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The Family of Shell and Tube Heat Exchangers

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The Family of Shell and Tube Heat Exchangers P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Family members with Simple Geometrical Features ... – PowerPoint PPT presentation

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Title: The Family of Shell and Tube Heat Exchangers


1
The Family of Shell and Tube Heat Exchangers
  • P M V Subbarao
  • Professor
  • Mechanical Engineering Department
  • I I T Delhi

Family members with Simple Geometrical Features
for Complex Fluid Flow.
2
Fixed tube sheet
3
U-Tube STHE
4
Floating Head STHE TEMA S
5
Floating Head STHE TEMA T
6
Cross Baffles
  • Baffles serve two purposes
  • Divert (direct) the flow across the bundle to Wet
    the the maximum tube surface area.
  • Support the tubes for structural rigidity,
    preventing tube vibration and sagging.
  • When the tube bundle employs baffles,
  • The heat transfer coefficient is higher than the
    coefficient for undisturbed flow around tubes
    without baffles.
  • For a baffled heat exchanger the higher heat
    transfer coefficients result from the increased
    turbulence.
  • the velocity of fluid fluctuates because of the
    constricted area between adjacent tubes across
    the bundle.
  • This also leads to developing flow for ever.

7
Avoid Developed Flow
8
Types of Baffle Plates Segmental Cut Baffles
  • The single and double segmental baffles are most
    frequently used.
  • They divert the flow most effectively across the
    tubes.
  • The baffle spacing must be chosen with care.
  • Optimal baffle spacing is somewhere between 40 -
    60 of the shell diameter.
  • Baffle cut of 25-35 is usually recommended.

9
Types of Baffle Plates
The triple segmental baffles are used for low
pressure applications.
10
Types of Baffle Plates
11
Types of Baffle Plates
Disc and ring baffles are composed of alternating
outer rings and inner discs, which direct the
flow radially across the tube field. The
potential bundle-to-shell bypass stream is
eliminated This baffle type is very effective
in pressure drop to heat transfer conversion
12
Types of Baffle Plates
In an orifice baffle shell-side-fluid flows
through the clearance between tube outside
diameter and baffle-hole diameter.
13
Thermal Analysis of Heat Exchanger
  • Known as heat exchanger specification problems
    and their solutions.
  • These are rating, design, and selection.

14
Rating Analysis
  • The rating problem is evaluating the
    thermo-hydraulic performance of a fully specified
    exchanger.
  • The rating program determines
  • the heat transfer rate and the fluid outlet
    temperatures for prescribed fluid flow rates,
    inlet temperatures, and
  • the pressure drop for an existing heat exchanger
  • therefore the heat transfer surface area and the
    flow passage dimensions are available.

15
The Rating Analysis
16
The Design (Sizing) Analysis
  • Design is the process of determining all
    essential constructional dimensions of an
    exchanger that must perform a given heat duty and
    respect limitations on shell-side and tube-side
    pressure drop.
  • In the Design (sizing) Analysis,
  • An appropriate heat exchanger type is selected.
  • The size to meet the specified hot and cold fluid
    inlet and outlet temperatures, flow rates, and
    pressure drop requirements, is determined.
  • Constraints
  • Minimum or maximum flow velocities,
  • Size and/or weight limitations,
  • Ease of cleaning and maintenance, erosion, tube
    vibration, and thermal expansion.
  • Each design problem has a number of potential
    solutions, but only one will have the best
    combination of characteristics and cost.

17
Basic Design Procedure
18
Basic Design Procedure
  • Heat exchanger must satisfy the Heat transfer
    requirements (design or process needs)
  • Allowable pressure drop (pumping capacity and
    cost)
  • Steps in designing a heat exchanger can be listed
    as
  • Identify the problem
  • Select an heat exchanger type
  • Calculate/Select initial design
  • parameters
  • Rate the initial design
  • Calculate thermal performance and pressure drops
    for shell and tube side.
  • Evaluate the design.
  • Is performance and cost acceptable?

19
The Selection Analysis
  • Selection means choosing a heat exchanger from
    among a number of units already existing.
  • Typically, these are standard units listed in
    catalogs of various manufacturers.
  • Sufficient manufacturers data usually exist to
    allow one to select comfortably oversized
    exchanger with respect to both area and pressure
    drop.
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