制冷的基础原理 CPI（西匹埃）工程服务 公司

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1 制冷的基础原理 CPI（西匹埃）工程服务 公司
The ability of liquids to absorb enormous quantities of heat as the vaporize is the basis of the modern mechanical refrigeration system. This presentation will focus on the properties of a refrigeration system, and the role of a lubricant in this system.

2 制冷剂（冷媒）的互溶性 润滑油溶解液化气体进入单相的能力 了解互溶特性的特性， 增加系统的知识 可互溶的 – 单一清晰的相
不能互溶的 – 两相 了解互溶特性的特性， 增加系统的知识 回油的特性 热传导（导热）的特性 To better understand the behavior of a lubricant in a refrigeration system, one needs to be aware of some of the described behaviors, and what these properties mean. The first property is Miscibility. Miscibility is defined as the ability of a lubricant to dissolve into a single, clear phase when mixed with liquefied refrigerant. It is important to note that this behavior ONLY applies when the refrigerant is condensed into a liquid. The reason that it is important to understand this property is that miscibility or the lack there of, plays a role in how the lubricant moves throughout the system.

3 互溶性图 可互溶的 可逆，不可互溶的 不互溶的 温度 浓度
This is an example of what a miscibility graph may look like. The two measured parameters for miscibility testing are concentration of oil in the liquefied refrigerant and temperature. This chart illustrates that separation temperature is dependent on both these conditions. Typically, oils are more miscible at lower concentrations. The other point worth noting is Critical Solution Temperature. This is shown by the two dots on the curve. This is the highest/lowest point at which a lubricant will stay in a single phase with he liquefied refrigerant. 不互溶的 浓度

4 制冷剂（冷媒）的溶解度 其数据是根据以下的属性来决定 动态值 有利于评估轴承粘性 压力 温度 制冷剂和润滑油的亲和力
Refrigerant solubility is the second critical property to understand in refrigeration systems. When an amount of refrigerant pressure and temperature is applied to a lubricant a fixed amount of dilution will occur. This property is a dynamic value, in that it can change dramatically with pressure and temperature. In addition, if no affinity exists between the refrigerant and the lubricant, the product will not experience any dilution. The property refrigerant solubility is most often applied/evaluated at compressor conditions.

5 制冷剂（冷媒）溶解度的控制 稀释最小化 过量的稀释 改善压缩效率 油膜厚度改善轴承润滑 不良的效率在于 不良的润滑 压缩 容量（体积的）
In addition to understanding what the refrigerant solubility value may be for a specific lubricant/refrigerant pair, CPI also focuses much of it’s research on understanding the importance of refrigerant solubility. We then specifically formulate our products to minimize solubility in the compressor. Reducing the solubility of the refrigerant in the lubricant improves the performance of the compressor. First, less refrigerant returning to the compressor results in higher viscosity. A better film is formed, and less heat is generated. Also, higher viscosity provides a more effective seal between the rotors. Secondly, less refrigerant improves the volumetric efficiency as less refrigerant is returned with he lubricant to be re-compressed.

6 密封管稳定性 The third property which is unique to refrigeration lubricants is sealed tube stability. In this test, and amount of refrigerant and oil are placed in a sealed glass tube or vessel. In addition, catalysts are often added to accelerate any potential reaction. The tube is then sealed, and aged for a prescribed period of time. At the end of the test the lubricant is evaluated for any physical changes (viscosity, TAN) as well as dissolved metals. 炉温在 °C

7 冷冻的循环 冷凝器 扩张装置 This slides illustrates the basics of a refrigeration system. While refrigeration systems have many different components depending on the type of refrigerant and equipment design, all systems operate in the basic fashion outlined in this slide. The refrigeration lubricant plays a role in each portion of the circuit. If one understands the specific behavior of the lubricant in each of these portions, it makes it possible to select the correct product for the different refrigeration applications. 压缩机 蒸发器

