Selection of tube spacing and fin spacing of finned tube heat exchanger

5a289e73a26ae8805

 

Under normal circumstances, the spacing and height of the finned tube heat exchanger mainly affect the fining ratio, which has a great relationship with the film heat transfer coefficient of the medium inside and outside the tube. If the heat transfer coefficients of the inner and outer films of the tube are quite different, a finned tube with a larger fin ratio, such as steam heating air, should be selected.


When there is a phase change in one side of the medium, the difference in heat transfer coefficient will be greater, such as the exchange of hot and cold air. When the hot air drops below the dew point, a finned tube heat exchanger can be used.


In the case of heat exchange between air and air without phase change, or heat exchange between water and water, a bare tube is usually more suitable. Of course, a low-finned tube can also be used, because at this time it is a weak heat supply coefficient, and strengthening either side of it will have a certain effect.


However, the effect of too large finning ratio is not obvious, and the best internal and external contact area of the tube is strengthened at the same time, and a threaded tube or a fluted tube can be used. The pitch of the fins is mainly to consider factors such as dust accumulation, dust formation, easy cleaning, etc., and at the same time, it must strictly comply with the equipment’s pressure drop requirements. When arranging, the distance between the tube and the tube is not easy to be too large, generally more than 1mm is suitable for tube layout.


In the process of heat exchange, when air flows through the finned tube heat exchanger, the front and back sides of the fin are mainly involved in heat exchange. There is only a small amount of radiant heat transfer in the middle of the two finned tubes, and the heat transfer effect is not obvious. Since this part has no fins and no resistance, the air is easy to penetrate.


In the process of air heating, the unheated cold air will neutralize the heated hot air passing through the middle of the fins, which reduces the heat exchange effect. Compared with foreign finned tube heat exchangers, tubes The spacing is only 0.5mm larger than the outer diameter of the fins, which shows the importance of the tube spacing when the fin tubes are arranged. The tube arrangement of the finned tube heat exchanger should be arranged in an equilateral triangle as far as possible.


The hot air passing through the first row encounters resistance in the second row, and there is a certain rebound wind, so that the 360° heat exchange of the entire fin tube does not have a dead angle. Therefore, the isosceles triangle arrangement should be avoided, and the square arrangement should not be used as much as possible, unless there are special requirements.


The pressure drop on the air side is a very important parameter in the design, which has a great relationship with the arrangement of the fin tube. When designing the fin tube arrangement, the ratio of the narrow gap flow surface to the windward surface should be calculated, so as to calculate according to the front wind speed. The air mass flow rate is calculated, and the friction coefficient is calculated for the dynamic viscosity of the air at different temperatures.

For more details please contact us.

2021 U bending tube heat exchanger basic features

Murphy U bend tubes packed

U-bending tube heat exchanger is a kind of shell-and-tube heat exchanger, which is composed of tube sheets, shells, tube bundles and other parts.

In the case of the same diameter, the U-bending tube heat exchanger has the largest heat exchange area; it has simple structure, compactness, high sealing performance, convenient maintenance and cleaning, minimum metal consumption under high temperature and high pressure, and the lowest cost; U-shaped tube replacement The heat exchanger has only one tube sheet, with good thermal compensation performance and strong pressure-bearing capacity, and is suitable for operation under high temperature and high pressure conditions.

Heat exchange tube

1. Ordinary heat exchange tube

The heat exchange tubes used for heat transfer usually adopt higher-level cold-drawn heat exchange tubes and common-level cold-drawn heat exchange tubes. The former is suitable for non-phase change heat transfer and vibration-prone occasions, and the latter is suitable for reboiling and condensation heat transfer. And general occasions without vibration.

There are many forms of heat exchange tubes. Smooth tube is the most traditional form. Because of its advantages of easy manufacturing and low cost per unit length, it is the most common in current applications. The pipe should be able to withstand a certain temperature difference and stress. When the fluid on the pipe side and the shell side is corrosive, the pipe should also have the ability to resist corrosion.

The length of the heat exchange tube is recommended to adopt the following series: 1.0m, 1.5m, 2.0m, 2.5m, 3.0m, 4.5m, 6.0m, 7.5m, 9.0m, 12.0m. For a certain heat exchange area, a longer heat exchange tube is more economical, so the heat exchanger in engineering is roughly a slender structure. However, if the heat exchange tube is too long, it will not be conducive to the installation and maintenance of the heat exchanger.

The material sources of the tube are very wide, including carbon steel, stainless steel, aluminum, copper, brass and its alloys, copper-nickel alloys, nickel, titanium, graphite, glass, etc. and other special materials. In addition to the use of a single material for the heat exchange tube, to meet production requirements, composite tubes are often used.

