This research investigated the performance of a solar‐assisted heat pump dryer (SAHPD) with heat recovery to reduce the amount of thermal energy needed for drying chili peppers. The dryer selected for the experimental study consisted of a heat pump, a greenhouse cover and multi trays. It was found that the SAHPD with recovery gave better drying performance than a traditional dying method. The dryer system can offer drying time, drying efficiency, coefficient of performance and specific energy consumption of approximately 24 hr, 33.2%, 3.17, and 2.21 kWh/kg, respectively. Furthermore, the SAHPD with heat recovery provided a higher drying performance than without the heat recovery although the ambient condition changed. Base on the economic analysis, the payback period and net present value of the SAHPD with heat recovery were approximately 1.9 years and 915.60 USD. The SAHPD with two drying rooms also yielded better drying performance than the SAHPD with one room. Practical applications Drying is the process of moisture reduction to a safe limit of moisture content, which allows agriculture to extend the shelf life of the crops by restraining the growth of microorganism. In chili peppers drying process, a solar assisted heat pump drying as one of hybrid solar dryers is preferred because heat and mass transfer rate are rather high and it offers the ability to operate both daytime and nighttime. However, the exhausted air to the ambient still has considerable thermal energy. Thus, the heat recovery system has been employed to design and fabricate inside the dryer. Findings of this research contribute to the evaluation of heat recovery in a typical solar assisted heat pump dryer in terms of drying efficiency and economic feasibility in order to be a guideline for small and medium‐sized enterprises.
A study of the wear mechanism on a reaction bonded silicon carbide (RB-SiC) subjected to fixed abrasive polishing and loose abrasive waterjet (AWJ) impact conditions is presented. It is found that the wear of the material is characterised by different mechanisms in its silicon and silicon carbide constituents. The surface polished by diamond abrasives appears with brittle fractures on the silicon carbide phase, while the silicon phase is found to be plastically deformed and embedded onto the surface of the fractured silicon carbide. Submicrometre surface finish can be obtained by polishing using silicon carbide abrasives, and the process is initiated through the penetration of abrasive tips into the softer silicon matrix.Since the progressive wear flattens the tips of abrasives, the penetration depth of abrasives into the material gradually decreases. When the penetration depth is below a critical value, ductile material removal mode becomes dominant in the removal process. When abrasives that are softer than the silicon carbide grains are sufficiently introduced onto the material surface by a slurry jet, wear can occur even at a pressure below the critical value for phase transformation of the silicon constituent. Wear takes place mainly through weakening the Si bond by erosion and wedging, which eventually releases the SiC grain from the material structure. It is feasible to use a relatively low-pressure alumina slurry jet to machine RB-SiC without causing any surface damage and the processed surface quality depends mainly on the material structure.
This paper presents an investigation on the influence of the drilling parameters such as feed rate, spindle speed and drill tool diameter onto the delamination factor of the jute reinforced unsaturated polyester composite. Natural fibre based composite are mostly used for commodity application and often subjected to drilling during applications and may generate delamination of drilled holes on the workpiece. The composite was fabricated using woven jute fibre via vacuum bagging method followed a high temperature curing using hot press. The fibre was kept at 40 vol. %. The main effect and the interaction between the specified factors of feed rate (20-100mm/min), spindle speed (500-1500 rpm) and drill tool diameter (4-8 mm) with delamination factor as corresponding respond was structured via the Response Surface Methodology (RSM) based on three-level Box-Behnken design of experiment and the ANOVA. The levels of importance of the process parameters on flexural properties are determined by using Analysis of Variance (ANOVA). The optimised drilling process parameters obtained as 24.38 mm/min of feed rate, 1146.14 rpm of spindle speed and 5.51 mm drill tool diameter achieved the most minimal delamination factor. The feed rate and spindle speed were perceived as the most influential drilling parameters on the delamination factor of the jute reinforced unsaturated polyester composite.
