JP2008542677A - Parallel flow evaporator with liquid trap for good flow distribution - Google Patents

Abstract

The parallel flow evaporator has a liquid trap that adjusts the speed of the refrigerant sent from the expansion device to the evaporator. In the simplest configuration, the liquid trap is a u-shaped pipe arranged vertically and connected to the inlet manifold of the evaporator. By providing the liquid trap, a small amount of liquid refrigerant is separated from the vapor phase depending on the conditions. This separated liquid tends to collect in the trap and narrows the flow cross-sectional area of the line leading to the evaporator inlet manifold. As this cross-sectional area decreases, the speed of the refrigerant passing through the line increases. In this way, as the small amount of liquid phase separates, the remaining refrigerant velocity increases, ensuring that further separation is greatly reduced or eliminated altogether. As a result, a uniform refrigerant flow is supplied to the evaporator, increasing the performance of the evaporator and improving the reliability of the system.

Description

  The present invention relates to a parallel flow evaporator, where a liquid trap is placed upstream of the inlet manifold to improve flow distribution between parallel channels, improve heat transfer, and system reliability. To increase.

  Refrigerant systems are utilized to control the temperature and humidity of air in various indoor environments that are regulated. In a typical refrigerant system operating in the cooling mode, the refrigerant is compressed by a compressor and sent to a condenser (ie, an outdoor heat exchanger in this case). In the condenser, heat exchange is performed between the external ambient air and the refrigerant. The refrigerant travels from the condenser to the expansion device, is expanded in the expansion device to a low pressure and low temperature, and then flows to the evaporator (ie, the indoor heat exchanger if the system operates in cooling mode). In the evaporator, heat is exchanged between the refrigerant and the indoor air in order to adjust the indoor air. When the refrigerant system is operating in the cooling mode, the evaporator cools the air supplied to the indoor environment and generally also dehumidifies it.

  One type of evaporator that can be utilized in a refrigerant system is a parallel flow evaporator. This type of evaporator has several parallel channels that transfer refrigerant between an inlet manifold and an outlet manifold. Each channel typically comprises a number of parallel internal channels having various cross-sectional shapes separated by an inner wall. Corrugated fins are placed between the channels to increase heat transfer and to add rigidity to the structure. Typically, the channels, manifolds and fins are made of similar materials such as aluminum and are attached to each other by brazing. In recent years, parallel flow evaporators have attracted much attention and attention in the air conditioning field due to their superior performance, compactness, rigid structure and high corrosion resistance. However, one concern with parallel flow evaporators is that the refrigerant distribution is uneven between the channels. The problem of non-uniform refrigerant distribution in parallel flow evaporators is usually caused by gravity and inadequate refrigerant velocity combined with the separation of the liquid phase from the vapor in the inlet manifold, which causes the evaporator channel to The amount of vapor refrigerant and liquid refrigerant passing through becomes uneven. Other events that lead to a non-uniform distribution include differences in the distance that the refrigerant flows from various channels to the outflow, pressure impedance non-uniformity, and heat transfer rate variation between channels.

  Known parallel flow evaporators typically include an inlet manifold and an outlet manifold having a cylindrical shape. The channels are usually made from the same aluminum extrusion that forms a flat tube. As the two-phase refrigerant enters the inlet manifold, the vapor phase and the liquid phase frequently separate. After the separation, the two phases move independently of each other, so the problem of uneven distribution of the refrigerant frequently occurs.

  When such a non-uniform distribution occurs, the performance of the heat exchanger is greatly reduced, causing liquid refrigerant to frequently exit the outlet manifold. This liquid refrigerant causes problems that impair reliability and permanent compressor damage. This is clearly undesirable.

  In the disclosed embodiment of the present invention, the parallel flow evaporator is provided with a liquid trap upstream of its inlet manifold. In this manner, if the refrigerant is moving at such a speed that the liquid phase and the vapor phase do not separate, the refrigerant can flow through the trap to the inlet manifold and to the evaporator channel with a substantially even distribution. . However, when the refrigerant is moving at such a low speed that liquid separation is likely to occur, the liquid is easily separated and collected in the liquid trap. As liquid accumulates in the liquid trap, the flow cross-sectional area for the remainder of the refrigerant is reduced. Since the flow cross-sectional area is smaller, the result is an increase in refrigerant velocity and a jet effect that transports droplets to the inlet manifold and limits further phase separation. This phenomenon is self-adjusting and reliably maintains sufficient refrigerant speed so that the liquid portion of the refrigerant is less likely to separate from the vapor.

  In one embodiment, instead of a single u-shaped trap, a serpentine channel formed by a number of such u-shaped structures is used.

