What is the air conditioner?
Air-cooled heat exchangers, also known as Fin Fan heat exchangers, are usually used in cases where water is not available or the desired process output temperature can be obtained due to the maximum ambient temperature.
Air cooling equipment can be a simpler solution compared to water cooling; Because in water cooled systems, more pumps, piping, central chillers or cooling towers are needed, which increases the cost of operation and maintenance of the system.
Air coolers are used in many different applications. .
Why should air coolers be used?
Undoubtedly, given the current water shortage and rising costs, along with recent concerns about water pollution and cooling towers, the industry's use of water-cooled heat exchangers has greatly decreased. As a result, when it is not possible to have more heat inside the plant, air cooled exchangers are the best choice. Now, a major part of the cooling process in refineries and chemical plants is done in air-cooled heat exchangers. Air cooling condensers are also used for power plants. The working principles are the same; But condensers may be very large.
Different models of air conditioners:
In general, there are two types of air coolers according to the location of the fan:
· First type: Force Draft Air Cooler
Second type: Induced Draft Air CoolerAerial air conditioner
In this case, the fan is placed at the bottom of the tubes and by blowing cool air on the tubes, it cools the fluid inside them. The cooling operation in these coolers is done with less power and moving less volume of air. Most air conditioners in the industry are of this type.
Advantages
- جهت کارکرد به توان کمتری نیاز است،
- تعمیر و نگهداری آسان بدلیل دسترسی بهتر به فن و سایر قطعات مکانیکیراحتتر انجام می گیرد
- دسترسی بهتر به دسته لولهها برای سرویس و تعویض تیوب ها،بسیار آسان است
- قابلیت کارکرد جهت دماهای ورودی بالاتر سیال فرآیندیتسهیل شده است.
Aerial air conditioner
In this case, the fan is placed on top of the pipes and by sucking air upwards from the pipes, it cools the fluid inside the pipe. This type of air cooler is very efficient due to the uniform distribution of air flow.
Advantages
- دسته لولهها در سمت مکش فن (پایین فن) قرار دارند و پلنیوم ۶۰٪ سطح تیوب باندل را پوشانده است که باعث محافظت در برابر عوامل جوی میشود و کنترل و پایداری بهتر فرآیند را به همراه دارد
- توزیع هوا بر روی کل دسته لوله ها، احتمال کمتر گردش مجدد هوای گرم بهتر صورت می گیرد.
- در اثر بروز نقص و یا خرابی فن اثر بیشتری دارد
- در این نوع کولر میزان صدای کمتری بر روی زمین شنیده میشود.
Factors influencing the design and optimization of air conditioner
- تعداد لوله ها
- طول لوله ها
- قطر لوله ها
- تعداد ردیفهای لوله
- نوع پره و تعداد پره در هر اینچ طول لوله بسیار مهم میباشند
- افزایش هر کدام از عوامل فوق باعث افزایش هزینه ساخت مبدل میشود.
We know that increasing the length or number of pipes increases the external surface of the pipes and increases the amount of heat transfer, but it also increases the pressure drop in the pipes. Also, reducing or increasing the diameter of the pipes has an effect on the speed of the fluid inside the pipes and subsequently on the amount of heat transfer and pressure drop.
Therefore, it is clear that in the design of the air cooling converter, considering these effects, the optimal number of tubes should be determined, and the ratio of the length to the width of an air converter should be reasonable. Unlike liquids, gases are compressible, which usually cause a small pressure drop in the air section of these converters. On the other hand, the low thermal conductivity of gases will lower the overall heat transfer coefficient of the converter even at low pressure drops. Due to the inevitability of this reduction in the overall heat transfer coefficient, the manufacturers and designers of this type of converters have tried to compensate this limitation by using tubes with finned and wide surfaces, and that is why fins are used for tubes. It is used to create more surface against the air and compensate for the relatively low heat transfer coefficient of the air.
But finning the tubes cannot always have the necessary application, and that is when the heat transfer coefficient of the fluid inside the tube is low and has a value similar to the heat transfer coefficient of the air on the side of the tube without fins, in this case the effect of finning The tube is significantly reduced and it is worth considering the use of a tube without fins.
How are the air conditioner made?
Normally, an air-cooled exchanger, for use in the process, consists of a finned tube with a rectangular box at both ends of the tubes.
Cooling air is supplied by one or more fans.
Usually the air moves up through a horizontal tube.
Depending on whether the air is forced or drawn through the pipe, fans can be forced or induced.
The space between the fan and the pipe is enclosed by a plenum chamber that directs the air.
Fans are usually electric motors that operate through some kind of speed reducer.
Speed takers are usually V-belts, HTD drives or right angle gears.
The fan drive assembly is supported by a steel mechanical drive support system.
They usually have There are vibration switches on each fan to automatically turn off the fan that is out of balance for some reason.