Chapter 3.3: Thermal Energy Storage Subsystem
Semester 1 TES can be accessed here
The TES subsystem is designed to achieve several key goals, including maximizing heat retention, increasing the amount of thermal energy stored, and attaining the highest possible operating temperature within the system.
This part of the study examines the TES box specifications, evaluates its heat-retention performance.
3.3.1 Proposed work from last semester
For TES development, we propose this design
Our new design is as below
3.3.2 TES specification and settings
3.3.2.1 TES specifications
The TES specification is the following:the Al plates used further work as a mesh that help the heat to be distributed evenly under low flow rate with holes that allow water to distribute
3.3.3. Experiments and Results
3.3.3.1. Experiment 1
Purpose: To assess the temperature uniformity and heat-retention performance of the TES with 12 paraffin-filled pipes and 5 L of water.
Method: The TES was filled with 12 paraffin-filled copper pipes and 5 L of water. After charging, the temperatures of water, PCM, TES air, and ambient air were recorded over time.
Hypothesis: The TES is expected to show small temperature differences between PCM and water, indicating uniform internal temperature and effective heat transfer. It is also expected to retain useful heat for about 6 hours, with the water temperature taking around 10 hours to cool from 55 °C to 40 °C.
Results: PCM and water temperatures remained close throughout the test, showing good temperature uniformity. The TES retained useful heat for about 6 hours, and the cooling trend suggests around 10 hours for water to drop from 55 °C to 40 °C.
Discussion: The close PCM and water temperatures indicate effective heat exchange and sufficient heat distribution within the TES. The gradual cooling trend also shows that the system can retain heat for an extended period.
Limitation: The result only reflects one TES setup under specific conditions. Ambient variation, heat loss, and measurement uncertainty may affect the cooling trend.
Conclusion: The TES showed uniform internal temperature and good heat-retention performance, indicating effective thermal storage.
3.3.3.2. Experiment 2
Objective: To compare the heat-retention performance of the TES with 12 pipes and 24 pipes based on the cooling time from 60 °C to 50 °C.
Method: The cooling profiles of the TES with 12 pipes and 24 pipes were compared using the recorded temperature graphs. The time taken for the water temperature to decrease from 60 °C to 50 °C was used as the main indicator of heat-retention performance.
Hypothesis: The TES with 24 pipes is expected to retain heat longer than the 12-pipe configuration, resulting in a longer cooling time from 60 °C to 50 °C.
Results: From the graphs, the 12-pipe TES took about 5.5 hours to cool from 60 °C to 50 °C, while the 24-pipe TES took about 9 hours. This shows that the 24-pipe configuration had a significantly longer heat-retention time.
Discussion: The longer cooling time of the 24-pipe TES suggests that increasing the number of PCM pipes improved the storage capacity and slowed down heat loss. This indicates better heat-retention performance compared with the 12-pipe TES.
Limitation: The comparison is based on graph estimation and may be affected by different initial conditions, ambient temperature, and measurement uncertainty.
Conclusion: The 24-pipe TES showed better heat-retention performance than the 12-pipe TES, as it required a longer time to cool from 60 °C to 50 °C.
3.3.4. Future Improvement
One improvement is to change the PCM material to a higher melting boil if the operating temperature is higher