Constructional collector heat transfer unit and air conditioner equipped therewith

A constructional collector heat transfer unit having a fluid-carrying heat transfer unit and a collector for the intermediate refrigerant storage as well as an air conditioner with a refrigerant circulating system equipped therewith are provided. In the case of the constructional collector heat transfer unit 3 according to the invention, the heat transfer unit 6 is arranged in the interior of a housing 7a of the collector 7 such that the fluid guided through the heat transfer unit comes in a thermal contact with refrigerant intermediately stored in the collector and removed from it, fluid connection lines 13a, 13b for the heat transfer unit extending through the collector housing. By means of this constructional collector heat transfer unit air conditioners can be equipped with an interior heat transfer device.

BACKGROUND AND SUMMARY OF THE INVENTION 
This application claims the priority of German application 196 35 454.4 
filed in Germany on Aug. 31, 1996, the disclosure of which is expressly 
incorporated by reference herein. 
The invention relates to a constructional collector heat transfer unit 
having a refrigerant circulating system and to an air conditioner 
utilizing the heat transfer system. Heat transfer devices and refrigerant 
collector tanks, in the following called collectors, are known components 
of air conditioners having a refrigerant circulating system, as used, for 
example, in vehicles. 
In German Published Patent Applications DE 43 19 293 A1 and DE 44 10 986 
A1, constructional collector heat transfer units are described in the form 
of constructional collector heat transfer units for vehicle air 
conditioners in which a tube-shaped collector is arranged laterally on a 
condenser of a tube fin block construction and in this case is in a 
fluidity connection with an adjoining condenser collector tube. This known 
constructional collector condenser unit is intended for use in air 
conditioners in which the collector is positioned in the refrigerant 
circulating system on the high-pressure side behind the condenser. 
On the other hand, air conditioners of the initially mentioned type are 
known in which the collector is arranged in the refrigerant circulating 
system on the low-pressure side behind the evaporator and a so-called 
interior heat transfer device is provided as an additional constructional 
unit by way of which the high-pressure side of the refrigerant circulating 
system between an air-cooled condenser and the expansion element is in a 
thermal contact with its low-pressure side between the collector and the 
compressor. 
The invention is based on the technical problems of providing a new type of 
space-saving constructional collector heat transfer unit and an air 
conditioner equipped therewith which contains a collector arranged on the 
low-pressure side and an interior heat transfer device. 
The invention solves these problems by providing a constructional collector 
heat transfer unit having a fluid-carrying heat transfer unit, and a 
collector for the intermediate storage of refrigerant, wherein the heat 
transfer unit is arranged in an interior space of a housing of the 
collector such that the fluid guided through the heat transfer unit comes 
in a thermal contact with the refrigerant through and intermediately 
stored in the collector, and wherein fluid connection lines for the heat 
transfer unit extend through the collector housing. 
In the case of the constructional collector heat transfer unit, the 
fluid-carrying heat transfer device unit is arranged in the interior of 
the collector, that is, of the refrigerant collector tank, this unit being 
constructed and positioned such that the fluid guided through the heat 
transfer unit comes in a thermal contact with the refrigerant 
intermediately stored in the collector tank and removed from it. For the 
feeding and discharging of the fluid guided through the heat transfer 
device unit, corresponding connection lines are guided through the 
collector housing. In this manner, the constructional unit can be used for 
air conditioners in the case of which a heat transmission is to take place 
between the refrigerant which, after the intermediate storage in the 
collector, is to be transmitted and a fluid guided through the heat 
transfer unit, which fluid may in particular be the same refrigerant in a 
different section of the refrigerant circulating system but does not have 
to be that refrigerant. 
In the case of certain preferred embodiments of a constructional collector 
heat transfer unit, the heat transfer unit is implemented by a tube 
construction with at least one flat-tube spiral having mutually spaced 
turns. The flat-tube spiral is inserted and axially covered in the 
collector housing such that the spiral space formed by the spaced 
flat-tube turns forms a spiral flow duct for the refrigerant removed from 
the collector. In this manner, the withdrawn refrigerant is in a thermal 
contact along the spiral turn path with the fluid guided in the interior 
of the flat tubes of the heat transfer unit. 
