Heat Exchanger Cleaning Case Study
http://dramarnathgiri.blogspot.in/2013/07/heat-exchanger-cleaning-case-study.html?q=HEAT+EXCHANGER
Anything can be fixed, so yes. Inspecting those systems with
Ultrasound can be done during production or if more pressure is desired,
use compressed air (always note not to override maximum system pressure
allowed!)
Alternatively the tone generator
method could be serving you as an alternative.Find the leak, fix it
& check again for final inspection!
Posted 7th July 2013 by Dr. Amar Nath Giri-NAGARJUNA-GROUP-NFCL
http://dramarnathgiri.blogspot.in/2013/06/heat-exchanger.html
The overall heat-transfer coefficient of a heat exchanger under operating conditions is reduced by fouling
Fouling and Heat Transfer
The overall heat-transfer coefficient of a heat exchanger under operating conditions is reduced by fouling
During operation with most liquids and some gases a dirt film
gradually builds up on the heat-transfer surface. The deposit is
referred to as fouling.
The increased thermal resistance of the deposit can generally be obtained only from actual tests or experience. The fouling factor can be determined from the relation
The increased thermal resistance of the deposit can generally be obtained only from actual tests or experience. The fouling factor can be determined from the relation
Rd = 1 / Ud - 1 / U (1)
where
Rd = fouling factor - or unit thermal resistance of the deposit (m2K/W)
Ud = thermal conductance of heat exchanger after fouling (W/m2K)
U = thermal conductance of clean heat exchanger (W/m2K)
(1) can also be expressed as:
Ud = 1 / (Rd + 1 / U)
Typical Fouling Factors
- Alcohol vapors : Rd = 0.00009 (m2K/W)
- Boiler feed water, treated above 325 K : Rd = 0.0002 (m2K/W)
- Fuel oil : Rd = 0.0009 (m2K/W)
- Industrial air : Rd = 0.0004 (m2K/W)
- Quenching oil : Rd = 0.0007 (m2K/W)
- Refrigerating liquid : Rd = 0.0002 (m2K/W)
- Seawater below 325 K : Rd = 0.00009 (m2K/W)
- Seawater above 325 K : Rd = 0.0002 (m2K/W)
- Steam : Rd = 0.00009 (m2K/W)
Posted 30th June 2013 by Dr. Amar Nath Giri-NAGARJUNA-GROUP-NFCL
Fouling Calculations
Fouling Calculations
Fouling
Calculations are the main simulation calculations in
The
Monitor™
computer program
.
On a case-by-case basis, the program determines the heat, material and
pressure balances over all the units in the network and the fouling coefficient
for each exchanger.
Network Balance Calculations
Solving
the Network balances involves calculating the heat, mass and pressure balances
on all the exchangers and other unit operations.
These balances use unit feed stream data along with user specifications
to calculate product stream information. The
calculations iterate until the network has converged for stream temperatures,
flows and pressures. If
Data Reconciliation has been run for a
case, the reconciled data will automatically be used in Fouling Calculations.
Exchanger Balances
The
flow rate and temperature of each feed to an exchanger are known.
One exit temperature must be specified.
The other exit temperature is determined by heat balance. The
calculated exit temperature may depend on the pressure so the pressure and heat
balances must be solved together. The
exchanger pressure drop is calculated from the flow rate, temperatures, fluid
properties and mechanical data. Instead
of using the calculated pressure drop, you may enter pressure values for
exchanger exit streams.
Actual Coefficient (Uactual)
The
Actual Heat Transfer Coefficient (sometimes called the Dirty Heat Transfer
Coefficient) is determined for each exchanger for each case from the equation:
Q = Uactual.A.MTDwhere:Q = duty, calculated from heat balance
Uactual = actual heat transfer coefficient
A = total exchanger area specified
MTD = Mean Temperature Difference
MTD
is calculated from the Logarithmic Mean Temperature Difference (LMTD) which, for
a counter-current heat exchanger, is defined by:
where
The
calculation of LMTD assumes that the exchanger is single pass.
However, most real exchangers have more than one pass.
The MTD is a modified value for the LMTD which takes into account the
number of shell and tube passes. MTD is determined by:
where: FT = LMTD correction factor.
Heat exchangers compilation
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Posted 17th May 2013 by Dr. Amar Nath Giri-NAGARJUNA-GROUP-NFCL