2. Efficient heat exchange tube

In order to simultaneously expand the effective heat transfer area inside and outside the tube or enhance heat transfer, and maximize the heat transfer coefficient of the tube side, the inner and outer surfaces of the heat exchange tube are rolled into various surface shapes, or a spoiler is inserted in the tube The components make the fluid inside and outside the tube generate turbulence at the same time and improve the performance of the heat exchange tube. A variety of high-efficiency heat exchange tubes have been developed. According to the heat exchange tube shape and enhanced heat transfer mechanism, it can be divided into rough surface tubes, finned tubes, self-supporting tubes, and inner plug-in tubes.

Most high-efficiency heat exchange tubes have the function of enhancing heat transfer both inside and outside the tube. According to different working conditions, the use of different combinations of high-efficiency heat exchange tubes and new tube bundle supports can achieve a relatively ideal heat transfer effect.

Tube bundle

The tube bundle is an assembly. It is assembled by pipes, baffle elements, tube plates, tie rods, fixed distance pipes, etc. The tube bundle fixes hundreds of tubes as a whole. The baffle elements can be baffles, baffle rods (or baffle grids) and other methods. The tie rods and distance tubes fixed on the tube plate maintain the baffle elements. the distance between.

In order to facilitate the tube bundle to be pulled out of the heat exchanger for maintenance, the weight of the tube bundle should not be too large, and at the same time, the accumulation of dirt and the formation of deposits should be allowed. The tube bundle cannot fill the entire shell, and there will be bypass fluid flowing through the gap between the tube bundle and the shell. In order to improve the flow state at the gap, a sealing strip or a fluid redistribution device should be considered.

Tube sheet

The tube sheet is one of the most important parts of the shell-and-tube heat exchanger. Most of the tube sheets are circular flat plates, and heat exchange tubes are arranged after drilling to withstand the pressure and temperature of the tube side and the shell side, and separate the fluid in the tube side and the shell side. The cost of the tube sheet directly influences the cost of the entire heat exchanger, and the safety and reliability of the tube sheet is also an important guarantee for the normal operation of the heat exchanger.

The tube sheet is the barrier between the shell side and the tube side. When the heat exchange medium is corroded or slightly corroded, the tube sheet is generally made of low carbon steel, low alloy steel or forged. When the heat exchange medium is corrosive, the tube sheet should be made of corrosion-resistant materials, such as stainless steel. However, when the thickness of the tube sheet is large, the overall stainless steel tube sheet is expensive. Composite steel plates are often used in engineering.

Tube box

Most shell-and-tube heat exchangers with a larger shell diameter adopt a tube box structure. The tube box is located at both ends of the heat exchanger, and its function is to evenly distribute the fluid from the pipeline to the heat exchange tubes and to collect the fluid in the tubes and send them out of the heat exchanger. In the multi-tube pass tube shell, the tube box also plays a role in changing the flow direction of the fluid.

The structure of the tube box is mainly determined by factors such as whether the heat exchanger needs to be cleaned or whether the tube bundle needs to be split. There are roughly two basic types: head type and cylinder type.

Connection between tube sheet and adjacent parts

In the heat exchanger, the tube sheet is the barrier between the tube side and the shell side, and the shell, the tube box and the tube are directly connected to the tube sheet. The connection between the tube sheet and the shell is divided into non-detachable and detachable. The former is like the connection between the tube sheet and the shell in a fixed tube sheet heat exchanger. 

The latter such as the connection between the tube sheet and the shell of the U-shaped tube type, floating head type, stuffing box type and sliding tube plate type heat exchanger. Non-detachable connection. The shell and the tube sheet are directly welded together; in a detachable connection, the tube sheet itself is usually not directly in contact with the shell, but indirectly connected to the shell through a flange or connected to the shell and the tube box. The two flanges are clamped and fixed.

Advantage

The U-bending tube heat exchanger has only one tube plate, and both ends of the tube are fixed on the same tube plate. The tube can be freely expanded and contracted, without thermal stress, and has good thermal compensation performance; the tube pass adopts a double tube pass, which has a longer process and a higher flow rate. High, good heat transfer performance, strong pressure-bearing capacity, tube bundles can be drawn out of the shell, easy to repair and clean, simple structure, low cost.

Disadvantage

Due to the limitation of the curvature radius of the elbow, the arrangement of heat exchange tubes is small, the distance between the innermost tubes of the tube bundle is large, the utilization rate of the tube sheet is low, and the shell side fluid is easy to form a short circuit, which is unfavorable for heat transfer. When the tube is leaked and damaged, only the U-bending tube at the periphery of the tube bundle can be easily replaced. The inner heat exchange tube cannot be replaced and can only be blocked. Moreover, a broken U-shaped tube is equivalent to two broken tubes, and the scrap rate is relatively high. high.

Application

The U-bending tube heat exchanger has relatively simple structure, low price, and strong pressure bearing capacity. It is suitable for the occasions where the temperature difference between the tube and the shell wall is large, or the shell side medium is easy to scale and needs to be cleaned, and the floating head type and fixed tube plate type are not suitable . It is especially suitable for high temperature, high pressure and high corrosive materials that are clean and not easy to scale in the pipe.

For more details please contact us.


