Proper management of post-harvest systems is one of the most crucial steps in reducing agricultural losses and waste. This study was aimed to find the effect of FORCED AIR pre-COOLING of dill using a window AIR conditioner on its shelf life. For this purpose, a metal frame with dimensions of 2×1×1 m was covered with a polyethylene foam sheet and a window AIR conditioner (after removing its thermostat) equipped with a controller was connected to one end of this chamber. In the next step, bunches of dill without packaging and the cardboard packaging with polyethylene liner were placed in three different conditions, including without pre-COOLING and keeping at ambient temperature, with pre-COOLING and keeping at ambient temperature, with pre-COOLING and keeping under refrigeration. The results showed that during 4 days of storage, bunches of dill kept at ambient temperature had more total loss (50-60%) but after that, packaging caused severe loss (100%) due to moisture accumulation. If cold storage and packaging was ignored after pre-COOLING, total loss would increase swiftly. For this reason pre-cooled dill with proper packaging and refrigeration showed the least amount of total loss (8.95±1.03%), physiological water loss (5.16±1.78%), pH (6.16±0.16), a*(-20.29±1.45) and the highest amount of moisture content (87.60±3.76), hardness (764±50 N), ascorbic acid (2.74±0.05 mg. g-1 of dill dry weight basis), total acceptance (4.1±0.65), L* (43.44±6.39), and b* (20.09±4.31).

The current study employs CFD to study the FORCED AIR COOLING of a pyramid shaped porous foam absorber. Herein, a three by three (3´3) array of porous foam absorbers heated with an external heat flux is modeled using the differential equations governing heat and fluid flow through porous media based on the Brinkman- Darcy flow equations and an effective thermal conductivity to account for the porous medium. The numerical simulations are carried out using the COMSOL commercial Computational Fluid Dynamics (CFD) Finite Element based software package. The results of this verification exercise were within 18% of the prior numerical results and within 14% of the archived measured results. Typical results for the velocity and temperature profiles within the porous foam absorbers are shown. A comparison of Nusselt number between our CFD simulations and the heat transfer theory is plotted, showing agreement on the order of 11%. A parametric study involving heat flux, COOLING AIR inlet velocity, porous foam porosity, and porous foam permeability showed that there is a relationship between porosity and the temperature distribution within the porous media. The primary finding of our study is that the more porous the foam absorber media is, the more dependent the effective thermal conductivity is on the thermal conductivity of the fluid used for COOLING. If the fluid is AIR, which has a very low thermal conductivity, the effective thermal conductivity is decreased as the porosity increases, thus diminishing removal of heat from the foam array via the COOLING AIR stream. Based on the parametric study, the best case operating conditions which may allow the pyramidal foam absorber to stay within the max allowable temperature are as follows: porosity = 0.472, inlet AIR COOLING velocity = 50 m/s.