In certain preferred embodiments, the heat transfer unit of the 
constructional collector heat transfer unit contains two flat-tube spirals 
which are arranged axially side-by-side separated by an intermediate 
bottom, these flat tube spirals being in a fluidity connection with one 
another by means of their two radially exterior ends or by means of their 
two radially interior spiral ends by way of a connection tube extending 
through the intermediate bottom. According to the selection of the 
connections, the flat-tube spirals may be fluidically connected in series 
or in parallel. Analogously, the two pertaining spiral-shaped flow ducts 
are connected by way of a connection opening in the intermediate bottom on 
mutually corresponding radial end areas and in this case, depending on the 
system design, are connected in series or in parallel. 
The air conditioners according to preferred embodiments which are equipped 
with a constructional collector heat transfer unit whose collector on the 
low-pressure side is arranged in the refrigerant circulating system behind 
an evaporator, while the heat transfer unit operates as a so-called 
interior heat exchange device which is used for the heat transmission 
between the high-pressure and low-pressure side of the refrigerant 
circulating system. As a result, a compact construction of the air 
conditioner, particularly of the system part concerning the collector and 
the interior heat transfer device can be implemented. In comparison to 
conventional systems of this type with a constructional unit of the 
interior heat transfer device separated from the collector, the connection 
line which is required there is saved in addition to the connection points 
between the collector and the interior heat transfer device. 
It was found that the inserting of such an interior heat transfer device, 
which causes a further cooling of the refrigerant on the high-pressure 
side behind the condenser connected with an overheating of the refrigerant 
taken in by the compressor on the low-pressure side, for certain air 
conditioners and refrigerants, permits an improvement of the refrigerating 
capacity and of the refrigerating capacity rate. In the case of air 
conditioners used for air-conditioning vehicles, the interior heat 
transfer device can also protect the compressor from damage caused by 
refrigerant taken in a liquid state. 
In the case of a further development of preferred embodiments of an air 
conditioner, the interior heat transfer device on the low-pressure side is 
situated in the outlet-side flow path of the collector and can therefore 
cause, for example, an overheating of the refrigerant withdrawn from the 
collecting space. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
The air conditioner which is illustrated in the block diagram of FIG. 1 and 
which can be used for air-conditioning a vehicle contains a refrigerant 
circulating system with a suitable refrigerant. On the high-pressure side, 
the refrigerant travels from a compressor 1 into a condenser 2 in which it 
is cooled by an ambient air flow. Then it reaches an interior heat 
transfer device which is part of a constructional collector heat transfer 
unit 3, which will be described in detail below. From the output side of 
the interior heat transfer device of this constructional unit 3, the 
refrigerant is supplied to an expansion element 4. The expanded 
refrigerant is guided through an evaporator 5 against which air flows on 
the exterior side; this air is therefore cooled and used for 
air-conditioning the vehicle interior. On the low-pressure side, the 
refrigerant is guided from the evaporator 5 to the collector part of the 
constructional collector heat transfer unit 3 which collector part has the 
function of intermediately storing the refrigerant. The reason is that in 
different operating conditions, different refrigerant quantities are found 
in the high-pressure or low-pressure part of the system, and the 
respective differential quantities of refrigerant can be stored in the 
collector and removed from it. The compressor will then withdraw the 
respective required amount of refrigerant from the compressor 1. 
By way of the interior heat transfer device of the constructional collector 
heat transfer unit 3, the pertaining high-pressure line section is in a 
thermal contact with the pertaining low-pressure line section, causing, on 
the one hand, a further cooling of the refrigerant on the high-pressure 
side in the flow direction behind the condenser 2 and, on the other hand, 
an overheating of the refrigerant sucked out of the collector by the 
compressor 1. It is found that, in the case of certain systems, the use of 
the interior heat transfer device permits an improvement of the 
refrigerating capacity and of the refrigerating capacity rate. Also, in 
this manner, the compressor may be protected from damage by refrigerant 
taken in the liquid state. 