How to buy the right fin tube in 2021?

Murphy copper finned tube

Like the low-fin tube, the medium-height finned tube is a single monolithic tube, made of a single material, but the fin is slightly taller, with a height of 3 mm or 1/3 inch. Of course, higher fin height provides greater surface area and greater heat transfer capacity.

Medium and high finned tubes are mainly made of copper alloy. We extrude the fins out of the wall of the tube to form a slightly larger diameter than the parent tube. Because copper provides high heat transfer in water applications, mid-height finned tubes are primarily used in the refrigeration, heating, and cooling industries. These tubes are commonly used in heaters, water heaters, process coolers, and heat exchangers. They are also used in oil heating and cooling applications.

The advantage of medium to high finned tubes is their flexible support in bending applications. We use a set of proprietary molds during the machining process, which form a special profile to extrude the heat sink from the tube. This results in a corrugated inner ridged surface that allows a small bending radius to be achieved — the potential for bending configurations is unlimited.

Not only can the outside diameter be controlled and slightly larger than the mother tube diameter, but the fin pitch is very suitable for bending – usually 11 fins per inch. After annealing during the manufacturing process, the tube can be bent.

Advantages of integral fin tube

Unlike the already applied finned tube, in which the fin is added as a separate material to the tube, the integrated tube extracts the fin from the tube itself. The finned tube is made of one material so there is no gap problem – the fin is always in contact with the tube because the fin and tube are one piece of material.

Without the risk of gaps, the all-in-one tube produces better heat transfer — although it is not as customizable as applied finned tubes, nor does it take advantage of the heating/cooling properties of various materials.

You do face certain limitations in terms of fin height and fin per inch. But find a homogeneous solution within those limits, and you’ll usually get a better product.

To bend or not to bend? Should the tubes be annealed or finished?

When planning a medium-high finned tube, the first factor you need to determine is whether the tube will be used for bending applications.

For straight applications, a fine finned tube can be purchased to be detached from the machine in a hardening state. However, if the pipe is to be bent, it needs to be bent through a heat treatment process called annealing, which is the process of placing the pipe in a controlled atmosphere furnace. We then bring the tubes back to room temperature in a specified time sequence that follows specifications such as baking recipes.

After annealing, the tube can be bent, coiled or made into any desired shape. Typical shapes include:

serpentine

Curved serpentine

Spiral screw

Conical spiral

Nested screw

Rectangular box

The flat spiral

Tapered flat screw

Determine the grain size of medium and high finned tube

In addition to deciding whether to use the medium-height finned tube for bending or straight tube applications, we also need to determine the grain size of the tube. We determine the grain size of the tube by examining the grain size of the tube microscopically. This is a factor that customers and suppliers need to agree on.

However, ASME codes tend to be a bit vague when it comes to grain sizes – there is a general range, but for bending applications we need to be more specific. One way to determine the ideal grain size is to construct a sample tube and try it out. We can mimic your end use on request, for example by winding the tube around a 5 “diameter die or making other appropriate measurements. We can bend the tube to the size you want and then send the sample to you for inspection.

Once we and the customer have determined which grain size is most suitable, we will begin full production of your order.

Custom fin tube

The truth is, many customers have been surprised by the power transfer capabilities of curved copper finned tubes. Some companies keep buying a product that is the worst fit for their app because they don’t know their options.

So when we ask, “Do you want the tube to be finned or annealed?” — This is a great opportunity to illustrate Murphy’s manufacturing prowess.

We do all our own finned tube manufacturing and machining in our in-house custom machining shop. Through decades of experimentation and innovative systems, we have developed a proprietary method for bending medium-height finned tubes.

We’ll make them cheaper than what you can get overseas.

If you have interest, please contact us!

 

Finned tube features and application in 2021

Murphy finned tube in warehouse

Classification of finned tubes

There are many types of finned tubes, and new varieties are constantly emerging. Generally, it can be classified according to the following aspects:

1. Classified by processing technology

1) extruded fin tube;

2) Welding and forming finned tubes (high-frequency welding finned tubes, submerged arc welding finned tubes);

3) Roll forming finned tube;

4) the finned tube is fitted and formed;

5) Casting finned tube;

6) Tension-wound finned tube;

7) Insert tube.

Classified by fin shape

1) Square finned tube (Square finned tube);

2), round finned tube;

3) spiral finned tube (spiral finned tube);

4) Longitudinal Finned Tube (Longitudinal Finned Tube)

5) Corrugated finned tube;

6) Helical Serrated Finned Tubes;

7) Needle-shaped finned tube;

8) Tonghao overall plate finned tube (plate fin);

9) inner finned tube (inner finned tube). and many more.

3. According to whether the fin material of the fin tube is the same as that of the base tube, it can be divided into:

1) single metal finned tube

2) bimetal composite finned tube

Single metal finned tubes are classified by material

1) copper finned tube;

2) aluminum finned tube;

3) Carbon steel finned tube;

4) stainless steel finned tube;

5) cast iron (cast steel) finned tube; etc.

