暖通空调专业外文翻译
暖通空调专业外文翻译
英文文献
Air Conditioning Systems
Air conditioning has rapidly grown over the past 50 years, from a luxury to a standard system included in most residential and commercial buildings. In 1970, 36% of residences in the U.S. were either fully air conditioned or utilized a room air conditioner for cooling (Blue, et al., 1979). By 1997, this number had more than doubled to 77%, and that year also marked the first time that over half (50.9%) of residences in the U.S. had central air conditioners (Census Bureau, 1999). An estimated 83% of all new
homes constructed in 1998 had central air conditioners (Census Bureau, 1999). Air conditioning has also grown rapidly in commercial buildings. From 1970 to 1995, the percentage of commercial buildings
with air conditioning increased from 54 to 73% (Jackson and Johnson, 1978, and DOE, 1998).
Air conditioning in buildings is usually accomplished with the use
of mechanical or heat-activated equipment. In most applications, the air conditioner must provide both cooling and dehumidification to maintain comfort in the building. Air conditioning systems are also used in other applications, such as automobiles, trucks, aircraft, ships, and
industrial facilities. However, the description of equipment in this
chapter is limited to those commonly used in commercial and residential buildings.
Commercial buildings range from large high-rise office buildings to the corner convenience store. Because of the range in size and types of buildings in the commercial sector, there is a wide variety of equipment applied in these buildings. For larger buildings, the air conditioning equipment is part of a total system design that includes items such as a piping system, air distribution system, and cooling tower. Proper design of these systems requires a qualified engineer. The residential building sector is dominated
by single family homes and low-rise apartments/condominiums. The cooling equipment applied in these buildings comes in standard “packages” that are
often both sized and installed by the air conditioning contractor.
The chapter starts with a general discussion of the vapor compression refrigeration cycle then moves to refrigerants and their selection, followed by packaged Chilled Water Systems。
1.1 Vapor Compression Cycle
Even though there is a large range in sizes and variety of air conditioning systems used in buildings, most systems utilize the vapor compression cycle to produce the desired cooling and dehumidification. This cycle is also used for refrigerating and freezing foods and for automotive air conditioning. The first patent on a mechanically driven refrigeration system was issued to Jacob Perkins in 1834 in London, and
the first viable commercial system was produced in 1857 by James Harrison and D.E. Siebe.Besides vapor compression, there are two less common methods used to produce cooling in buildings: the absorption cycle and evaporative cooling. These are described later in the chapter. With the vapor compression cycle, a working fluid, which is called the refrigerant, evaporates and condenses at suitable pressures for
practical equipment designs.
The four basic components in every vapor compression refrigeration system are the compressor, condenser, expansion device, and evaporator. The compressor raises the pressure of the refrigerant vapor so that the refrigerant saturation temperature is slightly above the temperature of the cooling medium used in the condenser. The type of compressor used depends on the application of the system. Large electric chillers typically use a centrifugal compressor while small residential equipment uses a reciprocating or scroll compressor.
The condenser is a heat exchanger used to reject heat from the refrigerant to a cooling medium. The refrigerant enters the condenser and usually leaves as a subcooled liquid. Typical cooling mediums used
in condensers are air and water. Most residential-sized equipment uses air as the cooling medium in the condenser, while many larger chillers use water. After leaving the condenser, the liquid refrigerant expands to a lower pressure in the expansion valve.
The expansion valve can be a passive device, such as a capillary
tube or
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short tube orifice, or an active device, such as a thermal expansion valve or electronic expansion valve. The purpose of the valve is toregulate the flow of refrigerant to the evaporator so that the refrigerant is superheated when it reaches the suction of the compressor.
At the exit of the expansion valve, the refrigerant is at a temperature below that of the medium (air or water) to be cooled. The refrigerant travels through a heat exchanger called the evaporator. It absorbs energy from the air or water circulated through the evaporator.
If air is circulated through the evaporator, the system is called a . If water is circulated through direct expansion system
the evaporator, it is called a chiller. In either case, the
refrigerant does
not make direct contact with the air or water in the evaporator. The refrigerant is converted from a low quality, two-phase fluid to a superheated
vapor under normal operating conditions in the evaporator. The vapor formed must be removed by the compressor at a sufficient rate to
maintain the low pressure in the evaporator and keep the cycle operating.
