Heat exchanger

Abstract

The invention is directed to a heat exchanger (10) having a block (2) which includes a plurality of tubes (11) for conducting a fluid therethrough. The heat exchanger also includes a collector (5) having a tube base (4). The tubes have tube end sections (11) and the tubes are inserted into the tube base so that the end sections are accommodated therein and extend into the collector to an insertion depth (x). The insertion depth (x) of the end sections (11a) is variable. The heat exchanger is preferably used as an evaporator in climate control systems for motor vehicles.

Description

BACKGROUND OF THE INVENTION [0001] Heat exchangers, for example, refrigerant vaporizers, are used in climate control systems for motor vehicles. These heat exchangers include essentially a block of tubes through which a refrigerant flows and which refrigerant is to be evaporated. Ribs are provided and the air, which is to be cooled, is passed over these ribs and is supplied to the interior of the vehicle. The tubes are connected to collector compartments or distributor compartments via which the refrigerant is supplied, redirected or conducted away. [0002] A problem, which occurs with all evaporators, is the uniform distribution of the refrigerant, which is injected into the evaporator, into all tubes. The refrigerant is expanded in an expansion element directly in advance of entry into the evaporator and is present at the injection location of the evaporator as a two-phase mixture comprising a vaporous refrigerant and a liquid refrigerant. If the evaporator tubes are not uniformly ...

AI Technical Summary

Benefits of technology

[0008] It has been determined that the refrigerant flow increases greatly with increasing distance from the location of injection up to the tube farthest remote therefrom. More specifically, the refrigerant flow is present in the region of the injection location as an intensely turbulent mixture of refrigerant vapor and liquid droplets. The refrigerant flow passes into a layered flow with increasing distance from the injection location. For a horizontal flow, a layer of liquid refrigerant and a layer of vaporous refrigerant thereabove forms in the geodetically bottom-lying region. The location of the transition from turbulent to layered flow is dependent upon the amount of the refrigerant mass flow. Because of varying insertion depths of the tubes, this phenomenon of the refrigerant flow can be taken into account and an approximately uniform distribution of the refrigerant is achieved to the individual tube cross sections. The solution of the invention is relatively easily realized and therefore cost effective, that is, by simply utilizing different tube lengths and / or insertion depths. It is possible that different insertion depths, at least in a portion of the tubes, can be realized also without different tube lengths when, for example, a compensation at the other end of the corresponding tube is provided. The following advantages are achieved: a uniform temperature distribution on the air side; a uniform, lower pressure drop in the tubes; and, a higher evaporator capacity.

Problems solved by technology

A problem, which occurs with all evaporators, is the uniform distribution of the refrigerant, which is injected into the evaporator, into all tubes.

Furthermore, an increased pressure drop can develop in the individual tubes which is damaging for the capacity of the evaporator.

These disadvantages are especially pronounced in the thermal part-load operation which, on an annual average, usually occurs most often, as opposed to the full-load operation.

These suggestions are characterized by an increased constructive complexity in the area of the inlet compartments of the evaporator which increases the manufacturing costs.

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