Classified by purpose

1) Finned tubes for air conditioning;

2) Finned tubes for air cooling;

3) Boiler: finned tube used by water wall, economizer and air preheater;

4) Finned tubes for industrial waste heat recovery;

5) other special purpose finned tubes; etc.

Finned tube features and application

Murphy finned tube in warehouse

The heat exchange principle of finned tube and the application of finned tube

The characteristics of finned tube 
In order to improve the heat exchange efficiency, fins are usually added on the surface of the heat exchange tube to increase the heat exchange.
The outer surface area (or inner surface area) of the tube, so as to achieve the purpose of improving the heat exchange efficiency, so
The heat exchange tubes are called finned tubes.
The finned tube is used as a heat exchange element and works under high temperature flue gas conditions for a long time, such as a pot
The finned tubes for furnace heat exchangers are used in harsh environments, high temperature and pressure, and corrosive atmosphere.
The finned tube should have a high performance index.
1) Anti-corrosion
2) Wear resistance (Anti-wear)
3) Low contact resistance (lower contact resistance)
4) High stability (Higher Stability)
5) Anti-fouling ability
High-frequency welding spiral finned tube is one of the most widely used spiral finned tubes.
It is widely used in power, metallurgy, cement industry preheat recovery and petrochemical industries. High
The frequency welding spiral fin tube uses the skin effect of high frequency current while the steel strip is wound around the steel tube.
And proximity effect, heating the steel strip and the outer surface of the steel pipe until the plastic state or melting, in the winding
The welding is completed under a certain pressure around the steel belt. This kind of high frequency welding is actually a solid phase welding.

Murphy copper finned tube

Compared with inlaying, brazing (or overall hot-dip galvanizing) and other methods, whether it is in product quality (fin’s

The welding rate is high, up to 95%), and the productivity and the degree of automation are more advanced.

Second, the principle of finned tube heat transfer

Below we discuss the heat transfer of the lower fin tube through an example of a specific heat transfer device thermal principle.

There is a heat exchanger that uses hot water to heat the air. The hot water flows in the tube and the air is outside the tube.

flow. For example, the hot air curtain for heating or the radiator on the car belong to this

A type of heat transfer, that is, the heat of the hot water is transferred through the tube wall to the cold fluid outside the tube—air.

It can be seen that the heat transfer process is closely related to the two convective heat transfer processes on both sides of the partition wall.

For the above example: the convective heat transfer coefficient on the water side of the tube is about 5000, while the

convective heat transfer coefficient on the air side is about 50, and the difference between the two is 100 times. Due to the heat exchange on the air side the “capacity” is much lower than the water side, which limits the performance of the heat exchange “capacity” of the water side and makes the air the side becomes the “bottleneck” of the heat transfer process, limiting the increase in heat transfer. 

To overcome the air side for the bottleneck effect, adding fins on the outer surface of the air side will be the most sensible choice.

After installing the fins, the original heat transfer area on the air side has been greatly expanded to make up for overcome the shortcomings of low heat transfer coefficient on the air side, the heat transfer is greatly improved.

The effect of adding fins can also be illustrated by the following more vivid example:

The immigration department at the border port assumes that Party A’s port has ten inspection ports and can be released every hour

5000 people, but there is only one ticket gate at Party B’s port, and it is very slow. It can only be released every hour.

Line 50 people. In this way, Party B’s side becomes a bottleneck for passenger clearance, making Party A’s “ability”

Can’t play. In order to increase the flow of customs clearance, the most effective way is to open a few more on the side of Party B.

Inspection port. This is the same as the principle of installing fins.

When should finned tubes be used for heat exchange?

After understanding the principle and function of finned tubes, where to choose finned tubes, there are the following principles:

(1) If the heat transfer coefficients on both sides of the tube are very different, the heat transfer coefficient should be small

Fins are installed on one side.

Example 1: The boiler economizer has water in the tube and flue gas out of the tube, and fins should be used on the flue gas side.

Example 2: Air cooler, liquid is in the tube, air flows out of the tube, fins should be added to the air

side.

Example 3: In the steam generator, water is boiled inside the tube, and flue gas flows outside the tube. Fins should be added to the

Smoke side. It should be noted that in the design, the side with the smaller heat transfer coefficient should be placed outside the tube as much as possible to facilitate the installation of fins.

(2) If the heat transfer coefficients on both sides of the tube are very small, in order to enhance heat transfer, the same

When installing fins, if there are structural difficulties, no fins can be added on both sides. under these circumstances,

If only fins are added to one side, there will be no obvious effect on the increase in heat transfer.

Example 1: The traditional tubular air preheater uses air inside the tube and flue gas outside the tube. because

It is the heat transfer of gas to gas, the heat transfer coefficients on both sides are very low, and it is difficult to add fins in the tube, so I had to use a bare tube.

