3-D Thermal Surface Effect
SURF152 may be used for various load and surface effect applications. It may be overlaid onto an area face of any 3-D thermal element. The element is applicable to 3-D thermal analyses. Various loads and surface effects may exist simultaneously. See SURF152 in the Mechanical APDL Theory Reference for more details about this element.
The geometry, node locations, and the coordinate system for this element are shown in Figure 152.1: SURF152 Geometry. The element is defined by four to ten nodes and by the material properties. The nodes for this element must share the nodes of the underlying solid element. An extra node (away from the base element) may be used for convection or radiation effects. Two extra nodes (away from the base element) may be used to more accurately capture convection effects. A triangular element may be formed by defining duplicate K and L node numbers as described in Degenerated Shape Elements. The element x-axis is parallel to the I-J side of the element.
The mass, volume, and heat-generation calculations use the element thicknesses at node I, J, K, and L (real constants TKI, TKJ, TKK, and TKL, respectively). Thickness TKI defaults to 0.0, and thicknesses TKJ, TKK, and TKL default to TKI. The mass calculation uses the density (material property DENS).
See Nodal Loading for a description of element loads. Convections or heat fluxes may be input as surface loads on the element.
The convection surface conductivity matrix calculation uses the film coefficient (input on the SFE command with KVAL = 0 and CONV as the label). If the extra node is used, its temperature becomes the bulk temperature. If the extra node is not used, the CONV value input with KVAL = 2 becomes the bulk temperature. The convection surface heat flow vector calculation uses the bulk temperature. On a given face, either a heat flux or a convection may be specified, but not both simultaneously.
For the extra node option (KEYOPT(5) = 1), film effectiveness and free stream temperatures may also be input for convection surface loads (input on the SFE command with the CONV label and KVAL = 3 and 4, respectively). If film effectiveness is input, bulk temperature is ignored.
Setting KEYOPT(7) = 1 multiplies the evaluated film coefficient by the empirical term ITS - TBIn, where TS is the element surface temperature, TB is the fluid bulk temperature, and n is an empirical coefficient (real constant ENN).
Convections and heat fluxes are multiplied by an area to obtain the heat flows. KEYOPT(12) determines whether the current area or the original area is selected for the calculation.
If KEYOPT(5) = 1 and flow information is available from FLUID116 with KEYOPT(2) = 1, the bulk temperature may
be adjusted to the adiabatic wall temperature using KEYOPT(6) = 1,
real constants OMEG (rotational speed) and NRF (recovery factor),
and the logic described in the Mechanical APDL Theory Reference. For this adjustment, the
axis of rotation may be defined as the global Cartesian X, Y or Z
coordinate axis (KEYOPT(3)). When using the OMEG real constant, you
can specify either numerical values or table inputs. If specifying
table inputs, enclose the table name in % signs (for example, %
tabname%). Rotational speed (OMEG) can vary
with time and location. Use the *DIM command to
dimension the table and identify the variables. For more information
and examples on using table inputs, see Array Parameters of the ANSYS Parametric Design Language Guide, Applying Loads Using
TABLE Type Array Parameters in the Basic Analysis Guide, and Doing a Thermal Analysis
Using Tabular Boundary Conditions in the Thermal Analysis Guide, as well
as the description of the *DIM command in the Command Reference.
A film coefficient specified by the SFE command may be modified by activating the user subroutine USERCV with the USRCAL command. USERCV may be used to modify the film coefficient of a surface element with or without an extra node. It may be used if the film coefficient is a function of temperature and/or location.
If the surface element has an extra node (KEYOPT(5) = 1), the bulk temperature and/or the film coefficient may be redefined in a general way by user programmable routine USRSURF116. USRSURF116 may be used if the bulk temperature and/or the film coefficient is a function of fluid properties, velocity and/or wall temperature. If a bulk temperature is determined by USRSURF116, it overrides any value specified by SFE or according to KEYOPT(6). Also, if a film coefficient is determined by USRSURF116, it overrides any values specified by SFE or USRCAL, USERCV. USRSURF116 calculation are activated by modifying the USRSURF116 subroutine and creating a customized version of ANSYS; there will be no change in functionality without modifying USRSURF116. For more information, see User-Programmable Features (UPFs) in the .
Heat generation rates are input on a per unit volume basis and may be input as an element body load at the nodes, using the BFE command. Element body loads are not applied to other elements connected at the same nodes. The node I heat generation HG(I) defaults to zero. If all other heat generations are unspecified, they default to HG(I). If all corner node heat generations are specified, each midside node heat generation defaults to the average heat generation of its adjacent corner nodes. For any other input heat generation pattern, unspecified heat generations default to zero. The heat generation load vector calculation uses the heat generation rate values.
