WO2018008129A1

WO2018008129A1 - Refrigeration cycle device

Info

Publication number: WO2018008129A1
Application number: PCT/JP2016/070168
Authority: WO
Inventors: 伊東　大輔; 佑太小宮
Original assignee: 三菱電機株式会社
Priority date: 2016-07-07
Filing date: 2016-07-07
Publication date: 2018-01-11

Abstract

A refrigeration cycle device according to the present invention is configured such that the distance L from the upwind-side end of the heat transfer tubes disposed on a first fin among a plurality of heat transfer tubes to the front edge of the first fin is within the range of 6.5 mm ≤ L ≤ 8.5 mm.

Description

Refrigeration cycle equipment

The present invention relates to a refrigeration cycle apparatus such as a refrigeration air conditioner used for applications such as refrigeration, refrigeration, and air conditioning.

For example, refrigeration and air conditioning equipment used for refrigeration, refrigeration, air conditioning, etc. at distribution bases such as refrigeration factories, food processing factories, agricultural and marine product processing factories, markets, distribution warehouses, and retail stores such as supermarkets and convenience stores. A refrigeration cycle apparatus is used as a refrigeration system. In recent years, a refrigeration cycle apparatus has been developed that uses a natural refrigerant (substance that naturally exists in nature, such as carbon dioxide (CO ₂ )), which has a low environmental load as a refrigerant (see, for example, Patent Document 1).

In addition, as a device for performing cooling at a low temperature of minus several tens of degrees, a dual refrigeration cycle apparatus having a high refrigeration cycle for circulating a high temperature side refrigerant and a low refrigeration cycle for circulating a low temperature side refrigerant has been proposed. ing. In such a binary refrigeration cycle apparatus, a low-side refrigeration cycle and a high-side refrigeration cycle are connected by a cascade condenser configured to exchange heat between the low-side condenser and the high-side evaporator. Yes.

However, in a refrigeration apparatus having a relatively low evaporation temperature used for refrigeration or refrigeration, the efficiency is remarkably reduced under high outside air temperature conditions, and the discharge gas temperature becomes very high as the evaporation temperature decreases. For this reason, the application of carbon dioxide refrigerant has not progressed. Therefore, a binary refrigeration cycle apparatus has been proposed in which carbon dioxide (carbon dioxide) is used for the low-side refrigerant and other refrigerant other than carbon dioxide is used for the high-side refrigerant (see, for example, Patent Document 2). .

JP 2010-60267 A Japanese Patent No. 3606043

In the binary refrigeration cycle apparatus described in Patent Document 2, an auxiliary condenser is installed in front of the cascade condenser in the low-side refrigeration cycle, and the refrigerant discharged from the low-side compressor is cooled by the auxiliary condenser. To improve driving efficiency.

However, when a conventional evaporator (tube diameter: 9.52 mm) is used in the low-source side refrigeration cycle, frost is likely to be formed because the interval between adjacent heat transfer tubes is narrow, and the evaporation temperature is reduced with a decrease in heat exchange efficiency due to frost formation. Decreases and the driving efficiency deteriorates. In other words, when frost begins to form on the evaporator, the frost hinders the flow of air and heat exchange between the air and the refrigerant cannot be performed, thereby lowering the evaporation temperature, which accelerates frost formation, and the refrigeration capacity rapidly increases. It will decline.

Also, since the amount of frost on the evaporator increases due to a decrease in the evaporation temperature, the air-conditioning operation time is shortened, and the average refrigeration capacity with respect to the operation time is significantly reduced. In particular, carbon dioxide has a smaller refrigeration effect than conventional refrigerants such as R32 and R410A. Therefore, it is necessary to increase the heat exchange area, but this increases the size and cost of the apparatus.

In order to improve the refrigerating capacity by this frost formation, it is considered to use an evaporator using a heat transfer tube having an outer diameter of 7 mm or less. However, the use of the refrigeration cycle apparatus, the number of heat transfer tube passes, the number of heat transfer tube stages, the flow rate of the refrigerant, etc. need to be considered together, and an evaporator using a heat transfer tube having an outer diameter of 7 mm or less may be simply used. That doesn't mean that. For example, when considering a case where an evaporator having a one-pass configuration is used as an evaporator of a large refrigerator having a large refrigerant flow rate and approximately the same number of heat transfer tube stages and passes, the pressure of the refrigerant for the one-pass configuration is considered. The loss increases and the evaporation temperature becomes lower than before. Therefore, it becomes easier for frost to arrive, and the operation efficiency is deteriorated.

Also, the frost formation is not determined only by the interval between the heat transfer tubes, but the relationship between the fin pitch, which is the distance between the fins, and the step pitch indicating the interval between the heat transfer tubes is also affected. Therefore, even if only the interval between the heat transfer tubes is improved, it does not solve the fundamental problem of frost formation.

The present invention has been made against the background of the above problems, and an object of the present invention is to obtain a refrigeration cycle apparatus that avoids blockage of an air passage due to frost formation and prevents a reduction in refrigeration capacity.

A refrigeration cycle apparatus according to the present invention is a refrigeration cycle apparatus including a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are connected in order, and the evaporator is along an air flow direction. A plurality of fins arranged in at least one row and a plurality of heat transfer tubes arranged to intersect with each of the plurality of fins, the plurality of fins being the most upstream in the air flow direction. The distance L from the windward end of the heat transfer tube in the first fin to the front edge of the first fin among the plurality of heat transfer tubes is 6.5 mm ≦ L ≦ 8.5 mm.

