DE10331518A1 - Heat exchanger for cooling air - Google Patents

Abstract

In a heat exchanger (13) for cooling air, a pipe (131, 231) has a streamlined cross section so that air flows along an outer surface of the pipe (131, 231) without stagnating. Therefore, moisture is less likely to adhere to the outer surface of the tube (131, 231). Accordingly, the formation of frost is restricted.

Description

The present invention relates on a heat exchanger for cooling of air. More specifically, the present invention relates to one Vaporizer for a refrigeration apparatus and a freezer.

According to an evaporator for a refrigeration apparatus, which in JP-A-2002-115934 is disclosed, tubes with substantially elliptically shaped cross sections are arranged such that longitudinal axes of the cross sections are parallel to an air flow direction. There are no outer fins between the tubes and the outer surfaces of the tubes are generally exposed to the air. With this configuration or arrangement, intensive frost is generated on sections of the pipe downstream of the air flow and the formation of frost between the pipes, which leads to the blocking of air passages, is limited. Accordingly, an air flow resistance is reduced and the cooling capacity of the evaporator is improved.

It is a task of the present Invention, a heat exchanger for cooling of air that is capable of efficiency of heat exchange to improve.

It is another object of the present invention a heat exchanger for cooling of air that is capable of freezing to be limited to the same.

According to one aspect of the present Invention contains a heat exchanger for cooling of air pipes through which fluid flows. The pipes are arranged so that outer surfaces in general are exposed to the air. The pipes have streamlined cross sections, so that air along the outer surfaces of the Pipes flows.

Because the air is even around the Pipes around, without stagnation or congestion, and is less likely to that moisture, which leads to frost, on the outer surfaces of the Pipes stuck. That is why the adherence of frost particles and the growth of frost is limited to the pipes. Reduced accordingly air resistance, and the efficiency or effectiveness of the heat exchange improves.

According to another aspect of includes the present invention a heat exchanger a flat tube through which fluid flows. The flat tube is like this arranged that a longitudinal center line its cross section is parallel to an air flow direction, and that flat tube is in a direction perpendicular to the air flow direction curled.

The heat exchanger is not with outer fins Mistake. Therefore, when moist air condenses around the pipes flows, Intensity of moisture at a position of the pipe downstream of the air flow and growing or becomes frost. Because the frost is parallel to that in a direction Air flow direction grows, the airflow is not blocked. Accordingly, resistance is reduced one flowing around the pipes or passing airflow, which increases the effectiveness of the heat exchange improved.

Other tasks, characteristics and advantages of present invention will become apparent from the following detailed description more apparent with reference to the accompanying drawings accomplished being similar Components with similar reference numerals and where:

1 FIG. 2 is a schematic perspective view of a refrigerated vehicle or refrigerated vehicle according to the first embodiment of the present invention,

2 4 is a schematic diagram of a vapor compression refrigerant cycle system of the refrigerated vehicle according to the first embodiment of the present invention;

3 4 is a perspective view of a rear end of the refrigerated vehicle according to the first embodiment of the present invention;

4 4 is a perspective view of an evaporator of the vapor compression refrigerant cycle system according to the first embodiment of the present invention;

5 4 is a partial perspective view of a core portion of the evaporator for explaining flows of air and refrigerant according to the first embodiment of the present invention;

6A FIG. 3 is a cross-sectional view of a tube of the evaporator according to the first embodiment of the present invention;

6B Fig. 4 is an explanatory view of the pipes according to the first embodiment of the present invention,

6C an enlarged partial view of an air downstream portion of the tube shown in 6b is for explaining an air flow around the air downstream portion of the pipe according to the first embodiment of the present invention,

7 FIG. 4 is a partial cross-sectional view of the evaporator showing a pipe arrangement according to the first embodiment of the present invention;

8th FIG. 4 is a timing chart for showing operating timings of an engine, doors, and a defrost valve according to the first embodiment of the present invention;

9A and 9B Are cross sectional views of tubes of the evaporator according to the second embodiment of the present invention,

10 FIG. 3 is a cross sectional view of a tube of the evaporator according to the third embodiment of the present invention;

11 FIG. 4 is a cross-sectional view of a tube of the evaporator according to the fourth embodiment of the present invention;

12 a psychrometric table or 4 is an illustration according to the fifth embodiment of the present invention,

13 4 is a partial perspective view of a tube of the evaporator according to the sixth embodiment of the present invention,

14 4 is a partial cross-sectional view of the tubes according to the sixth embodiment of the present invention;

15A FIG. 4 is a cross-sectional view of a tube of the evaporator according to the seventh embodiment of the present invention;

15B Fig. 4 is an explanatory view of the pipe according to the seventh embodiment of the present invention; and

15C an enlarged partial view of an air downstream portion of the tube shown in 15B for explaining an air flow around the air downstream portion of the pipe according to the seventh embodiment of the present invention.