8 系统零配件的功能 压缩机 冷凝器 膨胀阀 蒸发器 压缩气体 产生热 (提高气体温度) 移走压缩所产生的热 热的损失导致制冷剂（冷媒）的冷凝
液态制冷剂（冷媒）的压力 蒸发器 低压液体吸收热量 液态制冷剂（冷媒）转化为气体 The four main components for every refrigeration circuit are the compressor, condenser, expansion valve and evaporator. The compressor compresses the gas. The result is a transfer of the mechanical energy or work of the compressor into internal kinetic energy within the refrigerant. The temperature of the gas increases with the amount of work done. The condenser removes the heat of compression from the refrigerant. The result of this removal of heat is the liquefaction of the refrigerant. The expansion valve, or refrigerant control valve, meters the proper amount of refrigerant to the evaporator, reducing the pressure of the liquid so that it will vaporize in the evaporator at the desired low temperature. The function of the evaporator is to provide an efficient heat transfer surface through which heat can pass from the refrigerated space or product into the vaporizing refrigerant.

9 制冷循环 - 压缩机排气到冷凝器 制冷剂（冷媒） 气体 高压排放 气体的压缩热 润滑油 润滑压缩机 压缩机 带走压缩所产生的热
制冷循环 - 压缩机排气到冷凝器 制冷剂（冷媒） 气体 高压排放 气体的压缩热 润滑油 润滑压缩机 带走压缩所产生的热 大量 (> 99%) 从气体分离 少于 1% 流经气体分离器 可应用的属性 可溶度 稳定度 (高温) 压缩机 The compressor and discharge line deliver high pressure, high temperature gas to the condenser. The proper lubrication of the compressor is also the primary role of the lubricant for this portion of the system. In addition to lubricating the bearings of the compressor, the lubricant assists the compressor in sealing between gaps within the compressor and aids in the removal of heat from the compression process. Typically a separator is employed after the compressor to separate the lubricant from the discharging gas. The separator will effectively remove all (greater than 99%) of the lubricant from the gas stream. The primary property that is evaluated for lubricants in this portion of the system is solubility. You need to ensure that you have enough viscosity to lubricate the bearings, seal the voids and lubricate the seals.

10 制冷循环 – 可互溶的油 冷凝器到膨胀装置 冷凝器 制冷剂（冷媒） 从气体转化为液体的转变 较低的温度 高压 润滑油
The condenser functions as a heat exchanger for the system. It often uses air or water as the medium to reject heat. It is in the condenser that the importance of lubricant behavior with the refrigerant first becomes evident. If a lubricant is miscible with he refrigerant, it will dissolve into the condensing refrigerant, and be carried out into the system with the liquid refrigerant. For this reason, it is important to understand the miscibility characteristics of the lubricant in liquid refrigerant at high temperatures. 润滑油 与液态制冷剂（冷媒）的溶解 不会发生额外的分离 可应用的属性 互溶性

11 制冷循环 – 不可混合油的冷凝器延伸装置 冷凝器 冷冻油 从流体转变为气体 低温 低压 润滑性 上浮或下沉液态冷冻油 在冷凝器中的额外分离
The condenser functions as a heat exchanger for the system. It often uses air or water as the medium to reject heat. It is in the condenser that the importance of lubricant behavior with the refrigerant first becomes evident. If a lubricant is immiscible, and floats to the top of the liquefied refrigerant, it will create an insulating barrier, reducing the effectiveness of the condenser. If it sinks to the bottom of the condenser, it can be collected and returned to the compressor sump. For this reason, it is important to understand the miscibility characteristics of the lubricant in liquid refrigerant at high temperatures. 润滑性 上浮或下沉液态冷冻油 在冷凝器中的额外分离 过多的油量会减少液态冷冻油的效力 装入延伸装置 应用的属性 高温可混合性

