ASTM D7863-22

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7863 − 17 D7863 − 22
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*
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D2270 Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 °C and 100 °C
D2717 Test Method for Thermal Conductivity of Liquids (Withdrawn 2018)
D2766 Test Method for Specific Heat of Liquids and Solids (Withdrawn 2018)
D2879 Test Method for Vapor Pressure-Temperature Relationship and Initial Decomposition Temperature of Liquids by
Isoteniscope
D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4530 Test Method for Determination of Carbon Residue (Micro Method)
D6743 Test Method for Thermal Stability of Organic Heat Transfer Fluids
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.L0.06 on Non-Lubricating Process Fluids.
Current edition approved Aug. 1, 2017July 1, 2022. Published August 2017August 2022. Originally approved in 2013. Last previous edition approved in 20132017 as
D7863 – 13.D7863 – 17. DOI: 10.1520/D7863-17.10.1520/D7863-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D7042 Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer (and the Calculation of Kinematic
Viscosity)
E659 Test Method for Autoignition Temperature of Chemicals
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 For definitions of terms used in this guide, refer to Terminology D4175.
3.1.2 heat transfer fluid, n—a fluid which remains essentially a liquid while transferring heat to or from an apparatus or process,
although this guide does not preclude the evaluation of a heat transfer fluid that may be used in its vapor state.
3.1.2.1 Discussion—
Heat transfer fluids may be hydrocarbon or petroleum based such as polyglycols, esters, hydrogenated terphenyls, alkylated
aromatics, diphenyl-oxide/biphenyl blends, and mixtures of di- and triaryl-ethers. Small percentages of functional components
such as antioxidants, anti-wear and anti-corrosion agents, TBN, acid scavengers, or dispersants, or a combination thereof, can be
present.
3.1.3 heat transfer coeffıcient, n—a term, h, used to relate the amount of heat transfer per unit area at a given temperature
difference between two media and for purposes of this guide, the temperature difference is between a flow media and its
surrounding conduit.
3.1.3.1 Discussion—
The heat transfer coefficient for conditions applicable to fluids flowing in circular conduits under turbulent flow is referred to as
the convective heat transfer coefficient.
4. Summary of Guide
4.1 The convective heat transfer coefficient for flow in a circular conduit depends in a complicated way on many variables
including fluid properties (thermal conductivity, k, fluid viscosity, μ, fluid density, ρ, specific heat capacity, c ), system geometry,
p
the flow velocity, the value of the characteristic temperature difference between the wall and bulk fluid, and surface temperature
distribution. It is because of this complicated interaction of variables, test results can be biased because of the inherent
characteristics of the heat transfer apparatus, measurement methods, and the working definition for the heat transfer coefficient.
Direct measurement of the convective heat flow in circular conduits is emphasized in this guide.
4.2 This guide provides information for assembling a heat transfer apparatus and stresses the importance of providing reporting
information regarding the use and operation of the apparatus.
5. 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.
6. Test Apparatus and Supporting Equipment
6.1 Background—Convective heat transfer may be free (buoyant) or forced. Forced convection is associated with the forced
movement of the fluid and heat transfer of this type is emphasized herein. To greatly minimize to the buoyant contribution, the
Reynolds number should be sufficiently high to eliminate thermal stratification and provide a fully developed turbulent velocity
profile. The use of a vertical heated section also helps in this regard due to less likelihood of forming voids near the walls. To
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minimize the contribution of radiation heat transfer, which is proportional to the fourth power of temperature, high wall
temperatures (350 °C +) should be avoided. However, for those cases where high wall temperatures are present, corrections for
the radiant heat contribution are necessary. Conduction (heat flow through materials) will always be present to some extent and
the design of any test apparatus must account for all conduction paths, some of which contribute to heat losses. Energy balance,
that is, accounting for all heat flows in and out of the system, is important for accurate determination of heat transfer coefficients.
6.1.1 A conventional convective heat transfer apparatus pumps the fluid of interest through a heated tube where the amount of
energy absorbed by the fluid from the hot wall is measured. By allowing the walls to be cooler that the fluid, then cooling transfer
coefficients could be derived, but fluid heating is the focus of this guide. The heat transfer coefficient, h (W/cm °C) may be derived
through appropriate calculations. Two types of wall boundary conditions are generally employed: a constant wall temperature or
a constant heat flux where heat is distributed over a given area such as W/m . It is important to define the wall conditions because
the temperature distributions in the axial flow direction, dT/dz, for the wall and bulk fluid differ depending on wall condition.
Measurement of the wall temperature distribution may be used to verify boundary conditions and to obtain estimates of
experimental error.