Embodiments of the Present Invention are hereinafter with reference to the drawings described.

A heat exchanger for cooling air according to the first embodiment is for an evaporator, for example 13 of a refrigerated vehicle 1 which transports goods or freight, such as frozen food (frozen food), while keeping or cooling them, as in 1 is shown.

The refrigerated vehicle 1 has a freezer 2 (or a refrigerated container) for storing the loads. The freezer container 2 has an opening 18 and doors 3 . 4 at its rear end. The loads are through the opening 18 carried in and out.

A vapor compression refrigerant cycle system 5 for cooling air in the freezer container 2 is at the front of the refrigerated vehicle 1 assembled. As in 2 shown contains the system 5 a compressor 6 , a capacitor 9 (or a condenser), an electric fan or an electric fan blower 10 , a collecting vessel 11 , a pressure reducing device 12 , and an evaporator 13 ,

The compressor 6 is powered by an engine 8th via an electromagnetic clutch 7 driven. The condenser 9 cools high temperature, high pressure refrigerant (ie: refrigerant with high temperature and high pressure) which from the compressor 1 flows. The fan blower 10 blows cooling air to the condenser 9 , The collecting vessel 11 separates that from the capacitor 9 escaping refrigerant into gaseous and liquid refrigerant and leaves the liquid refrigerant to the pressure reducing device 12 flow out. The excess refrigerant is in the collection container 11 stored as the liquid refrigerant.

The pressure reducing device 12 decompresses the liquid refrigerant. In the evaporator 13 evaporates the refrigerant from the pressure reducing device 12 by or under absorption of heat from in the freezer 2 air to be blown. The evaporator 13 will be described in more detail later.

In addition, there is an accumulator or a storage vessel 14 between a refrigerant outlet of the evaporator 13 and a refrigerant inlet of the compressor 6 intended. The storage vessel 14 separates the refrigerant from the evaporator 13 flows out into gaseous refrigerant and into liquid refrigerant. The gaseous refrigerant is in the compressor 6 sucked and the liquid refrigerant is in the storage vessel 14 collected.

A bypass line 15 is arranged to deliver high temperature refrigerant (hot gas) from the compressor 6 to the evaporator 13 initiate while the pressure reducing device 12 is circumvented. The bypass line 15 is with a defrost valve 16 Mistake. The defrost valve 16 is an electromagnetic valve. The defrost valve 16 allows the hot gas to flow through the bypass line 15 ,

A blower device 19 is at the bottom of the opening 18 outside the freezer 2 intended. The fan means 19 forms an air curtain to separate the inside of the freezer 2 from the outside when the doors 3 . 4 are open. The fan means 19 contains cross flow fan 20 . 21 , each horizontally at the bottom of the opening 18 are placed. In the cross flow fans 20 . 21 air flows within cross sections that are perpendicular to axes of multi-blade cylinder fans 20a . 21a (for example, roller fans) (see JIS B0132 No. 1017).

Next is the evaporator 13 in detail with reference to the 4 to 6C described. As in 4 shown contains the evaporator 13 a plurality of pipes 131 , through which refrigerant flows, and tanks 133 which at or on elongated or longitudinal ends of the tubes 131 are connected to with the pipes 131 to communicate. The pipes 131 build or form a core section for exchanging heat between the refrigerant and air.

It is noted that outer fins, which are generally connected to outer surfaces of pipes, are not between the pipes 131 are provided so that outer surfaces of the pipes 131 are generally exposed to the air. As in 6A is shown have the pipes 131 streamlined cross-sections to limit or limit the possibility that the pipes 131 flowing air flows from the pipes 131 detach or remove at their downstream airflow sections (see for example "Fluids Engineering", University of Tokyo Press). The streamlined shape is symmetrical with respect to a longitudinal center line CL of the cross section. Upstream sections (front sides) of the tubes 131 are slightly curved. Below are the terms "downstream" or "upstream" with respect to a direction (A1) from through the evaporator 13 flowing air.