In the refrigeration cycle apparatus according to the present invention, the distance L from the windward end of the heat transfer tube to the front edge of the first fin in the first fin arranged at the most upstream among the plurality of heat transfer tubes is 6.5 mm ≦ Since L ≦ 8.5 mm, the ratio of the tube diameter of the heat transfer tube to the fin width can be within a range of 23% ≦ heat transfer tube diameter / fin width × 100 ≦ 42%, which can improve the cooling capacity reduction. .

It is a schematic block diagram which shows an example of the refrigerant circuit structure of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the specification of the low former side evaporator of the refrigerating-cycle apparatus which concerns on Embodiment 1 of this invention, (a) is the side view seen from the side, (b) is the front view seen from the front , Respectively. It is a graph showing the relationship between the distance L and average refrigeration capacity in an evaporator. It is a graph showing the relationship between (Fp−tf) × L and average refrigeration capacity in an evaporator. It is a graph showing the relationship between the ratio of the heat exchanger tube with respect to the fin width in an evaporator, and an average refrigerating capacity. It is a graph showing the relationship between the area Aj in an evaporator, and an average refrigerating capacity. It is a graph showing the relationship between the volume Vj and average refrigerating capacity in an evaporator. It is a schematic block diagram which shows an example of the refrigerant circuit structure of the refrigerating-cycle apparatus which concerns on Embodiment 2 of this invention.

Hereinafter, a refrigeration cycle apparatus according to the present invention will be described with reference to the drawings.
In addition, the structure, operation | movement, etc. which are demonstrated below are only examples, and the refrigeration cycle apparatus according to the present invention is not limited to such a structure, operation, or the like. Moreover, in each figure, the same code | symbol is attached | subjected to the same or similar thing, or attaching | subjecting code | symbol is abbreviate | omitted. Further, the illustration of the fine structure is simplified or omitted as appropriate. In addition, overlapping or similar descriptions are appropriately simplified or omitted.

In the following, the case where the refrigeration cycle apparatus according to the present invention is applied to a refrigeration apparatus is described. However, the present invention is not limited to such a case. For example, other refrigeration cycles such as a refrigeration apparatus and an air conditioner It may be applied to the device.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram showing an example of a refrigerant circuit configuration of a refrigeration cycle apparatus (hereinafter referred to as refrigeration cycle apparatus 100A) according to Embodiment 1 of the present invention. A refrigeration cycle apparatus 100A will be described with reference to FIG.

As shown in FIG. 1, the refrigeration cycle apparatus 100A has two refrigerant circuits (a low-side refrigeration cycle 10 and a high-side refrigeration cycle 20), and is configured to circulate refrigerant independently of each other. . In the refrigeration cycle apparatus 100A, in order to make the two refrigerant circuits in a multistage configuration, the high-side evaporator 24 and the low-side condenser 12 are coupled so as to be able to exchange heat between the refrigerants passing therethrough. The refrigerant-to-refrigerant heat exchanger (cascade condenser) 16 is configured.

Note that the level of temperature, pressure, etc. is not particularly determined in relation to absolute values, but is relatively determined in terms of the state and operation of the system, apparatus, etc.

<Configuration of low-source side refrigeration cycle 10>
The low-side refrigeration cycle 10 includes a low-side compressor 11, an auxiliary radiator 15, a low-side condenser 12, a low-side expansion valve 13, and a low-side evaporator 14 in this order as refrigerant piping. 18 is connected by piping.
The low-source side refrigeration cycle 10 corresponds to the “first refrigeration cycle” of the present invention.
The low-source compressor 11 corresponds to the “first compressor” of the present invention.
The low-side condenser 12 corresponds to the “first condenser” of the present invention.
The low-side expansion valve 13 corresponds to the “first expansion valve” of the present invention.
The low-side evaporator 14 corresponds to the “first evaporator” of the present invention.
The auxiliary radiator 15 corresponds to the “heat radiator” of the present invention.

The low-side compressor 11 sucks the refrigerant flowing through the low-side refrigeration cycle 10, compresses the refrigerant, and discharges it in a high temperature and high pressure state. For example, the low-side compressor 11 may be configured by a compressor of a type that can control the rotation speed by an inverter circuit or the like and adjust the discharge amount of the low-side refrigerant.

The auxiliary radiator 15 functions as a gas cooler, for example, and cools the gas refrigerant discharged from the low-side compressor 11 by heat exchange with, for example, outdoor air (outside air), water, brine, or the like as a heat source. . In this embodiment, the auxiliary radiator 15 will be described assuming that the heat source is the outside air and heat exchange is performed between the outside air and the refrigerant.

The low-source side condenser 12 exchanges heat between the refrigerant that has passed through the auxiliary radiator 15 and the refrigerant that flows through the high-side refrigeration cycle 20, and condenses the refrigerant that has passed through the auxiliary radiator 15 to form a liquid refrigerant (Condensed liquid). For example, here, a heat transfer tube or the like through which the refrigerant flowing through the low-source side refrigeration cycle 10 passes in the inter-refrigerant heat exchanger 16 serves as the low-source side condenser 12, and heat with the refrigerant flowing through the high-source side refrigeration cycle 20. Exchange shall be performed.