With the exception of the constructional collector heat transfer unit 3, 
the system of FIG. 1 is of a conventional nature and does not have to be 
explained in detail. The following will therefore be a specific discussion 
of the construction according to the invention of the constructional 
collector heat transfer unit 3 which combines two conventionally separated 
air conditioning components, specifically the collector and the heat 
transfer device in a special manner in a common constructional unit. 
A preferred implementation of the constructional collector heat transfer 
unit 3 according to the invention is illustrated in FIGS. 2 to 4. In the 
case of this constructional unit 3, a heat transfer unit 6 which can be 
used as an interior heat transfer device for the system of FIG. 1 is 
integrated in a collector 7 in that it is arranged in a cylindrical 
collector housing 7a adjoining a housing bottom 7b,in which case the 
housing 7a is closed off on the opposite side by means of a welded-on 
curved cover 7c. As heat-transfer-active elements, the heat transfer unit 
6 has two flat-tube spirals 6a, 6b of the same type which are each 
manufactured by a spiral winding of an extruded flat tube. The flat-tube 
spirals 6a, 6b are constructed with mutually spaced spiral turns so that 
the flat-tube exterior walls of each flat tube spiral 6a, 6b each define a 
corresponding spiral-shaped exterior space 8a, 8b. The two flat-tube 
spirals 6a, 6b are, in each case, entered into the collector housing 7a 
side-by-side in the axial direction with a spiral axis being parallel to 
the cylinder axis of the cylindrical collector housing 7a, in which case 
the two flat tube spirals 6a, 6b are separated from one another by way of 
an intermediate bottom 9. While one flat-tube spiral 6a rests against the 
bottom 7b of the collector housing 7a, a cover plate 20 closes off the 
heat transfer unit 6 on the opposite front face with respect to a 
refrigerant collecting space 10. On the one hand, the two flattube spirals 
6a, 6b are fixedly connected with the intermediate bottom 9 and, on the 
other hand, with the bottom 7b of the collector housing 7a or with the 
cover plate 20 by means of soldering. 
The two flat-tube spirals 6a, 6b are fluidically connected in series by way 
of a connection tube 11 which extends through a pertaining passage opening 
12 in the intermediate bottom 9 and is provided with two longitudinal 
slots into which the exterior ends of the two flat-tube spirals 6a, 6b are 
fitted and seal-soldered. For an additional stabilizing of the position, 
the connection tube 11 is soldered to the interior side of the collector 
housing 7a. The guiding of the fluid in the heat transfer unit 6 therefore 
takes place from the radially interior end of the one flat-tube spiral to 
its radially exterior end; from there, by way of the connection tube 11, 
to the radially exterior end of the other flat tube spiral; and in the 
other flat tube spiral, toward the interior to its radially interior end. 
Toward the radially interior ends of the flat-tube spirals 6a, 6b, the 
connection tubes 13a, 13b are guided through corresponding bores in the 
collector housing 7a and are welded to the latter. The two connection 
tubes 13a, 13b are disposed separated by the intermediate bottom 9 in a 
line and, by means of the mutually facing ends, are embedded in recesses 
of the intermediate bottom 9. They are provided with one axial slot 
respectively in an adjoining tube section , into which axial slot the 
radially interior end of the pertaining flat-tube spiral 6a, 6b is fitted 
and seal-soldered. 
As mentioned above, the collector function of the constructional collector 
heat transfer unit 3 is used for the intermediate storage of refrigerant. 