In the embodiment, a teardrop shape (a wing shape) is used as the streamline shape. A dimension (thickness) of the pipe 131 in a direction perpendicular to the center line CL increases to a maximum value at or in a substantially middle position of the pipe 131 with respect to the airflow direction A1 and reduces to the airflow downstream position.

Each of the pipes 131 is with a plurality of refrigerant passages 132 educated. The refrigerant passages 132 are parallel and in line from the upstream sections to the downstream position of the pipe 131 aligned. In the embodiment, the tube is 131 produced or formed, for example, by extrusion and drawing of aluminum. Thus the refrigerant passages 132 simultaneously with the shaping of the pipe 131 educated.

As in 5 is shown are the pipes 131 arranged in rows in directions perpendicular to the air flow direction A1. Furthermore, as in 7 is shown are the pipes 131 arranged in a staggered configuration. A first grouping distance Tp1 of the tubes 131 an upstream row is larger than a second grouping pitch Tp2 of the pipes 131 a downstream row. Here, the distances Tp1 and Tp2 are distances between the center lines CL of the pipes 131 in the directions perpendicular to the air flow direction A1.

The pipes 131 are in the same row with the same tank 133 fluidly connected. With a view to a wide projection or a wide projection area, the refrigerant flows from the upstream air side to the downstream air flow side in the evaporator 13 as shown by arrows R1.

An electronic control unit will be described next. A control unit 22 contains a computer like a microcomputer. The control unit 22 is programmed to operate the vapor compression refrigerant cycle system 5 to control on the basis of signals from the following sensors or sensors and switches.

A temperature sensor 24 detects an inside temperature of the freezer 2 , The inside temperature is controlled manually using a temperature control device 25 fixed or determined. For example, the indoor temperature is set within a range between -10 ° C and -20 ° C.

A switch 26 the refrigeration apparatus is operated manually. The refrigerant switch 26 generates on and off signals of the vapor compression refrigerant circuit system 5 , An engine operating switch 27 produces signals in accordance with on and off states of motor B. A door switch 28 is on a periphery of the opening 18 arranged. The door switch 28 is switched on and off in accordance with the opening and closing of the doors 3 . 4 ,

Furthermore, the control unit controls 22 the electromagnetic clutch 7 who have favourited Fans 10 . 17 , the defrost valve 16 , the blower unit 19 and the same.

Next, the refrigeration operation of the vehicle 1 with reference to 8th described. While the vehicle is running, the compressor turns on 6 by engine power 8th through the electromagnetic clutch 7 driven. The fans 10 . 17 are operated. The vapor compression refrigerant circuit system is also 5 on or in operation. So this is through the evaporator 13 chilled air in the freezer 2 through the fan 17 blown in, causing the loads in the freezer 2 be cooled. At this time, or at the same time, is the defrost valve 16 closed so that the refrigerant is not through the bypass line 15 flows.

If the engine 8th the fan stops moving the cargo in or out 17 the cooling unit 130 ( 1 ) switched off. Then when the doors 3 . 4 are opened, the door switch 28 turned on so that the cross flow fan 20 . 21 start operating. The air curtain goes from the bottom to the top of the opening 18 trained to limit the entry of outside air.

At this time, or at the same time, the defrost valve 16 open. Due to the pressure gap (or pressure difference) between the outlet of the compressor 6 and the upstream portion of the evaporator 13 the hot gas flows into the evaporator 13 through the bypass line 15 , Therefore the ice melts on the evaporator 13 to water and flows outwards. If the doors 3 . 4 are closed, the door switch 28 turned off and the defrost valve 16 closed.

Next are advantages of embodiment described.

Because the pipes 131 have streamlined cross-sections, the air flows evenly along the outer surface of the tubes 131 without stagnation, as in 6C is shown. It limits the condensation or adhesion of moisture, which results in the formation of frost (ice), on the outer surfaces of the pipes 131 , So the growth or

the formation of frost on the pipes 131 and also the adherence of frost particles on the pipes 131 limited. In the evaporator 13 In the embodiment, the amount of frost is reduced to substantially one fifth compared to previous (known) evaporators.