All mechanical cooling results in the production of heat energy that must be rejected through the condenser. In many instances, this heat energy is rejected to the environment directly to the air in the condenser or indirectly to water where it is rejected in a cooling tower. With some applications, it is possible to utilize this waste heat energy
to provide simultaneous heating to the building. Recovery of this waste heat at temperatures up to 65?C (150?F) can be used to reduce costs for space heating.
Capacities of air conditioning are often expressed in either tons or kilowatts (kW) of cooling. The ton is a unit of measure related to the ability of an ice plant to freeze one short ton (907 kg) of ice in 24 hr. Its value is 3.51 kW (12,000 Btu/hr). The kW of thermal cooling capacity produced by the air conditioner must not be confused with the amount of electrical power (also expressed in kW) required to produce the cooling effect.
2.1 Refrigerants Use and Selection
Up until the mid-1980s, refrigerant selection was not an issue in most
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building air conditioning applications because there were no regulations on the use of refrigerants. Many of the refrigerants historically used for building air conditioning applications have been chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Most of these refrigerants are nontoxic and nonflammable. However, recent U.S. federal regulations (EPA 1993a; EPA 1993b) and international agreements (UNEP, 1987) have placed restrictions on the production and use of CFCs and HCFCs. Hydrofluorocarbons (HFCs) are now being used in some applications where CFCs and HCFCs were used. Having an understanding of refrigerants can help a building owner or engineer make a more informed
decision about the best choice of refrigerants for specific applications. This section discusses the different refrigerants used in or proposed
for building air conditioning applications and the regulations affecting their use.
The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) has a standard numbering system,for identifying refrigerants (ASHRAE, 1992). Many popular CFC, HCFC, and HFC
refrigerants are in the methane and ethane series of refrigerants. They are called halocarbons, or halogenated hydrocarbons, because of the presence of halogen elements such as fluorine or chlorine (King, 1986).
Zeotropes and azeotropes are mixtures of two or more different refrigerants. A zeotropic mixture changes saturation temperatures as it evaporates (or condenses) at constant pressure. The phenomena is called temperature glide. At atmospheric pressure, R-407C has a boiling (bubble) point of –44?C (–47?F)
and a condensation (dew) point of –37?C (–35?F), which gives it a temperature
glide of 7?C (12?F). An azeotropic mixture behaves like a single component
refrigerant in that the saturation temperature does not change appreciably as it evaporates or condenses at constant pressure. R-410A has a small enough temperature glide (less than 5.5?C, 10?F) that it is considered a
near-azeotropic refrigerant mixture.
ASHRAE groups refrigerants by their toxicity and flammability (ASHRAE, 1994).Group A1 is nonflammable and least toxic, while Group B3 is flammable and
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most toxic. Toxicity is based on the upper safety limit for airborne exposure to the refrigerant. If the refrigerant is nontoxic in
quantities less than 400 parts per million, it is a Class A refrigerant. If exposure to less than 400 parts per million is toxic, then the substance is given the B designation. The numerical designations refer to the flammability of the refrigerant. The last column of Table 4.2.1 shows the toxicity and flammability rating of common refrigerants.
Refrigerant 22 is an HCFC, is used in many of the same applications, and is still the refrigerant of choice in many reciprocating and screw chillers as well as small commercial and residential packaged equipment. It operates at a much higher pressure than either R-11 or R-12. Restrictions on the production of HCFCs will start in 2004. In 2010, R-22 cannot be used in new air conditioning equipment. R-22 cannot be produced after 2020 (EPA, 1993b).
R-407C and R-410A are both mixtures of HFCs. Both are considered replacements for R-22. R-407C is expected to be a drop-in replacement refrigerant for R-22. Its evaporating and condensing pressures for air conditioning applications are close to those of R-22 (Table 4.2.3). However, replacement of R-22 with R-407C should be done only after consulting with the equipment manufacturer. At a minimum, the lubricant
and expansion device will need to be replaced. The first residential-sized air conditioning equipment using R-410A was introduced in the U.S. in 1998. Systems using R-410A operate at approximately 50% higher pressure than R-22 (Table 4.2.3); thus, R-410A cannot be used as a drop-in refrigerant for R-22. R-410A systems utilize compressors, expansion valves, and heat exchangers designed specifically for use with that refrigerant.
