Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids

Design of Packaging Vents for Cooling Fresh Horticultural Produce

Abstract This review focuses on the design of vents in packages used for handling horticulture produce. The studies on vent designs that are conducted to obtain fundamental understanding of the mechanisms by which different parameters affect the rate and homogeneity of the airflow and the cooling process are presented. Ventilated packages should be designed in such a way that they can provide a uniform airflow distribution and consequently uniform produce cooling. Total opening area and opening size and position show a significant effect on pressure drop, air distribution uniformity and cooling efficiency. Recent advances in measurement and mathematical modelling techniques have provided powerful tools to develop detailed investigations of local airflow rate and heat and mass transfer processes within complex packaging structures. The complexity of the physical structure of the packed systems and the biological variability of the produce make both experimental and model-based studies of transport processes challenging. In many of the available mathematical models, the packed structure is assumed as a porous medium; the limitations of the porous media approach are evident during vented package design studies principally when the containerto-produce dimension ratio is below a certain value. The complex and chaotic structure within horticultural produce ventilated packages during a forced-air precooling process complicates the numerical study of energy and mass transfer considering each individual produce. Future research efforts should be directed to detailed models of the vented package, the complex produce stacking within the package, as well as their interaction with adjacent produce, stacks and surrounding environment. For the validation of the numerical models, the development of better experimental techniques taking into account the complex packaging system is also very important

Engineering design of spraying systems for horticulturalapplications using computational fluid dynamics

Bij zowel voor- als naoogstbehandelingen van tuinbouwproducten wordt spuittechnologie gebruikt met het oog op een verbeterde productkwaliteit. Het onderzoek richtte zich op twee verschillende spuitsystemen in de productieketen van tuinbouwproducten: dwarsstroom boomgaardspuittoestellen met luchtondersteuning en bevochtingssystemen op basis van microverneveling. In de eerste toepassing leidt onoordeelkundig gebruik van de toepassingtechniek tot drift en milieuschade en fytotoxische effecten ten gevolge van overdosissen. De tweede toepassing beoogt het voorkomen van te sterke uitdroging van product, terwijl verkeerd gebruik leidt tot een afname van de koelefficiëntie en de uitgroei van microörganismen. In dit onderzoek beogen we een beter ontwerp en engineering van spuitsystemen. De hoofddoelstelling is het ontwikkelen van een modelgebaseerde methodologie voor ontwerp en engineering van spuitsystemen. De kern van deze methodologie is een 3-dimensioneel Computational Fluid Dynamics (CFD) model dat de relevante variabelen van het spuitproces in de verschillende toepassingen berekent als functie van de instelparameters en omgevingscondities. Het pad van de vernevelde druppels wordt voorspeld door middel van een Euleriaans-Lagrangiaans deeltjestransportmodel. Dit model brengt de effecten van turbulente dispersie, druppelverdamping, en de volledige koppeling van momentum, warmte- en massaoverdracht tussen de continue luchtfase en de discrete druppelfase in rekening. De berekeningen maken het voor het eerst mogelijk om voor elke specifieke configuratie een gedetailleerde en kwantitatieve evaluatie te maken van de spuitnevelverdeling, de luchtstroming, de depositie van de druppels, de temperatuur en de relatieve vochtigheid, zowel ruimtelijk als in functie van de tijd. Voor boomgaardspuiten werd een gevalideerd CFD model ontwikkeld dat rekening houdt met het profiel van de luchtondersteuning, de tractorsnelheid en de dopkarakteristieken. Zo werd het mogelijk ontwerp en instelling van spuittoestellen te verbeteren en te implementeren in de praktijk, met een verlaagd risico op drift en een uniformere spuitnevel. Dwarsstroom boomgaardspuittoestellen produceren een complex drie-dimensioneel profiel van de luchtondersteuning, dat niet kan beschreven worden met de bestaande theorie van luchtstralen. Het volledige 3-D profiel van de luchtstroming beïnvloedt in grote mate de beweging van de druppels, en is sterk afhankelijk van ventilatorsnelheid en tractorsnelheid. Het verticaal profiel van de spuitnevel wordt tevens sterk beïnvloed door de druppelgrootteverdeling van de spuitdoppen. Voor een reductie van drift, moeten het aandeel van fijnere druppels zo laag mogelijk worden gehouden, en de instellingen van de luchtondersteuning aangepast. Het gebruik van veldspuitdoppen werd aangereikt als een middel om dit te verwezenlijken. Voor bevochtingssystemen in koude bewaarruimten werd een gevalideerd multischaal CFD model ontwikkeld dat rekening houdt met het ontwerp van de bewaarruimte en koelinstallatie, de thermofysische producteigenschappen, de stapelwijze en de dopkarakteristieken. De plaatsing en instelling van bevochtigers en het ontwerp van de bewaarruimte werd aanzienlijk verbeterd om te komen tot een reductie van de condensatie en een verhoogde waarde en uniformere verdeling van de relatieve vochtigheid in de ruimte bij lage temperatuur. Het multischaalmodel bestaat enerzijds, op de kleinste schaal van de individuele box met producten, uit een gecombineerd discrete-elementen (DE) en CFD model en anderzijds, op de schaal van de complete bewaarruimte, uit een CFD model met een poreus-medium model van de productstapel. De anisotrope parameters van het poreus-medium model werden bepaald door het DE-CFD model. Er werd aangetoond dat deze multischaal aanpak resulteerde in nauwkeurigere voorspellingen van luchtsnelheid, temperatuur en relatieve vochtigheid in toepassingen met gestapelde producten. Intervalbevochtiging met hoge-druk doppen werd voorgesteld als oplossing voor het verhogen van de relatieve vochtigheid, reductie van de inkoeltijd en het verkleinen van vochtverlies van de producten in de bewaarruimte. Om te komen tot en reductie van excessieve condensatie, moet deze methode evenwel gecombineerd worden met een geoptimaliseerde plaatsing, druk en debiet van de doppen, een voldoende lang verdampingspad voor de vernevelde druppels en het juiste bevochtingsinterval en duur. De geoptimaliseerde waarden zijn specifiek voor een bepaalde bewaarruimte en toepassing. De resultaten toonden aan dat verbeteringen in de praktijk mogelijk zijn aan de hand van de generieke ontwerpmethodologie die in dit doctoraat werd ontwikkeld.status: publishe

