Refrigeration – Processes – Compressing – condensing and evaporating
Reexamination Certificate
1999-04-29
2001-01-09
Tanner, Harry B. (Department: 3744)
Refrigeration
Processes
Compressing, condensing and evaporating
C062S278000, C062S335000, C062S509000, C062S196400, C062SDIG002
Reexamination Certificate
active
06170272
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to refrigeration systems. More specifically, the present invention relates to direct expansion refrigeration systems having secondary subcooling.
BACKGROUND OF THE INVENTION
A simple refrigeration system includes a compressor (e.g., a single compressor or multiple compressors arranged in parallel), a condenser, an expansion valve, and an evaporator which are interconnected by a plurality of pipes. The compressor moves a refrigerant (e.g., a gaseous refrigerant such as HFC404, HCFC22, or the like) through the system. Typically, the refrigerant exits the compressor as a high-pressure vapor. From the compressor, the high-pressure vapor flows to the condenser. At the condenser, the high-pressure vapor condenses back to a liquid thereby giving off heat that is removed from the system. From the condenser, the condensed refrigerant is conveyed to the expansion valve which decompresses the refrigerant. The decompressed refrigerant is conveyed to the evaporator where the refrigerant transitions to a vapor. The evaporator is typically located within an area desired to be refrigerated (e.g., a refrigeration case). As the refrigerant is evaporated within the evaporator, the temperature within the evaporator drops thereby causing heat from the area desired to be refrigerated to flow into the evaporator. In this manner, the evaporator performs a cooling function. From the evaporator, the refrigerant is circulated back to the compressor and the cycle is repeated.
Refrigeration systems operate more efficiently if the refrigerant exiting the condenser is cooled prior to being evaporated. Commonly, the refrigerant of a primary refrigeration system is cooled by using a secondary refrigeration system. This type of cooling is frequently referred to as “mechanical subcooling.” If the secondary refrigeration system operates more efficiently than the primary system, there is an efficiency gain. This type of design is used often in commercial refrigeration systems for providing efficiency gain and for ensuring a solid column of refrigerant at the expansion device.
FIG. 1
illustrates a prior art refrigeration system
20
having mechanical subcooling. The refrigeration system
20
includes a primary system
22
and a secondary system
24
. The primary system
22
interfaces with the secondary system
24
at a heat exchanger
26
. At the heat exchanger
26
, the secondary system
24
is used to subcool the refrigerant of the primary system
22
.
The secondary system
24
includes a secondary compressor
28
, a secondary condenser
30
, a secondary expansion valve
32
and a secondary evaporator
34
. The secondary evaporator
34
is positioned within the heat exchanger
26
and functions to subcool the refrigerant of the primary system
22
.
The primary system
22
includes a primary compressor
36
, a primary condenser
38
, a receiver
40
, a primary expansion valve
42
, and a primary evaporator
44
.
FIG. 1
shows the refrigeration system
20
under normal operating conditions. At normal operating conditions, pressurized refrigerant vapor from the primary compressor
36
is condensed at the primary condenser
38
. Condensed refrigerant from the primary condenser
38
is held within the receiver
40
. From the receiver
40
, the refrigerant flows through the heat exchanger
26
where the refrigerant is cooled. The cooled refrigerant is then conveyed to the primary expansion valve
42
where the refrigerant is decompressed. A liquid pump
43
adds pressure to the cooled refrigerant to prevent any flashing of the refrigerant to a vapor before reaching the primary expansion valve
42
. Decompressed refrigerant from the primary expansion valve
42
is conveyed through the primary evaporator
44
where the refrigerant transitions to a vapor. The primary evaporator
44
is located within a region
48
desired to be cooled, and the evaporated refrigerant draws heat from the region
48
. After exiting the primary evaporator
44
, the refrigerant is cycled back to the primary compressor
36
and the sequence is repeated.
A problem with refrigeration systems such as the refrigeration system of
FIG. 1
is the accumulation of ice within the evaporator (e.g., on the evaporator coils). To overcome this problem, most refrigeration systems periodically use a defrost cycle to melt ice accumulation within the evaporator. For example, one type of refrigeration defrost technique involves interrupting refrigerant flow through the evaporator. Another type of refrigeration defrost technique involves interrupting refrigerant flow through the evaporator in combination with resistance heating.
FIG. 2
shows a defrost cycle that uses hot gas from the compressor
36
to defrost the evaporator
44
. In the defrost cycle, valve
50
is used to close fluid communication between the primary evaporator
44
and the intake of the primary compressor
36
. Valve
52
opens fluid communication between the outlet side of the primary compressor
36
and the primary evaporator
44
. In this manner, relatively hot defrost gas from the primary compressor
36
is pumped through suction line
54
and flows in a reverse direction through the primary evaporator
44
. As the hot defrost gas flows through the primary evaporator
44
, ice within the primary evaporator
44
is melted thereby cooling and condensing the defrost gas. The condensed refrigerant exits the primary evaporator
44
and bypasses the primary expansion valve
42
through bypass line
56
. Bypass line
56
includes a one-way check valve
58
that allows refrigerant from the primary evaporator
44
to bypass the primary expansion valve
42
, but prevents flow in an opposite direction. After bypassing the primary expansion valve
42
, the refrigerant flows through solenoid valve
60
to return line
62
. The return line
62
conveys the refrigerant back to the receiver
40
. During the defrost cycle, the valve
60
closes fluid communication between the liquid pump
43
and the expansion valve
42
.
SUMMARY OF THE INVENTION
One aspect of the present invention relates a refrigeration system including a compressor for compressing a refrigerant, a condenser in fluid communication with the compressor for condensing compressed refrigerant received from the compressor, and a reservoir in fluid communication with the condenser for holding condensed refrigerant received from the condenser. The system also includes a heat exchanger in fluid communication with the reservoir, an expansion device in fluid communication with the heat exchanger for decompressing cooled refrigerant received from the heat exchanger, and at least one evaporator in fluid communication with the expansion device for evaporating decompressed refrigerant received from the expansion device. The system further includes a suction line for providing fluid communication between the compressor and the evaporator, and a recirculation line for recirculating cooled refrigerant from the heat exchanger back to the reservoir to pre-cool the condensed refrigerant held within the reservoir. The pre-cooled refrigerant is conveyed from the reservoir to the heat exchanger to be further cooled. By pre-cooling the refrigerant mass kept in the reservoir, the mass of refrigerant in the reservoir creates a thermal fly wheel that dampens temperature variations of refrigerant liquid leaving the heat exchanger.
Another aspect of the present invention relates to a method for damping temperature fluctuations in a refrigeration system. The refrigeration system includes a compressor, a condenser, a reservoir, a heat exchanger, an expansion device and an evaporator. The method includes compressing a refrigerant at the compressor, conveying the refrigerant from the compressor to the condenser, and condensing the refrigerant at the condenser. The method also includes conveying the refrigerant from the condenser to the reservoir, conveying the refrigerant from the reservoir to the heat exchanger, and cooling the refrigerant at the heat exchanger to provide a cooled refrigerant. The meth
Merchant & Gould P.C.
Systematic Refrigeration, Inc.
Tanner Harry B.
LandOfFree
Refrigeration system with inertial subcooling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Refrigeration system with inertial subcooling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Refrigeration system with inertial subcooling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2487251