Introduction: Pomegranate (Punica grantum L. ) is classified into the family of Punicaceae. One of the most influential factors in postharvest life and quality of horticultural products is temperature. In preCOOLING, heat is reduced in fruit and vegetable after harvesting to prepare it quickly for transport and storage. Fikiin (1983), Dennis (1984) and Hass (1976) reported that cold AIR velocity is one of the effective factors in COOLING vegetables and fruits. Determining the time-temperature profiles is an important step in COOLING process of agricultural products. The objective of this study was the analysis of COOLING rate in the center (arils) and outer layer (peel) of pomegranate and comparison of the two sections at different cold AIR velocities. These results are useful for designing and optimizing the preCOOLING systems. Materials and Methods: The pomegranate variety was Rabab (thick peel) and the experiments were performed on arils (center) and peel (outer layer) of a pomegranate. The velocities of 0. 5, 1 and 1. 3 m s-1 were selected for testing. To perform the research, the COOLING instrument was designed and built at Department of Biosystems Engineering of Tabriz University, Tabriz, Iran. In each experiment six pt100 temperature sensors was used in a single pomegranate. The COOLING of pomegranate was continued until the central temperature reached to 10° C and then the instrument turned off. The average of AIR and product temperatures was 7. 2 and 22. 2° C, respectively. The following parameters were measured to analyze the process of preCOOLING: a) Dimensionless temperature (θ ), b) COOLING coefficient (C), c) Lag factor (J), d) Half-COOLING time (H), e) Seven-eighths COOLING time (S), f) COOLING heterogeneity, g) Fruit mass loss, h) Instantaneous COOLING rate, and i) convective heat transfer coefficient. Results and Discussion: At any AIR velocity, with increasing the radius from center to outer layer, the lag factor decreased and COOLING coefficient increased. Also, half-COOLING time and seven-eighths COOLING time reduced and so COOLING rate enhanced. Thus, despite a reduction lag factor, due to a significant increase in COOLING coefficient, half and seven-eighths COOLING declined. Dimensionless temperature, θ , less than 0. 2 and 0. 1 in the center and peel and at different velocities had little impact on the rate of COOLING in pomegranate. The difference in primary COOLING time (0-500 sec) and in high lag factor (greater than 1) occurred, which represents an internal resistance of heat transfer in fruit against the AIRflow. COOLING the center of pomegranate starts with time delay which causes the beginning of the COOLING curve becomes flat. Seven-eighths COOLING time is the part of half-COOLING time. The range of S was 2. 5-3. 5H in the present study. At first, COOLING heterogeneity at 0. 5 m s-1 was low in the center and peel of pomegranate and then with increasing the velocity up to 1 m s-1, it enhanced and again decreased at 1. 3 m s-1. After a period of COOLING (5000 sec), almost layers of pomegranate reached the same temperature and so heterogeneity reduced. The maximum instantaneous COOLING rate was 8. 09 × 10-4 º C s-1 at 1. 3 m s-1 in the center of pomegranate. By increasing the AIRflow velocity from 0. 5 to 1. 3 m s-1, the convective heat transfer coefficient increased from 11. 05 to 17. 51 W m-2 K-1. Therefore, the velocity of cold AIR is an important factor in variation of convective heat transfer coefficient. Conclusions: COOLING efficiency is evaluated based on rapid and uniformity of COOLING. COOLING curves against time reduced exponentially at the different AIRflow velocities in the center (aril) and outer layer (peel) of pomegranate. By increasing the AIR flow velocity, half and seven-eighths COOLING time reduced and COOLING rate increased that showed direct impact of this variable. The main reason was the variation of convective heat transfer coefficient. The lowest level of uniformity obtained at the highest velocity (1. 3 m s-1), which made more uniform temperature distribution in the fruit. The results showed that applied method in this experiment could be used for the fruits which are similar to sphere and could explain the unsteady heat transfer without complex calculations in the COOLING process. Based on the results of this research, the AIRflow velocity of 1. 3 m s-1 is recommended for FORCED AIR preCOOLING operations of pomegranate.

The objective of the present study was to detemine the influence of AIRflow velocities on preCOOLING process of pomegranate with thin peel (Shahvar variety), to evaluate the COOLING rate and temperature distribution in this product in order to design and optimize the preCOOLING system. FORCED AIR COOLING was applied for preCOOLING the center (arils) and peel (outer layer) of pomegranate. AIRflow velocities were 0.5, 1, and 1.3 m/s and the AIR temperature was 7.2°C in the AIR tunnel during the experiments. For calculating COOLING rates (half and seven-eighths COOLING time), lag factor and COOLING coefficient were determined from the experimental data by a regression analysis. Also, COOLING heterogeneity was evaluated in the center and outer layer of pomegranate at different AIRflow velocities. The results showed that with increasing the AIRflow velocity from 0.5 to 1.3 m/s, COOLING rates increased. Furthermore, with enhancing the AIRflow velocity, half and seven-eighths COOLING time decreased up to 19.35 and 21.76% in the center and by 32.95 and 19.63 in the peel, respectively. This finding was due to increasing convective heat transfer coefficient. COOLING heterogeneity decreased from 0.5 to 1 m/s and then increased at the AIRflow velocity of 1.3 m/s. This parameter was dependent on AIRflow velocity, COOLING coefficient and lag factor. The influence of AIRflow velocity was low after 6400s from starting the COOLING process both in center and in peel. The overall results demonstrated that application of this method can explain unsteady heat transfer in preCOOLING process of pomegranate and probably can be used for the other similarly shaped fruits.

