Lesson-13-Marine-Refrigeration

精品文档 1欢迎下载 Lesson 13 Marine Refrigeration 第 13 课 船舶制冷 1 Refrigeration is a process in which the temperature of a space or its contents is reduced to below that of their surroundings Marine refrigeration employs a system of components to remove heat from the space being cooled This heat is transferred to another body at a lower temperature The cooling of air for air conditioning entails a similar process The usual system employed for marine refrigeration plants is the vapor compression cycle 制冷就是将某个空间或其内物品的温度降至环境温度以下 船舶制冷利用一系列组件将热 量从被冷却空间移出 这部分热量被传递给另一低温物体 空调对空气的冷却过程与此类 似 船舶制冷装置通常采用的是蒸汽压缩循环系统 2 The basic components of any refrigeration system working on the vapor compression cycle are the compressor condenser expansion valve and evaporator or cooling coils The refrigeration fluid also known as refrigerant is alternately vaporized and liquefied during the refrigeration cycle The temperature at which a fluid boils or condenses is known as the saturation temperature and varies with pressure The compressor in a refrigeration system in raising the pressure of the vaporized refrigerant causes its saturation temperature to rise so that it is higher than that of the sea water used for cooling the condenser The compressor also promotes circulation of the refrigerant by pumping it around the system 压缩制冷系统的主要部件是压缩机 冷凝器 膨胀阀及蒸发器或冷却盘管 见图 13 1 制冷 液 即制冷剂 在制冷循环过程中交替蒸发和液化 流体沸腾或冷凝的温度称为 饱和温 度 此温度随着压力的变化而变化 制冷系统的压缩机用来使汽化的制冷剂压力升高 使 其饱和温度高于用来冷却冷凝器的海水的温度 压缩机的另一个作用是通过泵送制冷剂 从 蒸发盘管中抽出 压送到冷凝器 促进制冷剂在系统中的循环 3 In the condenser the refrigerant is liquefied by circulating sea water or air for domestic refrigerators Latent heat originally 精品文档 2欢迎下载 from the evaporator is thus transferred to the cooling medium The liquid refrigerant still at the pressure produced by the compressor passes t o the receiver and then t o the expansion valve 在冷凝器中 制冷剂被循环的海水液化 在家用冰箱中由空气液化 最初在蒸发器中吸收 的潜热被放出 传递给冷却介质 保持着压缩机出口压力的液态制冷剂流至储液器 进而 流至膨胀阀 4 The expansion valve is the regulator through which the refrigerant flows from the high pressure side of the system to the low pressure side Its throttling effect dictates the compressor delivery pressure which must be sufficient to give the refrigerant a saturation temperature which is higher than the temperature of the cooling medium 膨胀阀是制冷剂由系统的高压侧流至低压侧的调节器 节流降压 膨胀阀的节流作用控制 压缩机的排出压力 使其足以确保制冷剂的饱和温度高于冷却介质的温度 5 The pressure drop through the regulator causes the saturation temperature of the refrigerant to fall so that it will boil at the low temperature of the evaporator In fact as the liquid passes through the expansion valve the pressure drop makes its saturation temperature fall below its actual temperature Some of the liquid boils off at the expansion valve taking latent heat from the remainder and causing its temperature to drop 调节器 膨胀阀 的压降使制冷剂的饱和温度降低 这样就会在较低的蒸发器温度下沸腾 吸 热汽化 事实上 当冷却液流过膨胀阀时 压力的下降使它的饱和温度下降到其实际温度 以下 一部分冷却液流过膨胀阀时发生汽化 吸取剩余制冷剂的潜热 使其温度进一步下 降 6 The expansion valve throttles the liquid refrigerant and maintains the pressure difference between the condenser and the evaporator while supplying refrigerant to the evaporator at the correct rate It is thermostatically controlled in modern system 膨胀阀除了可以节流降压以保持冷凝器和蒸发器之间的压差外 还能自动调节制冷剂流量 现代制冷系统采用的是热力膨胀阀 7 The refrigerant entering the evaporator coil at a temperature lower than that of the surrounding receives latent heat and evaporates Later the heat is given up in the condenser when the refrigerant is again compressed and liquefied 进人蒸发器盘管的制冷剂温度低于环境温度 吸收潜热后蒸发 随后 这一热量在冷凝器 中释放出来 制冷剂再次压缩 液化 8 During operation a number of particular problems can occur which will affect the plant performance 工作过程中可能发生某些异常问题而影响装置的性能 9 An overcharge or excess refrigerant in the system will be seen as a high condenser pressure The refrigerant should be pumped to the condenser and the excess released from there 系统充入制冷剂过多会表现为冷凝器压力过高 应把制冷剂泵入冷凝器 释放多余部分 10 Air in the system will also show as a high condenser pressure 精品文档 3欢迎下载 With the condenser liquid outlet closed the refrigerant charge should be pumped in and cooled Releasing the purge valve will vent off the air which will have collected above the refrigerant 系统中混有空气也会表现为冷凝器压力过高 应关闭冷凝器液体出口 