Ammonia is widely used in industrial refrigeration applications and in ammonia water absorption chillers. It is moderately flammable and has a class B toxicity rating but has had limited applications in commercial buildings unless the chiller plant can be isolated from the building being cooled (Toth, 1994, Stoecker, 1994). As a refrigerant, ammonia has many desirable qualities. It has a high specific heat and high thermal conductivity. Its enthalpy of vaporization
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is typically 6 to 8 times higher than that of the commonly used halocarbons, and it provides higher heat transfer compared to halocarbons. It can be used in both reciprocating and centrifugal compressors.
Research is underway to investigate the use of natural refrigerants, such as carbon dioxide (R-744) and hydrocarbons in air conditioning and refrigeration systems (Bullock, 1997, and Kramer, 1991). Carbon dioxide operates at much higher pressures than conventional HCFCs or HFCs and requires operation above the critical point in typical air conditioning
applications. Hydrocarbon refrigerants, often thought of as too hazardous because of flammability, can be used in conventional compressors and have been used in industrial applications. R-290, propane, has operating pressures close to R-22 and has been proposed as a replacement for R-22 (Kramer, 1991). Currently, there are no commercial systems sold in the U.S. for building operations that use either carbon dioxide or flammable refrigerants.
3.1 Chilled Water Systems
Chilled water systems were used in less than 4% of commercial buildings in the U.S. in 1995. However, because chillers are usually installed in larger buildings, chillers cooled over 28% of the U.S. commercial building floor space that same year (DOE, 1998). Five types of chillers are commonly applied to commercial buildings: reciprocating, screw, scroll, centrifugal, and absorption. The first four utilize the vapor compression cycle to produce chilled water. They differ primarily in the type of compressor used. Absorption chillers utilize thermal energy (typically steam or combustion source) in an absorption cycle with either an ammonia-water or water-lithium bromide solution to produce chilled water.
3.2 Overall System
An estimated 86% of chillers are applied in multiple chiller arrangements like that shown in the figure (Bitondo and Tozzi, 1999). In chilled water systems, return water from the building is circulated through each chiller evaporator
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where it is cooled to an acceptable temperature (typically 4 to 7?C) (39 to
45?F). The chilled water is then distributed to water-to-air heat exchangers
spread throughout the facility. In these heat exchangers, air is cooled and dehumidified by the cold water. During the process, the
chilled water increases in temperature and must be returned to the
chiller(s).
The chillers are water-cooled chillers. Water is circulated through the condenser of each chiller where it absorbs heat energy rejected from the high pressure refrigerant. The water is then pumped to a cooling tower where the water is cooled through an evaporation process. Cooling towers are described in a later section. Chillers can also be air cooled. In this configuration, the condenserwould be a refrigerant-to-air heat exchanger with air absorbing the heat energy rejected by the high pressure refrigerant.
Chillers nominally range in capacities from 30 to 18,000 kW (8 to 5100 ton). Most chillers sold in the U.S. are electric and utilize vapor compression refrigeration to produce chilled water. Compressors for
these systems are either reciprocating, screw, scroll, or centrifugal in design. A small number of centrifugal chillers are sold that use either an internal combustion engine or steam drive instead of an electric
motor to drive the compressor.
The type of chiller used in a building depends on the application.
For large office buildings or in chiller plants serving multiple buildings, centrifugal compressors are often used. In applications under 1000 kW (280 tons) cooling capacities, reciprocating or screw chillers may be more appropriate. In smaller applications, below 100 kW (30 tons), reciprocating or scroll chillers are typically used.