Studying the impact characteristics of spray droplets on plant surfaces using a multiphase CFD model

peer reviewedThe impact characteristics of spray droplets on plant surfaces was investigated based on a multiphase computational fluid dynamics (CFD) model using the Volume Of Fluid (VOF) approach. The contact angle of the droplet on different surfaces was measured and included as a model parameter. The model was validated using experimental results that were conducted on different plant surfaces (apple, pear, cabbage and leek) and the model was applied to study the effect of droplet impact velocity, droplet diameter, formulation and surface topology on droplet impact characteristics. For each combination of model parameters, the model was capable of predicting the droplet impact outcome (adherence, rebound, splash and shattering). The results showed that multiphase CFD model has a capacity to predict the behavior of plant protection mixture droplets at impact on target surfaces

Design, development, and testing of rice-husk fueled mixed-flow rice dryer for small-scale rice producer farmers

In underdeveloped nations, rice is frequently harvested at a relatively high moisture content and then dried under the open sun to a storage moisture content. However, direct UV exposure, rain, dust, premature drying, contamination, and open sun drying are all associated with problems like poor grains, discolorations, and cracking. Commercial mechanical dryer utilization is not practical in remote regions due to the absence of electrical service, high startup costs, and ongoing operating expenses. In this work, a pilot mixed-flow rice drier that ran on rice husk energy and solar energy to power the driving fan was designed, produced, and tested. The major parts of the dryer assembly that were conceived and created were the combustion chamber, heat exchanger, and mixed-flow dryer. The results of the trial revealed that the combustion chamber's average temperature was 347.3 °C, the drying air at the heat exchanger output, where the drying chamber was attached, was 63.3 °C, and the combustion chamber and heat exchanger's respective efficiencies were 52.4% and 14.9%. The mixed-flow dryer powered by rice has a significantly lower operating cost than a comparable dryer powered by electricity, petrol, and diesel. The study makes it evident that such a reasonably priced and effective rice dryer might significantly help small-scale rice producers to extend the storage duration and maintain the quality of their product

Development and Testing of Solar Powered Evaporative Air-Cooling System with an Improved Performance

AbstractThis study proposes a new active direct evaporative cooling system that uses a bundle of cotton fibers as an evaporating surface and activated carbon as a moisture adsorbent. A two-stage evaporative cooling experimental setup consisting of an activated carbon adsorbent in between the cooling pad was designed, fabricated, and tested at Bahir Dar, Ethiopia. The fiber bundle (pad 1) was wetted with water and ambient air was forced through it using a fan then the air that exiting from pad 1 was forced through a bulk of activated carbon (moisture adsorbent), and then the air from the adsorbent passed through the second wetted fiber bundle (pad 2). The energy source for the fan and pump was the solar photovoltaic energy system. The average temperature drop of the cooler without the moisture adsorber was 9.33°C and with the inclusion of the moisture, the adsorber gave an additional temperature drop of 1.5°C to 4.95°C. During the hot dry season, the average relative humidity of the ambient air, pad 1 outlet, adsorbent outlet, and pad 2 outlets were 28.26%, 76.12%, 55%, and 88.2% respectively. The cooler with moisture adsorbent had a cooling capacity of 3653 W, an effectiveness of 94.25%, and a COP of 52.2. The developed solar evaporative cooling system can provide energy-efficient, sustainable, affordable cold air for different applications. The cooler could be used by small-scale farmers, wholesalers, and retailers for the cooling and storage of horticultural products to reduce the postharvest loss in fresh produces

Analysis of mechanical properties of vented corrugated container for fresh horticultural produce by finite element method

