The Application of Condenser
冷凝是使熱物體的溫度降低而發生相變化的過程，通常指物質從氣態變成液態的過程。如水蒸氣遇冷變成水，水遇冷變成冰。溫度越低，冷凝速度越快，效果越好。化工生產中一般以比較容易得到，成本低的水或空氣作冷凝的介質。冷凝和蒸發是作用相反的兩個物理過程。
Condensation is a process which reduces the temperature of hot object and causes phase change, usually it’s a process for substance to change from gaseous state to liquid state. For example, steam becomes water when it is cooled,water becomes ice when it is cooled. The lower temperature, the faster condensation rate and the better effect. In chemical production, usually use water or air as condensation medium, which is cheaper and easy to obtain. Condensation and evaporation are two physical processes that act in opposite directions.
在化工生產中，實現冷卻、冷凝的設備通常是間壁式換熱器。常用的冷卻、冷凝介質是冷水、鹽水等。一般情況下，冷水所達到的冷卻效果不低於0 ℃；濃度約為20%鹽水的冷卻效果為-15~0℃。冷卻、冷凝操作在化工生產中易被人們所忽視。實際上它很重要，而且嚴重影響安全生產。
In chemical production, the equipment for cooling and condensing is usually a dividing wall type heat exchanger, and the condensing medium is cold water, brine, and so on. Under normal circumstances, the cooling effect of cold water is not lower than 0℃, the cooling effect of brine whose concentration is 20% is -15~0 °C. Cooling and condensation operations are easily neglected in chemical production. In fact it is very important and seriously affects safe production.
冷凝過程的分類
Classification of the condensation process
冷凝過程主要分為兩種，一種稱為膜狀冷凝，另一種稱為滴狀冷凝。
The condensation process is mainly divided into two types, one called film condensation and the other called droplet condensation.
1、膜狀冷凝
1、Film condensation
冷凝液能很好地潤溼壁面，在壁面上形成一層連續的液膜，冷凝過程只在液膜與蒸氣的分界面上進行，冷凝放出的汽化相變焓必須穿過這層液膜才能傳到冷卻壁面上去，這種冷凝方式稱為膜狀冷凝。
The condensate can wet the wall well and form a layer of continuous liquid film on the wall. The condensation process is only carried out at the interface between the liquid film and the vapor. The vaporization phase of the condensation must pass through the liquid film and then transfer to the cooling wall, this condensation method is called film condensation.
絕大部分的冷凝過程屬於膜狀冷凝，這時，液膜層就成為主要的傳熱阻力，液膜的傳熱係數越高或液膜的厚度越薄，傳遞的熱量就越多。因此在設計冷凝器時，為了提高冷凝傳熱係數，就要考慮如何避免凝液膜不斷加厚，以及如何促使凝液膜減薄。例如，通常採用臥式冷凝器，就是因為在殼程中凝液不斷地從管子上滴落下來，使液膜層不會隨冷凝量的增加而不斷地加厚。
Most of condensation process belongs to film condensation. At this time, the liquid film layer becomes the main heat transfer resistance. The higher heat transfer coefficient of the liquid film or the thinner liquid film, the more heat is transferred. Therefore, when design the condenser, in order to increase the condensation heat transfer coefficient, it is necessary to consider how to avoid the continuous thickening of the condensate film and how to promote the condensate film thinning. For example, horizontal condenser is usually used because the condensate drips from the tubes continuously during the shell process, so that the liquid film layer will not thicken continuously as the amount of condensation increases.
2、滴狀冷凝
2、Droplet condensation
冷凝液不能很好地潤溼壁面，將在壁面上形成一個個小液珠，且不斷成長變大，液珠變大之後，由於受重力作用，會不斷地攜帶沿途的其他液珠沿壁流下，使壁面重複液珠的形成和成長過程，冷凝放出的汽化潛熱可直接傳遞給壁面，這種冷凝方式稱為滴狀冷凝。
The condensate does not wet the wall well, and form a small liquid bead on the wall surface, and it will grow and become larger. After the liquid bead becomes larger, due to the action of gravity, it's constantly carrying other droplets along the way flow down the wall. Repeat the formation and growth process of the liquid droplets, the latent heat of vaporization released by condensation can be directly transmitted to the wall surface. This condensation method is called droplet condensation.