6.1.2 A reliable method for setting up a constant heat flux condition is to utilize resistive heating of the conduit (the conduit acts
as a resistor when connected to the terminals of an electrical power supply). One advantage of this method is the relative ease for
measuring the electrical power input (Watts) and inferring the wall temperature from the temperature coefficient of resistance (α)
for the wall material. Constant wall temperature boundary conditions are established by surrounding the heat transfer conduit with
a medium at constant temperature (such as a thermal bath). A suggested setup for a constant flux heat transfer apparatus is shown
in Fig. 1.
6.1.3 The apparatus shown in Fig. 1 exhibits a free surface at atmospheric pressure within the reservoir and therefore the system
is open and non-pressurized. For fluids with low vapor pressure, it may be necessary to run a closed and pressurized system.
Desired bulk fluid temperature and wall temperatures will significantly impact the design and operation of the loop. Select seals
within the pump to be compatible with the fluid and withstand the operating pressure and temperature. For the loop shown, a
FIG. 1 Apparatus for Measuring the Convective Heat Transfer Coefficient
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constant speed pump with external bypass control is employed. Variable speed pumps with no bypass may be used; however, a
pump speed control unit will be necessary. The installation of a safety relief valve to prevent pressure buildup is recommended.
6.1.4 The electrically heated test section is shown in a vertical position. This arrangement generally prevents hot spots on the walls
from forming mainly due to fluid voids or the development of “convection cells” and stratified flows. The electrical resistance of
a steel or copper tube will be quite low, and therefore extremely high electrical currents are necessary to produce the desired heat
flux. For 0.5 in. diameter tubes of a few feet in length, it is not uncommon to see currents in the 1000 amp range. Employ large
copper buss bars to carry current to the heated tube. Accurate measurement of voltage and current will provide an accurate measure
of power delivered. Because of the presence of high currents, adequate safety systems should be employed.
6.1.5 Due to the high electrical currents and potentially extremely high tube temperature, both electrical and thermal isolation are
needed at each end of the heated section. Use ceramics that can be machined to manufacture isolators of desired characteristics.
Many ceramic materials can handle 1500 °F in an untreated condition, whereas simple heat treating of these materials will allow
for operation above 2500 °F. To further reduce heat losses, the heated tube will require substantial insulation. Ceramic blankets
work very well, especially for high temperature applications.
6.1.6 Document wall roughness of the heated section. Commercially drawn stainless steel tubing is preferred, but tube wall
roughness shall approach hydraulically smooth conditions with Darcy-Weisbach relative roughness values approaching 0.00001
or better.
6.1.7 The heated test section shall be easily removed for inspection and for possibly changing tube sizes. It is especially
advantageous to accommodate sectioning of the tube upon the completion of a test sequence for the purpose of examining deposits
on the tube wall via carbon burn off methods (Test Method D4530) or Auger electron spectroscopy. The latter method is a widely
used analytical technique for obtaining chemical composition of solid surfaces.
6.1.8 Do not exceed temperature limitations set by pump seals and other seals. For many installations, this means that extremely
hot fluids going through the loop (and heated section) will need to be cooled before they enter the pump. This cooling will set up
thermal cycling of the fluid by heating and cooling the fluid every time the fluid circulates through the loop.
6.2 Required Measurements—Measure temperature (wall and fluid) and flow rate to obtain sufficient information for calculating
the heat transfer coefficient. However, when comparing test results to observations of others, it is necessary to obtain fluid property
data and dimensions of the test sections. The reason, convective heat transfer predictions are usually cast in terms of
non-dimensional groups of Nusselt number, Reynolds number, and Prandtl number. Other non-dimensional groups may also be
applicable. Therefore values of fluid viscosity (Test Method D445 or D7042, Practice D2270), thermal conductivity (Test Method
D2717), fluid density (Test Method D1298 or D4052), and heat capacity (Test Method D2766) all as a function of temperature are
necessary for various heat transfer correlations.
6.2.1 Other properties of fluids are required for complete documentation and safety of operation. These include boiling range
distributions (Test Method D2887), vapor pressure-temperature relationship (Test Method D2879), and autoignition temperature
(Test Method E659).
6.2.2 Suggested test section temperature measurements are show in Fig. 2. This figure shows a constant heat flux boundary
FIG. 2 Temperature Measurements
Chourasia, A. R., and Chopra, D. R., Handbook of Instrumental Techniques for Analytical Chemistry, Chapter 42, 1997.
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condition. A constant wall temperature condition may also be imposed by surrounding the tube within an isothermal bath.
6.2.3 The subscript “b” denotes a bulk fluid temperature (sometimes referred to as the bulk mixing cup temperature) and the
subscript “w” denotes a wall temperature. It is suggested that five or more wall temperatures be obtained over the test section
length. For a constant heat flux condition, dT /dz is constant
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