Two-stage refrigeration system

Details Two-stage refrigeration system Two-stage refrigeration system

2001-04-11

2003-02-11

Doerrler, William C. (Department: 3744)

Refrigeration

Intermediate fluid container transferring heat to heat...

Flow line connected transfer fluid supply and heat exchanger

Reexamination Certificate

active

06516626

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a refrigeration system. More particularly the invention relates to an extremely low temperature two-stage refrigeration system capable of utilizing refrigerant vapor and a slurry of solid sublimatable refrigerant particles in a liquid.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,715,702 to Strong et al. (hereinafter Strong) describes a refrigeration system using a slurry of solid refrigerant particles of a first substance and a liquid of a second substance. More particularly, Strong, discloses a system with a mixing tank for supplying a slurry of solid, sublimatable particles in a liquid to a sublimator. The sublimator returns sublimated particles and remainder slurry to a separator. The separator returns slurry to the mixing tank and sends the sublimated particles to a compressor and condenser. The condenser returns liquid refrigerant to the mixing tank for a new cooling cycle.
Referring to
FIGS. 1 and 2
, illustrating the prior art refrigeration system of Strong, the figure numbering convention will include a (′) to indicate that it is a feature of the prior art. The refrigeration system of Strong discloses a mixing tank
37
′, separator
36
′, an evaporator
3
′, compressor
10
′, a condenser
15
′, and a receiver
16
′, for use with a slurry of solid sublimatable particles in a liquid. The mixing tank
37
′ has a first outlet
5
′, second outlet
34
′, a first inlet
31
′, and a second inlet
17
′. The evaporator
3
′ has an inlet
6
′ and an outlet
8
′. A first conduit
4
′ connects the first mixing tank outlet
5
′ to the inlet of the evaporator
6
′. The separator
36
′ has a first inlet
9
′, first outlet
31
′, and second outlet
12
′. A second conduit
7
′ connects the evaporator outlet
8
′ to the first separator inlet
9
′. The separator
36
′ discharges directly to the mixing tank
37
′ by the shared opening separator first outlet
31
′ and first inlet of the mixing tank
31
′. A pipe
34
′ and pressure regulator
35
′ transfers vapor between the mixing tank
37
′ and the separator
36
′. The compressor
10
′ has an inlet
11
′ and an outlet
14
′ and is connected to a condenser
15
′ followed by the receiver
16
′. A third conduit
13
′ connects the second outlet of the separator
12
′ to the compressor inlet
11
′. A fourth conduit
19
′ connects the receiver to the second inlet of the mixing tank
17
′.
One of the problems with Strong, that the present invention seeks to solve, includes the potential plugging of the system due to the particles of refrigerant clogging or freezing shut conduits, valves, or inlets and outlets. Another problem is the energy requirements for this system are very high. The present invention has several improvements for addressing the potential system plugging, and also for significantly reduces the energy requirements of the system.
SUMMARY OF THE INVENTION
The present invention provides a refrigeration system for use with a refrigerant vapor and a slurry of solid sublimatable refrigerant particles in a liquid, where the refrigerant used in conjunction with the invention is preferably carbon dioxide (CO
2
) and the liquid is preferably d'limonene.
In a first embodiment of the present invention the intermediate slurry tank receives and stores CO
2
vapor as well as a slurry of CO
2
particles in the d'limonene liquid. The intermediate slurry tank is preferably maintained below the triple point of CO
2
. The intermediate slurry tank sends the slurry to the evaporator, the slurry being fed through a pump or by utilizing pressure and/or gravity from the intermediate slurry tank. A main slurry tank receives and stores the discharge from evaporator. The main slurry tank sends the remaining slurry back to the intermediate slurry tank, and sends the vapor CO
2
to the compression system. The compression system also receives vapor CO
2
from the intermediate slurry vessel, compresses the vapor from the main slurry tank and intermediate slurry tank and send it to the condenser. The condenser sends the condensate to the condenser receiving tank. The condenser receiving tank stores the liquid CO
2
condensate and is maintained at a higher pressure than the intermediate slurry tank. The condenser receiving tank sends the liquid CO
2
back to the intermediate slurry tank. The liquid CO
2
is expanded either on its way to the intermediate slurry tank or in the tank itself. The expansion causes solid particles of CO
2
to form from the liquid CO
2
. These solid CO
2
particles are mixed into the slurry in intermediate slurry tank. The expansion of the liquid CO
2
also results in vapor CO
2
being produced.
In a further aspect of the present invention the conduit from the condenser receiving tank to the intermediate slurry tank may be modified to reduce refrigerant particle size as well as reducing the risk of plugging of the conduit or freezing of a valve in the conduit. The modifications may include: sloping the conduit, placing the point of refrigerant expansion close to the intermediate slurry tank, feeding gas into the system to add turbulence or heat, a special valve seat which forces the pressure drop to occur down stream of an expansion valve, or a direct injection system
200
to place the liquid refrigerant discharge directly into the intermediate slurry tank.
In a another aspect of the present invention a special slurry recirculation line is detailed. The recirculation line is designed to sweep the solid refrigerant particles off of a tank bottom to keep them suspended in the slurry.


REFERENCES:
patent: 3558731 (1971-01-01), Young
patent: 3757367 (1973-09-01), Campbell
patent: 3767724 (1973-10-01), Gouw
patent: 3788091 (1974-01-01), Miller
patent: 3819278 (1974-06-01), Muller
patent: 3869870 (1975-03-01), Kuehner
patent: 3870417 (1975-03-01), Bashark
patent: 3872682 (1975-03-01), Shook
patent: 3906742 (1975-09-01), Newton
patent: 4224801 (1980-09-01), Tyree, Jr.
patent: 4444023 (1984-04-01), Barbini et al.
patent: 4640099 (1987-02-01), Gibot
patent: 4690210 (1987-09-01), Niggemann et al.
patent: 5092133 (1992-03-01), Franklin
patent: 5104232 (1992-04-01), Lennox, III
patent: 5121611 (1992-06-01), Broderdorf et al.
patent: 5343715 (1994-09-01), Lang
patent: 5475487 (1995-12-01), Mariella, Jr. et al.
patent: 5715702 (1998-02-01), Strong et al.
patent: 5960411 (1999-09-01), Hartman
patent: 30 04 114 (1980-11-01), None

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