SURF252 Element Description

SURF252 is used for radiation surface loads and can be used only with the radiosity solver method. It can be overlaid onto a face of any 3-D thermal solid or shell element that supports temperature DOF. This element is applicable to 3-D thermal analyses. Various other loads and surface effects may exist simultaneously (e.g., SURF152 and SURF154 and SURF252 may be applied on the same solid element faces to support convection heat flux and radiation heat flux loads).

This element can be created only by the RSURF command. The surface must also have the RDSF flag.

Figure 252.1:  SURF252 Geometry

SURF252 Input Data

The geometry, node locations, and the coordinate system for this element are shown in Figure 252.1: SURF252 Geometry. The element is defined by three or four nodes, regardless of the underlying solid element.

You would typically generate SURF252 elements via the RSURF command, creating elements which are coincident with the solid element surface. However, if you are using decimation (RDEC), then the surface elements created will not coincide with the underlying solid element topology. See Figure 252.2: SURF252 Elements Without Coincident Nodes. Symmetrical SURF252 elements (produced when using the symmetry options [RSYMM]) will have no underlying solid elements. The RSURF command always produces extra nodes to define the SURF252 topology as shown in Figure 252.2: SURF252 Elements Without Coincident Nodes, regardless if RDEC is used.

Figure 252.2:  SURF252 Elements Without Coincident Nodes

You cannot apply any loads on this element. During solution, the element extracts the temperature of the solid element and computes the radiation heat flux, which is transferred back as a surface load to the solid element.

The next table summarizes the element input. Element Input gives a general description of element input.

SURF252 Output Data

Table 252.1: SURF252 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 151.3: SURF151 Item and Sequence Numbers:

Name

output quantity as defined in Table 252.1: SURF252 Item and Sequence Numbers

Item

predetermined Item label for ETABLE command

E

sequence number for single-valued or constant element data

I,J

sequence number for data at nodes I and J

Table 252.1:  SURF252 Item and Sequence Numbers

Name	Item	E
CENTROID X	NMISC	1
CENTROID Y	NMISC	2
CENTROID Z	NMISC	3
AREA	NMISC	4
TEMP	NMISC	5
EMISSIVITY	NMISC	6
Net outgoing radiation heat flux	NMISC	7
Emitted radiation heat flux	NMISC	8
Reflected radiation heat flux	NMISC	9
Incident radiant heat flux	NMISC	10
Enclosure No.	NMISC	18

The net radiation heat flux is the sum of the directly emitted radiation flux [εσT⁴] plus the reflected radiation flux [(1–ε)q_i] minus the incoming radiation [q_i], as shown in Figure 252.3: Net Radiation Heat Flux.

Figure 252.3:  Net Radiation Heat Flux

SURF252 Assumptions and Restrictions

SURF252 Product Restrictions

There are no product-specific restrictions for this element.