ASTM D7863-13
(Guide)Standard Guide for Evaluation of Convective Heat Transfer Coefficient of Liquids
Standard Guide for Evaluation of Convective Heat Transfer Coefficient of Liquids
SIGNIFICANCE AND USE
5.1 The reported values of convective heat transfer coefficients are somewhat dependent upon measurement technique and it is therefore the purpose of this guide to focus on methods to provide accurate measures of heat transfer and precise methods of reporting. The benefit of developing such a guide is to provide a well understood basis by which heat transfer performance of fluids may be accurately compared and reported.
5.2 For comparison of heat transfer performance of heat transfer fluids, measurement methods and test apparatus should be identical, but in reality heat transfer rigs show differences from rig to rig. Therefore, methods discussed in the guide are generally restricted to the use of heated tubes that have wall temperatures higher than the bulk fluid temperature and with turbulent flow conditions.
5.3 Similar test methods are found in the technical literature, however it is generally left to the user to report results in a format of their choosing and therefore direct comparisons of results can be challenging.
SCOPE
1.1 This guide covers general information, without specific limits, for selecting methods for evaluating the heating and cooling performance of liquids used to transfer heat where forced convection is the primary mode for heat transfer. Further, methods of comparison are presented to effectively and easily distinguish performance characteristics of the heat transfer fluids.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7863 − 13
Standard Guide for
Evaluation of Convective Heat Transfer Coefficient of
Liquids
This standard is issued under the fixed designation D7863; 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.
1. Scope uids by Isoteniscope
D4530 Test Method for Determination of Carbon Residue
1.1 This guide covers general information, without specific
(Micro Method)
limits, for selecting methods for evaluating the heating and
D6743 Test Method for Thermal Stability of Organic Heat
cooling performance of liquids used to transfer heat where
Transfer Fluids
forced convection is the primary mode for heat transfer.
E659 Test Method for Autoignition Temperature of Liquid
Further, methods of comparison are presented to effectively
Chemicals
and easily distinguish performance characteristics of the heat
transfer fluids.
3. Terminology
1.2 The values stated in SI units are to be regarded as
3.1 Definitions of Terms Specific to This Standard:
standard. No other units of measurement are included in this
3.1.1 heat transfer fluid, n—a fluid which remains essen-
standard.
tially a liquid while transferring heat to or from an apparatus or
1.3 This standard does not purport to address all of the
process,althoughthisguidedoesnotprecludetheevaluationof
safety concerns, if any, associated with its use. It is the
a heat transfer fluid that may be used in its vapor state.
responsibility of the user of this standard to establish appro-
3.1.1.1 Discussion—Heat transfer fluids may be hydrocar-
priate safety and health practices and determine the applica-
bon or petroleum based such as polyglycols, esters, hydroge-
bility of regulatory limitations prior to use.
nated terphenyls, alkylated aromatics, diphenyl-oxide/biphenyl
blends, mixtures of di- and triaryl-ethers. Small percentages of
2. Referenced Documents
functional components such as antioxidants, anti-wear and
2.1 ASTM Standards:
anti-corrosion agents, TBN, acid scavengers, or dispersants, or
D445 Test Method for Kinematic Viscosity of Transparent
a combination thereof, can be present.
and Opaque Liquids (and Calculation of Dynamic Viscos-
3.1.2 heat transfer coeffıcient, n—a term, h, used to relate
ity)
the amount of heat transfer per unit area at a given temperature
D1298 Test Method for Density, Relative Density, or API
difference between two media and for purposes of this guide,
Gravity of Crude Petroleum and Liquid Petroleum Prod-
the temperature difference is between a flow media and its
ucts by Hydrometer Method
surrounding conduit.
D2270 Practice for Calculating Viscosity Index from Kine-
3.1.2.1 Discussion—The heat transfer coefficient for condi-
matic Viscosity at 40 and 100°C
tions applicable to fluids flowing in circular conduits under
D2717 Test Method for Thermal Conductivity of Liquids
turbulent flow is referred to as the convective heat transfer
D2766 Test Method for Specific Heat of Liquids and Solids
coefficient.