Furthermore, the formation of frost on the downstream section of the pipes 131 limited as in 6C is shown. Because the moisture is not on the side surfaces of the pipes 131 on adheres, it is less likely that the air passages between the pipes 131 blocked by frost. Therefore the resistance of or against the air flow is not increased by the frost. Accordingly, the cooling capacity of the evaporator improves 13 ,

Because the pipes 131 the pipes are staggered 131 the downstream row is not arranged in thermal boundary layers through the pipes 131 the upstream row is generated. Therefore, the efficiency or effectiveness of the heat exchange of the evaporator improves 13 ,

In the second embodiment, a cross section of the refrigerant flow region is the most downstream refrigerant passage 132 (that is, the refrigerant passage 132 which is the last to be arranged in the air flow direction) larger than that of the most upstream refrigerant passage 132 (that is, the refrigerant passage 132 which is arranged first with respect to the air flow direction), as in 9A is shown.

Because the pipes 131 which have streamlined cross sections is the adhesion of moisture to the pipes 131 reduced. However, it is difficult to completely prevent the formation of frost. Although it is a small amount, frost forms on the downstream sections of the pipes 131 ,

Because the most downstream refrigerant passage 132 the flow area larger than that of the upstream refrigerant passage 132 has, a flow rate of the hot gas at the downstream portion of the pipes increases 131 , Therefore, it (the downstream section) is easily defrosted during the defrosting mode even if the downstream section of the pipes 131 is frozen. The refrigerant passage 132 can have substantially rectangular shaped cross sections, as in 9B is shown.

In the third embodiment, the cross sections of the refrigerant flow areas are in accordance with an outer dimension (size W) of the pipes 131 changed as in 10 is shown. In this embodiment, too, the evaporator 13 Advantages similar to those of the first embodiment.

In the fourth embodiment, the tubes have 131 streamlined cross-sections that are asymmetrical with respect to the center line CL, as in 11 is shown. In this embodiment, too, the evaporator 13 Advantages similar to those of the first embodiment.

In the fifth embodiment, the tubes are 131 with a deicing agent to limit the adherence of moisture and frost particles to the outer surfaces of the pipes 131 coated. For example, the deicing agent contains a super (water) repellent coating and a material with water repellent properties such as Teflon.

Referring to 12 is the temperature of the freezer container 20 for example, -20 ° C (T1). If the doors 3 . 4 open, outside air (e.g. 35 ° C, 60% relative humidity) enters the freezer 2 on. The air is quickly cooled to below freezing and the indoor air becomes oversaturated. For example, below the temperature T2, which is lower than the freezing point, a small amount of steam (M1) can exist as moisture (water vapor) in the indoor air.

Therefore, moisture (M2) in the outside air is supersaturated steam and is sublimed into sublimed particles or particles without liquefaction. The sublimed particles adhere to the outer surfaces of the pipes 131 on and grow or form frost. In the embodiment, the tubes are 131 coated with the deicing agent. Therefore it is less likely that the sublimed particles (frost particles) on the pipes 131 adhere. Accordingly, the growth of frost or its formation on the pipes 131 limited.

In the sixth embodiment, the evaporator contains 13 flat tubes 231 and tanks 233 , as in 13 is shown. The tanks 233 are at the ends of the pipes 231 connected. The pipes 231 are with a plurality of refrigerant passages 232 formed and manufactured by extrusion and drawing, similar to the first embodiment.

The pipes 231 are arranged such that the center lines CL of the cross sections are parallel to the air flow direction A1. Furthermore, the pipes 231 as it is in the 13 and 14 is shown, corrugated perpendicular to the air flow direction A1.

Straight sections 231b of the pipes 231 are by turning sections 231 connected. The pipes 231 are arranged so that the straight sections 231b are staggered, as in 14 is shown. For example, a grouping distance Tp4 of the straight sections 231b of the downstream pipe 231 smaller than a grouping distance Tp3 of the straight sections 231b of the upstream pipe 231 , Alternatively, the distances Tp3 and Tp4 can be the same.

In this embodiment, too, the tubes have 231 streamlined cross sections, similar to the first to fourth embodiments. The pipes accordingly 231 Advantages similar to those of the first to fourth embodiments.

In the seventh embodiment, the tube 231 essentially an elliptical cross section. The straight sections 231b of the pipes 231 contain substantially flat surfaces that are parallel to the airflow direction A1, as in FIGS 15A and 15B is shown. The upstream sides and the downstream sides of the straight sections 231b which the flat surfaces connect, are slightly curved. As in 15C is an air stagnation area at the air downstream portion of the tube 231 educated. The airflow around the pipe 231 around separates from the pipe 231 or detaches from it and swirls on the downstream section of the tube 231 as shown by arrows A2.