Example 2: Heat pipe air preheater, although the flue gas still heats the air, but due to the flue gas and

The air flows outside the tube, so finned tubes can be conveniently used on both the flue gas side and the air side, so that

the heat transfer is greatly increased.

(3) If the heat transfer coefficients on both sides of the tube are large, there is no need to use finned tubes.

Example 1: Water/water heat exchanger, when hot water is used to heat cold water, the heat transfer coefficients on both sides are sufficiently high, there is no need to use finned tubes. But in order to further enhance heat transfer, threaded pipe or

the corrugated tube replaces the light tube.

Example 2: In the condenser of a power plant, water vapor is condensed outside the tube, and water flows inside the tube. On both sides.

The heat transfer coefficient is very high, under normal circumstances, no need to use finned tubes.

 For more information, contact us

 

Stainless steel fin tube features and application in 2021

Murphy Steel Aluminum Composite Finned Tube

Processing technology and temperature change of stainless steel finned tube

Stainless steel finned tube is mainly used in production process of 304 type stainless steel processing, when making use of it is mainly used for two kinds of medium of heat transfer, laser welding stainless steel finned tube sophisticated technology, excellent performance, is the boiler, power generation, petrochemical industry, hvac, refrigeration, air conditioning industry such as heat, waste heat recycling alternatives.

Stainless steel finned tube in use can effectively improve the efficiency of the heat exchanger, to a certain extent, effectively prolong its life, reduce the volume and save material, the overall rolling finned tube without contact thermal resistance, heat transfer performance is good, high strength, thermal vibration and mechanical vibration resistance, thermal expansion performance is good.

The thermal contact resistance of the stainless steel finned tube is low, the product can maintain a stable low value within a large range of temperature changes, the heat transfer coefficient of the whole product is high, and it has good resistance to temperature change and vibration when in use, the heat transfer area per unit length is large, the heat transfer is high, the structure is reliable and the life is long; Finned surface smooth no burr, no wrinkle, not easy to scale, easy to clean and remove surface water, low flow resistance, can maintain good heat transfer performance for a long time.

The finned stainless steel tube has the characteristics of high strength, small flow loss, strong anti-corrosion performance, not easy to deform under long-term hot and cold working conditions and long service life. The whole rolled fin is smooth without burr, wrinkle and easy to clean. It is easy to remove the condensation water on the outer surface of the fin when wet cooling in heating and air conditioning engineering. It is not easy to dust and scale in drying, heating and other heat exchange occasions.

Murphy stainless steel fin tube

Stainless steel finned tube is highly adaptable.

Stainless steel finned tube in the use of its high heat transfer efficiency, due to the fin of the fluid disturbance makes the boundary layer constantly broken, because of the relatively large heat transfer coefficient, stainless steel finned tube because of the partition, the fin is very thin, with high thermal conductivity, so the finned tube heat exchanger can achieve very high efficiency.

Due to its compact operation, Murphy Thermal Technology laser-welded stainless steel finned tubes have an extended secondary surface during use, allowing surface areas of up to 1000 m2 /m3. The whole product is light and lightweight, because it is compact and mostly made of aluminum alloy. Now steel, copper and composite materials have also been mass-produced.

Laser welding of stainless steel finned tube has strong adaptability, and it is very suitable for the heat transfer between gas-gas, gas-liquid, liquid-liquid, various fluids and the phase transfer heat of the set state change during the operation. Through the arrangement and combination of the flow channel, it can adapt to different heat transfer conditions such as countercurrent, cross-current, multi-stream and multi-channel flow.

Stainless steel finned tube manufacturing process requirements are strict, the process is complex, easy to plug and corrosion resistance and cleaning maintenance is very difficult, so it can only be used for heat transfer medium clean, no corrosion, not easy to scale, not easy to deposit, not easy to plug the occasion.

Stainless steel finned tube to a certain extent regularly check whether the finned tube has sediment, coking, rust layer and other scaling adhesion, and immediate cleaning. At the same time, it is necessary to check whether the adhesive between the finned tube and the rubber gasket is tight, and whether the rubber gasket itself is intact, so as to avoid the leakage caused by the rubber gasket degumming and damage.

Matters needing attention when choosing stainless steel finned tube:

 

1 stainless steel aluminum finned tube, in the selection of stainless steel grades, whether to pay attention to its surface temperature requirements?

Stainless steel aluminum finned tube, in the selection of stainless steel grades, is to pay attention to its surface temperature requirements, and this is also one of the factors that must be considered. So in this case, the answer is yes. Moreover, for different grades of stainless steel, its surface temperature is not the same. For example, 304 stainless steel, its surface temperature is about 450℃, and 321 stainless steel, is 600℃ – 700℃.

2. In the finned tube radiator, are the different types of finned tubes different in terms of base tubes and finned materials? Stainless steel aluminum finned tube this kind, can it be used?

In finned tube radiators, there are different choices for different types of finned tubes in terms of base tubes and finned materials. Therefore, the answer to question 1 is yes. Moreover, its base tube can be copper tube, steel tube, and stainless steel tube, etc., while the fin can be copper belt, aluminum belt, or stainless steel belt. So, from this point of view, stainless steel aluminum finned tube this kind, can be used.