The low-side expansion valve 13 functions as a decompression device, a throttling device, and the like, and decompresses and expands the refrigerant flowing through the low-side refrigeration cycle 10. The low-source side expansion valve 13 may be composed of, for example, a flow rate control means such as an electronic expansion valve, a refrigerant flow rate adjustment means such as a capillary tube, a temperature-sensitive expansion valve, and the like.

The low element side evaporator 14 evaporates the refrigerant flowing through the low element side refrigeration cycle 10 by heat exchange with a cooling target, for example, and converts it into a gaseous refrigerant (evaporates and gasifies). The object to be cooled is cooled directly or indirectly by heat exchange with the refrigerant. When the object to be cooled is air, the low-side evaporator 14 is provided with a fan for promoting heat exchange.

<Configuration of the high-side refrigeration cycle 20>
The high-side refrigeration cycle 20 includes a high-side compressor 21, a high-side condenser 22, a high-side expansion valve 23, and a high-side evaporator 24 that are connected by a refrigerant pipe 28 in order. It is configured.
The high-side refrigeration cycle 20 corresponds to the “second refrigeration cycle” of the present invention.
The high-end compressor 21 corresponds to the “second compressor” of the present invention.
The high-side condenser 22 corresponds to the “second condenser” of the present invention.
The high-side expansion valve 23 corresponds to the “second expansion valve” of the present invention.
The high-side evaporator 24 corresponds to the “second evaporator” of the present invention.

The high-side compressor 21 sucks the refrigerant flowing through the high-side refrigeration cycle 20, compresses the refrigerant, and discharges it in a high temperature and high pressure state. The high-end compressor 21 may also be configured by a compressor of a type that can control the number of revolutions by an inverter circuit or the like and adjust the discharge amount of the high-end refrigerant.

The high-side condenser 22 performs, for example, heat exchange between outside air, water, brine, and the like and the refrigerant flowing through the high-side refrigeration cycle 20 to condense and liquefy the refrigerant. In this embodiment, the high-side condenser 22 will be described assuming that the heat source is the outside air and heat exchange is performed between the outside air and the refrigerant. Therefore, the high-side condenser 22 includes a high-side condenser fan 25 for promoting heat exchange. The high-side condenser fan 25 may be constituted by a blower of a type that can adjust the air volume, for example.

The high-side expansion valve 23 functions as a decompression device, a throttling device, and the like, and decompresses and expands the refrigerant flowing through the high-side refrigeration cycle 20. The high-side expansion valve 23 may be constituted by a flow rate control means such as an electronic expansion valve, or a refrigerant flow rate adjusting means such as a capillary tube or a temperature-sensitive expansion valve, for example, similarly to the low-side expansion valve 13.

The high-side evaporator 24 evaporates the refrigerant flowing through the high-side refrigeration cycle 20 by heat exchange. For example, here, the heat transfer tube or the like through which the refrigerant flowing through the high-side refrigeration cycle 20 passes in the inter-refrigerant heat exchanger 16 serves as the high-side evaporator 24, and heat with the refrigerant flowing through the low-side refrigeration cycle 10. Exchange shall be performed. In addition, you may comprise the heat exchanger 16 between refrigerant | coolants with a plate-type heat exchanger.

The inter-refrigerant heat exchanger 16 is a cascade heat exchanger that has the functions of the high-end evaporator 24 and the low-end condenser 12 and enables heat exchange between the high-end refrigerant and the low-end refrigerant. . The refrigeration cycle apparatus 100A has a multi-stage configuration of the high-source-side refrigeration cycle 20 and the low-source-side refrigeration cycle 10 via the inter-refrigerant heat exchanger 16, and performs heat exchange between the refrigerants. The circuit is configured to be linked.

<Refrigerant used for refrigeration cycle apparatus 100A>
In the refrigeration cycle apparatus 100A having such a configuration, a part of the low-end refrigeration cycle 10 (for example, the low-end evaporator 14) is included in an indoor load device such as a supermarket showcase. Sometimes. In such a case, for example, when the low-side refrigeration cycle 10 is opened by changing the connection of piping by changing the showcase or the like, the possibility of refrigerant leakage increases. Therefore, in the refrigeration cycle apparatus 100A, carbon dioxide that has a small influence on global warming is used as a low-source refrigerant that circulates the low-source refrigeration cycle 10 in consideration of refrigerant leakage. Note that a mixed refrigerant containing carbon dioxide may be used.

On the other hand, in the high-side refrigeration cycle 20, there is no opening of the refrigerant circuit due to rearrangement of the showcase. Therefore, in the refrigeration cycle apparatus 100A, for example, HFO (hydro-fluoro-olefin) refrigerant (HFO1234yf, HFO1234ze, etc.), HC refrigerant, carbon dioxide, ammonia, water, etc. are used as the high-side refrigerant circulating through the high-side refrigeration cycle 20. A refrigerant having a small influence on global warming such as can be used. Alternatively, since the high-end refrigeration cycle 20 is not opened, for example, an HFC refrigerant having a high global warming potential can be used from the viewpoint of cost and performance. In the refrigeration cycle apparatus 100A, a case where R32 is used as a high-side refrigerant that circulates the high-side refrigeration cycle 20 will be described as an example.

