Development of nanofluid based horizontal heat storage unit / Saman Paria

Saman , Paria (2016) Development of nanofluid based horizontal heat storage unit / Saman Paria. PhD thesis, University of Malaya.

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      Nanofluids are well suited to heat transfer and there are prospective applications in solar energy recovery. A number of studies on the performance of nanofluids in heat transfer have been conducted including their effect on the rearrangement of flow passage configurations. Use of Phase Change Material (PCM) as thermal energy storage (TES) unit is critical to solve the mismatch between energy supply and demand as well as to improve the efficient application of solar energy. The significant limitation in the tube-in-shell PCM storage is the volumetric expansion/shrinkage of PCM during charging and discharging process. Therefore, the PCM is not completely filled to the brim of the cavities. The principal objectives of the present study are to deal with the energy storage (melting or charging) and energy removal (solidification or discharging) processes by using Paraffin wax as a PCM in an unique horizontal shell and tube heat exchanger with 0, 24 and 48 radial fins in the laminar flow regime. The main source of irreversibility was through entropy generation from the phase change heat transfer, although the viscous dissipation was incorporated. The previous researchers have reported that the container must be filled up to 75% to 80% of its capacity. It is well known that the heat transfer equations for the heat exchangers is defined by the symmetric model. Thus, the PCM behavior is not controllable around the finned tube and it cannot follow the symmetric pattern. The motivation of this study was to design and construct a novel unit storage system with a hollow container around the horizontal cylindrical tube containing the PCM as the storage material. The effects of nanoparticle concentration were examined for various nano fluids, inlet temperature of heat transfer fluid (HTF), different HTF flow rates and the external fin surface areas to improve the heat transfer between the paraffin and HTF. The results indicate that the HTF flow rate has more influence on the paraffin charging process than at the discharging process. The charging time was reduced by varying the HTF flow rate and the fin density, 58% and 76% respectively. For design A, it can be found that the impact of increasing the fins in melting is 20% more than the solidification. In case of different designs (A and B) the effect of enhancement of the flow rate on melting is approximately 1.5 times more than that of the solidification. It has been observed that the impact of 10°C change at the inlet temperature on the melting process reduces the processing time around 50% than at the same temperature variation in the solidification process. Nano fluids have the minimum impact on the solidification process compared to that on the melting process. Use of nanofluids has reduced the melting time 3 to 5 times more compared to the reduction in solidification time. Incorporation of more fins could meltmore mass and shorten the melting completion time. In melting process, the fin effect is about 30% stronger than the alteration effect of Reynolds number.

      Item Type: Thesis (PhD)
      Additional Information: Thesis (PhD) - Faculty of Engineering, University of Malaya, 2016.
      Uncontrolled Keywords: Nanofluid; Heat transfer; Thermal energy storage (TES); Temperature; Reynolds number
      Subjects: T Technology > TJ Mechanical engineering and machinery
      Divisions: Faculty of Engineering
      Depositing User: Mr Mohd Safri Tahir
      Date Deposited: 20 Jun 2019 07:13
      Last Modified: 20 Jun 2019 07:13

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