滴狀冷凝的傳熱速率比膜狀冷凝高，可以達到膜狀冷凝的幾倍甚至十幾倍，其原因是蒸氣與管壁直接接觸，中間沒有比管壁傳熱係數小得多的液膜存在，同時傳熱的推動力是蒸氣與管壁溫度之差，這比膜狀冷凝時氣液界面與管壁溫度之差要大。儘管滴狀冷凝的傳熱效果很好，但在操作上不穩定，而且它所需要的特殊材質的冷凝表面也很難完全滿足，因此工業應用仍很有限。
The heat transfer rate of droplet condensation is higher than film condensation, which can reach several times or even dozen times as film condensation. The reason is that the steam contacts the tube wall directly, and there is no liquid film with much smaller heat transfer coefficient than the tube wall in the middle. At the same time, the driving force of heat transfer is temperature difference between steam and the tube wall, which is bigger difference between the gas-liquid interface and the wall temperature than film condensation. Although the heat transfer effect of the droplet condensation is good, the operation is unstable, and specially required condensation surface is difficult to be satisfied completely, so the industrial application is still limited.
冷凝器
Condenser
冷凝器是把蒸氣冷凝為液體的設備，在冷凝過程中蒸氣把熱量傳遞給冷卻劑。在石油化工過程中經常使用各種各樣的冷凝器，其中在兩相流動傳熱的冷凝過程中應用最為廣泛，如蒸餾塔頂氣體餾出物的冷凝、水蒸汽的冷凝、冷凍劑蒸氣的冷凝等。在冷凝過程中涉及到的主要設備有：管殼式冷凝器、空氣冷卻器、板式冷凝器和螺旋板式冷凝器等。
The condenser is a device that condenses vapor into liquid, steam transfers its heat to the coolant during condensation. A wide variety of condensers are often used in petrochemical process, where they are most widely used in the condensation of two-phase flow heat transfer, such as condensation of distillation tower top gas distillate, condensation of steam, and condensation of refrigerant vapor, etc. The main equipment in condensation process such as: shell and tube condenser, air cooler, plate condenser and spiral plate condenser.
蒸氣冷凝的過程還可以用來加熱或蒸發冷卻劑，因此根據換熱過程的不同目的，可以分別稱為冷凝器、蒸發器、再沸器或加熱器。管殼式冷凝器，其中浮頭式冷凝器結構如下圖所示。
The process of steam condensation can also be used to heat or evaporate the coolant, so according to different purpose of the heat exchange process,it can be called as condenser, evaporator, reboiler or heater. Take Shell-tube condenser as example, the structure of the floating head condenser is as shown in the following figure.
冷凝器的類型
Type of condenser
凝器按其冷卻形式可分為三大類型：水冷式、風冷式、蒸髮式及淋水式。
Condensers can be divided into three types according to their cooling form: water-cooled type, air-cooled, evaporative type and shower type.
水冷式
Water-cooled type condenser
在水冷式冷凝器中，製冷劑放出熱量被冷卻水帶走。冷卻水可以一次流過，也可以循環使用。當使用循環水時，需要有冷卻水塔或冷水池。水冷冷凝器有殼管式、套管式、沉浸式等結構形式。
In water-cooled type condenser, the heat released by the refrigerant is carried away by cooling water. Cooling water can flow once or it can be recycled. When use circulating water, cooling tower or cold water pool is required. The water-cooled condenser has shell-tube type,casing pipe type, and an immersed type,etc.
風冷式
Air-cooled type condenser
在風冷式冷凝器中，製冷劑放出的熱量被空氣帶走。它的結構形式主要為若干組銅管所組成，由於空氣傳熱性能很差，故通常都在銅管外增加肋片，以增加空氣側的傳熱面積，同時採用通風機來加速空氣流動，使空氣強制對流以增加散熱效果。
In air-cooled condenser, the heat released by the refrigerant is carried away by the air. It is mainly composed of several groups of copper tubes. Due to the poor heat transfer performance of air, ribs are usually added outside the copper tube to increase the heat transfer area on the air side, and a ventilator is used to accelerate the air to flow, force air convection to increase heat dissipation.
蒸髮式及淋水式
Evaporative and shower type condenser
在這類冷凝器中，製冷劑在管內冷凝，管外同時受到水及空氣的冷卻。
In this type of condenser, the refrigerant condenses in the tube, and the outside of the tube is simultaneously cooled by water and air.
當製冷系統的氟裡昂液態進入膨脹閥節流後送入蒸發器，屬於汽化過程，這時候需要吸收大量熱量，使被冷卻的價質溫度逐步降低，以達到製冷降溫的效果。那麼，按其被冷卻的介質種類可分為冷卻液體（水）的蒸發器(乾式蒸發器)和冷卻空氣用的蒸發器(表冷式蒸發器)這兩大類。
When the freon liquid in the refrigeration system enters the expansion valve and sent to the evaporator, it belongs to vaporization process. At this time, it is necessary to absorb plenty of heat, so that the temperature of the cooling medium is reduced gradually to achieve the cooling effect. Therefore, according to the types of medium which is cooled, it can be classified into two types:evaporator for cooling liquid (water) (dry evaporator) and evaporator for cooling air (surface cooled evaporator).
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