  In another disclosed embodiment, the refrigerant system is provided with a saving circuit, and a liquid trap is used on the line leading the branched two-phase refrigerant mixture to the economizer heat exchanger. This embodiment provides similar benefits and functions as for the first disclosed embodiment.

  The above and other features of the present invention can be best understood from the following specification and the accompanying drawings.

  In FIG. 1, a refrigerant system 20 having a parallel flow evaporator 22 is shown. As is known, the refrigerant travels downstream from the evaporator 22 to the compressor 24 and the condenser 26 and returns to the evaporator 22 through the expansion device 28. The refrigerant exiting the expansion device 28 is in a state where the vapor and the liquid are mixed. The evaporator 22 has a plurality of parallel channels 32 spaced from one another along an inlet manifold 34. Channel 32 and inlet manifold 34 are in fluid communication with each other. Further, the channel 32 is similarly disposed relative to the outlet manifold 35 and is in fluid communication with the outlet manifold 35. The fins 30 are disposed between the channels 32. Channel 32, fin 30, inlet manifold 34, and outlet manifold 35 are typically attached to each other by brazing. As is known, air is supplied and conditioned on the fins 30 and channels 32. The refrigerant evaporates in the channel 32 by the mutual heat transfer effect with the air supplied to the adjustment space.

  As described above, when the speed of the refrigerant approaching the inlet manifold 34 is low enough, the liquid refrigerant may be separated from the vapor. As a result, these two refrigerant phases are unevenly distributed between the channels 32. As shown in FIG. 1, the refrigerant is moving at a sufficient speed and the refrigerant phase is separated little or not.

  A tube 36 leading to the inlet manifold 34 is disposed downstream of the liquid trap 38. As shown in the figure, the liquid trap 38 has a u-shape and extends in a generally vertical direction. Thus, all liquids that tend to separate collect in the liquid trap 38.

  As shown in FIG. 2, the refrigerant velocity is insufficiently low compared to the state of FIG. 1 where the phases are not separated, and some amount of liquid refrigerant 40 has accumulated in the trap 38. For this reason, the remaining cross-sectional area 42 through which the refrigerant flows is greatly reduced. This increases the speed of the refrigerant traveling to the inlet manifold 34. As the refrigerant flow speed increases, the vapor refrigerant tends to carry its liquid phase to the channel 32 in a uniform manner, ensuring a generally even distribution. In effect, a jetting zone is formed and the vapor refrigerant is accelerated to limit further phase separation. Thus, by including the liquid trap 38 upstream of the header 34, the present invention self-regulates the speed of the refrigerant and separates the remaining liquid refrigerant from the vapor phase other than the small amount of liquid refrigerant 40 that was initially separated. This obfuscation ensures that the flow conditions in the inlet manifold 34 are uniform. The inlet manifold 34 must, of course, have an appropriate cross-sectional area and length that can maintain this uniform flow. Also, the liquid trap 38 needs to be placed in close proximity to the inlet manifold 34. The liquid trap 38 is preferably located within 5 inches from the inlet to the inlet manifold 34 and extends vertically below it. As a result, the performance of the evaporator is improved. This also ensures that no liquid refrigerant is present in the outlet manifold 35 of the evaporator and increases system reliability.

  Although the present invention is disclosed in a general evaporator, other heat exchangers (e.g., economizer heat exchangers (or so-called brazed plate heat exchangers)) that perform the evaporator function as well are equally equivalent to the present invention. Can benefit from.

  Furthermore, although the liquid trap 38 is shown in the simplest configuration, other configurations (such as multiple u-shaped segments coupled together, local flow impedance, etc.) are possible.

  Another embodiment 100 shown in FIG. 3 has a plurality of continuous u-shaped traps 102 upstream of the portion 104 leading to the inlet manifold 34. Each of the liquid traps 102 can collect a small amount of liquid refrigerant, increasing the speed of the vapor phase and promoting a uniform condition at the inlet of the inlet manifold 34.

  Another refrigerant system embodiment 110 is shown in FIG. In this embodiment, the compressor 112 sends the compressed refrigerant to the condenser 114. Line 116 branches from main refrigerant flow line 126 and extends through economizer expansion device 118. The liquid trap 120 adjusts the refrigerant flowing through the inlet 122 to the economizer heat exchanger 124. The liquid trap 120 provides the same function and operates as the embodiment of FIGS. It should be understood that the economizer heat exchanger 124 is structured to have adjacent channels so that heat exchange is performed between the refrigerant in the branch line 116 and the refrigerant in the mainstream line 126. The main flow line 126 sends the refrigerant to the outlet 128 and further passes through the main expansion device 130 to the evaporator 132. The present invention can utilize liquid traps in both the economizer heat exchanger 124 and the evaporator 132. The refrigerant returns from the evaporator 132 to the compressor 112. A line 134 downstream of the economizer heat exchanger 124 returns the branched refrigerant to an intermediate compression point in the compressor 112.

