Features and
Benefits
The CenTraVac® Chiller
Operating Cycle
Design Simplicity
Impellers are keyed directly to the motor shaft for high reliability and performance and low life-cycle costs.
Reliable Motor Cooling
The motor is engulfed in liquid refrigerant to provide efficient, complete
cooling at all load conditions. This system is reliable
and easy to maintain.
Fixed Orifice Flow Control
For proper refrigerant flow control at all load conditions, the CenTraVac design incorporates the Trane patented fixed orifice
system. It eliminates float valves, thermal expansion
valves and other moving parts. Since there are no
moving parts, reliability is increased.
Quiet Operation
With only one moving component — the rotor and impeller assembly — the Trane low speed, direct drive design operates
exceptionally quietly. The smoothly rotating CenTraVac
compressor is inherently quieter than other compressor types. Typical CenTraVac
chiller sound measurements are among the quietest
in the industry. Trane can guarantee sound levels with factory testing and measurements
in accordance with ARI standard 575.
The Reliability Standard
Just as a multi-stage turbine is more efficient than a single stage turbine, the CenTraVac multi-stage compressors are more
efficient and reliable than single- stage designs.
Direct Drive Design — No Gear Losses
The direct drive compressor operates without speed increasing gears, thus eliminating gear energy losses. Compressors
using gears suffer mesh losses and extra bearing losses
in the range of three to five percent at full load. Since these losses are fairly constant over the load range, increasingly
larger percentage losses result as load decreases.
Multiple Stages of Compression
The compressor operates more efficiently over a wide range of capacities,
virtually eliminating the need for energy wasting hot
gas bypass as typically found on single stage chillers.
The radial component of velocity determines the ability of the chiller to resist
interruption of smooth refrigerant flow when operating
at light loads and with high condensing temperatures.
This interruption in flow and unstable operation, called "surge" is avoided with the two-stage design.
Inlet Guide Vanes
Part load performance is further improved through use of moveable designed
variable inlet guide vanes. Inlet guide vanes improve
performance by throttling refrigerant gas flow to
exactly meet part load requirements and by prerotating refrigerant gas for optimum
entry into the impeller. Prerotation of refrigerant gas
minimizes turbulence and increases efficiency.
Two-Stage Economizer
The CVHE/CVHG CenTraVac chiller has a two-stage economizer — providing up to seven percent greater efficiency than
designs with no economizer. Since the CVHE/CVHG uses
three impellers, it is possible to flash refrigerant gas at two intermediate pressures between the evaporator and condenser
pressures, significantly increasing chiller efficiency.
This improvement in efficiency is not possible in single-stage chillers since all compression is done by one impeller.
Single Stage Economizer
The CVHF CenTraVac chiller has a single-stage economizer — providing up to
4 1 /2 percent greater efficiency than designs with no
economizer. Since the CVHF CenTraVac uses two impellers, it is possible to flash refrigerant gas at an intermediate pressure
between the evaporator and condenser pressures,
significantly increasing chiller efficiency. This
improvement in efficiency is not possible in single-stage chillers since all compression
is done by one impeller. |
