About Heat Exchange Unit - Fujitsu UTZ-BD035B Technical Manual

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
Heat-exchange element
air

Function of a heat exchanger
A heat exchanger effectively recovers cooled or heated room
temperatures and simultaneously ventilates air.

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
Indoor air
Outdoor
supply
exhaust
Heat exchange
element
20°C
0°C
6°C 14°C
Heat exchange
ratio at 70%
Heat Humidity
Cold and
dry air
Winter
Mechanism of total heat ex-
change
Heat
Indoor air
Humidity
s upply at 14
Cold air at
0
Outdoor
Humidity
exhaust at 6
Heat
Warm air at
20
 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 ross-flow elemen
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.
Heat exchange element with
Heat exchange element with
extended life
extended life
Changes in airflow resistance
Changes in airflow resistance
with the years of use
with the years of use
Initial 1st 2nd
Initial 1st 2nd
level year year
level year year
Service year
Service year
Long-life heat exchange element
Long-life heat exchange element
The end section is finished with the resin-formed
The end section is finished with the resin-formed
structure characterized by robustness
structure characterized by robustness
Bigger air-course per cell
Bigger air-course per cell
With the above features, airflow resistance affecting service life hardly rises.
With the above features, airflow resistance affecting service life hardly rises.
Conventional element
Conventional element
(corrugated structure)
(corrugated structure)
Heat exchanger
plate (paper)
Heat exchanger
plate (paper)
Spacing plate
(paper)
Spacing plate
(paper)
- (01-17) -
t
Counter-flow ele-
ment
Before cleaning the
cross-flow element Before cleaning the
cross-flow element
After cleaning the
cross-flow element After cleaning the
cross-flow element The counter-flow element
The counter-flow element
The cross-flow element
The cross-flow element
requires regular clean-ups.
requires regular clean-ups.
3rd 4th 5th 6th 7th 8th 9th 10th
3rd 4th 5th 6th 7th 8th 9th 10th
year year year year year year year year
year year year year year year year year
The counter-flow element requires no regular
The counter-flow element requires no regular
clean-up, as the resistance level hardly rise.
clean-up, as the resistance level hardly rise.
The fin structure is seldom crushed or damaged.
The fin structure is seldom crushed or damaged.
Dirt and dust are seldom attached.
Dirt and dust are seldom attached.
New-type element
New-type element
Hydraulic Heat exchanger
diameter plate (paper)
Heat exchanger
Hydraulic
plate (paper)
diameter
Spacing rib (resin)
Spacing rib (resin)
Hydraulic
diameter
Hydraulic
diameter