Refrigeration – Vortex tube – e.g. – ranque
Reexamination Certificate
2000-06-30
2001-09-25
Doerrler, William (Department: 3744)
Refrigeration
Vortex tube, e.g., ranque
Reexamination Certificate
active
06293108
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to refrigeration apparatus and a refrigeration process and more specifically relates to a novel refrigeration apparatus and process employing a mixture of different refrigerants.
BACKGROUND OF THE INVENTION
Refrigeration systems are well known which employ a single refrigerant, for example, CFC refrigerants such as R-12 and HCFC refrigerants such as R-22. These refrigerants, however, have serious environmental drawbacks and are being replaced by refrigerants of the HFC type such as R-32, R-125 and R-134a in different combinations.
The individual HFC refrigerants have diverse characteristics, as shown in the following table:
LATENT
HEAT
BOILING
HEAT
CONDENSER
EVAPORATOR
TRANSFER
FLAM-
DENSITY
POINT
(h
fg
)
PRESSURE
PRESSURE
CHARACT.
ABILITY
R-32
Light
Low
Large
High
High
Good
Yes
R-125
Heavy
Low
Small
High
High
Medium
No
R-134a
Medium
High
Medium
Low
Low
Poor
No
In many refrigeration systems, the following characteristics are preferred:
Density—heavy
Boiling Point—low at evaporator and high at condenser
Latent Heat—large
Condenser Pressure—low
Evaporator Pressure—high
Heat Transfer—good
Flamability—no
In the above, h
fg
is the enthalpy difference between 100% vapor and 100% liquid.
R-32 is a preferred refrigerant because of its high latent heat and high evaporator pressure which reduces the compressor work and thus the compressor size. That is, the compressor work W
COMPRESSOR
is defined as:
W
COMPRESSOR
=∫vdP
where
v=specific volume=1/density; and
P=pressure.
In a typical system, as evaporator pressure increases, the pressure change in the compressor is reduced, thus reducing the compressor work.
While R-32 has the best thermal characteristics, it is more flammable than the others, and carries with it the danger of fire. Consequently, R-32 is commonly mixed with non-flammable fluids such as R-125 and R-134a to reduce the fire danger.
Currently available mixture refrigerants include R-407c and R-410a. The former (R-407c) is one of the R-407 series refrigerants, which include R-407a, R-407b, R-407c, etc. The R-407 series is made of three refrigerants R-32, R-125 and R-134a. The last letter in the designation of R-407 indicates different composition ratios of R-32, R-125 and R-134a. For example, R-407c is made of R-32, R-125 and R-134a at a ratio of 23:25:52 based on mass. Similarly, R-410a is one of the R-410 series refrigerants which are made of two refrigerants R-32 and R-125. The last letter “a” in R-410a indicates that a composition ratio of R-32 and R-125 is 50:50 by mass. Depending on the composition ratio, the last letter can vary.
Several new HFC type refrigerants such as R-134a, R-407c and R-410a are known in attempts to get the best trade-off of flammability versus thermal efficiency. The first R-134a has replaced R-12 for automotive air conditioners, refrigerators and large chillers. This refrigerant has relatively poor heat transfer characteristics but in a typical system produces a pressure of about 8 atm at the evaporator and 16 atm at the condenser. Thus, the relatively small &Dgr;P at the compressor produces excellent efficiency. Therefore, this refrigerant has replaced R-12 for many applications, despite its poor heat transfer characteristics.
A second HFC type refrigerant is R-407c, which is a mixture of R-32, R-125 and R-134a in proportions of 23:25:52 respectively. This mixture, however, produces only about 6 atm at the evaporator and 20 atm at the condenser (like R-22) and has poor heat transfer characteristics due to the high proportion of R-134a.
A third HFC type refrigerant is R-410a, which is a mixture of R-32 and R-125 in a ratio of 50:50 respectively. This mixture, however, produces about 12 atm at the evaporator, but 30 atm at the condenser and requires a large compressor and compressor work.
It would be very desirable to provide a novel refrigeration system which would permit the use of an inflammable mixture of refrigerants, a reduced condenser pressure and an increased evaporator pressure; and which takes the best advantage of the properties of the individual fluids of the mixture.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the invention, a novel system and refrigeration process is provided in which a first component (for example, R-134a) is recirculated in the condenser while the other component or components (for example, R-32 and R- 125) are directed, without recirculation, to the evaporator to increase evaporator pressure and heat capacity. The composition of the circulating refrigerant may be controlled, as by a valve, in the recirculation path to effectively control thermal load variation.
In a preferred embodiment of the invention, the condenser is divided into two sections, with a vortex tube or other liquid-vapor separator between them to recirculate the liquid R- 134a through the first condenser structure.
The vortex tube, or the like, between condenser sections will:
1. Promote liquification in the first condenser by recirculating R-134a rich liquid into the first condenser section;
2. Pass vapor to the second condenser section which is rich in R-32 and R-125;
3. Follow thermal load variation by controlling the amount of recirculating R-134a.
In the novel system, liquid is returned to the inlet of the condenser using the vortex tube as a pump. Other pumps can be used, including venturi tubes.
The advantages produced by the invention include:
1. The use of an inflammable fluid;
2. A large heat capacity at evaporator;
3. A lower condenser pressure;
4. A higher vapor pressure in the evaporator, producing a lower specific volume v in the evaporator, thus reducing compressor work ∫vdP.
As a result of the above, the system requires lower compressor work to reduce compressor size, and produces higher latent heat in the evaporator, producing a more efficient evaporator.
REFERENCES:
patent: 2786341 (1957-03-01), Green
patent: 2839901 (1958-06-01), Green
patent: 2920457 (1960-01-01), Bartlett, Jr.
patent: 3413815 (1968-12-01), Granryd
patent: 5896753 (1999-04-01), Kwak et al.
patent: 6058717 (2000-05-01), Ide et al.
Bai Cheolho
Cho Young I.
Doerrler William
Drake Malik N.
Ostrolenk Faber Gerb & Soffen, LLP
Vortex Aircon
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