C. Patnaik, Stratview Research, Raipur,
The laws of thermodynamics include: energy
can neither be created nor destroyed, it can only be converted from one form to
another; and heat always moves downhill, from hotter objects to the colder
objects, unless the direction of heat flow is reversed using external energy.
When it comes to heat exchangers and
their workings, these—along
with the Zeroth law of thermodynamics—are the most important principles. Heat exchangers have been well-known
since the later part of the 1870s, the first time they were made and used in the
food and beverages industry.
As the years passed, heat exchangers were
employed in several industries, such as refrigeration, space heating and power
stations with advanced modifications. They became an important technology and
helped modern equipment in transferring heat from gas-to-gas, liquid-to-liquid
or liquid-to-gas in an efficient manner.
What are heat exchangers, and why are
they so significant to successful operations?
THE TECHNOLOGY: HEAT EXCHANGER TYPES
Simply put, a heat exchanger is a system
that is used to transfer heat from one medium to another, mainly through
conduction and convection, and occasionally through radiation. This gives heat
exchangers a unique utility in cooling and heating processes; therefore, they
are often used in space heating, refrigeration, petroleum refineries, natural
gas processing, power stations, petrochemical plants and sewage treatment plants,
Heat exchangers come in several types, and
are differentiated mainly based on two factors: the working mechanism and flow
Based on the working mechanism, three
main types of heat exchangers prevail: shell-and-tube heat exchangers, plate
heat exchangers and air-cooled heat exchangers. The workings and differences
between these variants of heat exchangers are discussed in the following
Shell-and-tube heat exchangers.
The name says it
all: a shell-and-tube heat exchanger consists of multiple tubes fitted inside a
pressured vessel, known as a shell (FIG.
1). One fluid flows
through the tubes and the other flows over them in the vessel to aid the
transfer of heat between them.
Some new technological advancements in shell-and-tube
heat exchangers include finned tubes, single- or two-phased heat transfer, and
single-, two- or multiple-pass configurations, among others. Shell-and-tube heat
exchangers are undergoing advancements in their selection technology, as well.
For example, in 2022, Bell & Gossett, an XYLEM brand, announced that it has
integrated ESP-Thermal, an online plate and shell-and-tube heat exchanger
selection program, into its ESP-Systemwize selection tool. This addition will
help engineers select and optimize the best heat exchanger to meet their goals
Double-pipe heat exchangers are another form
of shell-and-tube heat exchangers that employ a simple design utilizing two
concentric, cylindrical pipes. One fluid flows through a smaller tube and
another one passes through the larger tube, helping facilitate the exchange of
heat between the two fluids.
Air-cooled heat exchangers.
exchangers, like the general schematic shown in FIG. 2,
work on the principles of convection and conduction to dissipate heat from the
fluid to the outer atmosphere. In the process, the fluid is passed through the
tubes and the air stream is passed over the tube, helping dissipate the heat.
The air streams are produced from the fans mounted on the unit. These
exchangers are efficient in cooling or condensing water, chemicals or any other
fluid. Continuous efforts and investments by market players are being put into
improving the technology.
Plate heat exchangers.
Plate heat exchangers
of multiple thin, corrugated metal plates bundled together (FIG. 3). They are either bolted or welded
together, and two passages are created between the plates: one for cold fluid and
another for the hot fluid. Various modifications in the PHE provide plate-fin
heat exchangers, plate-and-frame heat exchangers, plate-and-shell heat
exchangers and spiral-plate heat exchangers, among others.
PHEs are a mature technology: the first patent
for a PHE was awarded to Albrecht Dracke of Germany in 1878, and they gained
popularity in the 1990s. According to research by the author’s company, among
these three types, PHEs have a greater market presence. Reasons for this
Additionally, development and innovations
continue in the segment to make PHEs more environment-friendly. For example, in
July 2022, Alfa Laval signed an agreement with SSAB to co-develop the world's first PHE to
be made using fossil-free steel. The goal is to have the first unit made with
hydrogen (H2)-reduced steel ready for 2023.
Flow configurations. Heat exchangers can be categorized depending
on their flow configuration—the
direction of flow of the fluids with respect to each other within the heat
exchangers. Four types of flow arrangements are prevalent and detailed in TABLE 1:
Impact of COVID-19.
The heat exchanger
market was adversely affected by the global pandemic in 2020 (and after). The
end-user industries of heat exchangers (e.g., oil and gas, petrochemicals,
refining) suffered heavily due to a decline in demands, manufacturing
restrictions, supply chain disintegration and shortage of labor, among other factors.
These conditions lead to a significant decline in the heat exchangers market of
11.9% in 2020, which caused the market value of heat exchangers to fall below
$13 B that year.
However, in 2021, after many
restrictions were lifted, the resumption of operations in the petrochemical,
chemical, oil and gas, and energy sectors buoyed the demand for heat exchangers.
This helped the market grow at a CAGR of 5.2%—with this resurgent growth rate, the market is
expected to reach a value of $18.3 B by 2027.
Asia-Pacific region leading the way.
Countries like China,
India and Japan are maintaining record-breaking growth rates in industries like
oil and gas, petrochemical, carbon capture, etc. The heat exchanger segment is
also strong in the Asia-Pacific region with a share of 33.9% in 2021. Factors include:
The Asia-Pacific region is also investing
heavily to develop sustainable technologies, which is proving to be a boon for
the heat exchangers market.
At the 26th Conference
of Parties (COP 26) organized in Glasgow, Scotland, 197 countries negotiated
and agreed on the Glasgow Climate Pact, which reaffirms the target of holding
the increase in the global average temperature to well below 2°C above pre-industrial
levels and pursue efforts to limit it at 1.5°C above pre-industrial levels. This has had a
major effect on manufacturing companies, which are now impelled to pursue
efforts to manufacture products while considering the environment.
Several companies are focusing on
developing environmentally-friendly steel for their heat exchangers, as well as
using environmentally-friendly cooling fluids, such as water, to absorb and
transfer waste heat.
The heat exchangers
market is emerging from a pandemic-caused growth slump and is poised to rebound
due to renewed demand as restrictions continue to be lifted. Major market
players are now investing heavily in environmentally-friendly new technologies.
With the re-establishment of supply
chains, a surge in required skilled labor and a rise in demand from end-use
industries, the future of heat exchangers is bright. HP
CHANDANA PATNAIK is a Senior Content
Writer at Stratview Research and an experienced technical writer with a passion
for exploring and explaining the latest technology developments in the heat and
refrigeration industry and their applications across other major segments,
including the oil and gas, petrochemicals and chemical industries. She is a
regular contributor to various magazines and blogs, and creates insightful and
engaging content that informs readers of the latest trends and developments in
her areas of expertise.