What type of heat exchanger is prone to fouling?
Shell-and-tube heat exchangers operate at comparatively low internal fluid velocities so are more susceptible to fouling than plate heat exchangers. To maintain efficient operation and higher transfer coefficients, keep the shell and tube heat transfer surfaces clean.
Which has lowest fouling factor?
Which one is having the lowest value of fouling factor? Explanation: Fouling factor for non-oil bearing system is 0.0001 while that of fuel gases, oil bearing system and engine exhaust are 0.0010, 0.0002 and 0.002 respectively.
Which heat exchanger is more efficient and why?
Counter flow heat exchangers are inherently more efficient than parallel flow heat exchangers because they create a more uniform temperature difference between the fluids, over the entire length of the fluid path.
Can fouling factor be negative?
“Negative” fouling. This can occur when fouling rate is quantified by monitoring heat transfer. Relatively small amounts of deposit can improve heat transfer, relative to clean surface, and give an appearance of “negative” fouling rate and negative total fouling amount.
How does fouling factors affect heat transfer?
The deposition of any undesired material on heat transfer surfaces is called fouling. Fouling increases the overall thermal resistance and lowers the overall heat transfer coefficient of heat exchangers. Fouling also impedes fluid flow, accelerates corrosion and increases pressure drop across heat exchangers.
What is difference between lmtd and Amtd?
Reason :- We are using LMTD to find out the average temperature difference throughout the length. We can use AMTD but it’s difficult(Not possible) to measure temperature difference throughout the length and then finding average of all of them.
How do you calculate fouling rate?
Fouling changes the surface of the wall between hot and cold fluids. As a result, the overall heat transfer rate through that surface is reduced….Typical fouling factor values.
|Fluid||Fouling Factor [(h⋅ft2⋅°F)/Btu]|
|Light gas oil||0.002|
|Heavy gas oil||0.003|
|Heavy fuel oil||0.005|
Which type of heat exchanger is best?
The parallel-flow heat exchanger is the most suitable one if the area is an important parameter where as the counter-flow heat exchanger for the maximum net gain. The maximum net gains for all heat exchanger types are given in Table 3.
Which type of heat exchanger is most effective?
counter flow heat exchanger
Each of the three types of heat exchangers (Parallel, Cross and Counter Flow) has advantages and disadvantages. But of the three, the counter flow heat exchanger design is the most efficient when comparing heat transfer rate per unit surface area.
How can fouling or scaling affect heat transfer performance of heat exchangers?
Scaling is a type of fouling caused by inorganic salts in the water circuit of the heat exchanger. It increases the pressure drop and insulates the heat transfer surface, thus preventing efficient heat transfer. The salts are therefore deposited on the warm surface when the cold water makes contact with it.
What causes fouling in heat exchangers?
Biological fouling is caused by the growth of organisms, such as algae, within the fluid that deposit onto the surfaces of the heat exchanger. Corrosion fouling occurs when a layer of corrosion products builds up on the surfaces of the tube, forming an extra layer of material that often has thermal resistance.
Should I replace heat exchanger?
There are only two options if a Heat Exchanger is bad: Replace the heat exchanger or replace the furnace. If the heat exchanger is under warranty, this option is a good way to go unless it is unavailable in the time frame needed, which can be immediate in cold weather.
Which type of heat exchanger is more efficient?
A shell and tube heat exchanger is more efficient as it can have multiple passes for the fluid to stay longer in contact with heating material (fluid in this case). Longer contact time and higher heat exchange surface area allows greater heat transfer rates which is in accordance with Nusselt ’s equation.
What factors affect heat exchanger corrosion?
Corrosion Fouling Corrosive fluids or impurity in fluids will corrode the heat-transfer surface of heat exchangers and produce precipitation. The degree of corrosion depends on factors such as components in fluids, temperature, pH of processed fluids .
How does a heat exchanger work in a furnace?
A furnace’s heat exchanger is a set of tubes or coils that are looped repeatedly through the air flow inside your furnace for the purpose of heating air. Simply put, the furnace heat exchanger is the part of your furnace that actually heats the air.