Mitsubishi Electric QAHV Série Manuel D'installation & D'instructions page 18

No. Component
Prevents pipe damage
Anti-freeze
6 due to freezing of the
heater
water circuit.
Improves the workability
7 Union joint
of replacing equipment.
Improves the workability
of cleaning the heat
8 Valve
exchanger and
replacing parts.
Prevents foreign
9 Strainer materials from entering
into 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.
Prevents the
a Flexible joint
propagation of vibration.
Water pressure Used to check the
b
gauge operation status.
Absorbs excessive
water pressure due to
c Expansion tank
expansion caused by a
rise in temperature.
Improves workability of
d Drain valve
replacing equipment.
Prevents rupturing of
e Safety valve
the water circuit.
2 Selection criteria for heat exchanger
Step 1 Determination of prerequisites for selection
I Heat exchanger capacity 40000 W (136000 BTU/h)
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 (9°F) or below.
II-1 Outlet hot water temperature (when secondary side outlet hot water temperature is set to 65°C (149°F)
(setting at the time of shipment))
• Secondary side circuit outlet hot water temperature: 65°C (149°F)
• Unit outlet hot water temperature: 70°C (158°F)
II-2 Inlet water temperature
• Secondary side inlet water temperature: 10°C (50°F)
• Unit inlet water temperature: 15°C (59°F)
III Used flow rate
(40000 W/(70-15)°C/4200 J/kg•K) × 60 s = 10.4 kg/min ≈ 10.4 ℓ/min ≈ 2.74 GPM
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 (7.9 GPM).
• Select a heat exchanger with a capacity of at least 40000 W (136000 BTU/h).
• Ensure that the shearing stress at the flow rate to be used will be 16 Pa (0.01 ftAq) 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).
Application
This component needs to be installed in a location where an ambient
temperature may fall to 0
Install these components in the two places of the chilled water passage section
and the high temperature water passage section to enable replacement.
Install these components in the two places of the chilled water passage section
and the high temperature water passage section to enable replacement.
Install a strainer with 60 mesh or better near the heat exchanger.
These components need to be installed in consideration of the pipe load as
pipes are easily damaged by bending.
Attach this component to each piping section to check the water pressure.
Select an expansion tank that is suitable for the system.
Install these components in the two places of the chilled water passage section
and the high temperature water passage section to enable replacement.
Be sure to provide an escape pipe to prevent discharged water from spraying on
passersby.
Remarks and notes on selecting and installing components
°C °
(32 F) or less.
GB-18