D2887 Test Method for Boiling Range Distribution of Pe-
troleum Fractions by Gas Chromatography
4. Summary of Guide
D2879 Test Method for Vapor Pressure-Temperature Rela-
4.1 The convective heat transfer coefficient for flow in a
tionship and Initial Decomposition Temperature of Liq-
circular conduit depends in a complicated way on many
variables including fluid properties (thermal conductivity, k,
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
fluid viscosity, µ, fluid density, ρ, specific heat capacity, c ),
p
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
system geometry, the flow velocity, the value of the character-
mittee D02.L0.06 on Non-Lubricating Process Fluids.
istic temperature difference between the wall and bulk fluid,
Current edition approved May 1, 2013. Published July 2013. DOI: 10.1520/
D7863-13.
and surface temperature distribution. It is because of this
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
complicated interaction of variables, test results can be biased
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
because of the inherent characteristics of the heat transfer
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. apparatus, measurement methods, and the working definition
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7863 − 13
for the heat transfer coefficient. Direct measurement of the h(W/cm °C)maybederivedthroughappropriatecalculations.
convective heat flow in circular conduits is emphasized in this Two types of wall boundary conditions are generally em-
guide.
ployed; a constant wall temperature or a constant heat flux
where heat is distributed over a given area such as W/m.Itis
4.2 This guide provides information for assembling a heat
importanttodefinethewallconditionsbecausethetemperature
transfer apparatus and stresses the importance of providing
distributions in the axial flow direction, dT/dz, for the wall and
reporting information regarding the use and operation of the
bulk fluid differ depending on wall condition. Measurement of
apparatus.
the wall temperature distribution may be used to verify
5. Significance and Use
boundary conditions and to obtain estimates of experimental
5.1 The reported values of convective heat transfer coeffi-
error.
cients are somewhat dependent upon measurement technique
6.1.2 A reliable method for setting up a constant heat flux
anditisthereforethepurposeofthisguidetofocusonmethods
condition is to utilize resistive heating of the conduit (the
to provide accurate measures of heat transfer and precise
conduit acts as a resistor when connected to the terminals of an
methodsofreporting.Thebenefitofdevelopingsuchaguideis
electrical power supply). One advantage of this method is the
to provide a well understood basis by which heat transfer
relative ease for measuring the electrical power input (Watts)
performance of fluids may be accurately compared and re-
and inferring the wall temperature from the temperature
ported.
coefficient of resistance (α) for the wall material. Constant wall
5.2 For comparison of heat transfer performance of heat
temperature boundary conditions are established by surround-
transferfluids,measurementmethodsandtestapparatusshould
ing the heat transfer conduit with a medium at constant
be identical, but in reality heat transfer rigs show differences
temperature (such as a thermal bath). A suggested setup for a
from rig to rig. Therefore, methods discussed in the guide are
constant flux heat transfer apparatus is shown in Fig. 1.
generally restricted to the use of heated tubes that have wall
6.1.3 The apparatus shown in Fig. 1 exhibits a free surface
temperatures higher than the bulk fluid temperature and with
at atmospheric pressure within the reservoir and therefore the
turbulent flow conditions.
system is open and non-pressurized. For fluids with low vapor
5.3 Similar test methods are found in the technical
pressure, it may be necessary to run a closed and pressurized
literature, however it is generally left to the user to report
system. Desired bulk fluid temperature and wall temperatures
results in a format of their choosing and therefore direct
will significantly impact the design and operation of the loop.
comparisons of results can be challenging.
Select seals within the pump to be compatible with the fluid
and withstand the operating pressure and temperature. For the
6. Test Apparatus and Supporting Equipment
loop shown, a constant speed pump with external bypass
6.1 Background—Convective heat transfer may be free
controlisemployed.Variablespeedpumpswithnobypassmay
(buoyant) or forced. Forced convection is associated with the
be used; however, a pump speed control unit will be necessary.
forced movement of the fluid and heat transfer of this type is
The installation of a safety relief valve to prevent pressure
emphasized herein. To greatly minimize to the buoyant
buildup is recommended.
contribution, the Reynolds Number should be sufficiently high
to eliminate thermal stratification and provide a fully devel- 6.1.4 The electrically heated test section is shown in a
oped turbulent velocity profile. The use of a vertical heated
vertical position. This arrangement generally prevents hot
section also helps in this regard due to less likelihood of
spots on the walls from forming mainly due to fluid voids or
forming voids near the walls. To minimize the contribution of
the development of “convection cells” and stratified flows.The
radiation heat transfer, which is proportional to the forth power
electrical resistance of a steel or copper tube will be quite low,
of temperature, high wall temperatures (350°C +) should be
and therefore extremely high electrical currents are necessary
avoided. However, for those cases where high wall tempera-
to produce the desired heat flux. For 0.5-in. diameter tubes of
tures are present, corrections for the radiant heat contribution
a few feet in length, it is not uncommon to see currents in the
are necessary. Conduction (heat flow through materials) will
1000 amp range. Employ large copper buss bars to carry
always be present to some extent and the design of any test
current to the heated tube. Accurate measurement of voltage
apparatus must account for all conduction paths, some of
and current will provide an accurate measure of power deliv-
which contribute to heat losses. Energy balance, that is,
ered. Because of the presence of high currents, adequate safety
accounting for all heat flows in and out of the system, is
systems should be employed.