For example, the carbon dioxide refrigerant used in the low-source side refrigeration cycle 10 has a smaller refrigeration effect than R32 used in the high-source side refrigeration cycle 20. Therefore, a large compressor power is required, and the operation efficiency is lower than R32 used in the high-source side refrigeration cycle 20. Therefore, the power consumption on the low-source side refrigeration cycle 10 side is reduced by increasing the capacity of the high-source side compressor 21 and decreasing the low-source side high pressure. And even if the power consumption on the high refrigeration cycle 20 side using R32 having high operation efficiency increases, the operation efficiency of the entire dual refrigeration apparatus is increased by increasing the work amount on the high refrigeration cycle 20 side. Improve.

Thus, in the refrigeration cycle apparatus 100A, the operating efficiency of the entire apparatus can be optimized by increasing the power consumption ratio of the high-efficiency high-side refrigeration cycle 20.

<Operation of the refrigeration cycle apparatus 100A>
The operation and the like of each component device of the refrigeration cycle apparatus 100A provided with the above-described binary refrigeration cycle will be described based on the flow of refrigerant circulating through each refrigerant circuit.

First, the operation of the high-side refrigeration cycle 20 will be described.
The high-end compressor 21 sucks in the high-end refrigerant (R32), compresses it, and discharges it in a high temperature and high pressure state. The high-side refrigerant discharged from the high-side compressor 21 flows into the high-side condenser 22. The high-side condenser 22 performs heat exchange between the outside air supplied from the high-side condenser fan 25 and the high-side refrigerant, and condenses and liquefies the high-side refrigerant.

The high-side refrigerant condensed and liquefied by the high-side condenser 22 passes through the high-side expansion valve 23. The high-side expansion valve 23 depressurizes the condensed high-side refrigerant. The high-side refrigerant whose pressure is reduced by the high-side expansion valve 23 flows into the high-side evaporator 24. The high-side evaporator 24 evaporates and gasifies the high-side refrigerant by heat exchange with the low-side refrigerant that passes through the low-side condenser 12. The high-side compressor 21 sucks the high-side refrigerant evaporated and gasified by the high-side evaporator 24.

Next, the operation of the low-source side refrigeration cycle 10 will be described.
The low-side compressor 11 sucks low-pressure side refrigerant (carbon dioxide), compresses it, and discharges it in a high temperature and high pressure state. The low-side refrigerant discharged from the low-side compressor 11 is cooled by the auxiliary radiator 15 and flows into the low-side condenser 12. The low-side condenser 12 condenses and liquefies the low-side refrigerant by heat exchange with the high-side refrigerant passing through the high-side evaporator 24.

The low-side refrigerant condensed and liquefied by the low-side condenser 12 passes through the low-side expansion valve 13. The low-side expansion valve 13 depressurizes the condensed low-side refrigerant. The low-side refrigerant whose pressure is reduced by the low-side expansion valve 13 flows into the low-side evaporator 14. The low-side evaporator 14 evaporates the low-side refrigerant by heat exchange with the object to be cooled. The low-side compressor 11 sucks the low-side refrigerant that has been vaporized and gasified by the low-side evaporator 14.

<Operating efficiency of refrigerant>
Next, the operation efficiency of the refrigerant will be specifically described.
If the theoretical COP, which is an index of operation efficiency, is high, a large latent heat of evaporation can be obtained with a small amount of compression power, and the refrigerant becomes highly efficient. The theoretical COP is obtained by (the enthalpy difference of the evaporator / the enthalpy difference of the compression process).

For example, the operating state of a general single-stage cycle refrigeration cycle apparatus operating at an outside air temperature of 32 ° C., that is, an evaporation temperature of −40 ° C., a condensation temperature of 40 ° C. (supercritical carbon dioxide has a high pressure of 8.8 MPa), inhalation The theoretical COP of each refrigerant under the conditions of superheating degree 5 ° C. and liquid supercooling degree 5 ° C. is as follows.

"1.25" for carbon dioxide, "1.98" for R32, "1.84" for HFO1234yf, "1.97" for HFO1234ze, "1.99" for propane, "2.05" for isobutane, ammonia Is “2.07”, R134a is “2.01”, R410A is “1.91”, R407C is “1.98”, and R404A is “1.76”.
It can be seen that carbon dioxide is a low-efficiency refrigerant having a lower COP than other HFO refrigerants, HFC refrigerants, HC refrigerants, and the like.

As described above, in the refrigeration cycle apparatus 100A, carbon dioxide is used for the low-source side refrigeration cycle 10. Since carbon dioxide has a higher refrigerant operating pressure than HFC refrigerants such as R404A or R410A, it is necessary to use new parts with a high design pressure. Therefore, in the refrigeration cycle apparatus 100A, in order to reduce costs so that parts of the refrigeration cycle apparatus using the conventional HFC refrigerant can be diverted, the design pressure of the low-source side refrigeration cycle 10 is set to the design pressure equivalent to the HFC refrigerant, for example, The pressure was reduced to 4.15 MPa equivalent to R410A.

The refrigeration cycle apparatus 100A can be widely applied to refrigeration or refrigeration equipment such as showcases, commercial refrigeration refrigerators, vending machines, etc. that require non-fluorocarbon refrigerants, reduction of CFC refrigerants, and energy saving of equipment. it can.

