Heat pump drive

A heat pump arrangement includes an evaporator, a first condenser and a compressor connected in a circuit containing a heat-carrying medium. The compressor is arranged downstream of the evaporator and the first condenser is arranged downstream of the compressor as viewed in the direction of the flow of the medium, whereby the compressor receives medium in the vapor phase from the evaporator and delivers medium in the liquid phase to the evaporator through the first condenser. The heat pump arrangement further has an expander, a second condenser connected downstream of the expander and a pump arranged between the output of the second condenser and the evaporator. The temperature in the first condenser which is designed for extracting useful heat is higher and the temperature in the second condenser is lower than the temperature in the evaporator and further, the expander which is driven by means of a first partial flow of the medium flowing from the evaporator is coupled in a force-transmitting manner with the pump as well as with the compressor for the remaining second partial flow of the medium flowing from the evaporator.

BACKGROUND OF THE INVENTION 
This invention relates to a heat pump arrangement which includes a circuit 
containing a heat-carrying medium, as well as an evaporator, a first 
condenser and a compressor connected in the circuit. The compressor is 
arranged in the circuit downstream of the evaporator as viewed in the 
direction of the flow of the medium and recirculates the medium through 
the first condenser to the evaporator. 
In the broad sense, heat pump arrangements of the above-outlined type serve 
for generating a useful temperature from a lower temperature difference. 
It is a desideratum, particularly when the above-noted temperature 
difference is small, to drive the heat pump arrangement with as little 
external energy input as possible. In known heat pump arrangements, the 
compressor is driven by external energy, for example, by an internal 
combustion engine or an electromotor. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an improved heat pump 
arrangement of the above-outlined type which needs no external energy for 
its operation. This, it is noted, does not mean the application of an 
energy derived from the above-noted temperature difference, but an 
additional mechanical drive energy. 
This object and others to become apparent as the specification progresses, 
are accomplished by the invention, according to which, briefly stated, the 
heat pump arrangement further has an expander, a second condenser 
connected downstream of the expander as viewed in the direction of the 
flow of the medium and a pump arranged between the output of the second 
condenser and the evaporator. The temperature in the first condenser which 
is designed for extracting useful heat is higher and the temperature in 
the second condenser is lower than the temperature in the evaporator and 
further, the expander which is driven by means of a first partial flow of 
the medium flowing from the evaporator is coupled in a force-transmitting 
manner with the pump as well as with the compressor for the remaining 
second partial flow of the medium flowing from the evaporator. 
Thus, according to the invention, the heat-carrying medium, such as a 
conventionally used coolant, for example, a halogenized hydrocarbon, is 
itself divided downstream of the evaporator, thus in the vapor phase, into 
two partial streams. The first partial stream is admitted to the expander 
for driving it to perform its expansion function, whereas the second 
partial stream is admitted to the compressor. The expander, the compressor 
and the pump are drivingly connected to one another, so that all three 
devices are driven by the first partial stream of the heat-carrying 
medium. Thus, the application of an external driving energy is dispensed 
with. 
The mechanical energy derived in the expander from the first partial stream 
of the heat-carrying medium admitted in the vapor phase, thus has to be 
equal--apart from frictional and heat transfer losses--to the sum of the 
energy necessary for the densification of the second partial stream in the 
compressor plus the energy which is necessary for driving the pump and 
which is to be introduced into the pump. The energy required for the 
compressor is ultimately dependent from the temperature difference between 
the first condenser at which the useful heat is taken and the evaporator, 
while the magnitude of the driving energy for the pump is in essence 
determined by the pressure difference between the evaporator and the 
second condenser. 
In principle it is feasible to design both the expander and the compressor 
as piston-and-cylinder assemblies. Taking into consideration the required 
driving connection also with the pump, it is, however, more advantageous 
to provide that the expander and the compressor are of the rotary type. In 
such a case the expander and the compressor themselves execute rotary 
motions which may be converted into driving displacements for the pump, 
for example, by means of a cam disc mounted on a shaft which is common to 
the expander and the compressor. The expander and the compressor may be of 
the turbine type; it is particularly expedient, however, to use a 
screw-type expander and a screw-type compressor since such structures are 
capable of generating large pressure differences even in case of 
non-constant operational conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to FIG. 1, there is shown an expander 1 and a compressor 2 
which receive the heat-carrying medium exiting in the vapor phase from an 
evaporator 3. Both the expander and the compressor are of the screw type. 
