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http://hdl.handle.net/11375/22814
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DC Field | Value | Language |
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dc.contributor.advisor | Lightstone, M. F. | - |
dc.contributor.advisor | Cotton, J. S. | - |
dc.contributor.author | Teamah, Hebatallah | - |
dc.date.accessioned | 2018-05-03T17:24:02Z | - |
dc.date.available | 2018-05-03T17:24:02Z | - |
dc.date.issued | 2018 | - |
dc.identifier.uri | http://hdl.handle.net/11375/22814 | - |
dc.description.abstract | Novel multi-tank thermal energy storage (TES) containing water and phase change materials (PCMs) was evaluated numerically. The multi-tank storage is based on the interconnection of small volume hot water storage tanks in series configuration. Water enters and exits the system directly and is used as the heat transfer fluid (HTF). PCMs are incorporated in the water tanks to investigate their latent energy storage capability. They are cascaded in a descending order of their melt temperatures to match the operating range of the system. The system was tested for the typical Canadian weather data and demand profiles. An in-house FORTRAN code was developed to solve the problem computationally. PCMs are placed in vertical cylinders and water flows along them within the tank shell. This is referred to as a hybrid system hereafter. Both component and system level analysis are presented in detail in the thesis. The developed mechanistic model was thoroughly validated and verified with published data with a very good agreement (<5% deviation). The main goal of the current work is to assess the dynamic performance of the proposed system when linked with the solar collector in the Solar Domestic Hot Water system (SDHW) context. Possible storage volume reduction relative to a water only system for the same benefit to the household is the primary objective. Component level analysis was conducted to understand the behavior of the hybrid system under isothermal charging conditions. It aided in the choice of key parameters when the entire system was modeled. The analysis shows that in narrow temperature operating ranges (around 10oC); the energy density of the hybrid system can be significantly increased to around five times relative to a system containing water only. This is attributed to the latent energy stored during the phase change. The main hindering factor is the low thermal conductivity of the PCM, which can be overcome by encapsulating the materail in small diameter cylinders and thus decrease the imposed thermal resistance on the system. On the system level, a hybrid single tank model was linked with the collector performance and the system was tested for typical days of Canadian weather with different demand profiles. The solar fraction of the hybrid system was compared to that of an identical system using water-only as the thermal storage medium. Solar fraction is the amount of energy delivered by the solar system relative to the total energy required by the load. The systems approach is critical since it allows for the coupled effects of SDHW components to be incorporated. The analysis clearly shows that incorporation of PCMs into the thermal storage results in enhanced solar fraction at small tank volumes (around 200 liters). In contrast, as the tank volume is increased, the benefit of the PCMs diminishes. An energy balance of the system reveals that, the benefits of the PCMs in small storage volumes are due to the reduction in the collector fluid inlet temperature which increases the pump run time and thus the solar energy collected. This conclusion presented a clarification for the mixed results from the literature concerned with the incorporation of PCMs in hot water tanks. Using the key parameters of the system level analysis for the single tank, the analysis was extended to the multi-tank system. The multi-tanks contain PCMs cascaded in a descending order of their melt temperature from the source to the load. The PCM was found to tune the bulk of the tank temperature around its melting temperature. This aided in having better sequential stratification between the tanks. Cooler water returning to collector relative to the single PCM case was maintained. Decreased collector losses and extended the pump activation time were obtained relative to the single PCM case. This resulted in an increase in the time period on the system was able to meet the load demand of hot water and hence augmented solar fraction. It was found that for a multi-residential building of three families, a 630 liter tank containing water only gives the same solar fraction provided by three cascaded 100 liters tank containing 50% PCMs by volume. The melting points of PCMs are (42oC, 32oC and 16oC) respectively. This guarantees more than 50% reduction in volume for the same benefit in the household side. | en_US |
dc.language.iso | en | en_US |
dc.title | Multi-tank hybrid energy storage using water and phase change materials in a direct system | en_US |
dc.type | Thesis | en_US |
dc.contributor.department | Mechanical Engineering | en_US |
dc.description.degreetype | Thesis | en_US |
dc.description.degree | Candidate in Philosophy | en_US |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Teamah-Hebatallah-final submission 201711-PhD.pdf | 3.81 MB | Adobe PDF | View/Open |
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