Chemical Engineeringhttp://repository.dkut.ac.ke:8080/xmlui/handle/123456789/46732024-03-28T11:38:36Z2024-03-28T11:38:36ZDual-Pump Vibrational Coherent Anti-Stokes Raman Scattering System Developed for Simultaneous Temperature and Relative Nitrogen–Water Vapor Concentration MeasurementsToo, AmonSidiropoulos, EvaggelosHolz, YannikKaruri, Nancy WangechiSeeger, Thomashttp://repository.dkut.ac.ke:8080/xmlui/handle/123456789/83622024-01-26T07:11:47Z2023-12-01T00:00:00ZDual-Pump Vibrational Coherent Anti-Stokes Raman Scattering System Developed for Simultaneous Temperature and Relative Nitrogen–Water Vapor Concentration Measurements
Too, Amon; Sidiropoulos, Evaggelos; Holz, Yannik; Karuri, Nancy Wangechi; Seeger, Thomas
Simultaneous gas phase temperature and water vapor concentration measurement are important to understand reacting flows such as combustion or gas reforming processes. Here, coherent anti-Stokes Raman scattering (CARS) offers the possibility for non-intrusive measurements with a high temporal and spatial resolution. Therefore, this work demonstrates the simultaneous measurement of temperature and relative water vapor–nitrogen concentrations by using dual-pump vibrational coherent anti-Stokes Raman scattering (DPVCARS). A calibration procedure is developed for a temperature range of 473 K to 673 K and a water vapor concentration of 24% to 46% at ambient pressure. This setup is tested with 500 CARS single pulse spectra taken in a gas cell at a known temperature and concentration. Based on these results, information about precision and accuracy can be delivered.
2023-12-01T00:00:00ZReviewing Perovskite Oxide-Based Materials for the Effective Treatment of Antibiotic-Polluted Environments: Challenges, Trends, and New InsightsAfonso Henrique da Silva JúniorCarlos Rafael Silva de OliveiraTarcisio Wolff LealLeandro PellenzSelene Maria de Arruda Guelli Ulson de SouzaAntônio Augusto Ulson de SouzaAntónio Benjamim MapossaRobert Kimutai TewoHilary Limo RuttoLuciano da SilvaAdriano da Silvahttp://repository.dkut.ac.ke:8080/xmlui/handle/123456789/83382024-01-25T07:04:29Z2023-12-01T00:00:00ZReviewing Perovskite Oxide-Based Materials for the Effective Treatment of Antibiotic-Polluted Environments: Challenges, Trends, and New Insights
Afonso Henrique da Silva Júnior; Carlos Rafael Silva de Oliveira; Tarcisio Wolff Leal; Leandro Pellenz; Selene Maria de Arruda Guelli Ulson de Souza; Antônio Augusto Ulson de Souza; António Benjamim Mapossa; Robert Kimutai Tewo; Hilary Limo Rutto; Luciano da Silva; Adriano da Silva
Society confronts the pressing environmental challenges posed by the pervasive presence of toxic pollutants in aquatic ecosystems. The repercussions of contaminant release extend far and wide, endangering marine life and human well-being. While various techniques such as bioremediation, filtration, and adsorption have been employed for wastewater treatment, they grapple with cost effectiveness and overall efficiency issues. Advanced oxidative processes, including photocatalysis and Fenton, have emerged as viable solutions in response to the emerging contaminants. However, the efficacy of photocatalysis largely hinges on the choice of catalyst. Their distinctive attributes, such as chemical defects and exceptional stability, make perovskite oxides a promising catalyst. These materials can be synthesized through diverse methods, rendering them versatile and adaptable for widespread applications. Ongoing research endeavors are diligently focused on enhancing the performance of perovskite oxides, optimizing their integration into catalytic processes, and exploring innovative approaches for material immobilization. This comprehensive review seeks to elucidate the most pivotal advances in perovskite oxides and their composites within the wastewater treatment domain. Additionally, it sheds light on burgeoning research trends and multifaceted challenges confronting this field, which present insights into techniques for treating the antibiotic-contaminated environment, delving into innovative strategies, green technologies, challenges, and emerging trends.
2023-12-01T00:00:00ZComputational modeling of spatial variation in moisture content and temperature distribution in corn at different superheated steam temperaturesKimwa, Mercy JepchirchirKaruri, NancyTanui, Josephathttp://repository.dkut.ac.ke:8080/xmlui/handle/123456789/79902023-05-30T15:47:51Z2023-05-01T00:00:00ZComputational modeling of spatial variation in moisture content and temperature distribution in corn at different superheated steam temperatures
Kimwa, Mercy Jepchirchir; Karuri, Nancy; Tanui, Josephat
The Superheated steam has been shown to be more effective than hot air
for drying corn. Modeling studies have been carried out in fluidized bed dryers to
determine the moisture and heat transfer characteristics of corn, but there are no
modeling studies for a single corn kernel. Knowledge of heat and mass transfer
characteristics in a single kernel would produce a better understanding of steam
characteristics needed for specific drying rates. The study sought to determine the
influence of steam temperature and velocity on the drying rate of a corn kernel. It
used computational fluid dynamics (CFD) to model the transfer of heat and moisture between the corn kernel and superheated steam. The simulation used cone
geometry to represent the corn kernel. The kernel had characteristic dimensions
and 20% initial moisture content. The condition of the steam, which was typical of
that found in industry, had temperatures of 120–200°C and velocities of 0.5–1.5 m/s.
There was a decrease in the duration of the initial condensation phase as the
temperature of superheated steam increased from 120°C to 200°C. The highest
steam temperature and velocity resulted in the shortest duration for steam condensation. Contrary to what has been reported, there was no moisture loss from the
corn kernel when exposed to superheated steam at 120°C, which may be due to
how heat was retained in the drying chamber. Thus, the processes of tapping steam
and retaining heat are important elements in the operation of industrial steam
driers.
2023-05-01T00:00:00ZThermal, mechanical and rheology of EVA/wax and wax/LLDPE blends as a carrier vehicle for investment casting patternTewoa, Robert KimutaiRutto, Hilary Limohttp://repository.dkut.ac.ke:8080/xmlui/handle/123456789/79892023-05-30T15:44:10Z2023-05-01T00:00:00ZThermal, mechanical and rheology of EVA/wax and wax/LLDPE blends as a carrier vehicle for investment casting pattern
Tewoa, Robert Kimutai; Rutto, Hilary Limo
Different ratios of wax/ethylene vinyl acetate (EVA) and wax/linear low-density polyethylene (LLDPE) blends were prepared using one-step extrusion process to investigate their potential as carrier vehicles for pattern material for investment casting. The thermal, mechanical and rheological properties were characterised. Thermal analysis was done by thermogravimetric analysis (TGA) and differential scanning calorimetry. Mechanical properties were characterised by three-point bending and thermomechanical analysis, whereas the rheological properties were characterised by oscillatory rheometry. The TGA analysis showed that the incorporation of EVA or LLDPE into wax matrix improved the thermal stability properties of the blend. This can be attributed to an enhanced phase adhesion. The melting and solidification behaviour of the blends had intermediate temperatures between wax and EVA. The EVA/wax blends displayed evident viscosity shifts as compared to the viscosity of wax. The incorporation of EVA into wax significantly altered its mechanical properties. Fourier transform infrared spectrometry for both wax/EVA and wax/LLDPE showed a predominant presence of CH2 and carbonyl group in the blend, and the mechanical properties of neat wax were improved when EVA and LLDPE were incorporated into wax.
2023-05-01T00:00:00Z