3 stainless steel aluminum finned tube, if there is dust or dirt, then, how to clean up?

Stainless steel aluminum fin tube, if there is dust or dirt, then, it is possible to use professional cleaning agent, that is, acid lotion, to remove clean, specifically, is to use acid lotion for scrubbing, so as to get a good removal effect. However, it is important to note that there can be no residual, so as not to cause rust and corrosion of the finned tube.

 For more information, contact us

 

Fin tube working principle and application

Murphy High frequency welded fin tube 2

The application of fin tube 

The application of finned tubes is now very extensive. Its main purpose is to exchange heat, so it is mainly installed on the surface of the heat exchange tube in order to improve the heat exchange efficiency. However, for the finned tube, there are still certain requirements for its performance, mainly including wear resistance, stability, etc., especially when used in a harsh environment, its performance is required It is better, in addition to having low contact thermal resistance and good dust prevention ability.

What principles should we follow when we use finned tubes for heat transfer?

(1) If the heat transfer coefficients on both sides of the tube are very different, finned tubes should be installed on the smaller side.

(2) If the heat transfer coefficients on both sides of the tube are very small, finned tubes can be installed on both sides, but do not only install one side, which will not be effective.
(3) If the heat transfer coefficients on both sides of the tube are large, do not install finned tubes.

Murphy heat exchanger finned tube heat exchanger aluminum in workshop

Working principle of fin tube

To understand the heat transfer principle of finned tubes, let’s first understand what the heat transfer coefficient is. The heat transfer coefficient refers to the amount of heat transfer per unit temperature difference and unit heat transfer area, which can reflect the heat transfer capacity between the fluid and the wall.

The finned tube is a heat exchanger composed of round tubes or smooth tubes, so how can we increase the heat transfer of the round tubes? One of the most effective methods is to use an expanded surface on the outer surface of the tube, that is, on the flue gas side, that is, a finned tube. 

Assuming that the actual heat transfer area of the finned tube is several times the outer surface area of the original smooth tube, although the heat transfer coefficient of the flue gas is still very low, the heat transfer effect reflected on the outer surface of the smooth tube will be greatly increased, so that the entire The heat transfer process is enhanced, and under the condition of a certain total heat transfer, the metal consumption of the equipment is reduced and the economy is improved.

Applications of fin tube

(1) Heat pipe air preheater series

Application: absorb waste heat from flue gas and heat combustion-supporting air to reduce fuel consumption and improve combustion conditions, thereby achieving energy saving; it can also absorb waste heat from flue gas to heat other gaseous media such as coal gas.

(2) Heat pipe economizer series

Application: It absorbs heat from the flue gas and uses it to heat the feed water. The heated water can be returned to the boiler (as an economizer) or used alone (as a water heater) to improve energy efficiency and achieve the purpose of energy saving.

(3) Heat pipe waste heat boiler (evaporator) series

Application: Use heat pipes as heat transfer elements to absorb higher temperature flue gas waste heat to generate steam. The generated steam can be fed into the steam pipe network (the pressure of the pipe network must be reached), or it can be used for power generation (with relatively high steam volume). Large and stable heat source) or other purposes. For steel mills, petrochemical plants and industrial furnaces, this is the most popular form of waste heat utilization.

 For more information, contact us

 

Why we use fin tube heat exchanger

Murphy High frequency welded fin tube

The application of fin tube heat exchangers

Today, Murphy team introduced you a heat exchanger, which is widely used in various fields such as textile, printing and dyeing, petroleum, chemical industry, electric power and so on, namely finned tube heat exchanger.

What is finned tube heat exchanger

The finned tube heat exchanger achieves the purpose of enhancing heat transfer coefficient by adding fins to the ordinary base fin tubes, and can have a heating effect. When heating is required, it can use high-temperature water, steam or high-temperature heat transfer oil to heat the air. When cooling is required, low-temperature water (such as chilled water) can be used to cool the air. Fin tubes heat exchangers are very popular in the industry and are widely used by enterprises.

Murphy heat exchanger finned tube heat exchanger aluminum in workshop

What should be paid attention to when choosing a finned heat exchanger?

Murphy will give you some suggestions. Of course, the specific matters depend on the specific situation and are for reference only. If the requirements for thermal performance are relatively high, a higher heat transfer rate value should be selected. The higher the value, the better the heat dissipation performance; if economic issues are taken into consideration, we can choose less metal consumption, which can reduce costs.

If you need more sanitation, we can choose a smooth surface and easy to clean; in terms of service life, finned heat exchanger can choose metal, which is not easy to be corroded and damaged. The service life is longer; then, we must also pay attention to protection during use to extend its use time and bring more convenience to our lives.

