Conference, Proceedings

6.E-04
4.E-04
ΔU (V)
2.E-04
0.E+00
step up
step down
pulse
0 1000 2000 3000 4000
t (s)
9.E-05
6.E-05
ΔU (V)
3.E-05
0.E+00
1.E-05
1.E-06
ΔU (V)
1.E-07
1.E-08
step up
step down
pulse
0 1000 2000 3000 4000
t (s)
Figure 3: Dependence of thermocouple voltage on the time for stepwise (up, down) and pulse transient
method in linear (left) and semi‐logarithmic scale (after stepwise responses derivation). As the heat source
was used photovoltaic cell.
The linearity of this dependence is more evident from the thermal response derivation (Figure
4). The diffusivity a = 2.25 ∙ 10 –7 m2 .s –1 was calculated for parameter R = 0.03 m (heat source
2
−3
−1
diameter) and for derivation value of 4a
R ≈1⋅10
s . This value correlates with the diffusivity
values that were calculated from the thermal response maxima determined by a standard
calculation (see Table I)
ΔT (K)
10
1
0.1
0 500 1000 1500 2000 2500
t (s)
0.010
0.008
0.006
0.004
0.002
0.000
-0.002
-0.004
Figure 4: Dependence of thermal response on the time for pulse transient method in semi‐logarithmic
2
scale and their derivation (right axis). Infinite limited value is proportional to 4a / R .
Table 1: Thermal parameters PMMA measured with different heat sources and different pulse types
a (m 2 .s –1 ) cp (J.kg –1 .K –1 ) λ (W.m –1 .K –1 ) ρ (kg.m –3 )
heat source: rectangle pulse 1.12 ∙ 10 –7 1.45 ∙ 10 3 1.93 ∙ 10 –1 1.18 ∙ 10 3
photovoltaic cell: rectangle pulse 1.66 ∙ 10 –7 0.81 ∙ 10 3 1.58 ∙ 10 –1 1.18 ∙ 10 3
photovoltaic cell: step up 1.39 ∙ 10 –7 2.23 ∙ 10 3 3.68 ∙ 10 –1 1.18 ∙ 10 3
photovoltaic cell: step down 2.90 ∙ 10 –7 8.69 ∙ 10 2 2.98 ∙ 10 –1 1.18 ∙ 10 3
1.E-03
1.E-04
1.E-05
1.E-06
205