Features and
Benefits
CenTraVac® Three-Stage P-H Diagram
The pressure-enthalphy (P-H) diagram describes refrigerant flow through the major CVHE/CVHG chiller components. This
diagram confirms the superior operating cycle
efficiency of the three- stage compressor and two-stage
economizer.
Evaporator — A liquid-gas refrigerant mixture enters the evaporator at state point 1. Liquid refrigerant is vaporized to
state point 2 as it absorbs heat from the system
cooling load. The vaporized refrigerant then flows into
the compressor first stage.
Compressor First Stage — Refrigerant gas is drawn from the evaporator into the first stage compressor. The first stage
impeller accelerates the gas increasing its temperature
and pressure to state point 3.
Compressor Second Stage — Refrigerant gas leaving the first stage compressor
is mixed with cooler refrigerant gas from the low
pressure side of the two-stage economizer. This mixing lowers the enthalpy of the mixture
entering the second stage. The second stage impeller
accelerates the gas, further increasing its temperature
and pressure to state point 4.
Compressor Third Stage — Refrigerant gas leaving the compressor second stage
is mixed with cooler refrigerant gas from the high
pressure side of the two-stage economizer. This mixing
lowers the enthalpy of the gas mixture entering the third stage compressor. The third stage impeller accelerates the gas,
further increasing its temperature and pressure to
state point 5, then discharges it to the condenser.
Condenser — Refrigerant gas enters the condenser where the system cooling
load and heat of compression are rejected to the
condenser water circuit. This heat rejection cools and
condenses the refrigerant gas to a liquid at state point 6.
Patented Two-Stage Economizer and Refrigerant Orifice System-Liquid refrigerant
leaving the condenser at state point 6 flows through
the first orifice and enters the high pressure side of the economizer. The purpose of this orifice and economizer is to preflash a
small amount of refrigerant at an intermediate pressure
called P1. P1 is between the evaporator and condenser pressures. Preflashing some liquid refrigerant cools the remaining liquid
to state point 7.
Refrigerant leaving the first stage economizer flows through the second orifice and enters the second stage economizer.
Some refrigerant is preflashed at intermediate pressure
P2. Preflashing the liquid refrigerant cools the remaining liquid to state point 8.
Another benefit of preflashing refrigerant is to increase the total evaporator
refrigeration effect from RE’ to RE. The two-stage
economizer provides a seven percent energy savings compared to chillers with no economizer.
To complete the operating cycle, liquid refrigerant leaving the economizer at state point 8 flows through a third orifice
system. Here, refrigerant pressure and temperature are
reduced to evaporator conditions at state point 1.
CenTraVac Two-Stage P-H Diagram
The pressure-enthalphy (P-H) diagram describes refrigerant flow through the major CVHF chiller components. This diagram
confirms the superior operating cycle efficiency of the
two- stage compressor and economizer.
Evaporator — A liquid-gas refrigerant mixture enters the evaporator at state point 1. Liquid refrigerant is vaporized to
state point 2 as it absorbs heat from the system
cooling load. The vaporized refrigerant then flows into
the compressor first stage.
Compressor First Stage — Refrigerant gas is drawn from the evaporator into the first stage compressor. The first stage
impeller accelerates the gas increasing its temperature
and pressure to state point 3.
Compressor Second Stage — Refrigerant gas leaving the first stage compressor
is mixed with cooler refrigerant gas from the
economizer. This mixing lowers the enthalpy of the
mixture entering the second stage. The second stage impeller accelerates the gas, further increasing its temperature and
pressure to state point 4.
Condenser — Refrigerant gas enters the condenser where the system cooling
load and heat of compression are rejected to the
condenser water circuit. This heat rejection cools and
condenses the refrigerant gas to a liquid at state point 6.
Economizer and Refrigerant Orifice System-Liquid refrigerant leaving the condenser at state point 6 flows through the
first orifice and enters the economizer. The purpose of
this orifice and economizer is to preflash a small
amount of refrigerant at an intermediate
pressure called P1. P1 is between the evaporator and
condenser pressures. Preflashing some liquid refrigerant cools the remaining liquid to state point 8.
Another benefit of flashing refrigerant is to increase the total evaporator refrigeration effect from RE’ to RE. The economizer
provides a 4 1 /2 percent energy savings compared to
chillers with no economizer.
To complete the operating cycle, liquid refrigerant leaving the economizer at state point 8 flows through a second orifice
system. Here, refrigerant pressure and temperature are
reduced to evaporator conditions at state point 1. |
