How does fouling factors affect heat transfer?
How does fouling factors affect heat transfer?
The fouling of heat exchangers may be defined as the accumulation of unwanted deposits on heat transfer surfaces. The foulant layer imposes an additional resistance to heat transfer and the narrowing of the flow area, due to the presence of deposit, results in an increased velocity for a given volumetric flow rate.
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.
What is fouling in heat transfer?
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.
How do you calculate fouling factor in heat exchanger?
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 |
How can fouling or scaling affect heat transfer performance of heat exchangers What are the possible ways to control or reduce fouling?
Fouling process depend on the extent and nature of the surface roughness. Is possible select materials with smaller surface roughness. Fouling or scaling in heat exchangers can be controlled by using clean fluids free from impurities. As fluids are not fully pure, there is a chance of fouling.
What is fouling in engineering?
Fouling is the settlement, and sometimes the growth, of undesired materials on solid surfaces in a way that reduces the efficiency of the affected part. It deteriorates protective coatings on the metals and reduces corrosion resistance as well as physical and mechanical properties of the material.
What does the overall heat transfer coefficient depend on?
The overall heat transfer coefficient (U) depends on individual heat transfer coefficients and the heat resistance offered by the tube-wall. We assume the coolant heat transfer coefficient (hcool) and the tube wall resistance remains constant.
How can fouling be reduced in a heat exchanger?
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 to calculate the fouling factor of a heat exchanger?
The fouling factor can be determined as. R d = 1 / U d – 1 / U (1) where . R d = fouling factor – or unit thermal resistance of deposit (m 2 K/W) U d = overall heat transfer coefficient of heat exchanger after fouling (W/m 2 K) U = overall heat transfer coefficient of clean heat exchanger (W/m 2 K) (1) can also be expressed as:
What does UD mean in heat transfer coefficient?
Ud = overall heat transfer coefficient of heat exchanger after fouling (W/m2K) U = overall heat transfer coefficient of clean heat exchanger (W/m2K) (1) can also be expressed as: Ud = 1 / (Rd + 1 / U)
What is the meaning of TS in heat transfer coefficient?
h: heat transfer coefficient, W/(m 2 K) Ts = Solid Surface temperature. K = Surrounding fluid area Temperature. It is used in calculating the heat transfer, typically by convection or phase transition between a fluid and a solid. The heat transfer coefficient has SI units in watts per squared meter kelvin: W/(m 2K).
How do you calculate heat transfer coefficient from heat flux?
Overall Heat Transfer Coefficient Table Chart: The heat transfer coefficient is the proportionality coefficient between the heat flux and the thermodynamic driving force for the flow of heat (i.e., the temperature difference, ΔT): h = q / (Ts – K)