important for accurate determination of heat transfer coeffi-
6.1.5 Due to the high electrical currents and potentially
cients.
extremely high tube temperature, both electrical and thermal
6.1.1 A conventional convective heat transfer apparatus
isolation are needed at each end of the heated section. Use
pumps the fluid of interest through a heated tube where the
ceramics that can be machined to manufacture isolators of
amount of energy absorbed by the fluid from the hot wall is
desired characteristics. Many ceramic materials can handle
measured. By allowing the walls to be cooler that the fluid,
1500°F in an untreated condition, whereas simple heat treating
then cooling transfer coefficients could be derived, but fluid
heating is the focus of this guide. The heat transfer coefficient, of these materials will allow for operation above 2500°F. To
D7863 − 13
FIG. 1 Apparatus for Measuring the Convective Heat Transfer Coefficient
further reduce heat losses, the heated tube will require substan- 6.2 Required Measurements—Measure temperature (wall
tial insulation. Ceramic blankets work very well, especially for and fluid) and flow rate to obtain sufficient information for
high temperature applications. calculating the heat transfer coefficient. However, when com-
6.1.6 Document wall roughness of the heated section. Com- paring test results to observations of others, it is necessary to
mercially drawn stainless steel tubing is preferred, but tube obtain fluid property data and dimensions of the test sections.
wall roughness shall approach hydraulically smooth conditions The reason, convective heat transfer predictions are usually
with Darcy-Weisbach relative roughness values approaching cast in terms of non-dimensional groups of Nusselt number,
0.00001 or better. Reynolds number, and Prandtl number. Other non-dimensional
6.1.7 The heated test section shall be easily removed for groups may also be applicable. Therefore values of fluid
inspection and for possibly changing tube sizes. It is especially viscosity (Test Method D445, Practice D2270), thermal con-
advantageous to accommodate sectioning of the tube upon the ductivity (Test Method D2717), fluid density (Test Method
completion of a test sequence for the purpose of examining D1298) and heat capacity (Test Method D2766) all as a
deposits on the tube wall via carbon burn off methods (Test function of temperature are necessary for various heat transfer
Method D4530) or Auger electron spectroscopy. The latter correlations.
method is a widely used analytical technique for obtaining
6.2.1 Other properties of fluids are required for complete
chemical composition of solid surfaces.
documentation and safety of operation. These include boiling
6.1.8 Do not exceed temperature limitations set by pump
range distributions (Test Method D2887), vapor pressure-
seals and other seals. For many installations, this means that
temperature relationship (Test Method D2879) and autoigni-
extremely hot fluids going through the loop (and heated
tion temperature (Test Method E659).
section)willneedtobecooledbeforetheyenterthepump.This
6.2.2 Suggested test section temperature measurements are
cooling will set up thermal cycling of the fluid by heating and
show in Fig. 2.This figure shows a constant heat flux boundary
cooling the fluid every time the fluid circulates through the
condition. A constant wall temperature condition may also be
loop.
imposed by surrounding the tube within an isothermal bath.
6.2.3 The subscript “b” denotes a bulk fluid temperature
(sometimesreferredtoasthebulkmixingcuptemperature)and
Chourasia,A. R., and Chopra, D. R., Handbook of Instrumental Techniques for
Analytical Chemistry, Chapter 42, 1997. the subscript “w” denotes a wall temperature. It is suggested
D7863 − 13
FIG. 2 Temperature Measurements
that five or more wall temperatures be obtained over the test Q 5 h ~πDL!~T 2 T ! (2)
1 01 b1
section length. For a constant heat flux condition, dT /dz is
w Q 5 h πDL T 2 T 1 T 2 T ⁄2 (3)
~ !@~ ! ~ !#
a 01 b1 02 b2
constant and the value of T increases form inlet to outlet and
w
Q 5 h πDL T 2 T 2 T 2 T ⁄
~ !@~ ! ~ !#
ln 01 b1 02 b2
in the case of a constant temperature wall, T is a constant over
w
ln@~T 2 T !⁄~T 2 T !# (4)
01 b1 02 b2
the entire length. These temperature distributions should be
reported along with the test results to ensure reasonable
6.3.2.1 Note that h is based on the initial temperature
comparisons of results from other sources.
difference (T -T ) , h is based on the arithmetic mean of the
0 b 1 a
6.2.4 If the wall thickness is large (more than 10 % of the
terminal temperature differences (T -T ) , and h is based on
0 b a ln
diameter), the inside wall temperature may be significantly
the corresponding logarithmic mean difference (T -T ) . The
0 b ln
different th
...
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