ISO 7345:2018 建物および建物コンポーネントの熱性能—物理量と定義 | ページ 6

3.1.1

heat

quantity of heat

Q

Note 1 to entry: Unit: J.

3.1.2

heat flow rate

Φ

Note 1 to entry: Unit: W.

3.1.3

density of heat flow rate

q

Note 1 to entry: The word “density” should be replaced by “areal density” when it may be confused with linear density (3.1.4) .

Note 2 to entry: Unit: W/m².

3.1.4

linear density of heat flow rate

q₁

Note 1 to entry: Unit: W/m.

3.1.5

thermal conductivity

λ

Note 1 to entry: A rigorous treatment of the concept of thermal conductivity is given in the annex, which also deals with the application of the concept of thermal conductivity to porous isotropic or anisotropic materials and the influence of temperature and test conditions.

Note 2 to entry: Unit: W/(m·K).

3.1.6

thermal resistivity

r

Note 1 to entry: A rigorous treatment of the concept of thermal resistivity is given in Annex A.

Note 2 to entry: Unit: (m·K)/W.

3.1.7

thermal resistance

R

Note 2 to entry: where d is the thickness of the layer.

Note 3 to entry: These definitions assume the definition of two reference temperatures, T₁ and T_2, and the area through which the density of heat flow rate is uniform.

Note 4 to entry: Thermal resistance can be related either to the material, structure or surface. If either T₁orT₂ is not the temperature of a solid surface, but that of a fluid, a reference temperature must be defined in each specific case (with reference to free or forced convection and radiation from surrounding surfaces, etc.).

Note 5 to entry: When quoting values of thermal resistance, T₁ and T₂ must be stated.

Note 6 to entry: “Thermal resistance” should be replaced by “areal thermal resistance” when it may be confused with linear thermal resistance (3.1.8) .

Note 7 to entry: Unit: (m²·K)/W.

3.1.8

linear thermal resistance

R_l

Note 1 to entry: This assumes the definition of two reference temperatures, T₁ and T₂, and the length along which the linear density of heat flow rate is uniform.

Note 2 to entry: If within the system either T₁orT₂ is not the temperature of a solid surface, but that of a fluid, a reference temperature must be defined in each specific case (with reference to free or forced convection and radiation from surrounding surfaces, etc.).

Note 3 to entry: When quoting values of linear thermal resistance, T₁ and T₂ must be stated.

Note 4 to entry: Unit: (m·K)/W.

3.1.9

surface coefficient of heat transfer

h

Note 1 to entry: This assumes the definition of the surface through which the heat is transferred, the temperature of the surface, T_s, and the ambient temperature, T_a (with reference to free or forced convection and radiation from surrounding surfaces. etc.). The surface us usually denoted by an index e for external and i for internal surface.

Note 2 to entry: Unit: W/(m²·K).

3.1.10

thermal conductance

L

Note 1 to entry: “Thermal conductance” should be replaced by “areal thermal conductance” when it may be confused with linear thermal conductance (3.1.11)

Note 2 to entry: Unit: W/(m²·K).

3.1.11

linear thermal conductance

L_l

W/(m·K)

Note 1 to entry: Unit: W/(m·K).

3.1.12

thermal transmittance

U

Note 1 to entry: This assumes the definition of the system, the two reference temperatures, T₁ and T₂, and other boundary conditions.

Note 2 to entry: “Thermal transmittance” should be replaced by “areal thermal transmittance” when it may be confused with linear thermal transmittance (3.1.13) .

Note 3 to entry: The reciprocal of the thermal transmittance is the total thermal resistance between the surroundings on both sides of the flat uniform system.

Note 4 to entry: Unit: W/(m²·K).

3.1.13

linear thermal transmittance

Ψ

Note 1 to entry: This assumes the definition of the system, the two reference temperatures, T₁ and T₂, and other boundary conditions.

Note 2 to entry: The reciprocal of the linear thermal transmittance is the total linear thermal resistance between the surroundings on each side of the system.

Note 3 to entry: When Ψ is used to characterize linear thermal bridges in the building envelope Ψ is not the total but the additional heat transfer due to the thermal bridge [i.e. additional to the heat transfer taken into account by the (areal) thermal transmittance U].

Note 4 to entry: Unit: W/(m·K).

3.1.14

heat capacity

C

Note 1 to entry: When the temperature of a system is increased by dT as a result of the addition of a small quantity of heat dQ, the quantity dQ/ dT is the heat capacity.

Note 2 to entry: Unit: J/K.

3.1.15

specific heat capacity

c

Note 1 to entry: Unit: J/(kg·K).

3.1.15.1

specific heat capacity at constant pressure

c_p

Note 1 to entry: Unit: J/(kg·K).

3.1.15.2

specific heat capacity at constant volume

c_v

Note 1 to entry: Unit: J/(kg·K).

3.1.16

thermal diffusivity

a

Note 1 to entry: For fluids the appropriate specific heat capacity is c_p .

Note 2 to entry: The definition assumes that the medium is homogeneous and opaque.

Note 3 to entry: The thermal diffusivity is relevant to the non-steady-state and may be measured directly or calculated from separately measured quantities by the above formula.

Note 4 to entry: Among others, thermal diffusivity accounts for the response of the temperature at a location inside a material to a change of temperature at the surface. The higher the thermal diffusivity of the material, the more sensitive the interior temperature is to changes of the surface temperature.

Note 5 to entry: Unit: m²/s.

3.1.17

thermal effusivity

b

Note 1 to entry: For fluids the appropriate specific heat capacity is c_p .

Note 2 to entry: This property is relevant to the non-steady-state. It may be measured or calculated from separately measured quantities by the above formula. Among others, thermal effusivity accounts for the response of a surface temperature to a change of the density of heat flow rate at the surface. The lower the thermal effusivity of the material the more sensitive the surface temperature is to changes of heat flow at the surface.

Note 3 to entry: Unit: J/(m²·K·s^1/2).

3.2.1

volumetric heat transfer coefficient

F_V

Note 2 to entry: Unit: W/(m³·K).

3.2.2

areal heat transfer coefficient

F_S, H′

Note 2 to entry: Unit: W/(m²·K).

3.2.3

ventilation rate

n

number of air changes in a defined volume divided by time

Note 1 to entry: Unit: h^-1.

Note 2 to entry: The unit for ventilation rate, h⁻¹, is not an SI unit. However, the number of air changes per hour is the generally accepted way to express ventilation rate.