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TRICOIL®
METHOD: PUMP ON/OFF COMPARISON
The
TRICOIL® method adjusts the air handling unit's Sensible
Heat Ratio (often called Sensible Heat Factor) to better match
the cooling load of the room as indicted by the Room Sensible
Heat Ratio. For example, consider the following performance
of a unit with the TRICOIL® system pump OFF and with the
TRICOIL® system pump ON.
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PUMP
OFF |
PUMP
ON |
| AIR
VOLUME |
10000
CFM |
10000
CFM |
ENTERING
AIR TEMPERATURE
HUMIDITY RATIO |
80
oF DB / 67 oF WB
0.0113 lb water / lb dry air
|
80
oF DB / 67 oF WB
0.0113 lb water / lb dry air
|
SUPPLY
AIR
TEMPERATURE
DEWPOINT
HUMIDITY RATIO |
55 oF DB / 53.8 oF WB
53 oF Dewpoint Temp
0.0085 lb water / lb dry air
|
59.5 oF DB / 53.8 oF WB
49.5 oF Dewpoint Temp
0.0075 lb water / lb dry air
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UNIT
COOLING PERFORMANCE
SENSIBLE
LATENT
TOTAL
UNIT SENSIBLE HEAT RATIO |
293.0 MBH
134.2 MBH
427.2 MBH
.69 SHR
|
244.1 MBH
183.1 MBH
427.2 MBH
.57 SHR
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ROOM
COOLING EFFECT
SENSIBLE
LATENT
ROOM SENSIBLE HEAT RATIO |
217.0 MBH
38.7 MBH
.85 SHR
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168.2 MBH (22% decrease)
87.1 MBH (123% increase)
.66 SHR
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The effect of the
pump on/off cycle is a change in the air conditioning unit's
sensible heat ratio. The low sensible heat ratio when the
pump is on (0.57) indicates that the unit provides more dehumidification
in proportion to the total cooling. Conversely, when the pump
is off the systems' sensible heat ratio is higher (0.69) indicating
the unit provides less dehumidification in proportion to the
total cooling.
Typical air conditioning
applications are characterized by a cooling load having a
moderate to high sensible heat ratio at full load operation
and a low sensible heat ratio at partial cooling load periods.
For this example the pump is turned on for the partial cooling
load providing a room sensible heat factor of 0.66. When the
indoor temperature rises, indicating full indoor cooling is
required, the pump is turned off providing a room sensible
heat factor of 0.85. Turning the pump off shifts a portion
of the unit's latent room cooling capacity to sensible cooling
capacity and conversely, turning the pump on shifts a portion
of the sensible cooling capacity to latent cooling capacity.
This psychrometric
chart illustrates the pump on and pump off operation of the
TRICOIL® Method.
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