Wall#

The Wall block simulates the process of heat transfer through a wall of flat or cylindrical geometry.

The wall is divided into n parts (see Fig. 1 and Fig. 2) in accordance with the specified block property, each part of the division has a mass and its own thermophysical properties.

The maximum amount of parts is 100.

Scheme of dividing wall into segments — Fig. 1 Wall segmentation diagram#

Fig. 2 - Wall divided into 3 segments and equivalent model from Heat exchange library blocks#

Heat flow in wall

Heat flow in flat wall (1):

(1)#\[Q=\frac{k \cdot F \cdot (T_1-T_2)}{b}\]

where:

k - material thermal conductivity factor;

F - heat exchange surface area;

b - wall thickness;

\(T_1\) - temperature of the previous design point;

\(T_2\) - temperature of the next design point.

Heat flow in cylindrical wall (2):

(2)#\[Q=\frac{2\cdot П \cdot k \cdot L \cdot (T_1-T_2)}{ln(\frac{d_н}{d_{вн}})}\]

where:

L - pipe length;

\(d_{out}\) - outer diameter of the pipe;

\(d_{in}\) - internal diameter of the pipe.

Segment temperatures

Segment temperatures are calculated according to the following equation (3):

(3)#\[Q=c\cdot m \cdot \frac{dT}{dt} \]

where:

Q - heat flux;

c - specific heat capacity;

m - weight;

T - segment temperature;

t - time.

Thermophysical properties

The material properties (heat capacity, thermal conductivity) for each cell can be set constant, or determined depending on the temperature.

Specific heat capacity

Constant - the constant specific heat capacity set by the user in the “Specific heat capacity” field is used

Table of values - the specific heat capacity obtained based on a linear dependence built from the values entered by the user in “Specific heat capacity curve” and “Temperature curve” fields is used.

Material - the heat capacity is used according to the selected material in the associated block Materials properties.

Thermal conductivity

Constant - the user-defined thermal conductivity is used in “Thermal conductivity” field.

Table of values - the thermal conductivity obtained based on linear dependence built from the values entered by the user in “Thermal conductivity curve” and “Temperature curve” fields is used.

Material - the thermal conductivity according to the selected material in the associated block Materials Properties is used.

When calculating thermal conductivity, the average temperature is used:

For a flat wall (4) :

(4)#\[T_{ср}= \frac{T_1+T_2}{2}\]

For a cylindrical wall (5) :

(5)#\[T_{ср}= (T_1-T_2) \cdot (\frac{d_н}{d_н-d_{вн}}-\frac{1}{ln(\frac{d_н}{d_{вн}})})+T_2\]

1. Properties#

Property	Default value	Description	Units of measurement
Number of parts	2	–	–
Mass	10.0	–	kg
Initial temperature	20.0	–	°С
Wall geometry type: Plane; Cylindrical	Plane	–	–
Surface area, available when selecting `Wall geometry type` - `Plane`	10.0	–	m\(^2\)
Wall thickness, available when selecting `Wall geometry type` - `Plane`	0.02	–	m
Inner diameter, available when selecting `Wall geometry type` - `Cylindrical`	0.02	–	m
Outer diameter, available when selecting `Wall geometry type` - `Cylindrical`	0.05	–	m
Length, available when selecting `Wall geometry type` - `Cylindrical`	10.0	–	m
Conductivity type: Constant; Table of values; Material	Constant	–	–
Thermal conductivity, available when selecting `Conductivity type` - `Constant`	1.7	–	W/(m \(\cdot\) К)
Thermal conductivity curve, available when selecting `Conductivity type` - `Table of values`	401.9;391.5;385.4;376.9;	–	W/(m \(\cdot\) К)
Temperature curve, available when selecting `Conductivity type` - `Table of values`	26.85;126.85;226.85;326.85;	–	°С
Specific heat type: Constant; Table of values; Material	Constant	–	-
Specific heat capacity, available when selecting `Specific heat type` - `Constant`	840.0	–	J/(kg \(\cdot\) К)
Specific heat capacity curve, available when selecting `Specific heat type` - `Table of values`	903.7; 951.3; 991.8; 1036.7	–	J/(kg \(\cdot\) К)
Temperature curve, available when selecting `Specific heat type` - `Table of values`	26.85; 126.85; 226.85; 326.85	–	°С
Material property, available when selecting `Specific heat type` - `Material`	–	–	–

2. Inputs and outputs#

Parameters	Input/output	Description	Units of measurement	Port type
Input	Input	-	-	HeatExchange
Output	Output	-	-	HeatExchange

In order to see the connection capabilities of the block, you need to go to page Description of block ports