Mitsubishi Electric QAHV, Руководство по установке и эксплуатации

Страница: 16 / 84

16
2 Selection criteria for heat exchanger
Step 1 Determination of prerequisites for selection
I Heat exchanger capacity 40000 W
II Estimation of outlet hot water and inlet water temperatures
As a guide, select a heat exchanger of which the temperature difference between the high temperature
section and the low temperature section will be 5
˚ C or below.
II-1 Outlet hot water temperature (when secondary side outlet hot water temperature is set to 65 ˚ C (setting
at the time of shipment))
• Secondary side circuit outlet hot water temperature: 65 ˚ C
• Unit outlet hot water temperature: 70 ˚ C
II-2 Inlet water temperature
• Secondary side inlet water temperature: 10 ˚ C
• Unit inlet water temperature: 15 ˚ C
III Used flow rate
(40000 W/(70-15) ˚ C/4200 J/kg•K) × 60 s = 10.4 kg/min ≈ 10.4 ℓ /min
Step 2 Determination of model
Notes on selection
• Select a heat exchanger that allows water to pass through both of the flow channels.
• Select a heat exchanger so that the pressure applied to the heat exchanger in the on-site system will not
exceed the maximum operating pressure of the heat exchanger.
• Select a heat exchanger that allows flowing at a flow rate of maximum 30 ℓ /min.
• Select a heat exchanger with a capacity of at least 40000 W.
• Ensure that the shearing stress at the flow rate to be used will be 16 Pa or more. (Refer to step 4.)
* To increase the shearing stress:
• When the area per plate is equal, select a vertically long heat exchanger.
• Select a heat exchanger of which NTU is high (although the heat transfer capacity improves as NTU
increases, the pressure loss becomes high).
8 Valve
Improves the workability
of cleaning the heat
exchanger and
replacing parts.
Install these components in the two places of the chilled water passage section
and the high temperature water passage section to enable replacement.
9 Strainer
Prevents foreign
materials from entering
into the heat exchanger.
Install a strainer with 60 mesh or better near the heat exchanger.
0 Air vent valve Bleeds air from the pipe. Install air vents in places where there is a risk of air accumulating.
a
Flexible joint
Prevents the
propagation of vibration. These components need to be installed in consideration of the pipe load as
pipes are easily damaged by bending.
b
Water pressure
gauge Used to check the
operation status.
Attach this component to each piping section to check the water pressure.
c Expansion tank
Absorbs excessive
water pressure due to
expansion caused by a
rise in temperature.
Select an expansion tank that is suitable for the system.
d Drain valve
Improves workability of
replacing equipment. Install these components in the two places of the chilled water passage section
and the high temperature water passage section to enable replacement.
e Safety valve
Prevents rupturing of
the water circuit. Be sure to provide an escape pipe to prevent discharged water from spraying on
passersby.
No. Component Application Remarks and notes on selecting and installing components
WT08219X05.book 16 ページ ２０１８年１０月１日 月曜日 午後７時４７分