Hybrid evaporator

Abstract

A laminate-type evaporator includes U-channel plates in combination with various configurations of dual cup and single cup plates, to control refrigerant pressure drop and achieve enhanced temperature spreads within the evaporator. The U-channel plates define one or more of the final refrigerant passes in the evaporator, and the dual cup and single cup plates define refrigerant passes upstream therefrom. Fins are disposed between adjacent plate pairs and extend to selected end edges of the U-channel plates to maximize the surface area available for heat exchange in the final refrigerant passes.

Description

FIELD OF THE INVENTION [0001] This invention relates to a heat exchanger, and more particularly, to an evaporator for the climate control system of a motor vehicle. DESCRIPTION OF THE RELATED ART [0002] Evaporators are well known in the art, and typically include a plurality of tubes having interiors through which refrigerant flows. Thermal energy, or heat, exchange occurs between ambient air flowing outside the tubes and the refrigerant flowing within. To enhance the amount of heat exchanged between the air and refrigerant, multiple fins are disposed between the adjacently positioned tubes. The fins are placed in contact with selected exterior surfaces of the tubes. This increases the surface area available for heat transfer from the air to the refrigerant circulating within the tubes, which in turn cools and dehumidifies the air as it flows across the exterior of the evaporator. [0003] Heat transfer from the air to the refrigerant is further enhanced by routing the refrigerant to ...

AI Technical Summary

Benefits of technology

[0008] Fins are disposed between the adjacent pairs of plates. Those fins disposed between adjacent pairs of the second plates are positioned in overlying relation to the return recesses and extend to the upper edges adjacent thereto for inducing a transfer of thermal energy between an airflow through the fins and the fluid flowing through the return recesses.

[0009] The subject invention overcomes the limitations of the art by providing an evaporator which utilizes U-channel plates in combination with various configurations of dual cup and single cup plates. The U-channel plates are utilized to define one or more of the final refrigerant passes in the evaporator, which aids in the distribution of the small quantity of liquid refrigerant that typically remains in those passes as the refrigerant vaporizes and its quality approaches unity. The dual and single cup plates are utilized in passes upstream from the U-channel plates to reduce the drop in pressure that would otherwise occur on the refrigerant side if U-channel plates were used throughout the evaporator. Extending the fins to the upper edges of the U-channel plates maximizes the surface area of the plates available for heat exchange in the final refrigerant passes.

Problems solved by technology

Unfortunately, because the refrigerant absorbs heat from the air, the cooling capacity of the refrigerant decreases with each additional pass the refrigerant makes.

The problem of non-uniform temperature of the discharge air is further exacerbated by the manner in which an evaporator core is designed.

For instance, non-uniform air temperature distribution occurs in such evaporators when a vehicle in which the evaporator is installed accelerates from rest.

In this situation, the compressor of the climate control system quickly draws refrigerant out of the evaporator, causing high refrigerant superheats to occur within the last passes of the evaporator.

However, the cooling capacity of such tubes is compromised by the increased pressure drop that occurs on the refrigerant side of the tubes, which is caused by the reduced cross-sectional area of the tubes available for refrigerant flow.

Although evaporators that utilize dual cup tubes to effectively create two cores through which the refrigerant flows in series first through one core and then the other achieve improved temperature spreads and greater cooling capacity than evaporators formed from U-channel tubes, increasing movement towards evaporator cores with smaller depths, necessitated by space constraints, has eroded these benefits.

The smaller the core depth, the narrower the cross-sectional area of the tubes through which the refrigerant must flow, and the greater the refrigerant pressure drop, which has a negative impact on the cooling capacity of the evaporator core.

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