ASTM C680-89(1995)e1
(Practice)Standard Practice for Determination of Heat Gain or Loss and the Surface Temperatures of Insulated Pipe and Equipment Systems by the Use of a Computer Program
Standard Practice for Determination of Heat Gain or Loss and the Surface Temperatures of Insulated Pipe and Equipment Systems by the Use of a Computer Program
SCOPE
1.1 The computer programs included in this practice provide a calculational procedure for predicting the heat loss or gain and surface temperatures of insulated pipe or equipment systems. This procedure is based upon an assumption of a uniform insulation system structure, that is, a straight run of pipe or flat wall section insulated with a uniform density insulation. Questions of applicability to real systems should be resolved by qualified personnel familiar with insulation systems design and analysis. In addition to applicability, calculational accuracy is also limited by the range and quality of the physical property data for the insulation materials and systems.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
e1
Designation: C 680 – 89 (Reapproved 1995)
Standard Practice for
Determination of Heat Gain or Loss and the Surface
Temperatures of Insulated Pipe and Equipment Systems by
the Use of a Computer Program
This standard is issued under the fixed designation C 680; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Safety Caveat and Keywords were added editorially in April 1995.
1. Scope Determine the Precision of a Test Method
2.2 ANSI Standards:
1.1 The computer programs included in this practice pro-
X3.5 Flow Chart Symbols and Their Usage in Information
vide a calculational procedure for predicting the heat loss or
Processing
gain and surface temperatures of insulated pipe or equipment
X3.9 Standard for Fortran Programming Language
systems. This procedure is based upon an assumption of a
uniform insulation system structure, that is, a straight run of
3. Terminology
pipe or flat wall section insulated with a uniform density
3.1 Definitions—For definitions of terms used in this prac-
insulation. Questions of applicability to real systems should be
tice, refer to Terminology C 168.
resolved by qualified personnel familiar with insulation sys-
3.2 Symbols:Symbols—The following symbols are used in
tems design and analysis. In addition to applicability, calcula-
the development of the equations for this practice. Other
tional accuracy is also limited by the range and quality of the
symbols will be introduced and defined in the detailed descrip-
physical property data for the insulation materials and systems.
tion of the development.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
where:
2 2
responsibility of the user of this standard to establish appro-
h 5 surface coefficient, Btu/(h·ft ·°F) (W/(m ·K))
priate safety and health practices and determine the applica-
k 5 thermal conductivity, Btu·in./(h·ft ·°F)(W/(m·K))
bility of regulatory limitations prior to use.
k 5 constant equivalent thermal conductivity introduced
a
by the Kirchhoff transformation, Btu·in./(h·ft ·F)
2. Referenced Documents
(W/(m·K))
2.1 ASTM Standards:
Q 5 total time rate of heat flow, Btu/h (W)
t
C 168 Terminology Relating to Thermal Insulating Materi-
Q 5 time rate of heat flow per unit length, Btu/h·ft (W/m)
l
2 2
als q 5 time rate of heat flow per unit area, Btu/(h·ft )
C 177 Test Method for Steady-State Heat Flux Measure-
(W/m )
2 2
R 5 thermal resistance, (°F·h·ft )/Btu (K·m /W)
ments and Thermal Transmission Properties by Means of
r 5 radius, in. (m)
the Guarded Hot Plate Apparatus
t 5 local temperature, °F (K)
C 335 Test Method for Steady-State Heat Transfer Proper-
t 5 temperature of inner surface of the insulation, °F (K)
ties of Horizontal Pipe Insulation i
t 5 temperature of ambient fluid and surroundings, °F
a
C 518 Test Method for Steady-State Heat Flux Measure-
(K)
ments and Thermal Transmission Properties by Means of
x 5 distance in direction of heat flow (thickness), in. (m)
the Heat Flow Meter Apparatus
C 585 Practice for Inner and Outer Diameters of Rigid
Thermal Insulation for Nominal Sizes of Pipe and Tubing
4. Summary of Practice
(NPS System)
4.1 The procedures used in this practice are based upon
E 691 Practice for Conducting an Interlaboratory Study to
standard steady-state heat transfer theory as outlined in text-
books and handbooks. The computer program combines the
This practice is under the jurisdiction of ASTM Committee C-16 on Thermal
functions of data input, analysis, and data output into an
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
Measurements.
Current edition approved Jan. 27, 1989. Published May 1989. Originally
e1
published as C 680 – 71. Last previous edition C 680 – 82 .