<Specification of low-side evaporator 14>
FIG. 2 is a schematic view showing the specifications of the low-side evaporator 14 of the refrigeration cycle apparatus 100A, where (a) shows a side view seen from the side, and (b) shows a front view seen from the front. ing. FIG. 3 is a graph showing the relationship between the distance L and the average refrigeration capacity in the evaporator. Based on FIG.2 and FIG.3, the specification 1 of the low former side evaporator 14 is demonstrated.

In FIG. 2, “tf” is the fin thickness, “Fp” is the fin pitch, “Dp” is the step pitch, “Rp” is the row pitch, “Fw” is the fin width, “do” "Indicates the diameter of each heat transfer tube. In FIG. 3, the vertical axis represents the average refrigeration capacity, and the horizontal axis represents the distance L. Furthermore, the average refrigeration capacity is expressed as a ratio with R410A used in the current refrigeration cycle apparatus.

The fin thickness tf is the thickness of each of the plurality of fins 32 having the same configuration.
The fin pitch Fp is an interval between the fins 32 adjacent in parallel among the plurality of fins 32.
The step pitch Dp is the interval between the heat transfer tubes 31 adjacent in the step direction among the plurality of heat transfer tubes 31.
The row pitch Rp is the distance between the heat transfer tubes 31 adjacent to each other in the air flow direction among the plurality of heat transfer tubes 31.
The fin width Fw is the distance in the short direction of each of the plurality of fins 32 having the same configuration.
The tube diameter do is the diameter of each of the plurality of heat transfer tubes 31 having the same configuration.

In the refrigeration cycle apparatus 100A, carbon dioxide having a low global warming potential is used as a low-side refrigerant that circulates the low-side refrigeration cycle 10. The low-side evaporator 14 of the low-side refrigeration cycle 10 includes a plurality of heat transfer tubes 31 and a plurality of rectangular plate-like members that are joined to each of the plurality of heat transfer tubes 31 by brazing, for example. And fins 32.

The fins 32 are configured in a row in the short direction along the air flow. In other words, the low-side evaporator 14 having low temperature and low pressure in the low-side refrigeration cycle 10 is configured by arranging a plurality of cut fins 32 in a line along the air flow direction. That is, one of the fins 32 arranged on the windward side in the longitudinal direction is opposed to the other longitudinal one of the fins 32 adjacent thereto, and the fins 32 are arranged in a line along the air flow direction. Yes. Each of the plurality of fins 32 has the same configuration. In addition, each of the plurality of fins 32 arranged in a row is arranged in parallel to form a plurality of rows (multiple rows) with a predetermined interval (fin pitch) therebetween.

The plurality of heat transfer tubes 31 intersect with each of the plurality of fins 32 and are arranged side by side in the longitudinal direction of the fins 32. And since the fin 32 is comprised in a line along the flow direction of air, the heat exchanger tube 31 is also arrange | positioned at the flow top and the leeward side of the air flow. Each of the plurality of heat transfer tubes 31 has the same configuration.

In FIG. 2, the fin 32 on the upstream side of the air flow, that is, the fin 32 disposed in the uppermost stream is illustrated as the first fin 32A, and the fin adjacent to the first fin 32A on the leeward side of the first fin 32A. 32 is illustrated as a second fin 32B. Here, the low-side evaporator 14 having a configuration in which two sets of fins 32 are arranged along the air flow is shown as an example, but the present invention is not limited to this. The vessel 14 may be configured by arranging three or more sets of fins 32 along the air flow direction.

And in the low element side evaporator 14, the distance L from the windward side edge part of the heat exchanger tube 31 in the most upstream side to the front edge of the 1st fin 32A is made into the range of 6.5 mm <= L <= 8.5mm. The heat transfer tube 31 on the most upstream side is the heat transfer tube 31 joined to the first fin 32A on the most upstream side.

FIG. 3 shows that when the distance L> 8.5 mm, the operating efficiency deteriorates and the average refrigeration capacity decreases. This is because, with the same fin width, the tube diameter is reduced and the distance L is increased, so that the pressure loss of the refrigerant becomes excessive, the operating efficiency is deteriorated, and the average refrigeration capacity is lowered. The ratio of the heat transfer tube diameter to the fin width is similarly reduced because the tube diameter is small, but the ratio of the heat transfer tube diameter to the fin width described above, which reduces the average refrigeration capacity, is less than 23%. is there.

On the other hand, it can be seen from FIG. 3 that the average refrigeration capacity decreases even at a distance L <6.5 mm. This is because at a distance L <6.5 mm, the tube diameter of the heat transfer tube is excessive, and the heat transfer coefficient in the tube decreases due to a decrease in the refrigerant flow rate. Further, when the distance L <6.5 mm, the distance between the heat transfer tube and the front edge side of the fin is reduced, and the front edge temperature of the fin is decreased, so that frost is likely to be generated and the refrigeration capacity is decreased. In addition, if the ratio of the heat transfer tube diameter to the fin width is in an area larger than 42%, the tube diameter increases, so the average capacity decreases due to a decrease in heat transfer coefficient in the tube and a deterioration in frost formation due to improved fin efficiency. .

