## 5 Conclusions  
An experimental platform was used to investigate the integration of solid-liquid LHTES modules into the temperature control system of modern and future handheld electronics. A mock tablet was used to record the temperature history in various positions in the device during experiments utilizing different temperature control solutions.  
The temperature history with an aluminum spreader was compared with that of an aluminum spreader with an \(n\)-eicosane-based LHTES module. It was first shown that thermal contact resistances are important in such a device, and that the use of TIM between the heater and the thermal spreader played a very important role in the heat transfer within the device. With the TIM and the spreader, it was shown that the LHTES module had a significant impact on the thermal response of the handheld device, reducing the mean and peak temperature of the device's components and increasing the time it can operate without reaching a threshold temperature on the surface (40 \({}^{\circ}\)C) or the components (80 \({}^{\circ}\)C). Without the LHTES module (with a heat rate of 7 W), the front surface (display)  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**4.5 W**} & \multicolumn{2}{c}{**7 W**} \\ \hline
**Temperature Control** & **Time to Overheat** & **Location of T Limit** & **Time to Overheat** & **Location of T Limit** \\
**Solution** & **(min)** & **Reached** & **(min)** & **Reached** \\ \hline none & 2.6 & \(T_{in\text{-}1}\) & 0.5 & \(T_{in\text{-}1}\) \\ heat spreader & 5.3 & \(T_{in\text{-}1}\) & 0.8 & \(T_{in\text{-}1}\) \\ heat spreader and TIM & - & n/a & 14.7 & \(T_{\text{F-}1}\) \\ LHTES and spreader & 15.3 & \(T_{in\text{-}1}\) & 0.8 & \(T_{in\text{-}1}\) \\ LHTES, spreader, and TIM & - & n/a & 19.2 & \(T_{\text{F-}1}\) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary of time required for the mock tablet to reach the respective temperature limits with a heat generation rate of 4.5 and 7 W.  
temperature reached the comfort limit after 14.7 min. After the addition of the LHTES module, the front surface reached the comfort limit after 19.2 min, and thus the LHTES module increased the safe operating time by approximately 30%.  
These findings are promising for the use of LHTES modules to enhance the performance of modern portable electronics, but the results are not transferable to all situations. Based on the present results, for lower power situations (4.5 W), the heat spreader and TIM are sufficient, and the impact of the LHTES module was limited to lowering the mean and peak temperature of the tablet components, which is still important in maximizing the lifetime of the electronic components. Additionally, LHTES modules require PCMs selected and optimized for the circumstances. At higher heat generation rates, the thermal storage in the LHTES modules used in this work would become insufficient. Further gains could potentially be made if the LHTES module could be made thicker. However, improving heat spreading to transport heat to all corners of the LHTES module is the most promising direction for further improvements.  
Conceptualization, D.G., M.A.W.; methodology, B.S.; formal analysis, B.S.; investigation, B.S.; writing--original draft preparation, B.S.; writing--review and editing, D.G., M.A.W.; supervision, D.G.; project administration, D.G.; funding acquisition, D.G., M.A.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Intel Corporation, grant number CG#9388323.  
The authors thank Intel Corporation for the financial and technical support that made this work possible, along with the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) for further laboratory financial assistance.  
The authors declare no conflict of interest.