How is fouling factor calculated?

How is fouling factor calculated?

The fouling factor, Rf, as well as the deposition rate, d, and the removal rate, r, can be expressed in the units of thermal resistance as m2·K/W or in the units of the rate of thickness change as m/s or units of mass change as kg/ m2· s.

What is the fouling coefficient?

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. …

Which one is having highest value of fouling factor?

Which one is having the highest value of fouling factor? Explanation: Fouling factor for liquid gasoline is 0.0008 while that of clean river, sea water and distilled water are 0.0002, 0.0001 and 0.0001 respectively. Fouling factor = 1/hS. 2.

What does fouling factor depend on?

Fouling factor (or dirt factor) definition It normally depends on the process fluid or service on any side (shell or tube) of the heat exchanger. Fouling or dirt factor is used for calculation of the overall heat transfer coefficient of a heat exchanger.

What is the difference between scaling and fouling?

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 is a high fouling factor?

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 minimise the frequency of cleaning.

What is water fouling?

The terms ‘fouling’ or ‘water fouling’ are general terms used to describe the presence or accumulation of unwanted material in water or on a component such as a heat exchanger. Fouled water is never optimal and can cause a variety of problems if left untreated.

How does fouling factor affect heat transfer?

Fouling has a significant impact on heat transfer across the heat exchanger surface, and therefore on the overall operational performance and the economics of the process. These side effects combine to increase the pressure drop across the heat exchanger, reducing flow rates and aggravating the problem further.

Is scaling a type of fouling?

What is fouling effect?

Fouling is the formation of unwanted material deposits on heat transfer surfaces during process heating and cooling. It occurs in all industries and most heat exchanger designs, with impacts ranging from heat transfer degradation to flow resistance and pressure drops.

What is the value of fouling factor for engine exhaust?

0.002
Solution: Fouling factor for engine exhaust is 0.002 while that of industrial liquids, fuel oil and turbine exhaust are 0.0002, 0.0010 and 0.0002 respectively.

What is difference between scaling and fouling?

Scaling. 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.

What causes the fouling rate to go down?

The reduction in fouling rate is almost certainly due also to the increased surface shear stress when wires were fitted. Figure 3.21. Fouling resistance curve on wired probe.

Why is the fouling rate lower on a wired probe?

The fouling rate for the wired probe, 8.7 × 10 −10 m 2 K W −1, was noticeably lower even at a higher surface temperature than that on the plain probe (3.0 × 10 −9 m 2 K W −1 ). The reduction in fouling rate is almost certainly due also to the increased surface shear stress when wires were fitted.

Why is there scatter in fouling resistance data?

When compared with the fouling resistance data found by Young et al. (2011) for the plain probe, it can be seen that there is now much more scatter in the experimental data. This is most probably due to the random removal of the deposit because of the higher shear force which is created on the wired probe at any given stirrer speed.

What is the Reynolds number for fouling resistance?

Here Rf is the fouling resistance (m 2 K J −1 ), Re the Reynolds number, EA the activation energy (J mol –1 ), and τ the shear stress (Pa).