Refrigeration – Refrigeration producer – Compressor-condenser-evaporator circuit
Reexamination Certificate
1999-07-09
2001-02-13
Tapolcai, William E. (Department: 3744)
Refrigeration
Refrigeration producer
Compressor-condenser-evaporator circuit
C062S116000, C417S391000, C417S406000
Reexamination Certificate
active
06185956
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of refrigeration, and more particularly to a single positive displacement machine (expressor) which allows for both expansion and compression of a two-phase flow mixture as is employed in chiller, air conditioning, heat pump, or refrigeration systems.
BACKGROUND OF THE INVENTION
First and referring to
FIG. 1
, a known refrigeration system
10
for a heat pump, refrigerator, chiller or air conditioner is shown schematically for background purposes. The known refrigeration system
10
includes a compressor
11
, driven by an electric motor
12
or other known means, that compresses vapor. The compressor
11
discharges compressed vapor, at high pressure and high temperature, into a condenser
13
where heat is extracted from the working fluid, causing condensation of the high pressure vapor into high pressure liquid. The high pressure liquid then flows from the condenser
13
into a throttling valve
14
which reduces the pressure of the liquid, causing partial flashing. This lower pressure fluid is then routed into an evaporator
15
in which the fluid absorbs heat, thereby converting the working fluid from the liquid to the vapor state. The vapor from the evaporator reenters the compressor
11
on the intake side.
FIG. 2
shows a vapor compression cycle PH (pressure v. enthalpy) diagram for the conventional refrigeration system shown in FIG.
1
. with pressure (P) represented along the ordinate and enthalphy (H) appearing along the abscissa. The vapor/compression cycle shows an adiabatic compression of vapor along line A, superheated cooling of the vapor occurring along line B
1
, followed by biphase isothermal condensation along line B
2
, and liquid subcooling along line B
3
. When the working fluid passes through a throttling valve, the working fluid undergoes isoenthalpic expansion, as indicated by vertical line C. Isobaric evaporation of the liquid in the evaporator is shown by horizontal line D.
As should be apparent from the preceding diagram, and with isoenthalpic expansion, the quality of the expanded refrigerant is increased because some of the compression energy of the condensed working fluid is consumed in transforming the liquid into vapor at the low pressure side of the system. For efficient operation, the quality of the working fluid; that is, the vapor fraction of the expanded refrigerant, should be as small as possible.
Referring to
FIG. 3
, an improved system has been developed, as described in commonly owned U.S. Pat. No. 5,467,613, in which a turbine expander
17
is substituted for the throttling valve expander. The turbine expander
17
receives the high pressure liquid from the condenser and drives a turbine rotor with the kinetic energy of the expanding working fluid. In other words, a portion of the energy imparted to the working fluid by the compressor is recovered in the expander as mechanical energy. Therefore, the turbine expander relieves some of the compressor load on the drive motor, so that the refrigeration cycle operates more efficiently than is possible with a throttling type of expander.
Typically, the turbine expander is either mechanically or electrically connected with the main compressor. A typical mechanical arrangement is illustrated in
FIG. 3. A
disadvantage of the direct coupling arrangement is that the turbine/expander must be placed in close proximity with the main compressor. This results in the need for additional piping in the system and consequently increases the implementation cost of the two-phase flow expander.
Another possible solution to the above problem, shown in
FIG. 4
, is to provide a stand alone turbine/expander which locally transfers its recovered mechanical power into electrical power through the use of a generator
18
. This transferred electrical power supplies a portion of the electrical power that is required to drive the motor
12
of the compressor
11
. The disadvantage with this system is the need for the additional electric generator, as well as the additional losses associated with the generator.
In addition, each of the systems shown in
FIGS. 3 and 4
require turbine/expanders which are run at fixed speeds. In actual system applications, however, fixed speed operation requires additional hardware to prevent hot gas by-pass from the condenser to the evaporator during part load conditions. As a consequence, the efficiency of existing throttle loss recovery systems deteriorates under part-load conditions. For example, for a system running at or below 50% capacity with reduced temperature lift, it has been found that power recovery of the turbine/expander is typically reduced to almost negligible amounts.
SUMMARY OF THE INVENTION
A primary object of the present invention is to improve the state of the art of throttle loss recovery systems.
Another primary object of the present invention is to improve the efficiency of a refrigeration system, but without requiring additional piping or the need of a generator or other apparatus.
Therefore and according to a preferred aspect of the present invention, there is provided a positive displacement machine comprising:
a first rotor having a plurality of helical lobes disposed about a rotor periphery;
at least one second rotor in meshing contact with said first rotor and having a plurality of helical grooves for receiving the lobes of said first rotor during rotation of said rotors in opposite directions; and
a housing defining a chamber enclosing the rotors and having an inlet port at one end and an outlet port at an opposing end, wherein the housing includes an intermediate port formed in a side wall of the chamber between the inlet port and the outlet port and in that the length of the rotors are sufficient to define during rotation of said first rotor in one direction an effectively closed expanding working chamber between the inlet and intermediate ports and an effectively closed contracting working chamber between the intermediate and outlet ports.
Preferably, a twin screw positive displacement machine (expressor) is provided having a pair of rotors which can be driven without motors, by fluid refrigerant passing through the rotors, though the machine can include a motor drive, if needed.
According to another preferred aspect of the present invention, there is provided a single fluid compression/expansion refrigeration apparatus which comprises;
a fill of fluid refrigerant that exists in the apparatus as liquid and a vapor;
a main compressor for compressing the vapor thereby adding compression energy to the refrigerant fluid, said compressor having an inlet to receive the fluid at a predetermined reduced pressure and an outlet from which the fluid is delivered at an elevated pressure;
a drive motor coupled to said main compressor for driving said main compressor;
condenser means for extracting heat from the refrigerant and converting the compressed vapor emerging from said main compressor into a liquid;
evaporator means for absorbing external heat into the refrigerant thereby converting liquid refrigerant into vapor; and
a plural rotary displacement machine disposed between said condenser means and an input to said evaporator means, said plural displacement machine comprising:
a first rotor having a plurality of helical lobes disposed about a rotor periphery;
at least one second rotor in meshing contact with said first rotor and having a plurality of helical grooves for receiving the lobes of said first rotor during rotation of said rotors in opposite directions; and
a housing defining a chamber enclosing the rotors and having an inlet port at one end and an outlet port at an opposing end, wherein the housing includes an intermediate port formed in a side wall of the chamber between the inlet port and the outlet port and in that the length of the rotors is sufficient to define during rotation of said first rotor in one direction an effectively closed expanding working chamber between the inlet and intermediate ports and an effectively closed contracting working chamber between the intermediate and
Carrier Corporation
Tapolcai William E.
Wall Marjama & Bilinski
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