Background and objectives: A considerable amounts of Fruits and vegetables is lost during the post-harvest stages. One of the most important processes that reduces fruit loss and extends their shelf life is pre-COOLING. In this process, biological activities of the products are decreased rapidly. The aim of this study was designing and constructing the FORCED AIR pre-COOLING system for horticultural products. Material Martials and methods: In this study, the FORCED AIR pre-COOLING system of horticultural products was designed and constructed according to the industrial pattern. To evaluate the performance and uniformity of COOLING process in the system, the preCOOLING of Peach was performed using fruit pallets with the three kinds of packages namely one-row package, two and three-row packages. In addition, the AIRflow rate was evaluated in three levels consists of 0. 5, 1 and 1. 5 liters per second per kilogram of product. Results: The evaluation of results indicated that the AIR velocity field was uniform around the constructed preCOOLING system with cross section dimension of 550×1200 mm and the height of 2050 mm. The suction fan power was 0. 5 hp and the COOLING capacity of the system about zero º C. Therefore, all fruits located in the different location of pallet were cooled with an acceptable uniformity viewpoint of the COOLING time and temperature. Also, the standard error of COOLING time was not significant. Among the studied factors, the effect of AIRflow rate on the average 3/4 th COOLING time of fruits in different boxes in the pallet and their standard deviation were significant. Increasing the AIRflow rate decreases the COOLING time and improves the uniformity of COOLING between the various packages, so that with three times increasing the AIRflow rate, the standard deviation decreases 59%. According to the results, the kind of package had a significant effect on the average 3/4 the COOLING time of fruits and the minimum and maximum COOLING time were related to the three rows and two rows boxes, respectively; but its effect on the standard deviation was not significant. Conclusion: The developed preCOOLING system could create and distribute of cold AIR uniformity between the fruits boxes in different locations of the pallet. There were no significant differences between the COOLING time of fruit in both AIRflow rate of 1 and 1. 5 lit s-1 kg p-1. Also, the rate of energy consumption is considerable in the high AIRflow rates. Therefore, it is recommended usage of cold AIRflow rate of 1 lit s-1 kg p-1. Although the three rows box had the lowest COOLING time, due to the mechanical damage probability, it's using had no advantage as compared to one-row box.

A FORCED convection AIR-COOLING of two identical heat sources mounted in a horizontal channel is numerically studied. Four effects of Reynolds number, separation distance, height and width of the components on the flow structure and heat transfer inside the channel have been examined. The entropy generation minimization method (EGM) is employed to optimize the heat transfer and fluid flow in the channel. The flow field is governed by the Navier– Stokes equation and the thermal field by the energy equation. The finite volume method and the SIMPLER algorithm are used to solve the continuity, momentum, energy and entropy generation equations. Results show that the mean Nusselt number increases with increase of the following parameters: Reynolds number, separation distance, height and width of the components. However, these parameters increase the total entropy generation, and thus provokes the degradation of the fan energy. The optimal values of separation distance, height and width heat source are: [(Sopt= 1 with W=0. 25, C=0. 25, Re=50, η =1. 134), (Copt=0. 3 with W=0. 25, S=0. 25, Re=100, η =0. 895) and (Wopt= 0. 1 S=0. 25, C=0. 25, Re=200, η =1. 004)], respectively, where η is the optimization factor (=Num/ST ∗ ) and is defined as the ratio of Nusselt number to the total entropy generation. Finally, the optimal and the best configuration for maximum heat transfer and minimum entropy generation is observed at Re=50, S=1, C=0. 25 and W=0. 25.

