WOLFRAM|DEMONSTRATIONS PROJECT

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Out[]=
​
plot to display
U value (
U
3
)
efficiency (ϵ)
flow rate (u)
surface heating (
U
1
, W/
2
m
K
1
2
3
4
conduction losses (
U
3
, W/
2
m
K
0.1
0.2
0.3
0.4
thermal conductivity (k, W/mK)
0.1
0.2
0.3
0.4
design pressure (ΔP, Pa)
2
4
6
8
color
U
1
= 2
U
1
= constant
U
0
= k/L
H/L = 2
option
​
ϕ (%)
0.243
L, H, D (cm)
{23.1,22.,1.3}
H/L
0.96
ϵ, NTU
{0.91,2.31}
U
0
,
U
1
{0.87,2}
U
2
,
U
3
{1.8,0.2}
u l/s/
2
m
​
10.6
Building envelopes designed to insulate are made of several material layers. This Demonstration shows how to optimize the size and spacing of air channels in a solid timber panel, so it works as a heat exchanger—a dynamic insulation. The incoming air is preheated by energy that would otherwise be lost to the exterior by conduction. Choose the rate of interior surface heating (
U
1
), the target conduction losses (
U
3
), the thermal conductivity of the material (
k
) and the design pressure (
ΔP
) provided by a fan or by thermal buoyancy (the stack effect). The Demonstration then gives the optimized geometry of the panel (
L,H,D,ϕ
), the heat-exchange efficiency (
ϵ,NTU
) and the ventilation flow rate (
u
).