12 制冷循环 –不相容油 膨胀装置到压缩机 制冷剂（冷媒） 从液体转变为气体 低温 低压 可应用的属性 低温互溶性 溶解度 – 对压缩机
密封管的稳定性 - 耐久性 润滑油 低温会导致润滑油“粘”在蒸发器上 对热传导有害 如果油沉, 用储压器. 如果浮油, 用刮油装置 膨胀装置 The expansion valve and evaporator is the portion of the system which delivers the desired result of a refrigeration system. The liquid refrigerant is metered through the expansion valve into the evaporator. If slugs of lubricant are present in the liquid refrigerant, it is possible to plug this valve, reducing the effective metering of the refrigerant. More importantly, high concentrations of separate lubricant in the evaporator may play a critical role in the ability of the system to produce the desired cooling effect. At low temperatures, the lubricant becomes viscous. This reduces the ability to flow, and makes the lubricant sticky. The result is a product which can adhere to the walls of the heat exchanger surface, reducing the transfer of energy. Knowing the miscibility properties allows the designer to manufacture a system to minimize this adverse property. In the case of ammonia, a sinking oil can be collected at the bottom of the evaporator with an accumulator. In halocarbon applications, oil that floats can be collected from the top of the vessel with a skimmer, or trough which collects the lubricant before it forms an insulating ‘blanket’. In some HFC applications the oil can also sink, acting like ammonia and mineral oil. 蒸发器 压缩机

13 不相容性在热交换器的膨胀表面所产生的冲击（影响）
管 散热片 – 膨胀表面 This slide provides a detailed view of the problem which can occur with excessive oil carryover in a flooded evaporator system that is using an immiscible oil. Flooded evaporators contain tube bundles which facilitate the heat transfer. These tube bundles typically contain expanded surfaces, which provide additional surface for the heat transfer to occur. A viscous, immiscible oil can adhere to these expanded surfaces, effectively preventing the transfer of heat. The result of this, is a gradual warming of the evaporator. This results in higher suction temperatures, and a general deterioration of the system performance. This is one reason that the low temperature viscosity and carryover rate needs to be closely examined in a flooded evaporator that uses an immiscible oil.

14 制冷循环 –相容油 膨胀装置到压缩机 制冷剂（冷媒） 从液体转变为气体 低温 低压 可应用的属性 低温互溶性 溶解度 – 流入压缩机
制冷循环 –相容油 膨胀装置到压缩机 制冷剂（冷媒） 从液体转变为气体 低温 低压 可应用的属性 低温互溶性 溶解度 – 流入压缩机 密封管的稳定度 - 耐久性 润滑油 润滑油溶于制冷剂（冷媒） 在低浓度(< 10%)下不影响热传导 DX 系统 –油随着气体的浮动 油浴式系统 – 油被蒸发 (储蓄压器或保持) 膨胀装置 Systems which employ a miscible oil typically do not experience the same heat transfer problems that are seen in immiscible systems. Carryover rates of as much as 10% lubricant are possible without any adverse effect on heat transfer. However, additional, specialized equipment is often needed in miscible systems to properly balance the oil carryover rate with oil return. Applications that have a flooded evaporator often use an accumulator, or still to concentrate oil for return to the compressor. This is a device which will take an amount of refrigerant and oil from the evaporator into a separate vessel. Here the refrigerant is boiled off, concentrating the oil. The drawback to using this system is that the refrigerant which is boiled off to concentrate the oil does not contribute to the cooling effect, and is essentially lost work. Another potential problem with the use of miscible oils in flooded evaporators is foaming. At elevated concentrations, oil can impart its foaming characteristics to the refrigerant. This results in a system imbalance, and poor performance. 蒸发器 压缩机

15 在制冷系统中选择润滑剂的建议 压缩机性能 系统性能 效率 耐久性 压缩机的设计 传热器 油回路 材料和组成 长期的清洁（稳定性）
This slide summarizes all of the parameters which must be evaluated when considering a lubricant for use in a refrigeration system. First is compressor performance. In this case the product must be sufficiently viscous enough to provide efficient, long term operation to the compressor. High viscosity provides lubrication to the bearings, and sealing of the compressor. The second consideration is system performance. In this case, the optimum lubricant should have minimal viscosity, be able to mix with the refrigerant and not have any material compatibility issues.