As an alternative to using the BFE command, you can specify heat generation rates directly at the nodes using the BF command. For more information on body loads, see Body Loads in the Basic Analysis Guide.
SURF152 allows for radiation between the surface and the extra node. The emissivity of the surface (input as material property EMIS for the material number of the element) is used for the radiation surface conductivity matrix. The form factor FORMF and the Stefan-Boltzmann constant SBCONST are also used for the radiation surface conductivity matrix. The form factor can be either input as a real constant (defaults to 1) using KEYOPT(9) = 1 or it can be calculated automatically as a cosine effect using KEYOPT(9) = 2 or 3. For information on how the cosine effect depends on basic element orientation and the extra node location, see the Mechanical APDL Theory Reference. There is no distance effect included in the cosine effect. The Stefan-Boltzmann constant defaults to 0.119x10-10 (Btu/hr*in2* °R4)).
When KEYOPT(4) = 0, an edge with a removed midside node implies that the temperature varies linearly, rather than parabolically, along that edge. See Quadratic Elements (Midside Nodes) in the Modeling and Meshing Guide for more information about the use of midside nodes.
|I, J, K, L if KEYOPT (4) = 1 and KEYOPT (5) = 0|
|I, J, K, L, M if KEYOPT (4) = 1 and KEYOPT (5) = 1|
|I, J, K, L, M, N if KEYOPT (4) = 1 and KEYOPT (5) = 2|
|I, J, K, L, M, N, O, P if KEYOPT (4) = 0 and KEYOPT (5) = 0|
|I, J, K, L, M, N, O, P, Q if KEYOPT (4) = 0 and KEYOPT (5) = 1|
|I, J, K, L, M, N, O, P, Q, R if KEYOPT (4) = 0 and KEYOPT (5) = 2|
|KEYOPT(11) Setting||DOF for all nodes except extra node(s)||DOF for extra node(s) (KEYOPT(5) = 1 or 2)|
|FORMF, SBCONST, (Blank), OMEG, NRF, VABS,|
|TKI, TKJ, TKK, TKL, (Blank), (Blank),|
|ENN, GC, JC|
|See Table 152.1: SURF152 Real Constants for a description of the real constants|
|MP command: DENS (density), EMIS (emissivity) if KEYOPT(9) > 0)|
face 1 (I-J-K-L) if KEYOPT(8) > 1
face 1 (I-J-K-L) if KEYOPT(8) = 1
HG(I), HG(J), HG(K), HG(L), and, if KEYOPT(4) = 0, HG(M), HG(N), HG(O), HG(P)
Adiabatic wall temperature option:
See Adiabatic Wall Temperature as Bulk Temperature for information on these options.
Recovery factor (FR) option:
See Adiabatic Wall Temperature as Bulk Temperature for information on these options.
Axis of symmetry:
OMEG used about global Cartesian X-axis
OMEG used about global Cartesian Y-axis
OMEG used about global Cartesian Z-axis
Has midside nodes
No midside nodes
No extra nodes. Use this option if the bulk temperature is known.
One extra node (optional if KEYOPT (8) > 1; required if KEYOPT (9) > 0). Valid for convection and radiation calculations. Use this option if the bulk temperature is unknown. The extra node gets the bulk temperature from a FLUID116 element.
Two extra nodes (optional if KEYOPT (8) > 1). Only valid for convection calculations. Use this option if the bulk temperature is unknown. The extra nodes get bulk temperatures from the two nodes of a FLUID116 element. This is generally more accurate than the one extra node option.
Use of bulk temperature:
Extra node temperature used as bulk temperature
Adiabatic wall temperature used as bulk temperature
Do not multiply film coefficient by empirical term.
Multiply film coefficient by empirical term |TS-TB|n.
Heat flux and convection loads:
Ignore heat flux and convection surface loads (if any)
Include heat flux, ignore convection
Use the following to include convection (ignore heat flux):
Evaluate film coefficient hf (if any) at average film temperature, (TS +TB)/2
Evaluate hf at element surface temperature, TS
Evaluate hf at fluid bulk temperature, TB
Evaluate hf at differential temperature, | TS - TB |
Radiation form factor calculation:
Do not include radiation
Use radiation with the form factor real constant
Use radiation with cosine effect calculated as an absolute value (ignore real constant)
Use radiation with cosine effect calculated as zero if negative (ignore real constant)
Label used for all nodal degrees of freedom (except for the extra node):
The extra node, if requested with KEYOPT(5) = 1, is always TEMP.
