Influence of nozzle arrangement on flow and heat transfer characteristics of arrays of circular impinging jets

The effect of jet arrangements on flow and heat transfer characteristics was experimentally and numerically investigatedfor arrays of impinging jets. The air jets discharge from round orifices and perpendicularly impinge on a surface within arectangular duct. Both the in-line and staggered arrangements, which have an array of 6×4 nozzles, were examined. A jet-toplate distance (H) and jet-to-jet distance (S) were fixed at H=2D and S=3D, respectively (where D is the round orificediameter). The experiments were carried out at jet Reynolds number Re=5,000, 7,500 and 13,400. Temperature distributions onthe impingement surface were measured using a Thermochromic Liquid Crystal sheet, and Nusselt number distributions wereevaluated using an image processing method. The flow characteristics on the impingement surface were visualized using theoil film technique. The numerical simulation employed to gain insight into the fluid flow of jets between the orifice plate andthe impingement wall was via computational fluid dynamics. The results reveal that the effect of crossflow on the impingingjets for the staggered arrangement is stronger than that in the case of in-line arrangement. In the latter case of in-line arrangement, the crossflow could pass throughout the passage between the rows of jets, whereas in the former case the crossflowwas hampered by the downstream jets. The average Nusselt number of the in-line arrangement is higher than that of thestaggered arrangement by approx. 13-20% in this study

Effect of combined microwave heating and impinging hot-air on rubberwood drying

Applying microwave heating and impinging hot-air is one of the most interesting methods to increase the higher drying rates of rubberwood drying based on acceptable quality. A maximum microwave power level of 200W at a frequency of 2.45GHz with maximum working temperature of 70°C, only hotair (70°C) and combined microwave (200W) - hotair (70°C) were choosed to evaluate the effect of rubberwood drying by different width sizes (1, 2, 3 and 4 in.) by 46 in. length by 1 in. thick. In all cases, the drying time is reduced significantly from 168 h to less than 8-15 h in various wood widths and resulted in saving to an extent of about 91% of drying time from initial moisture content ranges of 73%-49% to 15% percent of moisture level. Drying stresses from prong test no found during drying and total color of rubberwood changed after high temperature drying is a natural surface when compared to fresh wood. The values of six strength compared to the reference values are concentrated in the ranges of 16.9-23.9 (11.0)MPa for shearing strength parallel to grain, 4291.1-6701.6 (4350)N for hardness, 73.3-110.2 (66.0)MPa for MOR, 7059.5-12856.7 9240.0) MPa for MOE, 27.2-14.3 (5.0)MPa for compressive strength perpendicular to grain and 60.6-35.7 (32.0)MPa for compression strength parallel to grain. These results show that it is possible to develop a drying process for rubberwood using microwave-hot air in investigating further in this area.Rubberwood Technology and Management Research Group (ENG-51-2-7-02-0025-S), Faculty of Engineering, Prince of Songkla Universit

Facility Location Placement Optimisation for Bagged Cement Distribution During the COVID-19 Pandemic

This study was based on a challenge that one of Thailand's cement companies encountered in 2021 as a result of fierce competition in the Northeastern region and falling market share during the COVID-19 pandemic. Without a doubt, the management of supply chains played an essential role in this issue. As a result, this research addressed the company's distribution strategy by attempting to determine a new location for the distribution centre to achieve two conflicting objectives at the same time, namely, minimising total transportation cost and maximising service level (delivery lead time reduction). For the problem at hand, a linear programming model was developed. Once different options were identified, the pros and cons of each approach were evaluated, and then the distribution strategy was altered to meet the actual conditions. It was discovered that changing distribution centres in some locations was a successful strategy for shortening delivery lead times with an opportunity to achieve a 22% improvement in service level while still controlling transportation expenses prior to arriving at the end customers not beyond the target at 15% increased from the current strategy

Development and Validation of a Composite Learning Index for Cambodian High School Students

This study aimed to develop an instrument for measuring student learning and to establish a learning index for high school students. A sample of 1,619 Cambodian high school students was selected using a stratified random sampling technique. Data were collected through a 56-item questionnaire based on a 5-point Likert scale and were analyzed using various statistical methods including descriptive statistics, content analysis, objectivity analysis, correlation analysis, construct validity (using M-plus), reliability analysis (using the R-package for Windows), and t-test analysis. The instrument consists of two key components: “Learning to Know” and “Learning to Do”, each further broken down into ‘Process’ and ‘Outcome’ elements. Each of these sub-components were represented by three distinct indicators. The instrument demonstrated good content validity with an Item-Objective Congruence (IOC) index ranging between 0.50 and 1.00, and excellent construct validity, supported by a variety of goodness-of-fit indices (CFI = 1.00, TLI = 0.99, SRMSR = 0.01, RMSEA = 0.02). The instrument also showed high internal consistency with reliability coefficients ranging from 0.83 to 0.93. The criterion-related validity was confirmed through known-groups validation. Two methods—criterion-related and norm-related—were used to determine students’ learning index levels. For this study, the norm-related method was chosen. The learning index was categorized into four levels: low (0.000 - 0.062), medium (0.063 - 0.375), relatively high (0.376 - 0.680), and high (0.681 - 1.000). Percentile ranks were also calculated to provide additional context for interpreting the learning indices of Cambodian high school students

Effect of Research Training Environment on Doctoral Students’ Research Intentions

The research training environment (RTE) is an important factor for enhancing doctoral students’ research intentions (RI). This study aims to develop and validate the casual relationship model of the RTE and RI, mediated by research self-efficacy (RSE) and research engagement (RE), and examine differential RTE effects in years 1-3 of the doctoral program. The research sample consisted of 246 doctoral students in years 1-3 of their doctoral program, with the respondents randomly selected from 13 universities in Thailand. Data were collected via questionnaire and analyzed using an integrated generalized structured component analysis (IGSCA) with multigroup analysis. The findings have shown that there was no mediation effect of RE or RSE between the RTE and RI in the first year. In contrast, mediation effects of RE and RSE were found in the second (β = .097) and third years (β = .723) of the doctoral program. Based on the results, it is suggested that the RTE component associated with RSE should be established (e.g., allowing students to engage with their projects early and minimally) in the first year. Furthermore, it is recommended that RSE and RE be developed concurrently (e.g., encouraging students to share research ideas with others) in the second and third years