vevor heat exchanger
A heat exchanger is a heat transfer device that exchanges heat between two or more
process fluids. Heat exchangers have widespread industrial and domestic applica-
tions. Many types of heat exchangers have been developed for use in steam power
plants, chemical processing plants, building heat and air conditioning systems,
transportation power systems, and refrigeration units.
The actual design of heat exchangers is a complicated problem. It involves more
than heat-transfer analysis alone. Cost of fabrication and installation, weight, and
size play important roles in the selection of the final design from a total cost of
ownership point of view. In many cases, although cost is an important consider-
ation, size and footprint often tend to be the dominant factors in choosing a design
Heat Exchanger Types
A heat exchanger is a heat transfer device that exchanges heat between two or more
process fluids. Heat exchangers have widespread industrial and domestic applica-
tions. Many types of heat exchangers have been developed for use in steam power
plants, chemical processing plants, building heat and air conditioning systems,
transportation power systems, and refrigeration units.
The actual design of heat exchangers is a complicated problem. It involves more
than heat-transfer analysis alone. Cost of fabrication and installation, weight, and
size play important roles in the selection of the final design from a total cost of
ownership point of view. In many cases, although cost is an important consider-
ation, size and footprint often tend to be the dominant factors in choosing a design.
Most heat exchangers may be classified as one of several basic types.
Indirect Contact Type Heat Exchangers
In an indirect-contact heat exchanger, the fluid streams remain separate and the heat
transfers continuously through an impervious dividing wall or into and out of a wall
in a transient manner. Thus, ideally, there is no direct contact between thermally
interacting fluids. This type of heat exchanger, also referred to as a surface heat
exchanger, can be further classified into direct-transfer type, storage type, and
fluidized-bed exchangers
Direct Contact Type Heat Exchangers
In this type, heat transfers continuously from the hot fluid to the cold fluid through a
dividing wall. Although a simultaneous flow of two (or more) fluids is required in
the exchanger, there is no direct mixing of the two (or more) fluids because each
fluid flows in separate fluid passages. In general, there are no moving parts in most
such heat exchangers. This type of exchanger is designated as a recuperative heat
exchanger or simply as a recuperator. (Some examples of direct transfer type heat
exchangers are tubular, plate-type, and extended surface exchangers).
Note that the term recuperator is not commonly used in the process industry for
shell-and-tube and plate heat exchangers, although they are also considered
recuperators. Recuperators are further sub-classified as prime surface exchangers
and extended-surface exchangers. Prime surface exchangers do not employ fins or
extended surfaces on any fluid side. Plain tubular exchangers, shell-and-tube
exchangers with plain tubes, and plate exchangers are good examples of prime
surface exchangers.
Heat exchangers are used to transfer heat between two sources. The exchange can take place between a process stream and a utility stream (cold water, pressurized steam, etc), a process stream and a power source (electric heat), or between two process streams resulting in energy integration and reduction of external heat sources. Typically, a heat exchanger is used with two process streams. However, mutlistream heat exchangers are sometimes used with energy extensive processes, such as LNG processing, to reduce capital cost. The term heat exchanger applies to all equipment used to transfer heat between two streams. However, the term is commonly used to equipment in which two process streams exchange heat with each other. In the other hand, the term heater or cooler is used when the exchange occurs between a process stream and a plant service stream. Other terms used to describe heating equipment include: vaporizer and reboiler (for vaporization) and evaporator (for stream concentration). Exchangers can also be classified as fired (heat source is fuel combustion) and unfired exchangers. There are many types of heat exchangers applied in the process industry.
These types include:
1. Hairpin/Double pipe exchangers
2. Shell and tube exchangers
3. Plate and frame exchangers
4. Plate-fin exchangers
5. Spiral heat exchangers
6. Air coolers and condensers
7. Direct contact (quenching towers)
8. Fired heaters The selection of a heat exchanger depends on many factors including capital and operating costs, fouling, corrosion tendency, pressure drop, temperature ranges, and safety issues (tolerance to leakage).
HEAT EXCHANGER DESIGN PROCESS
1. Problem definition: design specifications
2. Selection of heat exchanger type
3. Thermo-hydraulic design
4. Mechanical design
5. Manufacturing, cost and process optimization considerations
A BRIEF INTRODUCTION ON CONVECTION HEAT TRANSFER
1) Similar variables and dimensionless parameters are encountered in both heat transfer and friction analysis.
2) If either heat transfer coefficient or friction factor is known, the analogy can be used to solve at least an approximate value for the other one as well.
3) A surface with a comparatively high heat transfer coefficient is bound to have also a comparatively high friction factor and thus pressure drop
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