The fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger , but they are often overstated by the end user in an attempt to minimize the frequency of cleaning. ...
What do you mean by fouling?
Fouling is the accumulation of unwanted material on solid surfaces . ... Fouling is usually distinguished from other surface-growth phenomena in that it occurs on a surface of a component, system, or plant performing a defined and useful function and that the fouling process impedes or interferes with this function.
What are the causes of fouling?
- Fluid velocity.
- Fluid temperature.
- Fluid chemistry.
- Materials of fabrication.
What is fouling factor formula?
During operation with liquids and gases a dirt film may build up on the heat exchanger surfaces . The deposit film is referred to as fouling. Increased thermal resistance caused by the deposit can normally only be obtained from tests or experience. The fouling factor can be determined as. R d = 1 / U d – 1 / U (1)
What is fouling factor how it affects the design of heat exchanger?
The fouling factor represents the theoretical resistance to the heat flow due to the build-up of a layer of dirt or other fouling substances on the tube surfaces of the heat exchanger . These dirt levels are often played down by the end user in an attempt to minimize the frequency of cleaning.
How do I reduce fouling?
The best way to avoid particulate fouling is to keep the cooling water clean and thereby prevent particles from entering the heat exchanger. However, in all cooling systems, and especially when using open cooling systems (with cooling towers), there will always be particles present in the cooling water.
How can fouling be controlled?
Increasing flow velocity increases the fluid shear stress which causes more removal. This results in lower fouling rates which resulting to lower fouling resistance. For weak deposits (particulate fouling), increasing the flow velocity may completely eliminate fouling.
What is the effect of fouling?
Fouling is a dynamic phenomenon which changes with time. 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 fouling in a gun?
: one of several rounds fired before a rifle match to warm the barrel and to furnish some fouling in order that the initial rounds of record fire pass through the bore under conditions similar to those obtaining for later rounds.
What are fouling organisms?
Fouling is the process by which organisms attach themselves to underwater objects, such as ship hulls . Hull fouling organisms include sessile biota, organisms that attach and stay fixed in one place (such as barnacles).
Which one is having the lowest value of 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.
What is K in Nusselt number?
In the case of the Biot number, k is the thermal conductivity of the solid. In the case of the Nusselt number, k is the thermal conductivity of the fluid flowing around the body.
What is scaling and fouling?
Scale and Fouling, which is a result of “Hardness” in water , is most often caused by calcium carbonate, calcium phosphate, or magnesium silicate. These compounds will precipitate out of the water stream and form deposits on heat transfer surfaces.
What are the limitations of lmtd method?
Assumptions and limitations
However, if the specific heat changes, the LMTD approach will no longer be accurate . A particular case for the LMTD are condensers and reboilers, where the latent heat associated to phase change is a special case of the hypothesis.
What is NTU in heat exchanger and what it indicates?
NTU is defined as:[11.74]NTU=UACminwhere U is the overall heat transfer coefficient (kW/m2K) , A is the heat transfer area of the heat exchanger (m2) and Cmin is the smallest thermal capacity of the two fluids (kW/K).
