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Heat Exchanger
Sistem Permesinan
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References :• Introduction to Marine Engineering
• Marine Auxiliary Machinery• Maritime Engineering Reference
Handbook• Marine engineering
Dedi Budi Purwanto ST.,MT.
Introduction
At different temperature and thermal contact
Transfer thermal energy
Between two or more fluids
Between a solid
surface and a fluid
Between solid
particulates and a fluids
Heat exchanger
Components fluids stream
Single Multiple
Typical applications
Heating (Evaporation)
Cooling (Condensatio
n)
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Introduction Design consideration:
Corrosion
Fouling
Fluid temperature
Operating pressures
Pressure drop
Viscosity
flow rate
Material of Construction
Cooper
Best heat transfer performance of all metal
High thermal conductivity
Relatively poor corrosion resistance
Brass (an alloy cooper & zinc)
Is stronger than cooper while still retaining high thermal conductivity
Suffer from corrosion
Aluminum
Is a lightweight metal and has high heat transfer efficiency at a comparatively low cost
corrosion resistance
Stainless steel
Excellent corrosion resistance
Lower heat transfer efficiency
expensive
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Types of Heat Exchangers According to the heat transfer
process
In indirect contact heat transfer
In direct contact heat transfer
According to construction
the heat exchanger may incorporate shell & tube, plated, spiral, or air-cooled construction.
According to flow arrangements
the heat exchanger may be either single pass or multi-pass. It may incorporate cross-flow, counter-flow, or co-current flow
According to the number of fluids
the heat exchanger may incorporate two, three, or more than three heat transfer fluids in the system.
According to heat transfer mechanism
the heat exchanger uses single-phase convection, two-phase convection, and/or radioactive heat transfer on each side of the exchange
According to process function
Condenser, chiller, heater, coolers
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According to Transfer processes
Wet surface direct evaporative coolers typically use pump circulating water system to keep the media wet
In a typically indirect evaporation air cooler, the essential element is a heat exchanger in which dry air contact heat exchange surface whose other sides are cooled evaporative
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According to Construction
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Tubular heat exchanger The configuration give a large surface area in a small volume
Flexibility design : Easily by changing the tube diameter, length and arrangement
Design for high pressure
Easily cleaned
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Tube pattern
Recommended tube pitch (distance between tube centre) is 1.25 times the tube outside diameter
Tube arrangement
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Tube Design1. Finned tube2. Surface tube3. Straight tube4. U – tube
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Shell type (pass arrangement)
a. One pass shell (E shell)
b. Split flow (G shell)
c. Divided shell (J shell)
d. Two pass shell with longitudinal baffle (F shell)
e. Double split flow (H shell)
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Baffle
The choice baffle type, spacing, and cut is determinate largely by flow rate, desired heat transfer rate, allowable pressure drop, tube support
Flow induced vibration Spacing used ranged from 0.2 to 1.0 shell diameter
Optimum spacing will usually be between 0.3 to 0.5 time the shell diameter
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Plate heat exchanger Cannot accommodate very high pressure, temperature.
Lower fouling due to high turbulence in the exchanger
Higher heat transfer efficiency
Material selection is critical due to the thin wall thicknesses
They can easily be taken apart into their individual component for cleaning, inspection, and maintenance
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There are three main types of plated heat exchangers
plate and frame heat exchangers,
consist of a number of corrugated metal plates in mutual contact
spiral plate heat exchangers, and
are a type of welded plate heat exchanger with two parallel curved (spiral shaped) metal plates.
These plates create extremely high turbulent flow in a counter-current pattern. can be used with high-viscosity fluids.
plate coil heat exchangers.
hybrid of tube heat exchangers and plate heat exchangers.
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Extended surface heat exchanger Large heat transfer surface area
Type
Tube fin
Plate fin
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Regenerative Is a storage type heat exchanger
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According to Flow Arrangement Particular flow arrangement is dependent:
Required exchanger affectivities
Available pressure drop
Minimum & maximum velocity
Allowable thermal stresses,
Temperature levels
Piping considerations
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Single pass exchanger Counter flow
Parallel flow
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Single pass exchanger Cross flow
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Multi pass exchanger Multiphase cross flow
Multiphase shell & tubes
Multiphase plate
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According to Process Function
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Chiller Chilled water temperatures can
range from 35 to 45 degrees Fahrenheit (1.5 to 7 degrees Celsius)
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Typical water-cooled chiller system Indirect water-side economizer
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Condenser condensing the exhaust steam
from a steam and transferring the waste heat away from the power station.
The function of the condenser is to condense exhaust steam from the steam turbine by rejecting the heat of vaporization to the cooling water passing through the condenser
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Types of condensers
a) air-cooled
b) water-cooled
c) evaporative
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Air cooled heat exchangers may be either forced draft or induced draft.
Forced draft heat exchangers "force" or push air through the unit by installing fans at the inlet below the tube bundle
Induced draft heat exchangers pull air through the unit by installing fans at the outlet above the tube bundle
Coolers
Cathodic Protection Reducing the corrosion rate of a metal.
The principle is based on “Supplying electrons to the base material”
Material cathodic
Zinc
Aluminium
Magnesium
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Aplikasi di Kapal Lubricating Oil Cooler
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FO & LO heater
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Hot Water Heater
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