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Selection Procedure |
General
Absorption refrigeration machines are usually selected to
provide required refrigeration capacity with the smallest practical machine of sufficient
size. Machine size is based on chilled water flow rates and temperatures specified for the
airside of the system.
Total air conditioning system first cost can be minimized
by a careful analysis of system operating parameters. The effect of flow rates and
temperatures, on both the building airside and the refrigeration machine selections,
should be investigated to establish the system that represents the best investment for the
owner.
In this selection, an example chiller performance
estimation will be made for particular operating conditions. A final selection must be
done by the local Trane sales engineer using the Trane Horizon™ Two-Stage Absorption Selection Program.
The information on the following pages provides performance
data at ARI standard conditions for: capacity in tons, efficiency, flow rates, and water
pressure drops. All capacities are based on fouling factors of .00025 hr-ft-F/Btu for the
evaporator and absorber/condenser waterside tubing. All final selections should be made
using the Trane Horizon™ Two-Stage Absorption Selection Program.
Fouling Factors
Unit performance at non-standard fouling factors may vary
from standard performance. Fouling factors estimate the heat transfer penalty that occurs
as the tubing gets dirty through normal chiller operation. ARI tube fouling standards are:
Fouling Factors @ ARI 560-1992
• Clean
0.00000
• Standard 0.00025
• Excessive 0.00075
All selections should have a minimum fouling factor of
0.00025 to better estimate the chiller performance in an equipment room and to comply with
ARI 560-1992. Any selection that uses a fouling factor above 0.00025 is a more
conservative estimate that should only be used if there is an abnormal amount of fouling
contaminants in the water system. The effect of non-standard fouling factors should be
determined by the Trane Absorption Selection Program.
Unit Performance with Fluid Media other than Water
Absorption chillers can be selected with a wide variety of
media other than water (evaporator and absorber/condenser, or both. For media other than
water, contact the local Trane sales office for chiller selections and information.
Prior to accessing the computer selection program, the
following data inputs should be tabulated:
• Hot water or Steam Energy Source
• Supply temperature or pressure of the hot water or
steam
• Two of the following three values must be given:
— Evaporator Delta T
— Evaporator Gpm
— Cooling Capacity
• Leaving Evaporator Water Temperature
• Entering Absorber Water Temperature
• Fouling Factors, evaporator and cooling water
Any limitations or restrictions should also be given (i.e.,
pressure drop, gpm, etc.)
There are many options that may also be selected.
• Type and thickness of tube material
• Type of solution flowing through the evaporator and
condenser loop.
Consult your local Trane sales engineer for a selection.
General Data Tables
Located in the general data tables are the evaporator and
absorber/condenser flows, pressure drops and the number of passes. Also included in these
tables are the weights, approximate dimensions and connection sizes.
Part Load Performance
The Horizon™ two-stage absorption chiller exhibits excellent part load
performance characteristics with IPLV values of up to 1.35. Air conditioning system loads
are usually significantly less than full load design conditions. Therefore, the absorption
chiller operates at full load a small percentage of the time. Part load absorption chiller
operation is normally associated with reduced tower water temperatures. At part load
operation, the heat rejected to the cooling tower is less than at full load operation.
Also, part load operation is typically associated with reduced outside wet bulb
temperatures, resulting in improved cooling tower performance. The net result of less heat
rejection and lower wet bulb temperature is cooler tower water entering the chiller and
improved unit performance. To determine specific unit part load performance, use of the
Horizon™
Two- Stage Absorption Selection Program is recommended.
Electrical Data
Total kW are shown for the Horizon™ two-stage absorption chiller
components. These include solution and refrigerant pump, motors, purge pump motor and
control panel. The unit is to be supplied with 200, 230, 460 or 575 volt, 3 phase, 60
hertz power or 190, 220, 380, 415 volt, 3 phase, for 50 hertz applications. Field wiring
should be properly sized in accordance with the National Electric Code or other applicable
local codes. All units are ETL listed.
Dimensional Drawings
The dimensional drawings illustrate overall measurements of
the unit. The recommended service clearances indicate clearances required to easily
service the Horizon™ two-stage absorption chiller. All catalog dimensional drawings are subject to
change. Current submittal drawings should be referred to for detailed dimensional
information. Contact the local Trane sales office for submittal information.
CAD Templates
CAD templates are available. These are 2D multi-view
drawing files that you can use to assist in plant design. |