16 影响润滑效果的因素 粘性 稳定性 润滑性 不足 – 对轴承不利 过剩 – 产生阻力, 增加阻力 当稀释时必须增加润滑
与润滑所需的润滑剂类型有关 This slides focuses on the needs of the lubricant in the compressor. Again,t he three main concerns are proper viscosity, long term stability and lubricity under the required conditions.

17 冷冻油选择的建议 脱水器温度 位置 可用空间 系统能力 规则 费用 物理位置 接近于人 直接的设备 长时期的冷却/系统
There are several considerations for the proper selection of a refrigerant in a new refrigeration and air conditioning system. The first one is the temperature at which the system will be operating. The optimized, proper refrigerant should have a boiling point in the same temperature range that the system will operate. This prevents the need for additional equipment to manipulate this boiling point. Another consideration is available space. For example, systems which use ammonia often require a secondary loop to deliver the cold to the proper location. This requires additional space. In contrast to this, halogenated systems are able to employ direct cooling, minimizing size requirements. System capacity is another driver in the selection of a refrigerant. Refrigerants have varying abilities to absorb heat. This value is known as the latent heat of vaporization. This value also impacts the sizing requirements. Regulations also play a role in selection of a refrigerant. Ammonia and hydrocarbon refrigerants such as propane have several regulations which limit their use in many locations. The next slides will focus on the opportunity for many of the types of refrigerants available today.

18 通用冷却剂 – 氨水 优点 冷却剂费用低 非常高的传热能力 缺点 有限的适用范围 (-45 to -15°C) 高设备成本 对人体有害
高浓度 易燃范围 Ammonia is the preferred refrigerant for many high cooling requirements such as food processing plants. The latent heat of ammonia is almost 5 times that of most other refrigerants. This means that ammonia can deliver five times the cooling with he same amount of refrigerant, or deliver the same amount of cold at one fifth the system size. In addition, ammonia is cheap. The cost of ammonia is approximately $0.90/lb.. In comparison, HFC based refrigerants typically cost $7.00 to $20.00/lb., and some regulated, CFC refrigerants now cost over $40.00/lb.. The main disadvantages to ammonia is the operating range, and toxicity. For this reason, the initial equipment costs tend to be higher than other systems.

19 通用冷冻剂 -卤化碳 优点 低设备费用消耗 化学提取范围广 无毒 缺点 易受新的规则影响 高冷却成本 低加热能力 移走高载荷热能力低
系统尺寸 Halocarbons covers a wide range of chemistry. These include refrigerants such as the new HFC, as well as HCFC and CFC’s. The two primary advantages with he use of halocarbons include the low cost of the equipment, and the fact that the refrigerants are very ‘people friendly’ in that they are non-toxic, and non-hazardous. The disadvantage is that the impact of these types of refrigerants on the ozone layer have now placed additional regulations on their use, increasing cost to manufacture and service this type of equipment. Also, halogenated refrigerants have much low latent heat of vaporization values, creating the need for either significantly larger systems or limiting their opportunity to applications with lower heat load requirements.

20 普通冷却剂 – 碳氢化合物 优点 制冷剂费用低 使用范围广 缺点 易燃 热能力平均
Hydrocarbons are a specialized class of refrigerants. These are typically employed in applications where there is a ready source of this type of gas such as chemical plants and refineries. As a refrigerant, they are not quite as efficient as ammonia, but have higher latent heat values than halocarbons. The primary consideration for the use of hydrocarbons is the explosive flammability concerns associated with these refrigerants.

21 在哪里可以找到冷却剂 氨水 卤烃 碳氢化合物 食物车间 大型冷冻储藏仓库 缓慢的加热／冷却 小型冷冻储藏仓库 超市 化学工厂
This slide outlines some of the typical locations for the various types of refrigerants which are used in the marketplace.

22 结论 润滑剂需考虑的事项 冷却剂需考虑的事项 系统设计
Overall, there are several considerations for the proper selection of a lubricant in a refrigeration system. Many of these are addressed in the design of the system. However, an awareness of these properties is useful in diagnosing problems which can occur with lubricants in operating systems.