How do you calculate fouling factor in heat exchanger?

Typical Fouling Factors

1. Alcohol vapors : R_d = 0.00009 (m²K/W)
2. Boiler feed water, treated above 325 K : R_d = 0.0002 (m²K/W)
3. Fuel oil : R_d = 0.0009 (m²K/W)
4. Industrial air : R_d = 0.0004 (m²K/W)
5. Quenching oil : R_d = 0.0007 (m²K/W)
6. Refrigerating liquid : R_d = 0.0002 (m²K/W)
7. Seawater below 325 K : R_d = 0.00009 (m²K/W)

Hereof, what is fouling factor in heat exchanger?

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.

Similarly, what is MTD in heat exchanger? For a heat exchanger with countercurrent flow, the mean temperature difference is known as the log mean temperature difference, ΔT_LM. The log mean temperature difference is the maximum mean temperature difference that can be achieved in any geometry of heat exchanger for any given set of inlet and outlet temperatures.

In this manner, what is the value of fouling factor for sea water?

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/h_S.

What is difference between scaling and fouling?

When cooling systems operate, water with fouling factors flow through the system: Hard water causes scaling, whereas seawater can cause biofilm, or growth of micro and macro species. Soft at first, fouling becomes hard if not treated and prevents the proper operation of the system.

Related Question Answers

How do you find the fouling factor?

Typical Fouling Factors

1. Alcohol vapors : R_d = 0.00009 (m²K/W)
2. Boiler feed water, treated above 325 K : R_d = 0.0002 (m²K/W)
3. Fuel oil : R_d = 0.0009 (m²K/W)
4. Industrial air : R_d = 0.0004 (m²K/W)
5. Quenching oil : R_d = 0.0007 (m²K/W)
6. Refrigerating liquid : R_d = 0.0002 (m²K/W)
7. Seawater below 325 K : R_d = 0.00009 (m²K/W)

Why are baffles provided in heat exchanger?

The main roles of a baffle in a shell and tube heat exchanger are to: Hold tubes in position (preventing sagging), both in production and operation. Prevent the effects of steam starvation, which is increased with both fluid velocity and the length of the exchanger. Direct shell-side fluid flow along tube field.

What are different types of heat exchangers?

Types of Heat Exchangers

• Shell and tube heat exchangers.
• Double pipe heat exchangers.
• Plate heat exchangers.
• Condensers, evaporators, and boilers.

What is NTU in heat exchanger?

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).

How does fouling factor 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 effective heat exchanger?

The effectiveness (ϵ) of a heat exchanger is defined as the ratio of the actual heat transfer to the maximum possible heat transfer.

What is the unit of fouling factor?

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 meant by fouling?

Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic).

What is Amtd?

AMTD = Arithmetic Mean Temperature Difference (^oF, ^oC) t_pi = primary inlet temperature (^oF, ^oC) t_po = primary outlet temperature (^oF, ^oC) t_si = secondary inlet temperature (^oF, ^oC) t_so = secondary outlet temperature (^oF, ^oC)

Which statement is true regarding steady state condition?

Which statement is true regarding steady state condition? Explanation: Heat influx is always equal to heat efflux. It is a function of space coordinates only.

When effectiveness and NTU method is used instead of lmtd method?

In heat exchanger analysis, if the fluid inlet and outlet temperatures are specified or can be determined by simple energy balance, the LMTD method can be used; but when these temperatures are not available The NTU or The Effectiveness method is used.

Which of the following is not associated with a heat exchanger?

3. Which of the following is not associated with a heat exchanger? Explanation: The correction factor i.e. Mc Adam's is associated with laminar film condensation on a vertical plate.

What is lumped heat capacity analysis?

The lumped-heat-capacity method of analysis is used in which no temperature gradient exists. This means that the internal resistance of the body (conduction) is negligible in comparison with the external resistance (convection). cp = specific heat of the body.

Why are fins provided on heat transferring surface?

In the study of heat transfer, fins are surfaces that extend from an object to increase the rate of heat transfer to or from the environment by increasing convection. Thus, adding a fin to an object, increases the surface area and can sometimes be an economical solution to heat transfer problems.

How do you stop heat exchangers from 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.

What is the value of convective coefficient of oil in case of forced convection?

What is the value of convective coefficient of oil in case of forced convection? 1460-3000 W/m² K.

Why lmtd is used in heat exchanger?

The log mean temperature difference (LMTD) is used to determine the temperature driving force for heat transfer in flow systems, most notably in heat exchangers. The use of the LMTD arises, straightforwardly, from the analysis of a heat exchanger with constant flow rate and fluid thermal properties.

How do you calculate log mean?

Divide the difference of x and y by the difference of ln x and ln y. Make sure that x and y are in the same order in the quotient and denominator of the fraction. In the example problem, 90/0.38 = 236.84. The logarithmic mean is 236.84.

What is cross flow heat exchanger?

A crossflow heat exchanger is designed so that the two fluids flow perpendicular to one another. This is typically utilized when one fluid is a liquid and the other is a gas, as in a car radiator in which hot water flowing left and right is cooled by air moving up or down, Bright Hub Engineering explained.

What is lmtd formula?

Log Mean Temperature Difference (LMTD) is an indicator of the average temperature difference between the hot and cold fluids in a heat exchanger. It is calculated using the following equation - ΔT₁ → the temperature difference between hot and cold fluids at one end of the heat exchanger.

What are the limitations of lmtd method?

Cause LMTD method can only be used in design of heat exchanger, when all terminal temperature are known or easily determined. The difficulty arises if temperature of fluid leaving are not known or possible to determined.

How do you find the lmtd of a heat exchanger?

by definition given above, LMTD for counter current flow = (60-50) / ln(60/50) = 10 / 0.1823 = 54.85⁰C. For co-current heat exchanger, ΔT₁ = TH1 - TC1 = 100 - 30 = 70⁰C (At first end hot and cold fluids enter the heat exchanger.)

What is parallel and counter flow heat exchanger?

Counter & Parallel Flow Heat Exchanger Calculator

A counter-flow heat exchanger is one in which the direction of the flow of one of the working fluids is opposite to the direction to the flow of the other fluid. In a parallel flow exchanger, both fluids in the heat exchanger flow in the same direction.

How do you calculate overall heat transfer coefficient in heat exchanger?

Composition

1. = the overall heat transfer coefficient (W/(m²•K))
2. = the contact area for each fluid side (m²) (with and expressing either surface)
3. = the thermal conductivity of the material (W/(m·K))
4. = the individual convection heat transfer coefficient for each fluid (W/(m²•K))
5. = the wall thickness (m).

What is overall heat transfer coefficient?

The overall heat transfer coefficient, or U-value, refers to how well heat is conducted through over a series of resistant mediums. Its units are the W/(m²°C) [Btu/(hr-ft²°F)].