3.3 Vapor Compression Chillers
The nominal capacity ranges for the four types of electrically
driven vapor compression chillers. Each chiller derives its name from
the type of compressor used in the chiller. The systems range in capacities from the smallest scroll (30 kW; 8 tons) to the largest centrifugal (18,000 kW; 5000 tons).Chillers can utilize either an HCFC (R-22 and R-123) or HFC (R-134a) refrigerant. The steady
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state efficiency of chillers is often stated as a ratio of the power input (in kW) to the chilling capacity (in tons). A capacity rating of one ton is equal to 3.52 kW or 12,000 btu/h. With this measure of efficiency, the smaller number is better. centrifugal chillers are the most efficient; whereas, reciprocating chillers have the worst
efficiency of the four types. The efficiency numbers provided in the table are the steady state full-load efficiency determined in accordance to ASHRAE Standard 30 (ASHRAE, 1995). These efficiency numbers do not include the auxiliary equipment, such as pumps and cooling tower fans
that can add from 0.06 to 0.31 kW/ton to the numbers shown
Chillers run at part load capacity most of the time. Only during the highest thermal loads in the building will a chiller operate near its rated capacity. As a consequence, it is important to know how the efficiency of the chiller varies with part load capacity. a representative data for the efficiency (in kW/ton) as a function of percentage full load capacity for a reciprocating, screw, and scroll chiller plus a centrifugal chiller with inlet vane control and one with variable frequency drive (VFD) for the compressor. The reciprocating chiller increases in efficiency as it operates at a smaller percentage of full load. In contrast, the efficiency of a centrifugal with inlet vane control is relatively constant until theload falls to about 60% of its rated capacity and its kW/ton increases to almost twice its fully loaded value.
In 1998, the Air Conditioning and Refrigeration Institute (ARI) developed a new standard that incorporates into their ratings part load performance of chillers (ARI 1998c). Part load efficiency is expressed by a single number called the integrated part load value (IPLV). The IPLV takes data similar to that in Figure 4.2.3 and weights it at the 25%, 50%, 75%, and 100% loads to produce a single integrated efficiency number. The weighting factors at these loads are 0.12, 0.45, 0.42, and 0.01, respectively. The equation to determine IPLV is:
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Most of the IPLV is determined by the efficiency at the 50% and 75% part load values. Manufacturers will provide, on request, IPLVs as well as part load efficiencies.
The four compressors used in vapor compression chillers are each briefly described below. While centrifugal and screw compressors are primarily used in chiller applications, reciprocating and scroll compressors are also used in smaller unitary packaged air conditioners and heat pumps.
3.4 Reciprocating Compressors
The reciprocating compressor is a positive displacement compressor. On the intake stroke of the piston, a fixed amount of gas is pulled into the cylinder. On the compression stroke, the gas is compressed until the discharge valve opens. The quantity of gas compressed on each stroke is equal to the displacement of the cylinder. Compressors used in chillers have multiple cylinders, depending on the capacity of the compressor. Reciprocating compressors use refrigerants with low specific volumes and relatively high pressures. Most reciprocating chillers used in building applications currently employ R-22.
Modern high-speed reciprocating compressors are generally limited to a pressure ratio of approximately nine. The reciprocating compressor is basically a constant-volume variable-head machine. It handles various discharge pressures with relatively small changes in inlet-volume
flow rate as shown by the heavy line (labeled 16 cylinders).Condenser operation in many chillers is related to ambient conditions, for example, through cooling towers,
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so that on cooler days the condenser pressure can be reduced. When
the air conditioning load is lowered, less refrigerant circulation is required. The resulting load characteristic is represented by the solid line that runs from the upper right to lower left.
The compressor must be capable of matching the pressure and flow requirements imposed by the system. The reciprocating compressor matches the imposed discharge pressure at any level up to its limiting pressure ratio. Varying capacity requirements can be met by providing devices
that unload individual or multiple cylinders. This unloading is accomplished by blocking the suction or discharge valves that open
either manually or automatically. Capacity can also be controlled
through the use of variable speed or multi-speed motors. When capacity control is implemented on a compressor, other factors at part-load conditions need to considered, such as (a) effect on compressor and sound when unloaders are used, (b) the need for good oil return vibration
because of lower refrigerant velocities, and (c) proper functioning of expansion devices at the lower capacities.
With most reciprocating compressors, oil is pumped into the refrigeration system from the compressor during normal operation. Systems must be designed carefully to return oil to the compressor crankcase to provide for continuous lubrication and also to avoid contaminating heat-exchanger surfaces.
Reciprocating compressors usually are arranged to start unloaded so that normal torque motors are adequate for starting. When gas engines are used for reciprocating compressor drives, careful matching of the torque requirements of the compressor and engine must be considered.
3.5 Screw Compressors
Screw compressors, first introduced in 1958 (Thevenot, 1979), are positive displacement compressors. They are available in the capacity ranges that overlap with reciprocating compressors and small centrifugal compressors. Both twin-screw and single-screw compressors are used in chillers. The twin-screw compressor is also called the helical rotary compressor. A cutaway of a
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twin-screw compressor design. There are two main rotors (screws). One is designated male and the other female .