When moist air around the pipe 231 flows or happens, moisture adheres to the downstream portion of the tube 231 on and becomes or grows to frost on the same. Because the pipe 231 is not provided with the outer fins, the frost only forms on the downstream section of the pipe 231 in the direction parallel to the air flow direction A1. The frost is less likely to be on the straight sections 231b is formed to block the air passages between them. Therefore, the resistance of the air flow decreases and therefore the cooling capacity of the evaporator improves 13 ,

As a modification, the refrigerant passages 132 . 232 have any (any) cross-sectional shape except circular and square. The grouping sections Tp1, Tp2, Tp3, Tp4 of the pipes 131 and the straight sections 231b can be changed. Likewise, the number of rows of tubes 131 not limited.

The present invention can be based on a refrigeration apparatus can be used for other purposes. For example, the present invention for one Cold storage be used. Furthermore, the present invention can be applied to a heat exchanger be applied, the air with tactile or free or unbound Heat cools. As well can the pipes with the streamlined Cross sections for another heat exchanger be used for heat exchange between fluid and air, which is different from a heat exchanger for cooling of air.

The present invention should not to the disclosed embodiments limited but can be implemented or executed in another way, without departing from the spirit of the invention.

In summary, it has one heat exchanger 13 for cooling air, a pipe 131 . 231 a streamlined cross section, allowing air to flow along an outer surface of the tube 131 . 231 flows without stagnating. Therefore, moisture is less likely to be on the outer surface of the pipe 131 . 231 adheres. Accordingly, the formation of frost is restricted.

Claims (14)

Heat exchanger ( 13 ) for cooling air, including pipes ( 131 . 231 ) through which fluid flows, the tubes ( 131 . 231 ) are arranged such that outer surfaces of the pipes ( 131 . 231 ) are generally exposed to the air, with the pipes ( 131 . 231 ) have streamlined cross-sections so that air along the outer surfaces of the pipes ( 131 . 231 ) flows. Heat exchanger according to claim 1, wherein the tubes ( 131 ) are arranged in a row in a staggered configuration. A heat exchanger according to claim 1 or 2, wherein each of the tubes ( 131 . 231 ) with a plurality of passages ( 132 . 232 ) through which the fluid flows, a most downstream passage with respect to an air flow direction (A1) having a cross section of a flow area that is larger than that of a most upstream passage. heat exchangers according to one of claims 1 to 3, the streamlined Cross section symmetrical with respect its longitudinal center line (CL) is. Heat exchanger according to one of claims 1 to 4, wherein the tubes ( 231 ) are corrugated in directions perpendicular to an air flow direction (A1). Heat exchanger for cooling air, comprising a flat tube ( 231 ) through which fluid flows, the tube ( 231 ) has an outer surface which is generally exposed to the air, the tube ( 231 ) is arranged such that a longitudinal center line (CL) of its cross section is parallel to an air flow direction (A1) and is corrugated in a direction perpendicular to the air flow direction (A1). A heat exchanger according to claim 6, wherein the tube ( 231 ) has an essentially elliptically shaped cross section. A heat exchanger according to claim 6, wherein the tube ( 231 ) has a streamlined cross-section so that air flows along the outer surface. heat exchangers according to claim 8, the streamlined Cross section symmetrical with respect the longitudinal center line (CL) of the cross section. Heat exchanger according to one of claims 6, 8 or 9, wherein a size of the cross section of the tube ( 231 ) is maximal in a direction perpendicular to the air flow direction (A1) at essentially an air flow position and to a position of the tube downstream of the air flow ( 231 ) reduced. Heat exchanger according to one of claims 6 to 10, wherein the tube ( 231 ) with a majority is formed of passages through which fluid flows, a most downstream passage with respect to the airflow direction (A1) having a cross section of a flow area larger than that of a most upstream passage. Heat exchanger according to one of claims 6 to 11, the further tank ( 233 ) at the ends of the pipes ( 232 ) are connected. Heat exchanger according to one of claims 1 to 12, wherein the tube ( 131 . 231 ) is coated with a deicing agent that limits the adherence of frost particles. Heat exchanger according to one of claims 1 to 13, wherein the tube ( 131 . 231 ) is coated with a water repellent.