Example7 Temperature Change of a Heating Plate by Changing Velocity and Temperature of Incoming Flow

General

Heat dissipation of a heating plate by the forced convection is solved by the transient analysis.
The behavior by changing velocity and temperature of the incoming fluid is analyzed.
The temperature distribution and the heat flux vectors are solved.
Unless specified in the list below, the default conditions are applied.

Analysis Space

Item

Setting

Analysis Space

Thickness in depth direction: 300mm

Model Unit

Analysis Conditions

Item	Setting
Solver	Fluid Analysis [Bernoulli] Thermal analysis [Watt]
Analysis Type	Fluid analysis: Transient analysis Thermal analysis: Transient analysis
Laminar Flow/Turbulent Flow	Select Turbulent Flow
Ambient Temperature	0[deg]
Meshing Setup	General Mesh size: 10[mm]

Tab

Setting Item

Setting

Transient Analysis

Table

Number	Calculation steps	Output steps	Timestep [s]
1	30	1	10

Initial Temperature

Use ambient temperature (0[deg])

Model

The material of Air (000_Air) is set to a rectangular sheet body. The boundary conditions of inlet and outlet are set on the left edge and the right edge respectively.

A heat source of thin flat plate is defined by the rectangle sheet body.

The slip wall outer boundary condition is applied to the top and bottom edges where the boundary condition is not set.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	air	000_Air(*)
1/Solid	hot	hot

* Available from the material DB

The material properties of the thin flat plate are set as follows.

Material Name	Tab	Properties
hot	Solid/Fluid	Solid
	Thermal conductivity	1×10^5
	Specific heat	1×10^3
	Density	1×10^3

The heat source of the thin flat plate is set on the heat source tab as follows.

Body Attribute Name	Tab	Setting
hot	Heat source	100W

Boundary Condition

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Setting

Inlet/Edge

Fluid-Thermal

Inlet

Forced Inflow
Specify flow velocity
10[m/s]

Select “Time dependency”.

Weight Function

Number	Time [s]	Weight
1	0	1
2	100	1
3	101	2
4	300	2

Incoming fluid temperature : Direct entry : 25[deg]

Select Time dependency.

Weight Function

Number	Time [s]	Weight
1	0	0
2	100	0
3	101	1
4	300	1

Outlet/Face

Fluid-Thermal

Outlet

Natural Outflow

Outer Boundary Condition

Fluid-Thermal

Slip Wall

–

The inflow velocity and the inflow temperature are changed by the weight function as below.

(1)0[s]～100[s]: inflow velocity 10[m/s], inflow temperature 0[deg]

(2)101[s]～200[s]: inflow velocity 20[m/s], inflow temperature 0[deg]

(3)201[s]～300[s]: inflow velocity 20[m/s], inflow temperature 25[deg]

Results

The temperature distribution after 100[s] is shown below.

The maximum temperature is 14.942 [deg].

Up to 100[s], the inflow velocity and the inflow temperature are the same as those of Example 2: Cooling of Plate by Forced Convection (Turbulent Flow).
Almost the same results as Example 2 are obtained.

Select [Temperature] of the table to show the graph.

The graph below shows only hot/maximum temperature.

(Double click the graph to show the plot option. Deselect [Display Y-axis (primary axis)] except hot/maximum temperature.)

The temperature in the domain (2) goes down as the inflow velocity increases. The temperature in the domain (3) goes higher as the inflow temperature goes up.