 m2 / s
In the case of low density, the material is considered as an insulating material.
Material table
Aluminium Iron Cast iron Copper Refractory
Density (P) Density (P) Density (P) Density (P) Density (P)
2,7 kg a litro 7,9 kg a litro 7,8 kg a litro 8,9 kg a litro 1,8 - 2 kg a litro
specific heat specific heat specific heat specific heat specific heat
(cp) (cp) (cp) (cp) (cp)
0.25 Wh/kg K 0.13 Wh/kg K 0.15 Wh/kg K 0.11 Wh/kg K 0.28 Wh/kg K
Conductivity Conductivity Conductivity Conductivity Conductivity
thermal ( λ ) thermal ( λ ) thermal ( λ ) thermal ( λ ) thermal ( λ )
237 W/mK 81 W /mK 42-50 W /mK 399 W /mK 0.8 W /mK
Diffusivity Diffusivity Diffusivity Diffusivity Diffusivity
Thermal (A) Thermal (A) Thermal (A) Thermal (A) Thermal (A)
98.8 in 10 -6 m2/s 22.8 in 10 -6 m2/s 10-13 in 10 -6 m2/s 117 in 10 -6 m2/s 0.4 in 10 -6 m2/s
Comparison of cast iron - refractory
Refractory Cast Iron
Cast iron is a material with a Refractory is a material with
high density (7.8), therefore capable of of a medium density (1.8-2),
accumulate a lot of heat, able to release heat very
but also to release it a lot slowly (thermal diffusion
fast (thermal diffusion 0.4). The conductivity value 0.8
10-12). In addition, the value 42-50 of indicates that it is a thermal material
thermal conductivity, indicates that it is capable of transmitting heat
a material capable of transmitting by radiation.
heat by transmission
convective (hot air). To heat the refractory it takes almost
twice as much energy as the
To heat cast iron you need less cast iron (0.28 Wh/kg K to heat the
energy compared to refractory (0.15 mass of 1 degree).
Wh/kg K to heat the mass by 1
degree). However, cast iron has a So the material is able to
thickness of its walls less than accumulate more energy (heat) from
refractory (therefore less volume) and release by radiation.
higher conductivity.
Comparison of cast iron - refractory
Cast iron Refractory
Density (P) 7.8 kg /litre 1.8-2 kg/liter
Specific heat (CP) 0.155 Wh/kg K 0.28 Wh/kg K
Thermal conductivity ( λ ) 42-50 W /mK 0.8 W /mK
10-12 in 10-6 0.4 in 10-6
Thermal diffusivity (a)
m2/s m2/s
Refractory Cast iron
Material from the stoves and pyrolysis
course. With Axel Berberich
