Transient plate temp

	Transient temperature distribution on a plate
Online calculator for the transient temperature distribution on a convection cooled plate with discrete heat sources. Check the diagram option and notice what happens when the red position marker is moved. Uncheck the diagram option and press the play button to start an animation. Related links Thermal design for electronics Thermal online tools Unit conversion Comments Your need to install a Java console to display this applet. All modern browsers have this option. General The purpose of this applet is is to show how analytical procedures can be used to create overviews. The solution is based on several nested Fourier series. The theory dealt with in the article: Transient 2-D Solution for a Convection Cooled Plate article. A limitation with solutions of this type is that they are based on the assumption of uniform heat transfer coefficient and uniform air temperature. This disadvantage can however be fairly well compensated for by a set of invisible heat sources. An air temperature compensation of this type is implemented in the procedure. Source A heat source is a rectangular area with a uniform heat flux. Up to 5 sources can be defined. The coordinate system has its origin in the lower left corner of the plate and the base point for the sources is the lower left corner. There is a fix 1 mm snap grid, which can be overwritten by specifying a position in the inputs. To expose the properties for a heat source: Use the 2-D mode and click on a heat source in the image. The active heat source is marked by a thicker frame. X-pos Is the X-coordinate position. Y-pos Is the Y-coordinate position. Width Is the X-coordinate width. Height Is the Y-coordinate width. Heat diss Is the heat dissipation of the source. The grayed area to the left shows the total heat dissipation on the plate. Cycle time Is the time it takes to complete a full cycle of the cyclic function specified. Phase Is used to push the heat dissipation cycle on the time scale it is expressed as degrees, (0 - 360), of the cycle time. Wave shape Is the shape of the cyclic time function. there are 3 possibilities. "Rectangular" specifies a rectangular wave function. "Sin" specifies a sin function. "Stat" specifies no variation in time. Add source/Del source Adds and removes a heat source. The source count is limited to 5. Plate Is any kind of plate provided that it can be simulated as a 2-D case. Check this up by calculating the thermal resistance in the Z-direction,(based on half the plate thickness) R=(thickness/2)/((conductivity)(source surface)) with the total thermal resistance for the system. Width Is the X-coordinate width. Height Is the Y-coordinate width. Thickness Is the thickness. Conductivity Is the thermal conductivity. For a PCB it can be calculated with the Thermal Conductivity for PCBs applet Density Is the density for the plate. For a PCB it can be calculated with the Thermal Conductivity for PCBs applet Specific heat Is the specific heat for the plate. For a PCB it can be calculated with the Thermal Conductivity for PCBs applet Coefficient Is the heat transfer coefficient fro the plate. It can be calculated with the Heat Transfer Coefficient for Parallel Plates applet. Air temp inc Is the air temperature rise at exit for maximum heat load. At calculation it varies proportionally to the heat load. It is automatically limited upwards to 80% of the inlet temperature difference if the plate had been isothermal. (max dT)/(static dT) Is the ratio of the temperature differences for the current and static case below the marker. 100% signifies no difference, 50% signifies a compleat damping of the dynamic heat dissipation component. Air temp inc Is the temperature increase of the air when passing the plate. It has a tendency to distort the curves. A first approach value of 0 is therefore recommended. Outputs* Diagram If checked, a diagram shows the temperature transient below the red marker. The X-axis spans over the largest period specified for a heat source. Tconst Is the thermal time constant for a heat source. Clicking on a heat source activates it. It is not defined for the marker. Editing Edit mode/Result mode Toggles between edit and result mode. All kinds of changes can be made in both modes. 3-D mode/2-D mode Toggles between the 2-D and the 3-D mode. Save last/Delete last Saves or deletes the last curve in the diagram. Maximum capacity is 5 curves. Save/read data Opens a panel that allows the user to save and read input data. Note Clicking in the diagram opens a panel with tabled results that can be copied and pasted into a spread sheet. Top of page

Transient temperature distribution on a plate

Online calculator for the transient temperature distribution on a convection cooled plate with discrete heat sources.

