Refrigeration apparatus and method

A refrigeration system employing an adiabatic expansion and an impulse generating means for the oscillatory compression and pumping of the working fluid. The impulse generating means is a venturi having a liquid inlet downstream of the throat with means for applying heat by a heat source, typically the waste heat of an automobile engine to the working fluid. The working fluid may be used to cool air through an evaporation in an automobile passenger compartment.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates to adiabatic expansion refrigeration systems and in 
particular to air conditioning systems having a readily accessible source 
of low-grade heat, such as in an automobile. 
Typical air conditioning refrigeration systems for automotive applications 
employ mechanical compressors to convert low-pressure vapor to 
high-pressure vapor in a closed refrigeration circuit and which employ 
adiabatic expansion and condensation to extract heat from the environment 
of the passenger compartment. The mechanical refrigeration circuit 
comprises a mechanical compressor, a vapor condenser and an evaporator or 
a refrigeration unit in a heat exchanger. In systems such as an automobile 
air conditioning system considerable power is expended in order to drive 
the compressor. The power is derived from the mechanical output of the 
internal combustion engine which increases the fuel consumption and may 
cause the engine to overheat. What is needed is an air conditioning system 
which does not waste fuel or cause excessive heating. 
2. Description of the Prior Art 
Absorption-type refrigeration systems are known which employ a heat source 
and highly endothermic reactants such as halide salts in water as heat 
absorption media. Such refrigeration systems operate on a principle of 
heat absorption by heat exchange with the environment upon contact with 
endothermic reaction products. The reactants involved in the endothermic 
reaction are typically separated by heating for recycling. Any substances 
having high endothermic affinity for one another and which can be 
separated by heating may in theory be used in an absorption refrigeration 
system. 
Also well-known are ammonia-absorption refrigeration cycle systems in which 
ammonia vapor is absorbed and extracted from ammonia solution. 
Ammonia-absorption systems are justified only in cases where a suitable 
source of heat is available which would otherwise be wasted. Ammonia is 
also known for use in adiabatic expansion refrigeration systems. All of 
these systems have been suggested for automotive applications. 
The following patents were uncovered in a review of prior art refrigeration 
systems: 
Tsunesuke Kubo et al., U.S. Pat. No. 3,077,083 issued Feb. 12, 1963; 
Pippert, U.S. Pat. No. 3,153,441 issued Oct. 20, 1964; 
Hess, Jr., U.S. Pat. No. 3,230,731 issued Jan. 25, 1966; and 
Eannarino et al., U.S. Pat. No. 3,535,888 issued Oct. 27, 1970. 
The known prior art suggests the use of absorption-type air conditioning 
systems in connection with automotive applications where there is a source 
of heat available which might otherwise be wasted. While the prior art 
suggests elimination of mechanical compressors, nothing is suggested which 
would be a suitable substitute for a mechanical compressor in an adiabatic 
expansion refrigeration system. 
SUMMARY OF THE INVENTION 
According to the present invention, a thermodynamic compressor is provided 
in an adiabatic expansion refrigeration system. The method of the 
invention includes heat-driven impulse compression of a working fluid in a 
closed adiabatic expansion refrigeration circuit. The impulse compression 
is provided by a venturi having no moving parts comprising a venturi 
throat into which heated vapors of the working fluid are introduced and an 
inlet port adjacent the low-pressure region of the venturi throat through 
which liquid working fluid is introduced. The venturi mechanism is 
operative in response to heat input to generate pressure oscillations or 
impulses which are sufficient to compress the refrigeration fluid in 
pressure oscillations or impulses. The invention has particular 
application in an automotive air conditioning system where a source of 
waste heat is available and where fuel consumption is a consideration. 
The invention has the advantage of eliminating a need for a mechanically 
driven compressor. 
The invention will be best understood by reference to the following 
detailed description taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
Referring to FIG. 1 there is shown one embodiment of a refrigeration 
apparatus 10 according to the invention. The apparatus 10 includes a 
condenser 12 in which heat in a refrigeration fluid is extracted and the 
fluid condensed to a liquid. The outlet is a supply line or condenser 
return 14 to an accumulator reservoir 16. The accumulator reservoir 16 is 
a sealed reservoir which maintains liquid and vapor in substantial thermal 
equilibrium thus resisting substantial pressure excursions. The reservoir 
16 has two liquid fluid outlets 17 and 21 which draw from that portion of 
the reservoir 16 normally occupied by the refrigeration fluid in a liquid 
state. 
A first liquid feed line 17 from the reservoir 16 is coupled to an 
expansion means, which is preferably a capillary expansion valve 18. The 
capillary expansion valve 18 is operative to expand the liquid refrigerant 
received through feed line 17 adiabatically. The outlet of the capillary 
expansion valve 18 is coupled to an evaporator 20, normally enclosed in 
the space to be cooled. The evaporator 20 is operative to draw heat from 
the surrounding environment on evaporation of adiabatically expanded 
liquid introduced at its inlet. 
The second liquid outlet of the reservoir 16 is a liquid feed line 21 
coupled through a metering valve 22 to an impulse generator unit 30. The 
outlet is coupled to a liquid inlet 26 of a venturi 36, having a gas 
input, a throat and a gas output, as hereinafter explained. 
