ASHRAE Journal - February 2020 - 46

ASHRAE - CELEBRATING 125 YEARS

FIGURE 12 TR6.

FIGURE 13 Broken cap tube.

standards for a building's cooling
equipment, though adoption is a
slow process. As a result of this slow
adoption, the DOE has stepped in
to regulate air-conditioning equipment, setting new, federallymandated guidelines to circumvent the
need for state-by-state adoption.
In 2003, the minimum seasonal
energy efficiency ratio (SEER) rating for residential air conditioning
systems in the U.S. was SEER 10,
which meant that most systems
used a fixed-orifice metering device
and only high-efficiency systems
used an active metering device like
a TXV. Then in 2004,7 the U.S. DOE
announced a new minimum SEER
standard of 13 for air-conditioning
and heat pump systems manufactured after January 23, 2006,
increasing the energy efficiency of
each system by 30%. With the new
SEER requirements, OEMs realized
that fixed-orifice throttling devices
would not be sufficient and the
demand for TXVs skyrocketed.

In the Rest of the World

The European Union (EU) started
aggressively combating climate
change in 2006, particularly through
tighter energy-efficiency regulations. The first initiative was the
Green Paper on Energy Efficiency,8

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which outlined its "Efficiency First"
policy. The Green Paper has since
been replaced multiple times with
ever-stricter efficiency standards,
the latest coming in 2016 as an
amendment to the 2012 Energy
Efficiency Directive. As in the U.S.,
TXVs have helped Europeans meet
ever-increasing efficiency demands.
China's plan to combat climate
change has been even more aggressive. Starting in 2012,9 China
launched the One Hundred Energy
Efficiency Standards Promotion
Projects, which have had a huge
impact on lowering the energy usage
of products used within the country,
especially residential air conditioners. As in the U.S. and Europe, TXVs
helped increase the efficiency of
cooling systems, though other measures were also employed, such as
variable-speed compressors.

The Future of TXVs10
Digitalization has been a growing trend for years, with no signs of
slowing. Add the more recent development of Internet of Things (IoT)
solutions, and it becomes clear that
the future-including the future of
the HVAC&R industry-is increased
control through digitalization. The
likely candidate for digitalizing TXVs
is the EEV introduced earlier.

FEBRUARY 2020

FIGURE 14 EEV.

EEVs, as seen in Figure 14, are topof-the-line throttling devices. While
TXVs are purely mechanical, EEVs
can be programmed to work with
the other components in the system,
allowing them to further optimize
performance and efficiency. While
EEVs can outperform TXVs, the
gains often do not justify the higher
cost. A standard TXV can increase
efficiency versus a fixed-orifice
device by about 30% for only a small
increase in cost, whereas an EEV will
be significantly more expensive,
and there is no guarantee that it will
improve efficiency.
One reason for the greater expense
is that EEVs need additional components to work properly, including
sensors and a controller. While TXVs
have been engineered to be selfcontained, EEVs are best seen as part
of a greater whole, operating according to the data the sensors collect and
the commands the controller and its
underlying software sends out. And
while a TXV can be a drop-in replacement for a piston or capillary tube,
the same cannot be said for an EEV.
Systems that require exact precision-such as data centers, mobile
phone network exchanges, and
server rooms-will benefit from having an EEV and complimentary components. However, an EEV is only as

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ASHRAE Journal - February 2020

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