The compression process is accomplished by reducing the volume of
the refrigerant with the rotary motion of screws. At the low pressure side of the compressor, a void is created when the rotors begin to
unmesh. Low pressure gas is drawn into the void between the rotors. As the rotors continue to turn, the gas is progressively compressed as it moves toward the discharge port. Once reaching a predetermined volume ratio, the discharge port is uncovered and the gas is discharged into the high pressure side of the system. At a rotation speed of 3600 rpm, a screw compressor has over 14,000 discharges per minute (ASHRAE, 1996).
Fixed suction and discharge ports are used with screw compressors instead of valves, as used in reciprocating compressors. These set the built-in volume
— the ratio of the volume of fluid space in the meshing rotors at the ratio
beginning of the compression process to the volume in the rotors as the discharge port is first exposed. Associated with the built-in volume ratio is a pressure ratio that depends on the properties of the refrigerant being compressed. Screw compressors have the capability to operate at pressure ratios of above 20:1 (ASHRAE, 1996). Peak efficiency is obtained if the discharge pressure imposed by the system matches the pressure developed by the rotors when the discharge port is exposed. If the interlobe pressure in the screws is greater or less than discharge pressure, energy losses occur but no harm is done to the compressor.
Capacity modulation is accomplished by slide valves that provide a variable suction bypass or delayed suction port closing, reducing the volume of refrigerant compressed. Continuously variable capacity control
is most common, but stepped capacity control is offered in some manufacturers’ machines.
Variable discharge porting is available on some machines to allow control of the built-in volume ratio during operation.
Oil is used in screw compressors to seal the extensive clearance spaces between the rotors, to cool the machines, to provide lubrication, and to serve
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as hydraulic fluid for the capacity controls. An oil separator is required for the compressor discharge flow to remove the oil from the high-pressure refrigerant so that performance of system heat exchangers will not be penalized and the oil can be returned for reinjection in the compressor.
Screw compressors can be direct driven at two-pole motor speeds (50 or 60 Hz). Their rotary motion makes these machines smooth running and quiet.
is high when the machines are applied properly. Screw compressors Reliability
