ABSTRACT
Abstract ..................................................................................................... 2 1.1 Introduction ...................................................................................... 3 1.2 The Importance of Precooling.......................................................... 5 1.3 Approaching the Optimum Precooling Method ............................... 6 1.3.1 How Does the Fresh Produce get Precooled? ...................... 7 1.3.2 Heat Load Calculations? ...................................................... 8 1.4 Types of Air Pre-Cooling Methods .................................................. 9 1.4.1 Natural Convection Air-Cooling
(Room Cooling Method) ...................................................... 9 1.4.1.1 Modified Room Cooling Method ........................ 12 1.4.2 Forced Air-Cooling ............................................................ 13 1.5 Packaging ....................................................................................... 17 1.6 Capacity Design ............................................................................. 18
1.7 System Classification ................................................................... 20 1.7.1 Wet Cooling System (Ice Banks) ..................................... 20 1.7.2 Dry System ...................................................................... 24 1.8 Mobile Pre-Cooling Facilities ...................................................... 26 1.9 Hydrocooling ............................................................................... 29 1.10 Vacuum Cooling ........................................................................... 34 1.11 Water Loss During Vacuum Cooling Determination ................... 39 1.12 Mathematical Modeling of Vacuum Cooling Process.................. 40 1.13 Features and Benefits of Vacuum Cooling .................................. 42 1.14 Slurry Ice ...................................................................................... 42 1.14.1 Direct Use of Slurry Ice ................................................. 43 1.14.2 Indirect Use of Slurry Ice ............................................... 46 1.15 Control of the Cold Chain Projects .............................................. 47 1.16 Variable Frequency Drive and Control Strategy .......................... 49 1.17 Temperature and Relative Humidity Control ............................... 52 1.18 Energy Saving .............................................................................. 56 1.19 Maintenance ................................................................................. 59 1.20 Conclusion ................................................................................... 60 Keywords ................................................................................................ 60 References ............................................................................................... 60
ABSTRACT
Temperature is the most single important factor that affects the quality and the shelf life and horticultural crops. The process of precooling is the removal of field heat as soon as possible after harvest since field heat arrest the deterioration and senescence process. The precooling process can be achieved via different methods forced air-cooling, hydrocooling, vacuum, slurry ice and evaporative cooling. Forced air precooling is the most common technique and is adapted to many commodities. The classification of the forced air precooling process includes wet deck system and the dry coil technique. Wet deck system is a mechanism, which provides air of low temperature and higher level of relative humidity, which minimizes the
weight loss of produce during the process of cooling. Dry coil system uses a direct expansion or secondary coolant coil sized to operate at a small temperature difference, which will maintain a high relative humidity of the leaving air stream. An evaluation of precooling systems is presented through the current study that exhibits a description of the theory behind each system and its different components. Different control, management and monitoring requirement are discussed with the most recent advances. Maintenance to extend the lifetime of the hard ware and maximize system credibility is also presented. Through this chapter, it is aimed to promote interest in precooling and encourage its use on a more widespread basis via the illustration of the different systems details.