How to increase the heat transfer capacity of the heat exchanger

Finned tube heat exchangers are still shoulder-arm heat exchangers to some extent. The main feature of the surface is that it has an extended heat transfer surface area. Therefore, the process is not only a one-time transfer. On the hot surface, but also on the secondary heat transfer surface area.

In addition to pouring the heat of the medium fluid on the high temperature side into the medium on the low temperature side, part of the heat is also transferred along the height of the fin surface, that is, along the height of the fin. It is a partition that pours heat into, and then the heat is transferred to the low temperature side by convection.

Maintenance method of finned tube

1. Regularly check whether the cleaning of each fin tube is completed, whether there are deposits, coking, scale, etc., and clean it immediately.

2. When you need to replace the rubber gasket or repair the degummed parts, you need to remove the fin tubes, put it on the table, remove the old gasket, or use fine sandpaper to polish the glue marks in the groove of the fin tube.

3. Every time you re-tighten the fin tube, pay attention to the position of the scale during the last tightening, and do not over tighten the rubber gasket, which may reduce the service life of the gasket.

4. When replacing the rubber gasket of the fin tube, all parts must be updated to avoid uneven gaps between the fins and affect the heat transfer effect.

 For more information, contact us

 

Fin tube pipe material and application

Murphy finned tube copper material

Classification of carbon steel pipes

Hot-rolled carbon steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.

Cold-rolled (dial) carbon steel pipes are divided into general steel pipes, low- and medium-pressure boiler steel pipes, high-pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, as well as carbon thin-wall steel pipes, alloy thin-wall steel pipes, and stainless steel pipes. Rusty thin-walled steel pipes, special-shaped steel pipes. The outer diameter of hot-rolled seamless pipe is generally greater than 32mm, and the wall thickness is 2.5-75mm. The outer diameter of cold-rolled seamless steel pipe can be up to 6mm and the wall thickness can be up to 0.25mm. The outer diameter of thin-walled pipe can be up to 5mm and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.

General carbon steel pipe: It is made of 10, 20, 30, 35, 45 and other high-quality carbon steels such as 16Mn, 5MnV and other low-alloy structural steels or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steels by hot rolling or cold rolling. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transportation pipelines. Seamless pipes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Carbon steel pipes are generally used to ensure the strength and flattening test. Hot-rolled steel pipes are delivered in hot-rolled state or heat-treated state; cold-rolled steel pipes are delivered in heat-treated state.

Preparation method of carbon steel pipe

The raw material of the carbon steel pipe is a round tube blank. The round tube blank is cut by a cutting machine into a blank of about 1 meter in length, and then sent to the furnace for heating via a conveyor belt. The billet is fed into the furnace and heated at a temperature of approximately 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue. After the round billet is out of the furnace, it must be pierced through a pressure punching machine. Generally, the more common piercing machine is the tapered roller piercing machine. This type of piercing machine has high production efficiency, good product quality, large perforation diameter expansion, and can wear a variety of steel types.

After piercing, the round tube billet is cross-rolled, tandem-rolled or squeezed by three rolls successively. After squeezing, take off the tube and calibrate. The sizing machine uses a tapered drill to rotate at a high speed into the steel blank to punch holes to form a steel pipe. The inner diameter of the steel pipe is determined by the length of the outer diameter of the drill bit of the sizing machine. After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened.

After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles, etc. inside the steel pipe, it will be detected. After the quality inspection of steel pipes, strict manual selection is required. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. It is hoisted into the warehouse by a crane.

Murphy copper fin tube pipe pipes

Connection method of copper pipe

 

Copper tube is also called red copper tube. A kind of non-ferrous metal pipe, which is pressed and drawn seamless pipe. Copper pipe has the characteristics of good electrical conductivity and thermal conductivity. It is the main material of electrical and heat-dissipating accessories for electronic products, and has become the choice of modern contractors for the installation of water pipes, heating and cooling pipes in all residential commercial buildings. The following is the connection method.

 

Non-processing compression type connection, the use of non-processing compression type pipe fittings to implement mechanical connection of copper pipes is a relatively simple construction method, simple operation and easy to master, construction personnel only need a little training to master the operating skills. It is a commonly used connection method in current engineering.

 

When connecting, as long as the end surface of the pipe cut can be kept perpendicular to the pipe axis, and the burrs at the cut are cleaned, the pipe fitting is assembled with the correct position of the snap ring and the nut is tightened to achieve a tight connection of the copper pipe. However, this connection method relies on the pressing force of the thread on the snap ring to keep the joint tight. Therefore, the joint should not be directly buried in the wall. It is advisable to lay the joint in a repairable position, so that once the compression force is loosened When leakage occurs, the nut can be tightened further to maintain the necessary pressure.

 

Cleaning of copper pipe

 

Copper pipe has the characteristics of good electrical conductivity and thermal conductivity. It is the main material of electronic products and heat dissipation accessories. It has become the choice of modern contractors for the installation of water pipes, heating and cooling pipes in all residential commercial buildings. Copper pipe has poor corrosion resistance, is easy to oxidize, and chemically reacts with some liquid substances, and is easy to bend and shape.