Therefore, in the low-side evaporator 14, since the distance L is in the range of 6.5 mm ≦ L ≦ 8.5 mm, the ratio of the heat transfer tube diameter to the fin width is 23% ≦ heat transfer tube diameter / fin width. It can be in the range of x100 ≦ 42%. By doing so, the low-side evaporator 14 can improve the refrigerating capacity reduction, and even when a carbon dioxide refrigerant is used, it is not necessary to increase the capacity of the heat exchanger. Therefore, according to the refrigeration cycle apparatus 100A, there is an effect that energy consumption can be reduced throughout the year without increasing the cost, and the apparatus can be made compact.

<Specification of low-side evaporator 14>
FIG. 4 is a graph showing the relationship between (Fp−tf) × L and the average refrigeration capacity in the evaporator. Based on FIG.2 and FIG.4, the specification 2 of the low former side evaporator 14 is demonstrated. In FIG. 4, the vertical axis represents the average refrigeration capacity, and the horizontal axis represents (Fp−tf) × L. Furthermore, the average refrigeration capacity is expressed as a ratio with R410A used in the current refrigeration cycle apparatus.

In the low-side evaporator 14, (Fp−tf) × L is in a range of 40 mm ² ≦ (Fp−tf) × L ≦ 52 mm ² .

From FIG. 4, it can be seen that when 40 mm ² > (Fp−tf) × L, the fin efficiency increases and the temperature of the windward fin tends to decrease. In addition, the wind speed passing through the wind path on the windward side increases, and the heat transfer rate from the fins to the air increases due to the leading edge effect. It also leads to.

On the other hand, FIG. 4 shows that the refrigerating capacity decreases even when 52 mm ² <(Fp−tf) × L. This is because if 52 mm ² <(Fp−tf) × L, the wind speed passing through the wind path on the windward side is lowered, and the heat transfer rate from the fin to the air is excessively lowered.

Therefore, in the low-side evaporator 14, (Fp−tf) × L is set to a range of 40 mm ² ≦ (Fp−tf) × L ≦ 52 mm ² . By doing so, the low-side evaporator 14 can suppress frost formation on the most upstream side, which is likely to be frosted and easily blocked, and the operation time becomes longer and the average refrigeration capacity is improved.

Note that the specification 2 of the low-side evaporator 14 may be combined with the specification 1 of the low-side evaporator 14. In this case, the effects of both the specification 1 and the specification 2 of the low-side evaporator 14 are exhibited.

<Specifications of low-side evaporator 14>
FIG. 5 is a graph showing the relationship between the ratio of the heat transfer tubes to the fin width in the evaporator and the average refrigeration capacity. FIG. 6 is a graph showing the relationship between the area Aj and the average refrigeration capacity in the evaporator. Based on FIGS. 2, 5, and 6, the third specification of the low-side evaporator 14 will be described. In FIG. 5, the vertical axis represents the average refrigeration capacity, and the horizontal axis represents the heat transfer tube diameter / fin width × 100%. In FIG. 6, the vertical axis represents the average refrigeration capacity, and the horizontal axis represents the area Aj. Furthermore, the average refrigeration capacity in FIGS. 5 and 6 is expressed as a ratio with R410A used in the current refrigeration cycle apparatus.

In the low-side evaporator 14, the area Aj = (Fp−tf) × (Dp / 2−do) is in the range of 23 mm ² ≦ Aj ≦ 47 mm ² .

From FIG. 6, it can be seen that the refrigeration capacity decreases when 23 mm ² > Aj. This is because if 23 mm ² > Aj, the tube diameter of the heat transfer tube is excessive and the heat transfer coefficient in the tube becomes small. In addition, since the distance between the fin and the heat transfer tube is reduced and the fin efficiency is increased, the fin temperature is lowered and the amount of frost is increased.

On the other hand, FIG. 6 shows that even if 47 mm ² <Aj, the refrigeration capacity decreases. This is because if 47 mm ² <Aj, the tube diameter of the heat transfer tube becomes too small, the refrigerant pressure loss increases, and the refrigerant circulation rate decreases.

Therefore, in the low-side evaporator 14, the area Aj is set to a range of 23 mm ² ≦ Aj ≦ 47 mm ² . By doing so, the low-side evaporator 14 has a reduced heat transfer area per unit area than before, but the frosting resistance is improved and the blockage due to Aj frost is less likely to occur. improves. Moreover, since the weight of the heat transfer tube can be reduced by reducing the diameter of the heat transfer tube, the cost of the heat exchanger can be reduced.

The specification 3 of the low-side evaporator 14 may be combined with at least one of the specification 1 and the specification 2 of the low-side evaporator 14. In this case, all the effects of the combined specifications are exhibited.

<Specification of low-side evaporator 14>
FIG. 7 is a graph showing the relationship between the volume Vj and the average refrigeration capacity in the evaporator. Based on FIG.2 and FIG.7, the specification 4 of the low original side evaporator 14 is demonstrated. In FIG. 7, the vertical axis represents the average refrigeration capacity, and the horizontal axis represents the volume Vj. The average refrigeration capacity is expressed as a ratio with R410A used in the current refrigeration cycle apparatus.

In the low-side evaporator 14, the volume Vj = (Fp−tf) × (Dp / 2−do) × (Rp−do) is in the range of 250 mm ³ ≦ Vj ≦ 800 mm ³ .

