Trane ctv-prc007-en manual Refrigeration, Cycle, Features and, Benefits, Design Simplicity

Features and	Refrigeration
Benefits	Cycle

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 41/2 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.

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