Check the diagram option and notice what happens when the red position marker is moved.

Uncheck the diagram option and press the play button to start an animation.

General

The purpose of this applet is is to show how analytical procedures can be used to create overviews.

The solution is based on several nested Fourier series. The theory dealt with in the article: Transient 2-D Solution for a Convection Cooled Plate article. A limitation with solutions of this type is that they are based on the assumption of uniform heat transfer coefficient and uniform air temperature. This disadvantage can however be fairly well compensated for by a set of invisible heat sources. An air temperature compensation of this type is implemented in the procedure.

Source

A heat source is a rectangular area with a uniform heat flux. Up to 5 sources can be defined. The coordinate system has its origin in the lower left corner of the plate and the base point for the sources is the lower left corner. There is a fix 1 mm snap grid, which can be overwritten by specifying a position in the inputs.

To expose the properties for a heat source: Use the 2-D mode and click on a heat source in the image. The active heat source is marked by a thicker frame.

X-pos
Is the X-coordinate position.

Y-pos
Is the Y-coordinate position.

Width
Is the X-coordinate width.

Height
Is the Y-coordinate width.

Heat diss
Is the heat dissipation of the source. The grayed area to the left shows the total heat dissipation on the plate.

Cycle time
Is the time it takes to complete a full cycle of the cyclic function specified.

Phase
Is used to push the heat dissipation cycle on the time scale it is expressed as degrees, (0 - 360), of the cycle time.

Wave shape
Is the shape of the cyclic time function. there are 3 possibilities. "Rectangular" specifies a rectangular wave function. "Sin" specifies a sin function. "Stat" specifies no variation in time.

Add source/Del source
Adds and removes a heat source. The source count is limited to 5.

Plate

Is any kind of plate provided that it can be simulated as a 2-D case. Check this up by calculating the thermal resistance in the Z-direction,(based on half the plate thickness)

R=(thickness/2)/((conductivity)*(source surface))

with the total thermal resistance for the system.

Width
Is the X-coordinate width.

Height
Is the Y-coordinate width.

Thickness
Is the thickness.

Conductivity
Is the thermal conductivity. For a PCB it can be calculated with the Thermal Conductivity for PCBs applet

Density
Is the density for the plate. For a PCB it can be calculated with the Thermal Conductivity for PCBs applet

Specific heat
Is the specific heat for the plate. For a PCB it can be calculated with the Thermal Conductivity for PCBs applet

Coefficient
Is the heat transfer coefficient fro the plate. It can be calculated with the Heat Transfer Coefficient for Parallel Plates applet.

Air temp inc
Is the air temperature rise at exit for maximum heat load. At calculation it varies proportionally to the heat load. It is automatically limited upwards to 80% of the inlet temperature difference if the plate had been isothermal.

(max dT)/(static dT)
Is the ratio of the temperature differences for the current and static case below the marker. 100% signifies no difference, 50% signifies a compleat damping of the dynamic heat dissipation component.

Air temp inc
Is the temperature increase of the air when passing the plate. It has a tendency to distort the curves. A first approach value of 0 is therefore recommended.

Outputs

Diagram
If checked, a diagram shows the temperature transient below the red marker. The X-axis spans over the largest period specified for a heat source.

Tconst
Is the thermal time constant for a heat source. Clicking on a heat source activates it. It is not defined for the marker.

Editing

Edit mode/Result mode
Toggles between edit and result mode. All kinds of changes can be made in both modes.

3-D mode/2-D mode
Toggles between the 2-D and the 3-D mode.

Save last/Delete last
Saves or deletes the last curve in the diagram. Maximum capacity is 5 curves.

Save/read data
Opens a panel that allows the user to save and read input data.

Note

Clicking in the diagram opens a panel with tabled results that can be copied and pasted into a spread sheet.

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