Postharvest technologies such as preCOOLING process and packaging have an important effect in the storage and marketing of fruits and vegetable. Proper designing of package and determination of performance parameters of preCOOLING process affect these technology. In this research, the various design of commercial packages as well as three levels of COOLING AIRflow rate were studied and their effects were evaluated on the 3 4 th, 7 8 th COOLING time and standard deviation of 3 4 th COOLING time. According to the results, the functional parameters and the best package was selected. Increasing in the AIRflow rate from 1 to 1. 5 L/s kgp had no significant effect on the standard deviation of 3 4 th COOLING time and decreased COOLING time just 11. 5%. Therefore, the AIRflow rate of 1 L/s kgp was selected as the optimum AIRflow rate in which the 3 4 th COOLING time and that's standard deviation were 87. 74 min and 15. 36, respectively. The results of preCOOLING process of peach using the commercial packages indicated that the 3 4 th COOLING time of fruit was in the range of 109. 3 to 94. 10 min and the standard deviation of 3 4 th COOLING time were varied from 11. 55 to 22. 22. The two and three layers packages had the lowest COOLING time, however, using of this package is not proper because of the high probability of fruit mechanical damage and heterogeneity of COOLING process. Using the one layer packages in the AIRflow rate of 1 L/s kgp (with 101. 3 and 155 min of 3 4 th and7 8 th COOLING time, respectively) is advisable with modifying its tray to reduce the preCOOLING time because of the energy consumption.

The Heller towers are the most common types of power plants COOLING towers، where their efficiency is very sensitive to wind. According to the general approach of COOLING systems designer، Direct dry COOLING (ACC) systems are more popular today in power plants located in arid areas. In Heller towers due to the empty space inside them, in this study, instead of proposing the replacement of ACC towers, the hybrid model is proposed, where steam is Directly passed into the ACC radiators without fan installed inside the Heller Tower, and condenses with a natural suction mechanism. The flow around the proposed model is investigated in three dimensions in two cases of no wind and at 8 different wind speeds with the assumption of incompressibility flow by the continuity, momentum, energy, and turbulence equations. The hybrid tower performance has been compared with the Fars power plant COOLING system and it has been shown that the proposed COOLING tower has performed 25% better than the Fars COOLING system in no wind condition. It has also performed better in wind conditions at different speeds except for speeds above 12. 5 m/s at a parallel and vertical array with the wind of ACCs. A vertical array of ACCs performance has been better than the parallel array. Therefore, the hybrid model with a vertical array of ACCs can be efficient to replace the COOLING system of the Fars power plant.

The purpose of the present study is to simulate a co-current pilot plant spray dryer with COOLING AIR jacket, AIR distributor and pressure nozzle, using a numerical technique. For the spray dryer, cooled AIR enters its secondary wall which has a helical passage around the drum and the main process fluid enters in the axial flow direction from an AIR distributor which is located on the top center position of the dryer. Fluid flow and heat transfer from the inner fluid to the surrounding AIR jacket is studied with a special treatment to predict convection heat transfer through the helix. By knowing the AIR temperature and flow velocity entering the jacket and the thermal condition of the process fluid entering the drum in a counter-current direction, combined free and FORCED turbulent convection heat transfer in the drum are investigated using the RNG k-e model of a turbulent model. Analyses were carried out using the SIMPLEC scheme and Euler-Lagrange model with and without spray water and milk to determine the pressure field, velocity distribution, temperature field of the process fluid throughout the drum and its wall, as well as the particles temperature and humidity, time of evaporation and diameter. Comparison of transient simulation of the particle size and time of evaporation with empirical relations is made for certain conditions. Validation of the numerical results with the experimental measurements shows good agreement.

A dry COOLING process has been developed in which nominal COOLING performance can be maintained even in high ambient temperature. Thermal energy is removed from COOLING water and dissipated to the atmosphere by means of water filled heat pipes. The principle of an AIR cooler using heat pipe as the heat transfer device is presented in this paper. A heat transfer mathematical model is developed to simulate the properties of the AIR cooler. The model based on e-NTU (effectiveness- Number of Transfer Units) method can be used to predict the performance of heat pipe AIR cooler. To improve the performance of heat pipe AIR cooler, the Ce/Cc and number of rows should be increased.