  It should be pointed out that although all inlet manifolds are shown in a horizontal configuration, the phenomenon of non-uniform distribution becomes more pronounced in a vertical arrangement. In such a situation, the advantages of the present invention are even more pronounced.

  While preferred embodiments of the present invention have been disclosed, those skilled in the art will appreciate that several modifications can be made without departing from the scope of the present invention. For this reason, the claims should be studied to determine the scope and content of the invention.

Sectional drawing of the evaporator incorporating this invention. FIG. 2 shows the evaporator of FIG. 1 in different flow states. The figure which shows another Example. The figure which shows another Example.

Claims (15)

A compressor for sending the compressed refrigerant to the condenser;
Refrigerant flowing from the condenser to the expansion device, and further flowing from the expansion device to the evaporator;
A line connecting the expansion device and the evaporator;
With
The evaporator has an inlet manifold, an outlet manifold, a plurality of channels that receive refrigerant from the inlet manifold and route refrigerant to the outlet manifold, and fins disposed between the channels,
A refrigerant system, wherein the line is provided with a liquid trap for collecting liquid separated from the vapor refrigerant flowing from the expansion device to the evaporator.   The refrigerant system of claim 1, wherein the liquid trap extends vertically below the inlet manifold.   The refrigerant system according to claim 1, wherein the liquid trap is formed by a generally u-shaped portion extending below the line.   The refrigerant system of claim 1, wherein the liquid trap is located within 5 inches of the inlet manifold.   The refrigerant system is further provided with an economizer circuit, the economizer circuit having an economizer heat exchanger, wherein the economizer heat exchanger connects a mainstream line to the economizer heat exchanger through an economizer expansion device. A branch line leading to an intermediate compression point of the compressor downstream of the economizer heat exchanger, and a liquid trap for collecting liquid separated from the vapor refrigerant flowing from the economizer expansion device to the economizer heat exchanger. The refrigerant system according to claim 1.   The refrigerant system according to claim 1, wherein the liquid trap includes a plurality of u-shaped liquid trap portions arranged in series and spaced apart from each other. Providing an evaporator having a plurality of tubes, the plurality of tubes receiving refrigerant from an inlet manifold, sending the refrigerant to an outlet manifold, and further sending the refrigerant from the outlet manifold to the compressor; Providing an evaporator, wherein the refrigerant is sent to a condenser and the refrigerant flows from the condenser to the expansion device and then returns to the evaporator;
Providing a fluid line connecting the expansion device to the evaporator, wherein the fluid line is provided with a fluid trap for capturing a liquid separated from vapor refrigerant;
Passing the refrigerant through the refrigerant system such that a liquid trap self adjusts the speed of the refrigerant as the liquid separates from the vapor refrigerant to deliver the refrigerant to the inlet manifold in a very uniform state. When,
A method of operating a refrigerant system, comprising: The refrigerant system further includes an economizer circuit, the economizer circuit includes an economizer heat exchanger, branches the refrigerant, and sends the branched refrigerant to the economizer heat exchanger via an economizer expansion device. The economizer circuit has a liquid trap provided to capture liquid separated from steam flowing from the economizer expansion device to the economizer heat exchanger,
In order to send the refrigerant to the economizer heat exchanger in a very uniform state, as the liquid is separated from the vapor refrigerant, the liquid trap passes through the economizer expansion device so as to self-adjust the refrigerant speed. The method of claim 7, further comprising sending a refrigerant to the economizer heat exchanger. A fluid line leading to the inlet manifold;
A liquid trap provided in the fluid line;
A heat exchanger having a plurality of channels for receiving fluid from the inlet manifold;
A heat exchanger and a fluid line system.   The heat exchanger and fluid line system according to claim 9, wherein the heat exchanger is an evaporator for a refrigerant system.   The heat exchanger and fluid line system according to claim 9, wherein the heat exchanger is an economizer heat exchanger for a refrigerant system.   The heat exchanger and fluid line system of claim 9, wherein the liquid trap extends vertically below the inlet manifold.   The heat exchanger and fluid line system of claim 9, wherein the liquid trap is generally formed by a u-shaped portion of the line that extends downward.   The heat exchanger and fluid line system of claim 9, wherein the liquid trap is located within 5 inches of the inlet manifold.   The heat exchanger and fluid line system according to claim 9, wherein the liquid trap is formed by a plurality of u-shaped structures arranged in series and spaced apart from each other.

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