Journal of Advanced Research in Numerical Heat Transfer

Exploration Of Key Approaches to Enhance Evacuated Tube Solar Collector Efficiency

Yasir Al-Abayechi — 2024-05-04

This research is carried out to investigate and examine the critical benefits and significant contributions of integrating nanoparticles into the ETSC system to enhance the thermal efficiency, thermal performance, temperature out, and energy storage of the ETSC. The Simcenter STAR-CCM+ 2022.1 software package implemented numerical analysis and thermal simulations. Further, a comparative analysis is conducted on two case studies to validate the critical role and contributions of employing the aluminum oxide nanomaterial in the solar collector system to enhance its thermal efficiency and improve its thermal performance and heat transfer, including (1) conventional ETSC and (2) ETSC with Al2O3. According to the numerical analysis and comparative study findings, the results of this research revealed that employing and adding the aluminum oxide nanomaterial into the ETSC system had contributed to several beneficial impacts and significant advantages. In addition, using Al2O3 achieved enhancements in the thermal efficiency, increases in the outlet collector’s temperature, improvements in the rate of heat flux of the pipes, the tube inside the collector, heat transfer of the hot water storage tank, and a rise in the temperature gradient the hot water temperature increased from (between 44.3 and 74.8 ºC) to (between 49.6-80.3 ºC). Besides, the velocity of the water flow inside the solar collector in the second case in which the aluminum oxide nanoparticles are used was higher due to the absorption of further solar radiation and thermal energy, which resulted in a considerable increase in the kinetic energy of water molecules from 0.01 to 0.07 m/s. Also, it was found that the velocity directions and profile were slightly more turbulent in the second case than the conventional solar collector due to more thermal energy absorbed and stored in the ETSC from solar radiation.

Water Vapor Movement on Mass and Heat Transport in the Perspective of Water Vapor Buoyancy: A Review

Khairul Ikhwan Mohd Jamalludin — 2024-05-04

In 1957, the governing equation of mass and heat transport in the soil or porous media was popularised, now commonly referred to as PdV theory. This governing equation helps to quantify and simulate the water, vapor and heat in porous media. But at the same time, due to the fundamental uncertainty parameter in the equation, it was continuously updated. The equation predicting vapor flux movement in the soil has been the subject of many investigations. The vapor enhancement factor (VEF) was introduced to overcome the issue. When VEF was introduced, a few researchers were able to quantify the factor, but could not provide the guiding mechanism representing the observation. In the latest review from a literature study, we found a new form of equation to improve the VEF. It comes from the basis of the universal gas law, which describes the volume expansion from liquid water to vapor, and also the vapor buoyancy. This study aims to review water vapor movement and vapor buoyancy phenomenon. Also, to identify the parameters of the equations that contribute to the vapor buoyancy effect. The water vapor movement should not be neglected in the governing equation because its contribution to the overall mass movement is significant. Vapor buoyancy is possible to become a mechanism out from VEF. The parameters that contribute to vapor buoyancy effect are gravity, soil temperature, vapor density and water salinity. Clearly, understanding vapor buoyancy effect helps us better predict the distribution of soil temperature and soil moisture content.

Numerical Simulation on the Spray Angle of the Dual-layer Hole Nozzle in a Partition Combustion System of the Diesel Engine

Lu Hongkun — 2024-05-04

To study the effect of the spray angles of the dual-layer hole nozzle on the combustion and emissions performance in the partition combustion system, the in-cylinder spray, mixture formation and combustion processes of the new combustion system were simulated and investigated using AVL FIRE software. The results show that, compared with the variation of the lower-layer spray angles, the change of the upper-layer spray angles has a great influence on the instantaneous heat release rate. The increasing spray angles of the lower-layer holes lead to reduced peak values of the heat release rate in the cylinder. In all the spray angle cases, the first fire area of the cylinder is in the B zone of the combustion chamber. Compared with lower-layer spray angle, the upper-layer spray angle has a greater impact on the airflow disturbance in the combustion chamber. Appropriately increasing the upper-layer spray angle facilitates the mixing of fuel and air in the combustion chamber and reduces the unburnt fuel equivalence ratio. When the spray angles of the upper- and lower-layer holes are 157° and 112°, respectively, the combustion indicates power has the largest value of 12.18 kW. At the same time, the Soot emission is also the smallest, with a value of 0.52 g/kW·h.

Analytical Solution for MHD Casson Nanofluid Flow and Heat Transfer due to Stretching Sheet in Porous Medium

Wan Nura’in Nabilah Noranuar — 2024-05-04

The feature of having a surface that can stretch has garnered attention in numerous industrial and engineering fields because of its advantages. Nevertheless, most fluid mechanics simulations for stretchable surfaces have predominantly relied on numerical solutions, with a notable lack of theoretical investigations into this matter. Consequently, the current research aims to contribute a theoretical exploration of heat transfer and boundary layer flow for Casson nanofluid on a linearly stretching sheet, considering the existence of porosity and magnetic field effects. Two distinct types of water-based nanofluids containing aluminium oxide and silicon dioxide are examined. By employing similarity transformations, the governing momentum and energy equations undergo transformation and subsequent analytical resolution using Laplace transformations. The resulting solutions are graphically presented to examine the influence of key parameters on temperature and velocity distribution. The analysis indicates that heat transfer is improved by the inclusion of nanoparticles, porosity, and a magnetic field. However, the velocity distribution slows down as a result of higher nanoparticle volume fraction, porosity, and magnetic field imposition.

Mathematical Solutions of Free Convection Flow of Casson Fluid in Channel with Accelerated Plate

Mohamad Riduan Hashim — 2024-05-04

This research develops mathematical solutions for Casson fluid flow with free convective phenomena within channels with an accelerated plate. The study transforms the governing energy and momentum equations into the dimensionless form using appropriate variables. The Laplace transformation is used to acquire analytical solutions. Dimensionless parameters, such as the Prandtl number, Grashof number, accelerated parameter, and Casson fluid parameter, are determined, which are further investigated for their impacts on the flow and thermal behaviour. Visual representations of the mathematical results for velocity and temperature are presented using MATHCAD software through graphical plots. The study observes that fluid velocity increases with higher values of Gr but decreases with increased Pr. Additionally, temperature profiles exhibit a decrease with higher Prandtl numbers and an increase with time. The obtained results are validated by comparing them with published results in limiting cases, showing good agreement, and confirming the accuracy and reliability of the research outcomes.