 

It is generally required that the hardness value of the heat exchange tube material is generally lower than the hardness value of the tube sheet. When there is stress corrosion, local annealing of the tube head should not be used to reduce the hardness of the heat exchange tube; the heat exchange tube with an outer diameter of less than 14mm Expansion joints should not be used for tube sheet connection. Expansion length: the nominal thickness of the tube sheet minus the smaller value of 3mm or 50mm.

 

Spiral copper pipes Spiral copper pipes are generally stronger than straight-sealed copper pipes, and can produce copper pipes with a larger diameter from a narrower blank. The standard of copper pipe material can also use blanks with the same width to produce copper pipes with different diameters. Smaller diameter copper pipes mostly use straight seam welding, and large diameter copper pipes mostly use spiral welding.

 

 For more information, contact us

Fin tube maintenance and comparison

Murphy Aluminum Composite Finned Tube

The long-term use of any item can not be separated from the care and maintenance. Murphy laser welding fin tube is no exception. So what are the specific aspects of fin tube maintenance?

Generally, when water is used for circulation at the beginning of operation, there may be slight leakage. When the temperature rises to the sterilization temperature, the leakage will disappear by itself. If the leakage does not stop, the finned tube must be compressed a little more. If it is still ineffective, it is necessary to open and check the rubber gasket. It is also possible that the finned tubes are arranged in the order of numbers on the fins, which should be corrected.

  1. Regularly check whether the finned tubes are complete, whether there are deposits, coking, rust layer and other scaling adhesion, and clean them immediately. At the same time, it is also necessary to check whether the adhesion between each fin tube and the rubber washer is tight, and whether the rubber washer itself is in good condition, so as to avoid leakage caused by rubber washer degumming and damage.
  1. The plate heat exchanger pressing nut and upper and lower guide rods shall be lubricated with lubricating grease frequently.
  1. Each instrument shall be regulated by a specially assigned person and operated and maintained in strict accordance with the operating procedures.
  1. When the rubber gasket needs to be replaced or the degummed part needs to be repaired, the finned tube shall be removed and placed on the table, and the old gasket shall be removed, or the glue traces in the groove of the finned tube shall be wiped out with fine sandpaper at the degumming position, and then the oil traces in the groove shall be wiped out with carbon tetrachloride or trichloroethylene, and then the back of the new rubber gasket shall be wiped out with fine sandpaper, similarly with carbon tetrachloride or trichloroethylene the alkene solvent wiped out the oil.                                                                                                  Then, apply a thin layer of glue on the back of the groove and rubber washer. Let it dry a little, but it still sticks. That is to say, the rubber washer is embedded in the groove, flattened around, and coated with a layer of talcum powder. Then install the fin tube and clamp it gently. According to the glue instructions, it can be used after a period of time.
  1. When recompressing the laser welded composite fin tube, pay attention to the scale position during the last compression. Do not over press the rubber gasket, so as to reduce the service life of the gasket.
  1. When replacing the rubber gasket of the finned tube, it is necessary to update all the segments so as to avoid uneven clearance between the fins and affect the heat transfer effect.
Murphy Steel Aluminum Composite Finned Tube

The difference between high frequency finned tube and laser welded stainless steel finned tube

At present, there are many kinds of fin tube, mainly high frequency welded fin tube. Although it is more advanced in product quality and production automation compared with inlay, brazing and other methods, due to the factors such as the root of high frequency welded finned tube is difficult to be welded through and there are wrinkles at the root, there are still many shortcomings in heat exchange efficiency and dust prevention convenience of high frequency welded finned tube.

Fin tube is a kind of heat exchange element. In order to improve the heat exchange efficiency, usually add fins on the surface of the heat exchange tube to increase the surface area (or internal surface area) of the heat exchange tube, so as to achieve the purpose of improving the heat exchange efficiency.

As a heat exchange element, fin tube works in the condition of high temperature flue gas for a long time, such as the working environment of finned tube for boiler heat exchanger is bad, high temperature and pressure, and it is in corrosive atmosphere, which requires the finned tube to have high performance index.

1) anti corrosion

2) anti wear

3) low contact resistance

4) high stability

5) dust prevention capacity

Advantages of Murphy thermal technology laser welding stainless steel fin tube:

  1. Using pulse laser welding technology, the welding of the winding piece is completed synchronously, and the welding adhesion rate of the segment piece reaches 100%.
  1. Laser welding is metallurgical combination, and the welding strength of segment can reach more than 600MPa.
  1. The laser welding machine adopts the servo drive system, and the transmission accuracy can reach the level of hundredth meter.
  1. The distance between laser welded fins and tubes can be ≤ 2.5mm, and the heat dissipation area is increased by nearly 50% compared with that of high frequency welded tubes (the distance between fins and tubes is ≥ 4.5mm). The consumption per unit area is less, and the volume of heat exchanger can be greatly reduced.
For more information, contact us hier.