A Multi-Scale Three-Dimensional CFD Model of a Full Loaded Cool Storage
-
Seyed Majid Sajadiye
,
Hojjat Ahmadi
Abstract
A multi-scale three-dimensional computational fluid dynamics (CFD) model was developed to predict airflow, heat and mass transfer in a typical full loaded cool storage. In order to reduce the computational costs, the porous media parameters of the bed of the apples inside the vented containers were extracted using a series of wind tunnel CFD simulations and then applied in the cool storage model. The model was validated against experiments by means of velocity, product temperature, and product weight loss measurements in cool storage. The errors of about 23.2 and 9.1% were achieved for velocity magnitude prediction in the cool storage and the product weight loss after 54 days of cooling in the loaded cool storage, respectively. The model over predicted the cooling rate of the products temperature; however, it showed a good trend of cooling rate. About 11°C difference was observed between the hottest and the coldest product temperatures at half cooling time by experiments that were in good agreement with the simulation results with about 10°C. This difference changes versus time of cooling and reached to about 4°C at the end of the cooling time. The product’s temperature heterogeneity was predicted 1.9°C between the 7 and 9 hours of cooling and reduced to 0.6°C at the end of the cooling. The multi-scale model was capable of predicting air velocity, product temperature, and weight loss with reasonable accuracy and was reliable enough for numerical studies on larger domain with high reduction in computational costs.
Appendix
| Nomenclature | ||
| Ao | tube surface area of heat exchanger, m2 | |
| As | specific area, m2 m–3 | |
| aw | water activity | |
| C | Forchheimer drag coefficient (inertial resistance), m–1 | |
| cpma | heat capacity of moist air, J kg–1 °C–1 | |
| D | diffusion of water vapor in the air, m2 s–1 | |
| Dh | diameter of heat exchanger tube, m | |
| E | total energy, J | |
| Gh | mass velocity at minimum flow area of heat exchanger, kg m2 s–1 | |
| ha | air film mass transfer coefficient, kg m–2 s–1 Pa–1 | |
| hh | heat transfer coefficient of heat exchanger, W m–2 °C–1 | |
| hJ | static enthalpy, J kg–1 | |
| hl | latent heat of water at 0°C, J kg–1 | |
| hm | bulk product mass transfer coefficient, kg m–2 s–1 Pa–1 | |
| hs | skin mass transfer coefficient, kg m–2 s–1 Pa–1 | |
| j, JP | heat exchanger factors | |
| JJ | diffusion flux of species, kg m–2 s–1 | |
 | transpiration rate per unit area of product surface kg s–1 m–2 | |
| k | turbulent kinetic energy, m2 s–2 | |
| keff | effective thermal conductivity of porous zone, W m–1 °C–1 | |
| p | pressure, Pa | |
| Pr | prandtle number | |
| Psat | saturated vapor pressure, Pa | |
| Pva | vapor pressure on the surrounding air, Pa | |
| Pvp | vapor pressure on the product surface, Pa | |
| qp | rate of respiratory heat generation per unit mass of product J s–1 kg–1 | |
| Re | Reynolds number | |
 | gas constant for water vapor, 461.52 J mol–1 K–1 | |
| RH | relative humidity | |
| Sc | Schmidt number | |
| Sh | Sherwood number | |
| Sh | volumetric heat sources (energy source term), J m–3 s–1 | |
| Si | momentum source term, kg m–2 s–2 | |
| t | time, s | |
| T | temperature, K | |
| Tave | overall average of container’s temperature, K | |
| Tavedev | average of the absolute deviations of temperature, K | |
| Tc | volume average temperature of a container, K | |
| u | velocity, m s–1 | |
| ui, uj | mean velocity components in X-, Y-, and Z-directions, m s–1 | |
 ,  | fluctuating velocity components, m s–1 | |
| us | superficial velocity, m s–1 | |
| Vh | volume of heat exchanger, m3 | |
| vmin | air velocity at minimum flow area of heat exchanger unit | |
| xi, xj | Cartesian coordinates, m | |
| YW | mass fraction of water vapor in the moist air | |
| α | Darcy permeability, m2 | |
| γ | Porosity | |
| δij | Kronecker delta | |
| ε | turbulent dissipation rate, m2 s–3 | |
| μ | dynamic viscosity, kg m–1 s–1 | |
| μt | turbulent viscosity, kg m–1 s–1 | |
| ρbulk | apple bulk density, kg m–3 | |
| ρma | moist air density, kg m–3 | |
| Sub- and super-scripts | ||
| c | cooler (fan and heat exchanger) | |
| f | fan | |
| h | heat exchanger | |
| i, j | Cartesian coordinate index | |
| ma | moist air | |
| p | product (apple) | |
| sat | Saturation | |
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- Obtention of Rosemary Essential Oil Concentrates by Molecular Distillation and Free Radical Scavenging Capacity Analysis
- Effects of Feed Powder Quantity and Compression Pressure on the Tensile Strength of Eurycoma longifolia Jack Tablets Using Different Binders
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- An Intelligent Signal Processing Method for High-Speed Weighing System
- Influence of Osmotic Pre-treatment on Convective Drying Kinetics of Figs
- Influence of Drying on the Properties of Pears of the Rocha Variety (Pyrus communis
- Preparation, Storage and Distribution of Coated and Uncoated Chicken Meat Products
- Modelling the Effect of Processing Parameters of Continuous Flow High Pressure Throttling System and Microfluidizer on Particle Size Distribution of Soymilk
- Optimization of Headspace Sampling Using Solid-Phase Microextraction (SPME) for Volatile Components in Starfruit Juice
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