Fujitsu UTZ-BD025B, Техническое руководство

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- (01-17) -
4. DESIGN SECTION
4-1. ABOUT HEAT EXCHANGE UNIT
4-1-1. BASIC ENGIN

BASIC PRINCIPLE AND
STRUCTURE OF THE HEAT
EXCHANGER

Basic principle of a heat exchanger
The basic principle of a heat exchanger is as indicated
below. As heat moves from a high-temperature area to a
low-temperature area together with humidity, the heated and
moist air moves the heat and humidity to colder and drier air
by passing through a heat-exchange element.
Warm and moist
air
Heat-exchange element
Heat
Humidity
Cold and
dry air

Function of a heat exchanger
A heat exchanger effectively recovers cooled or heated room
temperatures and simultaneously ventilates air.
Winter

Mechanism of a heat exchange element
The heat exchange element can allow the exhaust air from
inside and the fresh air from outside to transmit temperature
and humidity without being mixed up.
Indoor exhaust
Outdoor inlet
Mechanism of total heat ex-
change
Heat
Indoor air
upply at 14
Humidity
s
Cold air at
0
Indoor air
supply
Outdoor
exhaust
Outdoor
exhaust at 6
Humidity
Heat exchange
element
0 ° C
6 ° C 14 ° C
20 ° C
Heat exchange
ratio at 70%
Warm air at
20
Heat

ADVANTAGES OF THE HEAT
EXCHANGE ELEMENT

The height of the heat exchange element
reduced by 20%
The upper and lower protrusions have been cut out (see the figure
below). The newly adopted counter-flow
heat exchange system has made the
entire unit much thinner from 287mm
to 230mm, and realized the same
performance as in the conventional
cross-flow heat exchange element.
Comparison of heat exchange elements
C t ross-flow elemen
Counter-flow ele-
ment
While airflows are directly crossed in the cross-flow ele-
ment, the counter-flow element allows airflow to be retained
for longer time (or longer distance). In this manner, the
thinner system can maintain the heat exchange perform-
ance attained by its thicker counterpart.

Total heat exchange efficiency improved by
6%
The adoption of the counter-flow element has improved
the total heat exchange ratio by about 6%, significantly
contributing to energy saving.

Long-life heat exchange element
By adopting nonwoven fabric filter with excellent dust
collection efficiency and improving the air course shapes,
a long-life heat exchange system has been realized, which
does not require regular cleaning of the heat exchange
element.
cross-flow element
After cleaning the
cross-flow element
The counter-flow element
Heat exchange element with
extended life
The cross-flow element
requires regular clean-ups.
A
irf
lo
w
re
si
st
an
ce
Changes in airflow resistance
with the years of use
C
le
an
ed
U
se
d
Initial
level
1st
year
2nd
year
3rd
year
4th
year
5th
year
6th
year
7th
year
8th
year
9th
year
10th
year
Service year
The counter-flow element requires no regular
clean-up, as the resistance level hardly rise.
Long-life heat exchange element
Conventional element
(corrugated structure)
With the above features, airflow resistance affecting service life hardly rises.
The end section is finished with the resin-formed
structure characterized by robustness
Bigger air-course per cell
The fin structure is seldom crushed or damaged.
Dirt and dust are seldom attached.
New-type element
Heat exchanger
plate (paper)
Hydraulic
diameter
Spacing plate
(paper)
Spacing rib (resin)
Heat exchanger
plate (paper)
Hydraulic
diameter
Before cleaning the cross-flow element
After cleaning the
cross-flow element
The counter-flow element
Heat exchange element with
extended life
The cross-flow element
requires regular clean-ups.
A
irf
lo
w
re
si
st
an
ce
Changes in airflow resistance
with the years of use
C
le
an
ed
U
se
d
Initial
level
1st
year
2nd
year
3rd
year
4th
year
5th
year
6th
year
7th
year
8th
year
9th
year
10th
year
Service year
The counter-flow element requires no regular
clean-up, as the resistance level hardly rise.
Long-life heat exchange element
Conventional element
(corrugated structure)
With the above features, airflow resistance affecting service life hardly rises.
The end section is finished with the resin-formed
structure characterized by robustness
Bigger air-course per cell
The fin structure is seldom crushed or damaged.
Dirt and dust are seldom attached.
New-type element
Heat exchanger
plate (paper)
Hydraulic
diameter
Spacing plate
(paper)
Spacing rib (resin)
Heat exchanger
plate (paper)
Hydraulic
diameter
Before cleaning the