Abstract Corrugated containers are used to transport horticultural fresh produce through the cold chain environment that requires these boxes to have venting to maintain an air flow channel between the surroundings and the inside of the containers. Ventilated packages should be designed in such a way that they can provide a uniform airflow distribution and consequently uniform produce cooling. Total opening area and opening size and position show significant effect on pressure drop, air distribution uniformity and cooling efficiency. The presence of ventilation holes causes a loss of material in the box. As a result the compression strength required for shipping and stacking is compromised and can result in damage to contents. Strength of corrugated board containers is crucial for preserving the content, while an optimization of corrugated board containers is essential to save money and resources. Vibration and shocks acting on pallets during transportation are transferred to the corrugated boxes and considerably reduce the integrity and life time of the boxes. This study was initiated to understand the loss in mechanical behaviour of corrugated containers as a function of size, shape and location of ventilation holes used for extending shelf life for fresh produce with good air flow. Model was used to study the effect of total opening area and opening size and position on mechanical properties. The von-Mises stress increased with ventilated opening. It also introduces the methodology of a packaging design project and discusses results of its application for design and optimization of packages, based on finite element model (FEM). The scope of this study focuses on presenting alternative corrugated packaging designs considering the proper ventilation for fresh produce industry

Optimizing precooling of large beef carcasses using a comprehensive computational fluid dynamics model

Precooling has been questioned as a suitable step in the process of beef carcass cooling. Model-based optimization was performed to identify optimum operating conditions for different heavy-muscled beef carcass cooling practices in slaughterhouses with both precooling and cooling stages. The study was conducted using a validated computational fluid dynamics model of the beef carcass cooling process. The precooling practice was optimized based on a weighted impact function taking into account energy consumption, weight loss, cooling time, and heat shortening duration. The values of these output variables were dependent on air temperature, air velocity, and precooling time. The results clearly show the benefit of using a precooling unit that operates with an optimum precooling time, cooling air temperature, and velocity. Using a weighted impact function of energy cost and quality, a precooling time of 4 hr using -30 degrees C but low air velocity (0.58 m s(-1)) appeared more beneficial than precooling using high airflow fans with high energy consumption. The eventual optimum operation conditions depend on the impact variable that the operator wants to minimize and is a trade-off between adverse effects on energy use and meat quality. Practical applications The comprehensive computational fluid dynamics model can be applied to optimize the operation and design of carcass precooling system. Carcass cooling system operators can make a choice of the impact variable they want to minimize and use the approach to determine the optimum operating condition of the cooling system. The approach can be applied to develop carcass cooling procedure that could potentially minimize the energy consumption and maximize the quality of the carcass

Evaluation of a chicory root cold store humidification system using computational fluid dynamics

Humidification of chicory root cold stores helps in maintaining the quality and extending the postharvest storage time of chicory roots. Low evaporation rate of the sprayed droplets at such sub-zero temperatures (-2 degrees C to -1 degrees C) favours surface deposition that could have an adverse effect on the efficiency of the storage room. A three-dimensional computational fluid dynamics (CFD) model was developed and used to predict the storage room air velocity, temperature and humidity distributions, and fate of the water droplets that were sprayed for humidifying the storage room. The humidification system in a chicory root cold store was then optimized. The efficiency of the humidification system was affected by length of cold air deflector, stack height, number of nozzles and duration of humidification. Elongating the air deflector, reducing the stack height, reducing the number of nozzles and shortening the humidification time increased the amount of droplet evaporated and decreased the amount of droplet deposited on the stack. The following combinations of room design and operating parameters could clearly give the best performance of the humidification system: deflector length of 0.8 m, two nozzles with an interval humidification of 1.5 min on and 2 min off cycle and stack height of 3.4 m. (C) 2009 Elsevier Ltd. All rights reserved.status: publishe

Nutritional, Physicochemical, Functional, and Textural Properties of Red Pepper (Capsicum annuum L.), Red Onion (Allium cepa), Ginger (Zingiber officinale), and Garlic (Allium sativum): Main Ingredients for the Preparation of Spicy Foods in Ethiopia

Spices are known to have important benefits in our daily diet, and it is common to see industrial and traditional spicy foods in our households and markets. In the present work, a systematic profiling of the nutritional, physicochemical, and textural properties of red pepper, garlic, red onion, and ginger was conducted. The detailed data of forty eight (48) parameters that consisted of macronutrients, micronutrients, physicochemical properties, functional property, and rheological properties of each of the components were organized. The result showed that red pepper had the highest content of crude protein (14.7%), crude fat (11.3%), crude fiber (38.57%), ash (6.7%), redness (a∗ value) (32.5), CI (37.4%), and porosity (37.43%) compared to garlic, ginger, and red onion. Garlic had the highest content of carbohydrate content (76.42%), energy (346.58 kcal), pH (6.03), total soluble solid (26.76), particle size (D90, 561 µm), and volume weighted mean (238 µm) which is related to the high antimicrobial and antioxidant quality of garlic. Red onion had the highest content of Zn (71.16 mg/100 g), Na (94.5 mg/100 g), and Ca (71.16 mg/100 g) indicating that it is a rich source of minerals. The availability of data about the nutritional, physicochemical, functional, and textural properties of the ingredients is crucial for the production and formulation of industrial and traditional spicy foods with the highest quality and stability