An experimental investigation of the hole machining performance for woven carbon-fiber reinforced PEEK (polyetheretherketone) sheets by an abrasive waterjet (AWJ) is presented. It is shown that AWJ machining can produce good quality holes if the cutting parameters are properly selected. Plausible trends of the hole quality with respect to the process parameters are discussed. Nozzle traverse speed and intended or programmed hole size are found to have a significant effect on the diameter error of the machined holes, hole roundness, and hole wall inclination angle, while water pressure and abrasive mass flow rate exhibit an insignificant effect. An increase in the traverse speed decreases the overall hole quality, while an increase in the programmed hole diameter decreases the hole diameter error and roundness error, but increases the hole wall inclination. There is not any clear trend of the hole wall surface roughness with respect to the process parameters. Moreover, high water pressures may result in hole defects, such as entrance surface chipping, delamination, internal cracking and fiber pull-out. It is found that the optimum process parameters are about 200 MPa water pressure, 2 mm/s nozzle traverse speed and 7.0 g/s abrasive mass flow rate. Recommendations are made for compensating for the hole size deviation and empirical models are fianlly developed for these hole characteristics.
The “Vein” in a shrimp is its digestive tract filled with grit, sand, and sediments stretching along the back of the abdomen. In most shrimp market forms, presence of vein is highly restricted and limited according to the U.S. standard for imports. This research aims to develop an image‐based approach for detection of improperly deveined shrimps. Two hundred shrimp images were subjected to a sequence of image processing techniques before extracting significant parameters from grayscale images. These parameters include shape measurements and pixel value measurements drawn from an image histogram. In this research, disqualified shrimps were identified by two classification techniques: linear discriminant analysis and support vector machine (SVM). Better than 98% classification accuracy was obtained with the SVM using a polynomial kernel function. The success of this research has filled a void left by past studies to facilitate fully automated shrimp quality inspection. Practical applications Rising wages and labor scarcity are among critical problems to seafood industries, along with low productivity due to ergonomics limitations. Such problems will be even worse in the near future and automated machines are becoming a popular alternative to tackle them. These machines must be driven by an intelligent processing unit capable of handling unavoidable variability naturally found in agricultural products. In most shrimp market forms, presence of veins is highly restricted and limited by the U.S. standards for imports. Deveining always leaves remnants of uncertain length. Employing statistical learning techniques, the approach developed in this study can accurately and automatically discriminate shrimps by acceptability based on the vein. Findings of this research contribute to the development of a fully automated shrimp processing machine, supporting sustainability of the industry by reducing reliance on labor policies and workforce availability.
Over the years, plastic water bottle manufacturing, especially PET (Polyethylene terephthalate) bottle has been steadily increasing due to its toughness, transparency, and chemical properties. However, most manufacturers have to spare time, and cost, verifying their prototypes in accordance to the Thai Industrial Standard (TIS) before any mass production can start. This paper aims to overcome some of these problems by using Finite Element Method (FEM) to study bottle mechanical properties, particularly maximum stress and deformation that can be employed to evaluate performance and optimal thickness. From simulation results the optimal thickness of a 6-liter bottle, that its maximum stress can still be kept under critical value, is 0.45 mm. The thinner and lighter bottle reduces the amount of material usage. The FEM simulation also speeds up and alleviates some necessary testing procedures in a prototype designing process.
A computational fluid dynamics (CFD) study of the impact characteristics and stagnation formation on a solid target surface by an abrasive waterjet at supersonic velocities is presented to understand the impact process. A CFD model is developed and verified by experimental water and particle velocities and then used to simulate the jet impact process. The trends of the stagnation formation and its effect on the jet flow with respect to the jetting and impacting parameters are amply discussed. It is found that stagnation formation at the impact site increases with an increase in the impact time, nozzle standoff distance and nozzle diameter, while the initial peak velocity at the nozzle exit has little effect on the size of the stagnation zone. It is shown that stagnation markedly changes the water and particle flow direction, so that the particle impact angle is varied and the jet impact area is enlarged. The jet structure may be classified to have a free jet flow region, a jet deflection region with a stagnation zone and a wall jet region. Furthermore, the stagnation affects significantly the waterjet and particle energy transferred to the target surface. The average particle velocity across the jet is reduced by approximately one third due to the damping effect of the stagnation under the conditions considered in this study.
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