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dc.contributor.advisorMawire, A.
dc.contributor.advisorShabo, A.B.
dc.contributor.authorLefenya, Tlotlo Marvel
dc.date.accessioned2021-12-09T10:06:53Z
dc.date.available2021-12-09T10:06:53Z
dc.date.issued2021
dc.identifier.urihttps://orcid.org/0000-0002-5176-5092
dc.identifier.urihttp://hdl.handle.net/10394/38204
dc.descriptionMSc (Physics), North-West University, Mafikeng Campusen_US
dc.description.abstractA packed bed latent heat storage system consisting of aluminium encapsulated eutectic solder (Sn63Pb37) capsules is experimentally evaluated during charging and discharging cycles. Sunflower Oil is used as the heat transfer fluid in the experiments. The effect of the flowrate on the charging performance is evaluated using three charging flowrates namely; 4 ml/s (low), 6 ml/s (medium) and 8 ml/s (high). The storage system is also evaluated with three different set heater charging temperatures (260 oC (low), 280 oC (medium) and 300 oC (high)). Discharging experiments are performed with the three different flowrates to evaluate the effect of the flowrate on the discharging characteristics. Charging and discharging results are presented in terms of the axial storage tank profiles, the energy rates and the exergy rates. The overall performance of the storage system is evaluated in terms of the energy and exergy storage efficiencies. The charging energy and exergy rates are seen to increase with the charging flowrate at the expense of a greater charging duration since higher flowrates tend to cool down the heater. The best charging flowrate of 6 ml/s is suggested which ensures a reasonable duration of charging, reasonable thermal stratification and reasonably high energy and exergy charging rates. The effect of the set heater temperature on the charging energy and exergy rates is insignificant as compared to the effect of the flowrate. The best set charging temperature of 280 oC is also suggested by the experimental tests. Increasing the flowrate results in faster heat transfer with higher peak energy and exergy rates during discharging. However, the stored energy and exergy is utilized for a shorter duration as compared to the lowest flowrate. Energy and exergy storage efficiencies decrease with an increase in the flowrate and the highest flowrate shows the lowest values due to the longer charging duration and the shorter discharging duration. The set heater charging temperature shows only a marginal effect on the energy and exergy storage efficiencies. A comparison of the energy and exergy rates of the solder during charging and discharging with adipic acid shows slightly better performance during charging cycles for adipic acid. For discharging cycles, the solder shows a better performance. After evaluating the performance of the eutectic solder packed bed system, its thermal performance is compared to two other packed bed latent heat medium temperature thermal energy (TES) storage systems during charging and discharging cycles at low flowrate (4 ml/s), medium flowrate (6 ml/s) and high flowrate (8 ml/s). The two phase change materials (PCMs) used in the storage systems are adipic acid and erythritol. The performances of these TES systems are evaluated in terms of the temperature profiles, total energy, total exergy, useful energy and useful exergy, during charging and discharging. Erythritol did not undergo phase transition during discharging at all the flowrates due to supercooling. The erythritol TES system shows the greatest efficiencies with regards to all the performance parameters considered with an overall energy efficiency of about 39.1 %. The efficiencies of all the TES systems generally decrease with an increase in the HTF flowrate. Though the eutectic solder TES stored and discharged greater quantities of energy at all the flowrates, its performance was hampered by the low degree of thermal stratification in its tank thus leading to long charging and discharging times. At the highest flowrate, the adipic acid TES possessed higher efficiencies that the eutectic solder TES in terms of useful energy and useful exergy. Erythritol charges up for the shortest duration, followed by adipic acid and lastly by the eutectic solder as a result of the combined effect of a lower thermal mass induced by a lower melting temperature and increased convective heat transfer. Erythritol shows a superior performance in terms of the charging energy and exergy rates since it shows higher values due to its lower melting point which induces more convective heat transfer and a greater degree of thermal stratification.en_US
dc.language.isoenen_US
dc.publisherNorth-West University (South Africa)en_US
dc.subjectAdipic aciden_US
dc.subjectErythritolen_US
dc.subjectEutectic solderen_US
dc.subjectPacked bed latent heat storage systemen_US
dc.subjectThermal performanceen_US
dc.titlePerformance comparison of packed bed latent heat storage systems for medium temperature applicationsen_US
dc.typeThesisen_US
dc.description.thesistypeMastersen_US
dc.contributor.researchID18027938 - Mawire, Ashmore (Supervisor)


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