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UNIT IIIREFRIGERATION AND FREEZING GAIN NEW EMPHASIS Bill Drennan, Food Engineering, March, 1989. It is clear that food production must be expanded steadily at a high rate and particularly in the developing countries, in order to keep pace with population growth and in order to improve the quantity and quality of the daily rations in a large part of the world. Food technology, and refrigeration in particular, will have an extremely important task in future: to provide a system of emergency reserves and worldwide food exchange without excessive waste. These jobs can, in principle, be done by using existing technology on a much larger scale, for instance in handling of cereals. However, the situation is different for perishable foods where the losses are much higher and the costs often prohibitive with present day technology. It is obvious that better and more efficient handling methods are required. In very many cases the refrigeration procedures – chilling or freezing - seem to offer the best prospects for development. Although the theoretical background appears to be sufficient for practical use, the technical methods are capable of improvement. There is no doubt that the future holds a great challenge for the refrigeration engineer in the food industry, as in so many other important fields. Some years ago an energy crisis threatened to put freezing and refrigeration equipment into a risk group. Frozen foods were to be replaced by dried products. Today, however, frozen food is the fastest–growing category in the food industry. And there is rising consumer demand for more and more refrigerated products. There are many reasons for this turn-around, but two stand out above all others. Energy costs have not risen as fast as expected. And modern refrigeration and freezing equipment have joined the high tech club. Frozen and refrigerated foods are enjoying a surge in popularity because consumers are willing to pay for increased convenience and freshness. As a result, many manufacturers have entered the refrigerated foods field. Meeting the Challenge. Today’s cooling and freezing systems feature higher speeds, computer control and greater efficiency. Some systems are combined with other cooling methods, to reduce both machine size and freezing costs. In general, the current trend in refrigeration and freezing equipment is to meet today and tomorrow’s challenges with both imagination and new technology. And one of major trends is energy management devices and supervisory monitoring equipment. These devices can be handled from a central location via normal telecommunication systems. Another trend can be seen in current developments: conventional electromechanical controls are being replaced by microprocessor and computer-based ones. A prime example of such supervisory control introduced recently is FES MicroNet. This computer-based control system networks refrigeration equipment together, and coordinates the system’s entire operation from a central location for optimum efficiency, reduced energy costs and extended machine life. It automatically sequences compressors; controls head pressure and evaporator defrost and displays all pre-alarms and failures in the order they occurred. The real advantage of new controlling systems is that you can pre-program your equipment for optimum operating efficiency, under varying conditions. That can permit virtually unattended plants. Refrigeration / freezing experts expect increased modernization of existing facilities. According to Robert J.Vig , of Vilter Manufacturing Corp., “there will be larger systems and more centralized warehousing with less operating personnel per pound of product and more electronic gadgets. Changes in equipment. Since the late 1980’s refrigeration and freezing equipment has undergone considerable change. In many cases, these developments were dictated by new varieties of food products; in other cases, the refrigeration industry initiated better freezing methods. There have appeared some new types of refrigeration units; for example, Variable Retention Time freezers in which one or more products with different freezing times can be frozen automatically and simultaneously. New compressors are becoming increasingly versatile and energy efficient. Screw compressors are the major types in use today. The trend is away from reciprocating compressors. Though, Vilter Manufacturing Corp. has introduced a versatile reciprocating compressor, capable of holding a wide range of applications. Its design allows it to be used with virtually any industrial refrigerant at compression ratio of up 8:1 with ammonia and up to 14:1 with some halocarbons. Interest is very high in individual quick freezing (IQF] units that are incorporated into a processing line. IQF freezers are designed for odd-shaped products, products that are to be frozen individually, and continuous processes. Product is taken by conveyor belt through a freezing area. Existing equipment has been improved, too. Blast freezers are being automated and improvements are being made in other areas by simply replacing old units by more effective and large equipment. Cost containment is a major concern. The substitution of synthetic materials (for instance, substituting Nylon or Teflon for stainless steel) has led to lower costs and, in some instances, better performance. Even system featuring low operating cost are changing. Plate freezing, for example, is the lowest cost method of freezing product. However, more and more large processors are now requesting systems with automatic operation, many of them using microprocessor controls. Conclusions. High-tech is changing new equipment for refrigeration and freezing food products. Today’s efficient cooling and freezing systems feature high speeds, microprocessor controls. There are appearing a lot of new kinds of refrigeration systems that save energy and can handle the almost endless variety of convenience foods created over recent years. What’s coming in the future? The refrigeration industry is entering era of innovative, highly improved equipment. Designers are now offering highly developed freezers that are far ahead of the parent equipment offered just a few years ago. Tremendous improvements in reliability and lower maintenance costs are also being offered. Примечание к тексту:
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