# Numerical Design and Laboratory Testing of Encapsulated PCM Panels for PCM-Air Heat Exchangers
## 1 Introduction
The result shows that parallel protrusions upstream to grooves perform better \(\left(Re=5000\), \(\frac{Nu}{Nu_{o}}=1.40;\ Re=20,000,\frac{Nu}{Nu_{o}}\approx 1.44\right)\) than other cases \(\left(Re=5000\), \(\frac{Nu}{Nu_{o}}\approx 1.35;Re=20,000,\frac{Nu}{Nu_{o}}\approx 1.3\)-\(1.32\right)\) with an increase in the average Nusselt number ratio when the Reynolds number increases. [PERSON] and [PERSON] [14] experimented with four different shaped ridges: wedge pointing upstream, wedge pointing downstream, triangular and rectangular ridge staggered and in-line over a turbulent channel (\(Re=4000\)-\(16,000\)). The result shows im  
Figure 1: Section and bird-eye view of a channel showing various obstructions and their arrangement (not in scale). provements in heat transfer compared to a smooth channel where the wedge downstream in-line produced the best performance in terms of Nusselt number ratio (\(Nu/Nu_{o}\cong 4.4\)) and the rectangular (\(Nu/Nu_{o}\cong 3.7\)) was the worst. When pressure drop is taken into account, the triangular staggered channel has the best thermal performance \(\left(\eta=\left(\frac{Nu}{Nu_{o}}\right)/\left(\frac{Ap}{Ap_{o}}\right)^{1/3} \cong 1\text{-}1.1\right)\) followed by triangular in-line and staggered upstream wedge. Following from the previous study, [PERSON] et al. [15] experimentally studied different heights of triangular ridges staggered and in-line through a constant heat-flux channel for Reynolds number from 5000 to 22,000. The result shows an increase of approximately 1.8-4 in terms of Nusselt number when compared to a smooth channel, and a variation of thermal performance up to 1.3. The studies presented above confirm that the inclusion of ridges over a channel is an efficient solution to enhance the heat transfer. They also suggest that rounded ridges are preferred due to a smaller increase in pressure drop when compared to other ridges; they also incur lower cost of production. To evaluate, validate and also understand the impact of simplifications made during the numerical simulation process, laboratory tests are imperative. The experiments commonly used by researchers to evaluate heat transfer due to heat transfer augmentation use thermocouples [14; 16; 17], infrared cameras [10; 18; 19; 20; 21] and CCD cameras with a thermochromic liquid crystal layer or a colour processing system [11; 22; 23]. The first uses thermocouples before and after the channel to evaluate the overall heat transfer with different ridges. Furthermore, thermocouples were fitted on channels surface to measure temperature distribution on the wall, ensure the steady state of the test and calculate the heat of convection. In cases that the local Nusselt number field is important, an infrared or a CCD camera allows a better understanding of the heat exchange. This was confirmed by [PERSON] et al. [10]. His infrared camera experiment and CFD simulations showed the importance of the separation and reattachment region and also shown a higher increase of heat transfer effectiveness at laminar flow rate. Most researchers focus on the improvement of heat transfer in the channel and pressure drop by the panel and literature findings have informed the shapes examined and presented in this paper. However, practical considerations such as cost of production, rigidity and ease of manufacturing would improve the uptake of the proposed design and therefore these are also considered for the final recommendation. This paper focuses on the development, fabrication and validation of a new panel design considering five key performance indicators (KPIs) (a) heat transfer, (b) pressure drop, (c) rigidity, (d) cost of production and (e) ease of manufacturing. Laboratory testing used thermocouples because the focus is on the overall performance of the panel rather than the localized effects.