Returning to the evaporator 20, vapor from the evaporator 20 is introduced 
through a vapor feed line 28 to the impulse generator unit 30. A heat 
input means 32 is provided in the impulse generator unit 30 through a heat 
exchanger 33, which may be in the vapor inlet path. The heat input means 
32 may be any source of heat, but it is preferably the exhaust manifold of 
an internal combustion engine. 
The source of heat Q.sub.S is heat in the waste combustion products of 
internal combustion engine. Any heat not transferred through the heat 
exchanger 33 is expelled from the heat input means as waste heat Q.sub.E. 
The heat exchanger 33 is coupled to the gas inlet of the venturi 36 in the 
impulse generator unit 30. The venturi gas outlet is coupled through a 
return 34 for vapor which is in turn coupled to the inlet of the condenser 
12, thus forming a thermodynamic system with closed fluid system, heat 
input and exhaust and a thermodynamically driven pump. 
In the impulse generator unit 30 there are shown three check valves 24, 29 
and 31. These check valves are respectively in the liquid feed line 21, 
the vapor feed line 28 and the vapor exhaust line 34. These check valves 
24, 29 and 31 are operative to assure that flow of fluid is unidirectional 
into the condenser 12, in the indicated direction. Check valves physically 
distinct from the venturi 36 may not be necessarily due to inherent 
characteristics of the venturi 36 in operation. However, such check valves 
may be employed as a measure of redundancy. 
Turning to FIG. 2A and FIG. 2B, there are shown two embodiments of the 
impulse generator unit 30. In each embodiment of the impulse generator 
unit 30 the venturi 36 is a tube which comprises a constrictive throat 
section 38 having a converging section 40 for vapor inlet of one side and 
a diverging section 42 for vapor outlet on the side of the throat section 
38 opposing the convergent section. The inlet to the converging section 40 
is coupled from a chamber comprising the heat exchanger 33 which is in 
thermal communication with the heat input means 32. The outlet of the 
diverging section 42 is coupled to the vapor return 34 which in turn is 
coupled to the inlet of the condenser 12 (FIG. 1). 
The one-way check valve 24 in the liquid feed line 21 may be a simple 
spring biased ball check valve. The liquid inlet 26 to the impulse 
generator is disposed, in one embodiment (FIG. 2A), in the diverging 
section 42 of the venturi 36 defining a port 44 for introducing liquid in 
a downstream direction into the vapor path. 
In another embodiment (FIG. 2B), the liquid inlet 26 to the venturi 36 is 
disposed at the constrictive throat section 38 as a tube to define an 
inlet port 44 in the throat 38 of the venturi 36. The nozzle of the port 
44 is disposed to direct fluid in a downstream direction toward the 
diverging section 42. 
Since the operation of the invention is not immediately obvious, the 
following explanation is offered. Vapor and liquid are introduced into the 
impulse generator 30 through the vapor feed line 28 and liquid inlet 26. 
Heat is introduced into the impulse generator 30 through a heat source 32. 
The liquid from the liquid inlet 26 (which itself may be heated above the 
temperature of vaporization) drips or trickles into the region containing 
heated fluid. Upon encountering the heated vapor and relatively low 
pressure in the venturi 36, the liquid expands rapidly and it vaporizes. A 
pressure impulse is thereby created in the venturi 36. The impulse 
pressure is such as to cause the vapor to be drawn from the vapor inlet 28 
and to propel the fluids introduced through both port 44 and the throat 38 
from the vapor inlet 28 along the diverging section 42 toward the vapor 
return 34. The impulse generator unit 30 is operative to both compress 
vapors introduced at the vapor inlet 28 and to propel it, together with 
the added liquid, now vaporized, through the vapor return 34. Accordingly, 
the pressure-volume relationship of the vapor line and the related travel 
time of impulses along the vapor path, particularly between the venturi 
throat 38 and the region of condensation within the condenser 12 (where 
the fluid becomes essentially incompressible), should have an effect on 
the oscillation frequency of the impulse generator unit 30. 
The entire refrigeration apparatus 10 is a closed fluid system in that 
there are no external inlets or outlets for vapor or liquid to the 
refrigerant paths. The accumulator reservoir 16 is operative both as a 
liquid storage reservoir and as a pressure ballast relative to the 
pressure oscillation of the impulse generator unit 30. 
A number of alternative embodiments are within the contemplation of the 
invention. For example, the heat of the heat input means 32 may be applied 
directly to the venturi 36. Similarly, heat can be applied to the liquid 
in the liquid inlet line 26 rather than to the vapor feed line coupled to 
the vapor inlet of the venturi 36. Alternatively, heat may be applied at 
both sites. A second venturi might also be used downstream of the liquid 
inlet in order to further pressurize high velocity fluid in the return 
path to the condenser 12. 
A variety of refrigerants can be employed in a cooling system according to 
the invention. For example, lithium bromide, lithium chloride and Freon 
may be used with the internal pressure of the system being selected to 
assure that there a vapor-liquid transition through the evaporator and the 
condenser. In addition, the efficiency can be enhanced by adding 
convective heat transfer mechanisms such as fans to the condenser and to 
the evaporator. Except for such items as fans and possibly optional check 
valves, there are no moving parts in the system. 
The invention has now been explained with reference to specific 
embodiments. Other embodiments will be apparent to those of ordinary skill 
in the art. For example, while the invention has been described in terms 
of impulse pump, under some conditions, a system according to the 
invention may operate with a steady state stream through the venturi and 
still provide refrigeration. It is therefore not intended that this 
invention be limited except as indicated by the appended claims.