Area to use for the heat-flow calculation:
Current area (default)
Film coefficient matrix key:
Program determines whether to use diagonal or consistent film coefficient matrix (default).
Use a diagonal film coefficient matrix.
Use a consistent matrix for the film coefficient.
Table 152.1: SURF152 Real Constants
|4||OMEGA||Angular velocity (KEYOPT(6) = 1)|
|6||VABS||Absolute value of fluid velocity (KEYOPT(1) = 0)|
|7||TKI||Thickness at node I|
|8||TKJ||Thickness at node J (defaults to TKI)|
|9||TKK||Thickness at node K (defaults to TKI)|
|10||TKL||Thickness at node L (defaults to TKI)|
|14||GC||Gravitational constant used for units consistency|
|15||JC||Joule constant used to convert work units to heat units|
The solution output associated with the element is in two forms:
Nodal degree of freedom results included in the overall nodal solution
Additional element output as shown in Table 152.2: SURF152 Element Output Definitions
Convection heat flux is positive out of the element; applied heat flux is positive into the element. A general description of solution output is given in Solution Output. See the Basic Analysis Guide for ways to view results.
The Element Output Definitions table uses the following notation:
A colon (:) in the Name column indicates that the item can be accessed by the Component Name method (ETABLE, ESOL). The O column indicates the availability of the items in the file Jobname.OUT. The R column indicates the availability of the items in the results file.
In either the O or R columns, “Y” indicates that the item is always available, a number refers to a table footnote that describes when the item is conditionally available, and “-” indicates that the item is not available.
Table 152.2: SURF152 Element Output Definitions
|SURFACE NODES||Nodes - I, J, K, L||Y||Y|
|EXTRA NODE||Extra node (if present)||Y||Y|
|XC, YC, ZC||Location where results are reported||Y||7|
|VN(X, Y, Z)||Components of unit vector normal to center of element||-||Y|
|MASS||Mass of element||-||1|
|HGEN||Heat generations HG(I), HG(J), HG(K), HG(L), HG(M), HG(N), HG(O), HG(P)||2||-|
|HEAT GEN. RATE||Heat generation rate over entire element (HGTOT)||2||2|
|HFLUX||Input heat flux at nodes I, J, K, L||3||-|
|HEAT FLOW RATE||Input heat flux heat flow rate over element surface area (HFCTOT)||3||3|
|HFILM||Film coefficient at each face node||4||4|
|TBULK||Bulk temperature at each face node or temperature of extra node||4||4|
|TAVG||Average surface temperature||4||4|
|TAW||Adiabatic wall temperature||5||5|
|SPHTFL||Specific heat of the fluid||5||5|
|CONV. HEAT RATE||Convection heat flow rate over element surface area (HFCTOT)||4||4|
|CONV. HEAT RATE/AREA||Average convection heat flow rate per unit area||4||-|
|EMISSUR||Average emissivity of surface (for element material number)||6||6|
|EMISEXT||Emissivity of extra node||6||6|
|TEMPSUR||Average temperature of surface||6||6|
|TEMPEXT||Temperature of extra node||6||6|
|FORM FACTOR||Average form factor of element||6||6|
|RAD. HEAT RATE||Radiation heat flow rate over entire element (HRTOT)||6||6|
|RAD. HEAT RATE/AREA||Average radiation heat flow rate per unit area||6||-|
Available only at centroid as a *GET item.
Table 152.3: SURF152 Item and Sequence Numbers lists output available through the ETABLE command using the Sequence Number method. See The General Postprocessor (POST1) in the Basic Analysis Guide and The Item and Sequence Number Table in this reference for more information. The following notation is used in Table 152.3: SURF152 Item and Sequence Numbers:
Table 152.3: SURF152 Item and Sequence Numbers
|Output Quantity Name||ETABLE and ESOL Command Input|
The element must not have a zero area.
If KEYOPT(9) > 0 (radiation is used):
element is nonlinear and requires an iterative solution
extra node must be present.
if KEYOPT(4) = 0, midside nodes may not be dropped.
If real constants TKI, TKJ, TKK, TKL (in-plane thicknesses), and TKPS (out-of-plane thickness) are defined for the element, the element volume is greater than zero. If BF, BFE, or BFUNIF commands are issued under this circumstance, heat generation loads are activated. However, the damping matrix is not activated even though the element volume is greater than zero.
When used in the product(s) listed below, the stated product-specific restrictions apply to this element in addition to the general assumptions and restrictions given in the previous section.
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