Such arrangements are conventional by themselves; they are disclosed, for 
example, in U.S. Pat. No. 3,630,040. After passing through a shutoff valve 
4, the vaporized heat-carrying medium is divided into a first partial 
stream 5 and a second partial stream 6 by means of a conventional stream 
splitter 17. The first partial stream 5 is admitted to the expander 1 for 
driving the same. The expander 1 and the compressor 2 are coupled by two 
shafts 7 and 8 in the sense of transferring the driving motions. On the 
shaft 8 there is mounted a cam 9 which converts the rotary motions of the 
shaft 8 into driving motions for the pump 10. Thus, the first partial 
stream 5 of the heat-carrying medium drives the expander 1, the compressor 
2 and the pump 10 for the heat-carrying medium which has to be returned in 
the liquid phase through the return conduit 11 to the evaporator 3. 
The heat-carrying medium which forms the second partial stream 6 and which 
is compressed in the compressor 2, is admitted into the first condenser 12 
which, for extracting useful heat, may be designed as a heat exchanger and 
then the heat-carrying medium is returned to the inlet of the evaporator 3 
in the liquid phase through a conduit 13 and an injection valve 14. 
Instead of an injection valve any other device may find application which 
is adapted to maintain the pressure difference between the first condenser 
12 and the evaporator 3. 
The pump 10 serves for returning the first partial stream 5--again 
liquified in the second condenser 15--to the inlet of the evaporator 3. 
The expander 1, the compressor 2 and the pump 10 are arranged in a common 
housing 16, whose seals may be of particularly simple structure, because 
none of the moving parts project out of the housing 16. 
Turning now to the diagram illustrated in FIG. 2, there is shown the course 
of the pressure p of the heat-carrying medium as a function of the 
enthalpy h. The lower quadrilateral curve shows the behavior of the first 
partial stream 5 which, as was explained above, serves for driving the 
expander 1, whereas the upper quadrilateral curve illustrates the behavior 
of the second partial stream 6. In parantheses there are shown the 
reference numerals of those components of the heat pump arrangement 
illustrated in FIG. 1 which are associated with the point on the curves 
situated next to the numeral. The curves progress in the direction of the 
arrows. p1, p2 and p3 are the pressure valves and t1, t2 and t3 are the 
temperature valves of the heat-carrying medium in the second condenser 15, 
in the evaporator 3 and in the first condenser 12, respectively. The 
pressure and the temperature thus vary in the same sense in this sequence. 
There is further shown the enthalpy difference .DELTA.h which is a measure 
of the energy to be applied to the liquid pump 10. 
The division of the heat-carrying medium into the two streams 5 and 6 as 
well as the arrangement particularly of the expander, the compressor and 
the pump have to be such that the enthalpy difference between the points 
(3) and (15) on the diagram is identical to the enthalpy difference 
between the points (3) and (12) of the diagram, plus the enthalpy 
difference .DELTA.h, while an addition for losses has to be taken into 
account. The energy to be applied to the pump, that is, the enthalpy 
difference .DELTA.h is independent from the difference between the 
pressures p1 and p2, since the pump has to bring the liquid working medium 
in the return conduit 11 from the pressure p1 in the second condenser 15 
to the pressure p2 in the evaporator 3. 
In the description which follows, the mode of operation of the entire heat 
pump arrangement will be summarized with reference to the diagram of FIG. 
2. 
The heat-carrying medium, for example, a halogenized hydrocarbon or another 
liquid of low boiling point is evaporated in the evaporator 3 by means of 
heat admission thereto, so that it has a temperature t2 at a pressure p2. 
The first partial stream 5 expands in the expander 1 and drives the 
latter, as well as the compressor 2 and the pump 10 and is admitted into 
the second condenser 15 which may also be designated as a source of 
refrigeration. In the second condenser 15 the heat-carrying medium assumes 
the temperature t1 and the pressure p1. THe pump 10 delivers the again 
liquified heat-carrying medium from the second condenser 15 back into the 
evaporator 3 while its pressure is increased from p1 to p2. 
The second partial stream 6 of the heat-carrying medium, on the other hand, 
is admitted into the compressor 2 and therefrom into the first condenser 
12 where it is condensed while it releases condensation heat and assumes 
the temperature value t3 and the pressure value p3. The liquid 
heat-carrying medium is, through the conduit 13, admitted to the 
evaporator 3 as well; during this occurrence the injection valve 14 
maintains the difference between the pressures p3 and p2. 
It is an advantage of the compact structure of the described preferred 
embodiment that is is free from sealing problems, since the moving 
components within the housing 16 need not be accessible from the outside 
during operation, because the energy required for driving the expander, 
the compressor and the liquid pump are directly derived from the 
heat-carrying medium circulating within the system. 
It is to be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.