Browsing by Author "Huang, Huijian"
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- ItemEvaluating a novel UV device for wastewater disinfection : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Environmental Technology and Sustainable Energy at Massey University, Manawatu Campus, Palmerston North, New Zealand(Massey University, 2014) Huang, HuijianUV disinfection is the most common method used in wastewater disinfection. However, some types of wastewater effluent have a low UV transmittance (UVT), which cannot be disinfected efficiently by a commercial UV reactor. A novel UV reactor (called the project prototype) was developed, which has a different type of reactor hydraulics than a typical commercial UV reactor. This change in hydraulics is believed to be an innovative method of improving the low UVT fluid disinfection. The main purpose of this project is to evaluate the feasibility the project prototype. The settings of the project prototype were first refined, and then compared to a control reactor, which was used to mimic a commercial UV reactor (called the commercial unit) at a range of UV doses. The UV dose was manipulated by changing the number of operated UV lamps and operated flow rate of the reactors. The disinfection performance of the reactors was not only compared at conventional wastewater treatment plants, but also at stabilization ponds. Within the conventional wastewater treatment plants, the reactors were tested using the effluent from the primary, secondary and tertiary treatment stages. In total, the reactors were compared twelve times at seven different wastewater treatment sites. The results show that the project prototype was, on average, 1.4 times worse than the commercial unit at treating tertiary wastewater, where the wastewater had a high UVT (55 to 65%). This high UVT value favours the use of the commercial unit, as it is designed for this UVT range. However, at a low UVT range, the project prototype performed, on average, 1.4 times better than the commercial unit, at treating secondary wastewater, where the wastewater had UVT of 22 to 55 %. In the stabilization pond tests, where the UVT was 11 to 25%, the project prototype performed 2.1 times better than the commercial unit on average, and up to 8 times better at one location. In the primary treatment test, where the UVT of the wastewater was extremely low (5%), the project prototype, on average, performed 4.5 times better than the commercial unit, and in one case up to 13 times better than the commercial unit. The research found that the project prototype has an advantage when treating low UVT fluid and great potential in the commercial market. The project prototype performs better than the commercial unit at stabilization ponds. This suggests that the project prototype would be a viable option for pond treated wastewater disinfection. In addition, the project prototype offers superior performance on primary treated wastewater. This indicates the potential application at marine outfalls (primary treated wastewater), and the possibility of primary wastewater disinfection for irrigation. Overall, this research confirms the feasibility of the novel reactor in wastewater disinfection.
- ItemA systematic approach for developing and manufacturing fruit simulators : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Engineering, Massey University, Palmerston North, New Zealand(Massey University, 2023) Huang, HuijianDue to the high cost, variable nature and seasonal availability of fruit, conducting large scale experiments for research purposes is not easy. A fruit simulator is a physical tool that mimics the mechanistic features and properties of the targeted fruit; hence, it can be used as a replacement for the fruit in research experiments. This study focuses on developing simulators for heat transfer experiments, especially in horticultural produce precooling. A framework for developing the simulator was established based on the importance of each mechanistic feature. Depending on the application's needs, the simulator can mimic different length scale levels of the targeted fruit, such as the individual fruit, the bulk stacking of the fruit or sub-units of the fruit (e.g., a punnet/bag of table grapes). The scale level determines whether certain mechanistic features are important and affects the values of the thermal properties that must be matched. For example, a simulator that mimics a punnet of fruit with enclosed air pockets has an effective thermal conductivity and volumetric heat capacity that includes contributions from the thermal properties of the fruit and air, which provides more room for material selection. Based on this framework, a systematic approach for the simulator manufacture and material selection was developed. Three different simulators were developed based on the framework: kiwifruit, apple and table grape simulators. The comparison of a simulator and real fruit precooling trials showed good agreement, validating the approach and demonstrating the feasibility of using simulators in postharvest research. The kiwifruit simulator was validated at different experimental scale levels, from individual kiwifruit to multiple kiwifruit boxes containing numerous individual kiwifruit simulators (which reflected pallet scale precooling). During the simulator development, the concept of a time-scaled approach was identified and was explored. In theory, if the volumetric heat capacity of a simulator becomes smaller while the Bi of the simulator remains the same, the heating/cooling time of the simulator in an experiment will decrease proportionally according to the Fourier number (Fo). This approach was validated via the three simulators developed in this study. The validation of the simulators confirms the feasibility of this time-scaled concept. This approach has a significant advantage in reducing the experimental time and easing the material selection process for the simulator manufacture. In the table grape simulator development, a process of using CT scans of the bulk packaged system to study the bulk shape and effective properties of the fruit subunits (bags) were developed, where the bulk shape and effective thermal properties of a bag of table grape were determined based on the process. A set of bag shaped fruit simulators was then manufactured with equivalent bulk thermal conductivity and used to validate the bulk simulator approach by comparison of cooling rates with real fruit. Overall, this study has successfully developed a generalised heat transfer simulator development framework. In addition, this study validated the feasibility and applicability of the time-scaling approach, which could be helpful for any future experiments. Furthermore, this study has developed a process to use CT scanning to determine a bulk object's bulk shape and effective property. The outcomes of the work pave the way for carrying out postharvest and packaging optimisation experimental trials with reduced variability, greater ease and without seasonal constraints. The simulator development framework provides a basis for further expansion of these concepts into other applications beyond the heat transfer focus that they were developed for in this work.