Refrigeration – Refrigeration producer – Heat exchange between diverse function elements
Reexamination Certificate
2000-09-20
2002-08-20
Esquivel, Denise L. (Department: 3744)
Refrigeration
Refrigeration producer
Heat exchange between diverse function elements
C062S113000, C165S177000, C165S179000, C165S184000, C165S156000
Reexamination Certificate
active
06434972
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German patent document 199 44 951.1 filed Sep. 20, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention concerns an air conditioner with a refrigerant loop which includes an evaporator, a compressor which transfers the refrigerant from a low-pressure side to a high-pressure side, an accumulator positioned between the evaporator and a compressor on the low-pressure side, and an internal heat exchanger having a heat transfer channel on the high-pressure side and a heat transfer channel on the low-pressure side in thermal contact with same.
These types of air conditioners are particularly used in motor vehicles, e.g. in the form of CO
2
air conditioners. The internal heat exchanger serves to transfer heat from the refrigerant on the high-pressure side to the refrigerant on the low-pressure side, whereby the so-called coefficient of performance, i.e., the ratio of refrigeration capacity and input power of the air conditioner, is significantly increased.
An air conditioner of this type is disclosed in the German disclosure document DE 196 35 454 A1. The internal heat exchanger is integrated herein with the accumulator into a modular unit in that it is housed inside an accumulator housing, e.g. in the form of a flat tube spiral with the windings separated from one another.
Furthermore, using a coaxial tube with two lengthwise fluid-separated tube channels in thermal contact as an internal heat exchanger for an air conditioner in order to undercool the high-pressure side refrigerant before an expansion valve through heat transfer to the low-pressure side refrigerant is known. A coaxial tube serving this purpose is described in the German patent specification DE 1 208 314, in which an internal tube is concentrically surrounded by an external tube and is provided with internal lengthwise ribbing to increase the heat transfer surface area. A wire screw can be placed between the external tube and the internal tube in order to lengthen the effective heat transfer flow path. Internal tube designs are also indicated as known herein in which the internal tube is folded into a star shape or in which the internal tube has a sheet metal helix inserted to produce a twisting flow.
An air conditioner for a motor vehicle is also known in which an internal heat exchanger is combined with an evaporator and an expansion valve into an integral modular unit. This type of combination of the internal heat exchanger on or into the evaporator is, however, frequently connected with a relatively high overall space requirement, which can lead to problems, particularly in the confined installation conditions of motor vehicles.
An integrated accumulator-heat exchanger modular unit was disclosed in the prior German patent application No. 199 03 833.3 (not previously published), in which the internal heat exchanger is formed by a spiral coaxial tube accommodated in the condenser housing.
The invention has as its basis the technical problem of the provision of an air conditioner with an internal heat exchanger of the type described initially which is relatively simple to produce and requires relatively little additional overall space for a predetermined heat transfer performance.
Certain preferred embodiments of the invention solve this problem by the provision of an air conditioner of the above noted type, wherein the internal heat exchanger contains a multichannel tube wound into one of a radial spiral and a meander shape.
Certain preferred embodiments of the invention further solve this problem by positioning turbulence elements on ridges, or providing spiral ridges between concentric coaxial multichannel tubes.
In certain preferred embodiments, the air conditioner has an internal heat exchanger which contains a multichannel tube which is wound into a radial spiral or meander shape. The necessary overall length can thereby be kept significantly smaller than the effective heat transfer flow path length, whereby only one single (multichannel) tube must be bent.
In an air conditioner further developed according to certain preferred embodiments, the multichannel tube is formed, in a way advantageous for production engineering, from a coaxial tube comprising either an extruded internal tube with external ridges inserted in an external tube, an extruded external tube with internal ridges into which an internal tube is inserted, or a one-piece extruded tube with integrated ridges between the internal and external tubes. The ridges are preferably spiraled, in order to make the flow path length for the relevant heat transfer channel longer than the overall length of the coaxial tube.
In a further development of certain preferred embodiments, turbulence elements are provided on the ridges, or the ridges are spiral-shaped. This contributes to a further intensifying of the heat transfer. The turbulence elements could, for example, be formed by slits in the ridges or by tailored projections on the ridges.
In the air conditioner according to certain preferred embodiments of the invention, the internal heat exchanger contains a multichannel tube positioned in the air current path of an air current used to cool the condenser/gas cooler and thereby supplements the cooling of the internal heat exchanger, increasing the undercooling of the refrigerant on the low-pressure side and thereby the degree of effectiveness of the entire air conditioner.
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.
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Geiger Wolfgang
Krauss Hans-Joachim
Mittelstrass Hagen
Sickelmann Michael
Staffa Karl-Heinz
Behr GmbH & Co.
Crowell & Moring LLP
Esquivel Denise L.
Norman Marc
LandOfFree
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