FIG. 4 shows a typical refrigerant liquid level 14 when the constructional 
collector heat transfer unit 3 is arranged with a horizontal longitudinal 
cylinder axis. On the one hand, a connection tube 15, which extends 
through the cover 7c of the collector housing 7a and is welded to it, is 
used as a connection for the refrigerant collecting space 10, by way of 
which connection tube 15, when used in the air conditioner of FIG. 1, the 
refrigerant is supplied which comes from the evaporator 5. On the other 
hand, a withdrawal tube 17 is provided which, by means of one end, ends in 
a U-shaped bend 17a situated transversely to the longitudinal cylinder 
axis of the collector housing 7a, which bend 17a extending with its curved 
center section provided with one or several inlet bores into the lower 
area of the refrigerant collecting space 10 and ending with an open end 
17c in the upper area of the collecting space 10. On the other side, the 
U-shaped tube bend changes into an axial tube section 17c which is welded 
by means of its face to the cover plate 20 which there, in turn, has a 
passage bore 18 by way of which the withdrawal tube 17 is in a fluidity 
connection with the radially interior area of the adjoining spiral space 
8b. 
Furthermore, the two spiral spaces 8a, 8b are in a fluidity connection with 
one another by way of a bore 19 in the intermediate bottom 9 by means of 
their radially exterior end sections. By way of a connection bore 16 in 
the bottom 7b of the collector housing 7a, the adjoining spiral space 8a 
is connected to the outside by means of its radially interior end section. 
In this manner, the two spiral spaces 8a, 8b formed by the respective 
flat-tube spiral 6a, 6b which are axially closed off on the one side by 
the intermediate bottom 9 and, on the other side, by the housing bottom 7b 
or the cover plate 20 with the exception of the described connection and 
connecting openings, form two flow ducts, which are serially connected 
behind one another, for the refrigerant which is guided through the 
collector heat transfer unit 3 and is intermediately stored there. In this 
case, the refrigerant is in a thermal contact along its flow path through 
the spiral flow ducts 8a, 8b with the fluid guided through the interior of 
the flat-tube spirals 6a, 6b, for the purpose of which the flat tubes 
consist of a highly thermally conductive material. 
The use of the illustrated constructional collector heat transfer unit 7 
therefore permits a heat transmission between a fluid guided through the 
flat-tube spirals 6a, 6b and the refrigerant which is withdrawn again 
after the collection. In this case, depending on the connection of the 
constructional collector heat transfer unit 7 to the adjacent 
air-conditioning components, a heat transmission can be achieved in the 
countercurrent as well as in the co-current. In a preferred use for the 
system of FIG. 1, the high-pressure-side refrigerant flows through the 
flat-tube spirals 6a, 6b of the heat transfer unit 6 of the constructional 
collector heat transfer unit 3, while the refrigerant withdrawn by the 
compressor 1 after the previous intermediate storage from the 
constructional collector heat transfer unit 3 is guided in the 
countercurrent thereto through the flow ducts 8a, 8b which are connected 
behind one another. For this purpose, the constructional collector heat 
transfer device unit 3 is connected by means of its heat transfer 
connection 13a, which is on the left in FIGS. 2 and 4, to the refrigerant 
high-pressure line branching off the condenser 2 and is connected to the 
refrigerant high-pressure line leading to the expansion element 4 by means 
of its heat transfer connection 13b which is on the right in FIGS. 2 and 
4. The low-pressure line coming from the evaporator 5 extends to the 
cover-side connection tube 15 of the constructional collector heat 
transfer unit 3, while the withdrawal line leading to the compressor 1 is 
connected to the housing-bottom-side connection bore 16. This results in 
the following course of the flow. 
Coming from the condenser 2, on the high-pressure side, the refrigerant 
enters, for example, at a temperature of between approximately 30.degree. 