From FIG. 7, it can be seen that when Vj <250 mm ³ , the refrigerating capacity decreases. This is because when Vj <250 mm ³ , the frost-melted droplets freeze, and this becomes a thermal resistance. Specifically, when Vj <250 mm ³ , the distance between the heat transfer tubes in the air flow direction is reduced, and the fin efficiency is increased. And since the droplet which the frost melt | dissolved at the time of defrosting becomes easy to be hold | maintained between heat exchanger tubes, defrosting property worsens. When the operation is started without defrosting, the droplets freeze, which becomes a thermal resistance, and the refrigerating capacity is reduced. When normal operation and defrosting operation are repeated, this ice expands in volume, causing deformation and destruction of the fins and heat transfer tubes.

On the other hand, it can be seen from FIG. 7 that the refrigerating capacity decreases even when Vj> 800 mm ³ . This is because when Vj> 800 mm ³ , the tube diameter of the heat transfer tube becomes too small, and the heat transfer area outside the tube decreases. Further, the distance between the front edge of the fin and the heat transfer tube becomes excessive, the fin efficiency is lowered, and the heat transfer coefficient outside the tube is also lowered, so that the heat exchange performance is also deteriorated.

Therefore, in the low-side evaporator 14, the volume Vj is in the range of 250 mm ³ ≦ Vj ≦ 800 mm ³ . By carrying out like this, the low former side evaporator 14 becomes the thing excellent in frost formation property and defrosting property. Therefore, the refrigeration cycle apparatus 100A can exhibit high refrigeration capacity even when carbon dioxide is used as the refrigerant.

The specification 4 of the low-side evaporator 14 may be combined with at least one of the specifications 1 to 3 of the low-side evaporator 14. In this case, all the effects of the combined specifications are exhibited.

The refrigeration cycle apparatus 100A can be used by being applied to an apparatus equipped with a refrigeration cycle, such as a refrigeration air conditioner (for example, a refrigeration apparatus, a refrigeration apparatus, a room air conditioner, a packaged air conditioner, a building multi air conditioner, etc.), a heat pump water heater, and the like. it can.

Embodiment 2. FIG.
FIG. 8 is a schematic configuration diagram showing an example of a refrigerant circuit configuration of a refrigeration cycle apparatus (hereinafter referred to as refrigeration cycle apparatus 100B) according to Embodiment 2 of the present invention. The refrigeration cycle apparatus 100B will be described based on FIG.

In the first embodiment, the refrigeration cycle apparatus 100A provided with the dual refrigeration cycle has been described as an example. In the second embodiment, the refrigeration cycle apparatus 100B provided with one refrigerant circuit will be described.
It should be noted that the levels of temperature, pressure, etc. are not particularly determined in relation to absolute values, but are relatively determined in terms of the state and operation of the system, apparatus, and the like.

As shown in FIG. 8, the refrigeration cycle apparatus 100B has one refrigerant circuit (refrigeration cycle 50) and is configured to circulate the refrigerant.
The refrigeration cycle 50 is configured by connecting a compressor 51, a condenser 52, an expansion valve 53, and an evaporator 54 in order by a refrigerant pipe 58.

The compressor 51 sucks the refrigerant flowing through the refrigeration cycle 50, compresses the refrigerant, and discharges it in a high temperature and high pressure state. For example, the compressor 51 may be configured by a compressor of a type that can control the number of revolutions by an inverter circuit or the like and adjust the discharge amount of the low-source side refrigerant.

The condenser 52 performs, for example, heat exchange between outside air, water, brine, and the like and the refrigerant flowing through the refrigeration cycle 50 to condense and liquefy the refrigerant. In this embodiment, the description will be made assuming that the condenser 52 uses the heat source as the outside air and performs heat exchange between the outside air and the refrigerant. Therefore, the condenser 52 has a condenser fan 55a for promoting heat exchange. For example, the condenser fan 55a may be a blower of a type that can adjust the air volume.

The expansion valve 53 functions as a decompression device, a throttling device, etc., and decompresses and expands the refrigerant flowing through the refrigeration cycle 50. The expansion valve 53 may be constituted by a flow rate control means such as an electronic expansion valve, or a refrigerant flow rate adjustment means such as a capillary tube or a temperature-sensitive expansion valve.

The evaporator 54 evaporates the refrigerant flowing through the refrigeration cycle 50 by heat exchange with the object to be cooled, for example, to form a gas (gas) refrigerant (evaporate gas). The object to be cooled is cooled directly or indirectly by heat exchange with the refrigerant. The evaporator 54 is assumed to have an evaporator fan 55b for promoting heat exchange. For example, the evaporator fan 55b may be a blower of a type that can adjust the air volume.

<Refrigerant used for refrigeration cycle apparatus 100B>
In the refrigeration cycle apparatus 100B having such a configuration, for example, a refrigerant having a small influence on global warming such as an HFO refrigerant, an HC refrigerant, carbon dioxide, ammonia, and water can be used. Alternatively, for example, an HFC refrigerant having a high global warming potential can be used from the viewpoint of cost and performance.

<Operation of refrigeration cycle apparatus 100B>
The operation | movement of each component apparatus of the above refrigeration cycle apparatuses 100B etc. are demonstrated based on the flow of the refrigerant | coolant which circulates through each refrigerant circuit.