将制冷剂泵入后冷 却 打开放气阀 放出聚集在制冷剂上方的空气 11 Under charge will show as a low compressor pressure and large bubbles in the liquid line sight glass A leak test should then be carried out over the system to determine the fault and enable its rectification A quicker and more sensitive method for freon plants is to use a leak detector lamp The freon is drawn into the flame and the flame will change color going from green to blue depending on the concentration of the gas 制冷剂不足会表现为压缩机压力过低 并且可以在制冷剂液体管线观察窗看到大量气泡 应对整个系统进行检漏测试以确定故障位置并解决问题 氟利昂装置比较迅速灵敏的检查 方法是使用检漏灯 氟利昂与火焰接触时 火焰颜色根据气体中氟利昂的浓度的不同相应 地从绿逐渐变蓝 12 Moisture in the system may change to ice and close up the regulating valve resulting in a drop in pressure on the evaporator side and a rise in pressure on the condenser side The drier should be examined and the drying chemicals will probably require replacing 系统中的水分会结冰堵塞调节阀 从而导致蒸发器一侧压力下降 冷凝器一侧压力上升 应检查干燥器 可能需要更换化学干燥剂 13 Refrigeration plants are protected by high pressure cut outs low pressure cut outs oil failure cut outs and safety valves or bursting discs 制冷装置的保护设备有高压断路器 低压断路器 滑油失压断路器和安全阀或防爆盘 B Multiple Choice 选择题 Question 1 is based on paragraph 1 根据课文第 1 段回答问题 1 In the process of liquid changes into gas 在 过程中 液体变成气体 答案 C A frosting汽化 B condensing冷凝 C evaporating蒸发 D compressing压缩 Questions 2 11 are based on paragraphs 2 8 根据课文第 2 8 段回答问题 2 11 2 The saturation temperature changes with 饱和温度随 改变 答案 B A the air density空气密度 B pressure压力 C the present atmospheric pressure现场的大气压 D surrounding temperature环境温度 3 In the refrigerant is liquefied by circulating sea water 在 中 制冷剂被循环的海水液化 答案 A 精品文档 4欢迎下载 A the condenser 冷凝器 B the compressor压缩机 C the expansion valve膨胀阀 D the evaporator蒸发器 4 is used to regulate the refrigerant flows from the high pressure side of the system to the low pressure side 4 用来调节系统中从高压侧到低压侧的制冷剂的流量 答案 D A Condenser冷凝器 B Compressor压缩机 C Evaporator 蒸发器 D The expansion valve膨胀阀 5 throttles the liquid refrigerant and maintains the pressure difference between the condenser and the evaporator 5 用来对液态制冷剂节流以保持冷凝器和蒸发器之间的压差 答案 A A The expansion valve膨胀阀 B Evaporate蒸发器 C Compressor压缩机 D Condenser冷凝器 6 supplies refrigerant to the evaporator at the correct rate 6 向蒸发器以适当的速率供给制冷剂 答案 A A The expansion valve膨胀阀 B The evaporate蒸发器 C The compressor压缩机 D The condenser冷凝器 7 A refrigerant boils and vaporizes in the in a compression refrigeration system 7 在压缩式制冷系统中 制冷剂沸腾并在 中蒸发 答案 D A liquid receiver储液器 B compressor压缩机 C condenser冷凝器 D cooling coil冷却盘管 8 The boiling and condensation points of a refrigerant depend on the exerted upon it 8 制冷剂的沸腾和冷凝点取决于施加于其上的 答案 A A pressure压力 B temperature温度 C superheat过热度 D super cool过冷度 9 The refrigerant entering the evaporator coil at a temperature than that of the surrounding secondary coolant air or brine receives latent heat and 9 制冷剂进人蒸发器盘管 温度于环境温度 载冷剂 空气或盐水 吸收潜热 答案 B A higher condenses 高 冷凝 B lower evaporates低 蒸发 精品文档 5欢迎下载 C lower compresses低 压缩 D higher evaporates 高 蒸发 10 Which of the following terms would best describe the temperature at which boils at a given pressure 10 下列哪个词最能形容在给定压力下的沸点 答案 B 根据课文第 9 13 段回答问题 12 130 A Degree of saturation 饱和度 B Saturation temperature 饱和温度 C Superheated temperature 过热温度 D Degree of superheat 过热度 11 Which of the following terms represents the form of heat removed from the refrigerant in the condenser of a refrigeration system 11 在制冷系统的冷凝器中 热量以哪种形式从制冷剂中转出 答案 A A Latent heat of vaporization 蒸发潜热 B Heat of compression 压缩热 C Superheat 过热 D All of the above 以上全部 Questions 12 13 are based on paragraphs 9 13 12 may result in a drop in pressure on the evaporator side and a rise in pressure on the condenser side 12 可能导致蒸发器端压力下降 冷凝器端压力上升 答案 C A Overcharge过量充气 B Air in the system系统中有空气 C Moisture in the system系统中有水分 D Leakage in the system系统中有泄漏 13 What is the quicker and more sensitive method for freon plants to detect leaks of refrigerant 13 哪种方法能更快速和更敏感地检测到氟利昂装置中制冷剂的泄漏 答案 D A By painting over all joints with a soapy water solution 在所有接头 处涂抹肥皂水溶液 B By the use of a sight glass 使用视镜 C By using acid solution 使用酸性溶液 D By using a leak detector lamp 使用检漏灯 Task 2 Vocabulary and Structure 任务 2 词汇与结构 A Technical Terms专业术语 Translate the following