are compact so they can be changed out readily for replacement or maintenance. The efficiency of the best screw compressors matches or exceeds that of the best reciprocating compressors at full load. High isentropic and volumetric efficiencies can be achieved with screw compressors because there are no suction or discharge valves and small
clearance volumes. Screw compressors for building applications generally use either R-134a or R-22.
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中文译文
空调系统
过去 50 年以来，空调得到了快速的发展，从曾经的奢侈品发展到可应用于大
多数住宅和商业建筑的比较标准的系统。在 1970 年的美国， 36% 的住宅不是全
空气调节就是利用一个房间空调器冷却;到1997年，这一数字达到了 77%，在那年作的第一次市场调查表明，在美国有超过一半的住宅安装了中央空调 (人口普查局, 1999)。在1998年，83%的新建住宅安装了中央空调 ( 人口普查局, 1999)。中央
空调在商业建筑物中也得到了快速的发展，从 1970年到1995年，有空调的商业
建筑物的百分比从54%增加到
。 73%(杰克森和詹森,1978)
建筑物中的空气调节通常是利用机械设备或热交换设备完成.在大多数应用
中，建筑物中的空调器为维持舒适要求必须既能制冷又能除湿，空调系统也用于其他的场所，例如汽车、卡车、飞机、船和工业设备，然而，在本章中，仅说明空调在商业和住宅建筑中的应用。
商业的建筑物从比较大的多层的办公大楼到街角的便利商店，占地面积和类型
差别很大，因此应用于这类建筑的设备类型比较多样，对于比较大型的建筑物，空调设备设计是总系统设计的一部分，这部分包括如下项目:例如一个管道系统设
计，空气分配系统设计，和冷却塔设计等。这些系统的正确设计需要一个有资质的工程师才能完成。居住的建筑物(即研究对象)被划分成单独的家庭或共有式公寓，应用于这些建筑物的冷却设备通常都是标准化组装的，由空调厂家进行设计尺寸和安装。
本章节首先对蒸汽压缩制冷循环作一个概述，接着介绍制冷剂及制冷剂的选择，最后介绍冷水机组。
1.1 蒸汽压缩循环
虽然空调系统应用在建筑物中有较大的尺寸和多样性,大多数的系统利用蒸汽压缩循环来制取需要的冷量和除湿，这个循环也用于制冷和冰冻食物和汽车的空调，在1834年，一个名叫帕金斯的人在伦敦获得了机械制冷系统的第一专利权，在1857年，詹姆士和赛博生产出第一个有活力的商业系统，除了蒸汽压缩循环之外 , 有两种不常用的制冷方法在建筑物中被应用: 吸收式循环和蒸发式冷却，这些将在后面的章节中讲到。对于蒸汽压缩制冷循环，有一种叫制冷剂的工作液体，它能在适当的工艺设备设计压力下蒸发和冷凝。
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每个蒸汽压缩制冷系统中都有四大部件，它们是压缩机、冷凝器、节流装置和蒸发器。压缩机提升制冷剂的蒸汽压力以便使制冷剂的饱和温度微高于在冷凝器中冷却介质温度，使用的压缩机类型和系统的设备有关，比较大的电冷却设备使用一个离心式的压缩机而小的住宅设备使用的是一种往复或漩涡式压缩机。
冷凝器是一个热交换器，用于将制冷剂的热量传递到冷却介质中，制冷剂进入冷凝器变成过冷液体，用于冷凝器中的典型冷却介质是空气和水，大多数住宅建筑的冷凝器中使用空气作为冷却介质，而大型系统的冷凝器中采用水作为冷却介质。
液体制冷剂在离开冷凝器之后，在膨胀阀中节流到一个更低的压力。膨胀阀是一个节流的装置，例如毛细管或有孔的短管，或一个活动的装置，例如热力膨胀阀或电子膨胀阀，膨胀阀的作用是到蒸发器中分流制冷剂以便当它到压缩物吸入口的时候, 制冷剂处于过热状态，在膨胀阀的出口，制冷剂的温度在介质(空气或水) 的温度以下。之后制冷剂经过一个热交换器叫做蒸发器，它吸收通过蒸发器的空气或水的热量，如果空气经过蒸发器在流通,该系统叫做一个直接膨胀式系统，如果
水经过蒸发器在流通,它叫做冷却设备，在任何情况下，在蒸发器中的制冷剂不直接和空气或水接触，在蒸发器中，制冷剂从一个低品位的两相液体转换成在正常的工艺条件下过热的蒸汽。蒸汽的形成要以一定的足够速度被压缩机排出以维持在蒸发器中低压和保持循环进行。
所有在生产中的机械冷却产生的热量必须经过冷凝器散发，在许多例子中，在冷凝器中这个热能被直接散发到环境的空气中或间接地散发到一个冷却塔的水中。在一些应用中，利用这些废热向建筑物提供热量是可能的，回收这些最高温度为65?(150?F)的废热可以减少建筑物中采暖的费用。
空调的制冷能力常用冷吨或千瓦 (千瓦) 来表示，冷吨是一个度量单位，它与制冰厂在 24小时内使1吨 (907 公斤)的水结冰的能力有关，其值是3.51千瓦(12,000 Btu/hr)，空调的冷却能力不要和产生冷量所需的电能相互混淆。
2.1 制冷剂的使用和选择
直到20世纪80年代中叶，制冷剂的选择在大多数的建筑物空调设备中不是一个问题，因为在制冷剂的使用上还没有统一的的标准，在以前，用于建筑物空调设备的大多数制冷剂是氟氯碳化物和氟氯碳氢化物，且大多数的制冷剂是无毒的和不可燃的，然而，最近的美国联邦的标准 (环保署 1993a;环保署 1993b) 和国际的协议 (UNEP,1987) 已经限制了氟氯碳化物和氟氯碳氢化物的制造和使用，现在，氟氯碳化物和氟氯碳氢化物在一些场合依然被使用，对制冷剂的理解能帮助建筑物拥有者或者工程师更好的了解
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关于为特定的设备下如何选择制冷剂，这里将讨论不同制冷剂的使用并给出影响它们使用的建筑空调设备和标准。
美国社会的供暖、制冷和空调工程师学会(ASHRAE)有一个标准的限制系统 (表4.2.1)用来区分制冷剂，许多流行的氟氯碳化物，氟氯碳氢化物和氟碳化物的制冷