ASTM C108-46(2009)

Standard Symbols for Heat Transmission

General Information

• Status: Historical
• Publication Date: 28-Feb-2009
• ICS: 01.080.20 - Graphical symbols for use on specific equipment
• ICS: 27.010 - Energy and heat transfer engineering in general
• Technical Committee: C08 - Refractories
• Drafting Committee: C08.02 - Thermal Properties

Relations

• Replaces: ASTM C108-46(2004) - Standard Symbols for Heat Transmission
• Effective Date: 01-Mar-2009
• Referred By: ASTM D2442-75(2020) - Standard Specification for Alumina Ceramics for Electrical and Electronic Applications
• Effective Date: 01-Mar-2009

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C108 − 46(Reapproved 2009)
Standard Symbols for
Heat Transmission
This standard is issued under the fixed designation C108; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
SPECIAL PRACTICES RELATING TO HEAT FLOW
c = specific heat
TERMS
T = temperature on absolute scale
Terms Ending in “ivity”—Terms ending in “ivity” designate
characteristics of materials, normally independent of size or
t = temperature, degrees Celsius or Fahrenheit
shape, sometimes called “specific properties.”
t, τ = time
Examples: Conductivity and resistivity.
W = weight; quantity of matter measured in pounds, kilograms, etc.
Terms Ending in “ance”—Terms ending in “ance” designate
properties of a particular object, depending not only on the
w = flow rate; pounds, kilograms, etc., per unit of time
material, but also upon size and shape, sometimes called
q = heat flow rate; time rate of heat transferred for a particular setup
“total quantities.”
with any value of area A
Examples: Conductance and transmittance.
q is in general the time derivative of total quantity of heat
Terms Ending in “ion”—Terms ending in “ion” designate
transferred. For steady-state heat flow, q is total quantity of heat
divided by time.
time rate of the process of transfer; flux, flow rate.
Examples: Conduction and transmission.
k = thermal conductivity; heat flow rate, per unit of area, per “degree
per unit of length”
Transmission—“Transmission,” “transmissivity,” “transmit-
tance” usually refer to transfer by one or more of the
dq/dA52ksdt/dLd general expression giving value at each
processes of conduction, convection, and radiation.
point
k5 q/A / ∆t/L for substantially uniform and steady-state
s d s d
Conduction—“Conduction,” “conductivity,” “conductance”
heat flow through a homogeneous medium of thickness L,
usually refer to transfer within a medium, and without bodily
with plane parallel faces of area A, and a constant tempera-
displacement as occurs with convection, and without transfer ture difference ∆t applied to the faces
at a distance as occurs with radiation.
1/k = thermal resistivity; reciprocal of conductivity
HEAT FLOW SYMBOLS
R = thermal resistance; degrees, per unit of heat flow rate, for a particu-
lar body or setup (where the area may not be known)
A = area
p = density; pounds, kilograms, etc., per unit of volume R5∆t/q for substantially uniform and steady-state heat flow,
generally
L = length of path of heat flow
R5L/kA for substantially uniform and steady-state heat flow
through a homogeneous medium of thickness L with plane
Q = total quantity of heat transferred (with subscripts for particular cases
parallel faces of area A
and to distinguish for Q for volume rate)
1/R = thermal conductance; reciprocal of thermal resistance (C is also
Q = volume rate; discharge by volume; fluid rate of flow by volume.
used)
(There also is used q with a subscript to distinguish from heat flow
rate.)
1/RA = thermal conductance per unit of area; heat flow, rate, per unit of
area, per degree
These symbols are under the jurisdiction of ASTM Committee C08 on
RA = thermal resistance of unit area; degrees, per “unit of heat flow rate
Refractories and are the direct responsibility of Subcommittee C08.02 on Thermal per unit of area.” R is used for resistance for a setup with a particu-
Properties. lar area (which may not be known) and RA for resistance of unit
area. In some British texts R is used for thermal resistance of unit
Current edition approved March 1, 2009. Published March 2009. Originally
area, here called RA
approved in 1934. Last previous edition approved in 2004 as C108–46
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