# Passive Thermal Management of Tablet PCs Using Phase Change Materials: Intermittent Operation
## 2 Experimental Setup
### Sources of Uncertainties  
The uncertainties of the type-T thermocouples are \(\pm\)0.5 \({}^{\circ}\)C. The uncertainties of the power measurement were up to \(\pm\)8% due mostly to the voltage supply uncertainty of up to \(\pm\)4%. The uncertainty in supplied voltage was measure by taking multiple reading from a multi-meter for a given set position of the dial in the variac. Then the uncertainty in power was calculated from the power-voltage relationship (Equation (1)) provided by the heater manufacturer:  
\[q^{\prime\prime}=\frac{P_{R}V^{2}}{V_{R}^{2}} \tag{1}\]  
where rated power density (\(P_{R}\)) and voltage (\(V_{R}\)) for current heater are 10 W/in\({}^{2}\) and 28 VAC, respectively. Maximum uncertainties in the supplied power and supplied voltage for different power  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Encapsulation** & **Base Area** & **Average Thickness** & **Amount of PCM, \(m_{\text{ppm}}\)** & **Total Latent Heat (k)** & \(m_{\text{ppm}}\times\Delta_{\text{fsfs}}H\) \\ \hline Size 1 & \(6^{\prime}\times 2.6^{\prime}\) (152.4 \(\times\) 66 mm\({}^{3}\)) & \(1/16^{\prime}\) (2 mm) & 16 g & 3.82 & 3.25 \\ Size 2 & \(7^{\prime}\times 1.5^{\prime\prime}\) (177.8 \(\times\) 38 mm\({}^{2}\)) & \(1/16^{\prime}\) (2 mm) & 11 g & 2.63 & 2.27 \\ Size 3 & \(7^{\prime}\times 34^{\prime\prime}\) (177.8 \(\times\) 6 mm\({}^{2}\)) & \(1/16^{\prime}\) (2 mm) & 25 g & 6.00 & 5.15 \\ Thickness 1 & \(2^{\prime}\times 2^{\prime}\) (51 \(\times\) 5 mm\({}^{2}\)) & 0.13” (3 mm) & 6 g & 1.42 & 1.23 \\ Thickness 2 & \(2^{\prime}\times 2^{\prime}\) (51 \(\times\) 51 mm\({}^{2}\)) & 0.16” (4 mm) & 8 g & 1.89 & 1.64 \\ Thickness 3 & \(2^{\prime}\times 2^{\prime}\) (51 \(\times\) 51 mm\({}^{2}\)) & 0.20” (5 mm) & 10 g & 2.36 & 2.05 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Summary of dimensional attributes of encapsulations, amount of PCMs, and latent heat used.  
\begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Observations** & **PCMs** & \multicolumn{2}{c}{**Size of TES Unit**} & **Inclination** & **Power Input** & **Operation Mode** \\ \hline \multirow{4}{*}{Melting-Solidification of PCMs} & \multirow{4}{*}{\(n\)-eicosane PT-37} & Size 1 (16 g) & 0\({}^{\circ}\) (horizontal) & 4 W & 3 cycles of: \\  & & & & 6 W & Charging—15 min. \\  & & Size 2 (11 g) & 45\({}^{\circ}\) & 6 W & Discharging—15 min. \\  & & Size 2 (11 g) & 90\({}^{\circ}\) (vertical) & 8 W & \\ \hline \multirow{4}{*}{Performance of the Table PC} & \multirow{4}{*}{\(n\)-eicosane PT-37} & Size 1 (16 g) & 0\({}^{\circ}\) (horizontal) & 2 W & \\  & & Size 2 (11g) & 45\({}^{\circ}\) & 2 W & 3 cycles of: \\ \cline{1-1} \cline{2-5}  & & Size 3 (25 g) & 45\({}^{\circ}\) & 4 W & Charging—15 min. \\ \cline{1-1} \cline{2-5}  & & 2\({}^{\circ}\times\) \(2^{\prime}\times\) 0.12” (6 g) & 6 W & \\ \cline{1-1}  & & 2\({}^{\circ}\times\) \(2^{\prime}\times\) 0.16” (8 g) & 90\({}^{\circ}\) (vertical) & 8 W & \\ \cline{1-1} \cline{2-5}  & & 2\({}^{\circ}\times\) \(2^{\prime}\times\) 0.20” (10 g) & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary of experiments done in the intermittent operation.  
input levels can be seen in Table 4. The inconsistency in voltage supply mainly occurred due to the voltage drop of the variac caused by other lab equipment using the same power line; those uncertainties are still low and did not influence repeatability of the experiments, as demonstrated in the first half of this study [15].