4.3Refrigeration 制 冷

Refrigeration was used by ancient civilizations when it was naturally available. The Roman rulers had slaves transport ice and snow from the high mountains to be used to preserve foods and to provide cool beverages in hot weather. Such natural sources of refrigeration were, of course, extremely limited in terms of location, temperatures, and scope. Means of producing refrigeration with machinery, called mechanical refrigeration, began to be developed in the 1850s. Today the refrigeration industry is a vast and essential part of any technological society, with yearly sales of equipment amounting to billions of dollars in the United States alone. 当能自然地制冷时，曾为古代文明所利用。罗马统治者让奴隶们从高山上搬运冰、雪，用来保存食物，并在暑热时提供冷饮。当然，这种制冷的自然资源就地点、气温和范围而言是极其有限的。使用机械产生冷量的方式称作机械制冷，是19世纪20年代开始发展起来的。当今，制冷工业是任何技术社会的庞大而重要的一部分，仅在美国设备年销售额就达到数十亿美元。 Uses of Refrigeration

It is convenient to classify the applications of refrigeration into the following categories: domestic, commercial, industrial, and air conditioning. Sometimes transportation is listed as a separate category. Domestic refrigeration is used for food preparation and preservation, ice making, and cooling beverages in the household. Commercial refrigeration is used in retail stores, restaurants, and institutions, for purposes the same as those in the household. Industrial refrigeration in the food industry is needed in processing, preparation, and largescale preservation. This includes use in food chilling and freezing plants, cold storage warehouses, breweries, and dairies, to name a few. Hundreds of other industries use refrigeration; among them are ice making plants, oil refineries, pharmaceuticals. Of course ice skating rinks need refrigeration.

Refrigeration is also widely used in both comfort air conditioning for people and in industrial air conditioning. Industrial air conditioning is used to create the air temperatures, humidity, and cleanliness required for manufacturing processes. Computers require a controlled environment. 1． 制冷的用途

制冷的用途可以简便的分为下列几类：家用、商用、工业用和空气调节。有时，运输被单独列为一类。家用制冷用于家庭的食物制备和保存，制冰和冰镇饮料。商业制冷多用在零售店、餐厅和公共机关，与家用制冷目的一样。食品工业中的工业制冷用语食品加工与制备，以及大规模的保存。略举几项，它包括在食品冷藏冷冻厂、冷藏库、酿酒厂和乳制品厂中的应用。成百上千的其他工业也使用制冷，其中有制冰厂、炼油厂、制药厂。当然滑冰厂需要制冷。

Methods of Refrigeration

Refrigeration, commonly spoken of as a cooling process is more correctly defined as the removal of heat from a substance to bri

ng it to or keep it at a desirable low temperature, below the temperature of the surroundings. The most widespread method of producing mechanical refrigeration is called the vapor compression system. In this system a volatile liquid refrigerant is evaporated in an evaporator; this process results in a removal of heat (cooling) from the substance to be cooled. A compressor and condenser are required to maintain the evaporation process and to recover the refrigerant for reuse. 2. 制冷的方法

制冷，通常所说的冷却过程，可更加正确地定义为“从一物质中排除热量，使其达到或保持在一理想的低温状态，低于周围环境的温度。”传播最为广泛的机械制冷的方法称为蒸汽压缩系统。在此系统中，易发挥的液态制冷剂在一个蒸发器内蒸发，其结果是使用热量从被冷却物质排出（冷却）。为了维持蒸发过程和使制冷剂复员再用，需设置压缩机和冷凝器。 另一种广泛使用的方法称为吸收式制冷系统。在制冷过程中制冷剂蒸发（如同在蒸汽压缩系统中一样），但这种蒸发是通过在另一种液体中吸收制冷剂来维持的。

Another widely used method is called the absorption refrigeration system. In this process a refrigerant is evaporated (as with the vapor compression system), but the evaporation is maintained by absorbing the refrigerant in another fluid.

Other refrigeration methods are thermoelectric, steam jet, and air cycle refrigeration. These systems are used only in special applications and heir functioning will not be explained here. Thermoelectric refrigeration is still quite expensive; some small tabletop domestic refrigerators are cooled by this method. Steam jet refrigeration is inefficient. Often used on ships in the past ,it has been largely replaced by the vapor compression system The air cycle is sometimes used in air conditioning of aircraft cabins. Refrigeration at extremely low temperatures, below about-200F (-130C), is called cryogenics. Special systems are used to achieve these conditions. One use of refrigeration at ultralow temperatures is to separate oxygen and nitrogen from air and to liquefy them. 其他制冷方法有热电式、蒸气喷射和空气循环制冷。这些系统仅用于特殊用途，它们的工作原理在此不做解释。热电式制冷仍相当昂贵；一些桌置式小型家用冰箱用这种方法制冷。蒸气喷射制冷效率不高，过去常用于船舶，现已大量被蒸气压缩系统所代替。空气循环制冷有时用于机舱空调。以极低的温度制冷，低于大约-200 0F（-1300C）被称作低温技术。要用特殊的设备达到这种状态。超低温制冷的一种用途是从空气中分离氧和氮，并使它们液化。

Refrigeration Equipment制冷设备

The main equipment components of vapor compression refrigeration system are the familiar evaporator, compressor, and condenser. The equipment may be separate or of the unitary （also called self-contained ）type.Unitary equipment is assembled in the factory.The household refrigerator is a common example of unitary equipment .Obvious advantages of

unitary equipment are that it is more compact and less expensive to

manufacture if made in large quantities.蒸气压缩系统的主要设备组件是熟悉的蒸发、压缩机和冷凝器。设备可能是分离的或整体式的（也称作整装的）。整体式设备是在工厂组装的。家用冰箱是整体式设备的普通实例。整体式设备明显的优点上更加紧凑，并在大批量生产时较便宜。

There is a variety of commercial refrigeration equipment;each has a specific function.Reach-in cabinets,walk-in coolers,and display cases are widely used in the food service business.Automatic ice makers ,drinking water cools,and refrigerated vending machines are also commonly encountered equipment.

商业用制冷设备种类繁多；每种都有其指定的功能。开式冷柜、开放式冷藏柜和陈列柜，他们都广泛应用于食品工业中。自动制冰机，冷饮机，自动售卖制冷机也都是常见的设备。 Air conditioning includes theheating ,cooling ,humidifying,dehumidifying ,and cleaning(filtering)of air in internal environments.Occasionally it will be necessary to mention some aspects of air conditioning when we deal with the interface between the two subjects.A study of the fundamentals and equipment involved in air conditioning is nevertheless of great value even for those primarily interested in refrigeration.

内部环境空气调节器包括加热、制冷、加湿、除湿、净化（过滤）。偶尔，当我们处理学科交叉时，有必要提及空气调节的一些方面。然而，对于那些制冷感兴趣的人来说吗，对空气调节中涉及的基本原理和设备的研究具有重大意义。