Annual Book of ASTM Standards, Vol 14.02.
Annual Book of ASTM Standards, Vol 04.06.
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
C 680
easy-to-use, interactive computer program. By making the because of the iterative nature of the method, is best handled by
program interactive, little operator training is needed to per- computers.
form fast, accurate calculations.
5.5 The thermal conductivity of most insulating materials
4.2 The operation of the computer program follows the
changes with mean temperature. Since most thermal insulating
procedure listed below: materials rely on enclosed air spaces for their effectiveness,
4.2.1 Data Input—The computer requests and the operator this change is generally continuous and can be mathematically
inserts information that describes the system and operating approximated. In the cryogenic region where one or more
environment. The data include: components of the air condense, a more detailed mathematical
treatment may be required. For those insulations that depend
4.2.1.1 Analysis Identification.
on high molecular weight, that is, fluorinated hydrocarbons, for
4.2.1.2 Date.
their insulating effectiveness, gas condensation will occur at
4.2.1.3 Ambient Temperature.
higher temperatures and produce sharp changes of conductivity
4.2.1.4 Surface coefficient or ambient wind speed, insula-
in the moderate temperature range. For this reason, it is
tion system surface emittance, and orientation.
necessary to consider the temperature conductivity dependence
4.2.1.5 System Description—Layer number, material, and
of an insulation system when calculating thermal performance.
thicknesses.
The use of a single value thermal conductivity at the mean
4.2.2 Analysis—Once input data is entered, the program
temperature will provide less accurate predictions, especially
calculates the surface coefficients (if not entered directly) and
when bridging regions where strong temperature dependence
the layer resistances, then uses that data to calculate the heat
occurs.
losses and surface temperatures. The program continues to
5.6 The use of this practice by both manufacturers and users
repeat the analysis using the previous temperature data to
of thermal insulations will provide standardized engineering
update the estimates of layer resistance until the temperatures
data of sufficient accuracy for predicting thermal insulation
at each surface repeat with a specified tolerance.
performance.
4.2.3 Once convergence of the temperatures is reached, the
5.7 Computers are now readily available to most producers
program prints a table giving the input data, the resulting heat
and consumers of thermal insulation to permit the use of this
flows, and the inner surface and external surface temperatures.
practice.
5. Significance and Use 5.8 Two separate computer programs are described in this
practice as a guide for calculation of the heat loss or gain, and
5.1 Manufacturers of thermal insulations express the perfor-
surface temperatures, of insulated pipe and equipment systems.
mance of their products in charts and tables showing heat gain
The range of application of these programs and the reliability
or loss per lineal foot of pipe or square foot of equipment
of the output is a primary function of the range and quality of
surface. These data are presented for typical operating tem-
the input data. Both programs are intended for use with an
peratures, pipe sizes, and surface orientations (facing up, down,
“interactive” terminal. With this system, intermediate output
or horizontal) for several insulation thicknesses. The insulation
guides the user to make programming adjustments to the input
surface temperature is often shown for each condition, to
parameters as necessary. The computer controls the terminal
provide the user with information on personnel protection or
interactively with program-generated instructions and ques-
surface condensation. Additional information on effects of
tions, prompting user response. This facilitates problem solu-
wind velocity, jacket emittance, and ambient conditions may
tion and increases the probability of successful computer runs.
also be required to properly select an insulation system. Due to
5.8.1 Program C 608E is designed for an interactive solu-
the infinite combinations of size, temperature, humidity, thick-
tion of equipment heat transfer problems.
ness, jacket properties, surface emittance, orientation, ambient
5.8.2 Program C 608P is designed for interactive solution of
conditions, etc., it is not practical to publish data for each
piping-system problems. The subroutine SELECT has been
possible case.
written to provide input for the nominal iron pipe sizes as
5.2 Users of thermal insulation, faced with the problem of
shown in Practice C 585, Tables 1 and 3. The use of this
designing large systems of insulated piping and equipment,
program for tubing-systems problems is possible by rewriting
encounter substantial engineering costs to obtain the required
subroutine SELECT such that the tabular data contain the
thermal information. This cost can be substantially reduced by
appropriate data for tubing rather than piping systems (Practice
both the use of accurate engineering data tables, or by the use
C 585, Tables 2 and 4).
of available computer analysis tools, or both.
