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Food Preservation Methods
Published in İbrahim Dinçer, Heat Transfer in Food Cooling Applications, 1997
Chilling is a cooling process which is applied to food products above their freezing point (i.e., minus 1°C). In practice, the term cooling or precooling or chilling is frequently used. The most important chilling operation is precooling. Precooling is a cooling process in which the field temperature of fruits and vegetables is reduced to their storage and/or transportation temperature as quickly as possible after harvest. This reduces the rates of biochemical and microbiological changes, maintains the shelf life of fresh food products, and extends the storage period [17–20]. In general, four common methods of precooling (vacuum cooling, hydrocooling, air cooling, and hydraircooling) have found application. Vacuum cooling is used for certain vegetable crops. It is basically an evaporative cooling process in which water is supplied externally or by the commodity being cooled. Hydrocooling uses chilled water to cool perishable commodities. Forced air cooling utilizes air as a cooling medium. Recent research on unit load systems led to an experimental concept of precooling called hydraircooling. This method utilizes a mixture of refrigerated air and water in a fine mist spray that is circulated around and through the stack by forced convection. For the cooling of fruits and vegetables, the precooling method is often determined by factors such as cost, convenience, effectiveness, simplicity, processing conditions, utilization of equipment in relation to the total packing operation, personal preference, and product requirements. Detailed information on precooling and its applications, along with technical and operational aspects, is given in Chapter 2.
Cooling
Published in Fang Zhu, Baitun Yang, Power Transformer Design Practices, 2021
Due to high velocity of forced air, heat exchange on the air side increased. Compared to natural air cooling, with the same amount of loss to be dissipated, the oil will be cooled further, the oil temperature rise, ΔΘoil in wdg, will decrease and branch C-D will be somewhat more curvedly bended, as shown in Figure 7.4 case (a). It is said that by changing from natural air cooling to forced air cooling, the cooling can be improved about 2.6 times at the same ambient temperature [3]. The effect of radiator altitude on oil rises is same as the ONAN case since the nature of oil flow doesn’t change.
Food Refrigeration Aspects
Published in Mohammed M. Farid, Mathematical Modeling of Food Processing, 2010
Forced-air cooling is widely used because it is simple, economical, sanitary and relatively noncorrosive to equipment. Its major disadvantages are the dangers of excessive dehydration and possibility of freezing the product if air temperatures below 0°C are used. Some products cooled with air are meat, citrus fruits, grapes, cantaloupes, green beans, strawberries, plums, nectarines, sweet cherries, cauliflowers and apricots.
Effects of a liquid cooling vest on physiological and perceptual responses while wearing stab-resistant body armor in a hot environment
Published in International Journal of Occupational Safety and Ergonomics, 2022
Mengqi Yuan, Yuchen Wei, Qiqi An, Jie Yang
Stab-resistant body armor (SRBA) is widely used to protect personnel from operational hazards [1,2], and dramatically increases field survival rates and reduces the risk of mortality [3–5]. However, SRBA has a negative effect on the physiological [6–9] and perceptual [10,11] responses of the wearer, which may lead to heat stress and reduce movement and work performance. Cooling systems are one of the most feasible approaches to reduce heat stress and improve the thermal comfort and working efficiency of personnel in military, aerospace, firefighting and industrial environments (e.g., mining, iron, glass and rubber foundries) [12,13]. Cooling systems can be either passive cooling systems (e.g., phase change material) or active cooling systems (e.g., liquid cooling and forced air ventilation).
Mechanism design and simulation analysis of a new high-speed PET preform removal machine
Published in Mechanics Based Design of Structures and Machines, 2022
Zeng Huang, Chenxue Wang, Yujie Du
The PET preform needs to be cooled before unloading. The cooling method used in this design is forced air cooling. Forced air cooling method following the first law of thermodynamics is mainly adopted in the design. According to the principles of heat transfer, the convective heat transfer process satisfies (Eq. (37)). where Q is the heat transferred from the PET preform to the environment per unit time, is the convective heat transfer coefficient, A is the area of the PET preform in contact with air, T1 is the average temperature of the preform surface, and Ta is home temperature.