C. and 80.degree. C. and a pressure corresponding to the thermodynamic 
characteristics of the used refrigerant, by way of the inlet tube 13a into 
the radially interior end of the first flat-tube spiral 6a and then flows 
in a spiral manner through this spiral 6a radially to the outside to its 
radially exterior end where it changes by way of the connection tube 11 to 
the radially exterior end of the second flat-tube spiral 6b. From there, 
it flows in a spiral manner radially to the interior to the radially 
interior end of the second flat-tube spiral 6b and is then discharged 
again by way of the outlet tube 13b in a cooled state from the collector 
heat transfer unit 3. 
On the low-pressure side, for example, at a temperature of between 
approximately -10.degree. C. and +20.degree. C. and a pressure 
corresponding to the thermodynamic characteristics of the used 
refrigerant, the refrigerant, by way of the inlet pipe 15 coming from the 
evaporator 5 enters into the collecting space 10 in which generally liquid 
as well as gaseous refrigerant is situated as well as possibly 
refrigerator oil if the system is filled properly. By way of one or 
several bores in the U-bend 17a of the withdrawal tube 17, as the result 
of the suction effect of the compressor 1, a defined flow rate of liquid 
refrigerant together with the refrigerant entering in a gaseous state by 
way of the open tube end 17c is sucked off. The refrigerant will then 
usually in two phases flow by way of the bore 18 in the cover plate 20 
into the radially interior area of the adjoining spiral flow duct 8b; that 
is, close to the outlet area for the high-pressure-side refrigerant flow 
in the interior of the flat-tube spirals 6a, 6b. The low-pressure side 
refrigerant taken in by the compressor 1 will then flow in the 
countercurrent to the high-pressure-side refrigerant flow in this flow 
duct 8b radially to the outside until it changes in its radial exterior 
section by way of the connection bore 19 in the intermediate bottom 9 into 
the radial exterior area of the other flow duct 8a where it continues in 
the countercurrent to the high-pressure-side refrigerant flow in a spiral 
manner radially toward the interior, until, in the radially interior area, 
by way of the connection bore 16 in the housing bottom 7b, it leaves the 
constructional collector heat transfer unit 3. 
When flowing through the flow ducts 8a. 8b, which are serially connected by 
way of the connection bore 19 in the intermediate bottom 9, the 
refrigerant taken in by the compressor is in a thermal contact with the 
high-pressure refrigerant flow guided through the interior of the 
flat-tube spirals 6a, 6b which are serially connected behind one another 
and is heated in the process so that it is generally overheated and 
possibly liquid refrigerant is largely evaporated before the refrigerant 
leaves the constructional collector heat transfer unit 3. 
As mentioned above, the interior heat transfer device 6 integrated here in 
a refrigerant collecting tank by means of the constructional collector 
heat transfer unit improves the refrigerating capacity of the air 
conditioner of FIG. 1 by the additional refrigerant cooling on the 
high-pressure side and the suction gas overheating of the refrigerant on 
the low-pressure side. It is understood that the heat transmission in the 
interior heat transfer device 6, can take place instead of as described in 
the countercurrent, as an alternative, in the co-current, for the purpose 
of which the high-pressure-side connections 13a, 13b only have to be 
connected in an exchanged manner. Furthermore, it is understood that 
modifications in the construction of the constructional collector heat 
transfer unit 3 are also contemplated; for example, as required, heat 
conduction fins can be provided for a further improvement of the heat 
transmission between the turns of the flat-tube spirals 6a, 6b, that is, 
in the flow ducts 8a, 8b. As further variants, the two flat-tube spirals 
can be fluidically connected in parallel by corresponding modifications of 
the connections and/or can be connected with one another with their 
radially interior ends, in the latter case, the connections extending to 
their radially exterior ends. Analogous modifications are conceivable for 
the flow ducts 8a, 8b. 
The illustrated and other constructional collector heat transfer units 
according to the invention can be used not only for the air conditioner of 
FIG. 1 but in any other air conditioner where the requirement exists of a 
heat transmission between the refrigerant intermediately stored in a 
refrigerant collecting tank and another fluid flow which does not 
necessary have to be part of the actual refrigerant circulation of the 
system. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.