5.8.3 Combinations of the two programs are possible by
5.3 The use of analysis procedures described in this practice
using an initial selector program that would select the option
can also apply to existing systems. For example, C 680 is
being used and elimination of one of the k curve and surface
referenced for use with Procedures C 1057 and C 1055 for burn
coefficient subroutines that are identical in each program.
hazard evaluation for heated surfaces. Infrared inspection or in
situ heat flux measurements are often used in conjunction with 5.8.4 These programs are designed to obtain results identi-
cal to the previous batch program of the 1971 edition of this
C 680 to evaluate insulation system performance and durability
on operating systems. This type analysis is often made prior to practice. The only major changes are the use of an interactive
terminal and the addition of a subroutine for calculating surface
system upgrades or replacements.
coefficient.
5.4 The calculation of heat loss or gain and surface tem-
perature of an insulated system is mathematically complex and 5.9 The user of this practice may wish to modify the data
C 680
input and report sections of the computer program presented is dependent on temperature. Existing methods of thermal
here to fit individual needs. Also, additional calculations may conductivity measurement account for the thermal conduction,
be desired to include other data such as system costs or convection, and radiation occurring within the insulation. After
economic thickness. No conflict with this method in making the basic equations are developed, they are extended to
these modifications exists, provided that the user has demon- composite (multiple-layer) cases and supplemented with pro-
strated compatibility. Compatibility is demonstrated using a vision for heat flow from the outer surface by convection or
series of test cases covering the range for which the new radiation, or both.
method is to be used. For those cases, results for the heat flow 6.3 Equations—Case 1, Slab Insulation:
and surface temperatures must be identical, within the resolu- 6.3.1 Case 1 is a slab of insulation shown in Fig. 1 having
tion of the method, to those obtained using the method width W, height H, and thickness T. It is assumed that heat flow
described herein. occurs only in the thickness of x direction. It is also assumed
5.10 This practice has been prepared to provide input and that the temperature t of the surface at x is the same as the
1 1
output data that conforms to the system of units commonly equipment surface temperature and the time rate of heat flow
used by United States industry. Although modification of the per unit area entering the surface at x is designated q . The
1 1
input/output routines would provide an SI equivalent of the time rate of heat flow per unit area leaving the surfaces at x is
heat-flow results, no such “metric” equivalent is available for q .
the other portions of the program. To date, there is no accepted 6.3.1.1 For the assumption of steady-state (time-
metric dimensions system for pipe and insulation systems for independent) condition, the law of conservation of energy
cyclindrical shapes. The dimensions in use in Europe are the SI dictates that for any layer the time rate of heat flow in must
dimension equivalents of the American sizes, and in addition equal the time rate of heat flow out, i.e., there is no net storage
have different designations in each country. Therefore, due to of energy inside the layer.
the complexity of providing a standardized equivalent of this 6.3.1.2 Taking thin sections of thickness Dx, energy bal-
procedure, no SI version of this practice has been prepared. At ances may be written for these sections as follows:
the time in which an international standardization of piping and Case 1:
insulation sizing occurs, this practice can be rewritten to meet
~WHq! | 2 ~WHq! | 5 0 (1)
x x1Dx
those needs. This system has also been demonstrated to
NOTE 1—The vertical line with a subscript indicates the point at which
calculate the heat loss for bare systems by the inclusion of the
the previous parameter is evaluated. For example: q| reads the time
x+ Dx
pipe/equipment wall thermal resistance into the equation sys-
rate of heat flow per unit area, evaluated at x + Dx.
tem. This modification, although possible, is beyond the scope
6.3.1.3 After dividing Eq 1 by − WHDx and taking the limit
of this practice.
as Dx approaches zero, the differential equation for heat
6. Method of Calculation
transfer is obtained for the one-dimensional case:
6.1 Approach:
~d/dx!q 5 0 (2)
6.1.1 This calculation of heat gain or loss, and surface
6.3.1.4 Integrating Eq 2 and imposing the condition of heat
temperature, requires (1) that the thermal insulation be homo-
flow stability on the result yields the following:
geneous as outlined by the definition of thermal conductivity in
q 5 q 5 q (3)
1 2
Terminology C 168; (2) that the pipe size and equipment
operating temperature be known; (3) that the insulation thick-
ness be known; (4) that the surface coefficient of the system be
known, or sufficient information be available to estimate it as
described in 7.4; and (5) that the relation between thermal
conductivity and mean temperature for the insulation be known
in detail as described in 7.3.
6.1.2 The solution is a computer procedure calling for (1)
estimation of the s
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