Compressor 51 sucks in refrigerant, compresses it, discharges it in a high temperature and high pressure state. The discharged refrigerant flows into the condenser 52. The condenser 52 exchanges heat between the outside air supplied from the condenser fan 55a and the refrigerant, and condenses and liquefies the refrigerant. The condensed and liquefied refrigerant passes through the expansion valve 53. The expansion valve 53 depressurizes the condensed and liquefied refrigerant. The decompressed refrigerant flows into the evaporator 54. The evaporator 54 evaporates the refrigerant by heat exchange with the object to be cooled. The compressor 51 sucks the evaporated gas refrigerant.

<Specifications of the evaporator 54>
It is assumed that the evaporator 54 has the same configuration as that shown in FIG. 2 and employs at least one of the specifications of the low-source evaporator 14 described in the first embodiment.
By configuring the refrigeration cycle apparatus 100B in this manner, it is possible to achieve the same effects as the effects exhibited by the refrigeration cycle apparatus 100A according to Embodiment 1.

The refrigeration cycle apparatus 100B is an apparatus equipped with a refrigeration cycle, such as a refrigeration air conditioner (for example, a refrigeration apparatus, a refrigeration apparatus, a room air conditioner, a packaged air conditioner, a multi air conditioner for buildings), a heat pump water heater, etc. It can be used by applying to.

10 Low-source-side refrigeration cycle, 11 Low-source-side compressor, 12 Low-source-side condenser, 13 Low-source-side expansion valve, 14 Low-source-side evaporator, 15 Auxiliary radiator, 16 Inter-refrigerant heat exchanger, 18 Refrigerant piping , 20 Higher refrigeration cycle, 21 Higher compressor, 22 Higher condenser, 23 Higher expansion valve, 24 Higher evaporator, 25 Higher condenser fan, 28 Refrigerant piping, 31 Transmission Heat pipe, 32 fin, 32A 1st fin, 32B 2nd fin, 50 refrigeration cycle, 51 compressor, 52 condenser, 53 expansion valve, 54 evaporator, 55a condenser fan, 55b evaporator fan, 58 refrigerant piping , 100A refrigeration cycle apparatus, 100B refrigeration cycle apparatus.

Claims

A refrigeration cycle apparatus comprising a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are connected in order,
The evaporator is
A plurality of fins arranged in at least one row along the air flow direction;
A plurality of heat transfer tubes arranged to intersect each of the plurality of fins,
The plurality of fins include a first fin disposed in the uppermost stream in the air flow direction,
A refrigeration cycle apparatus in which the distance L from the windward end of the heat transfer tube in the first fin to the front edge of the first fin among the plurality of heat transfer tubes is in a range of 6.5 mm ≦ L ≦ 8.5 mm .
The plurality of fins are arranged in parallel to form a plurality of rows at intervals in a direction perpendicular to the air flow direction,
A fin pitch which is an interval between fins adjacent in parallel among the plurality of fins is Fp,
The thickness of each of the plurality of fins is tf,
The refrigeration cycle apparatus according to claim 1, wherein (Fp-tf) x L is in a range of 40 mm 2 ≤ (Fp-tf) x L ≤ 52 mm 2 .
Each of the plurality of fins is configured in a rectangular shape, and is arranged such that the short direction is the air flow direction,
The plurality of heat transfer tubes are arranged in the longitudinal direction of each of the plurality of fins,
A fin pitch which is an interval between fins adjacent in parallel among the plurality of fins is Fp,
The thickness of each of the plurality of fins is tf,
The step pitch, which is the interval between the heat transfer tubes adjacent in the longitudinal direction of the fin among the plurality of heat transfer tubes, is Dp,
The tube diameter of each of the plurality of heat transfer tubes is do,
(Fp−tf) × (Dp / 2−do) is defined as area Aj,
The refrigeration cycle apparatus according to claim 2, wherein the Aj is in a range of 21 mm 2 ≦ Aj ≦ 57 mm 2 .
Each of the plurality of fins is configured in a rectangular shape, and is arranged such that the short direction is the air flow direction,
The plurality of heat transfer tubes are arranged in the longitudinal direction of each of the plurality of fins,
A fin pitch which is an interval between fins adjacent in parallel among the plurality of fins is Fp,
The thickness of each of the plurality of fins is tf,
The step pitch, which is the interval between the heat transfer tubes adjacent in the longitudinal direction of the fin among the plurality of heat transfer tubes, is Dp,
The tube diameter of each of the plurality of heat transfer tubes is do,
Among the plurality of heat transfer tubes, the row pitch that is the interval between the heat transfer tubes adjacent in the air flow direction is Rp,
(Fp−tf) × (Dp / 2−do) × (Rp−do) is defined as a volume Vj,
The refrigeration cycle apparatus according to claim 2 or 3, wherein the Vj is in a range of 250 mm 3 ≤ Vj ≤ 800 mm 3 .
A first refrigeration cycle in which a first compressor, a radiator, a first condenser, a first expansion valve, and a first evaporator are connected in order,
A second refrigeration cycle in which a second compressor, a second condenser, a second expansion valve, and a second evaporator are connected in order,
The first condenser and the second evaporator are configured to exchange heat,
A refrigeration cycle apparatus, wherein the first evaporator includes the evaporator according to any one of claims 1 to 4.
Carbon dioxide is used as a refrigerant for circulating the first refrigeration cycle,
The refrigeration cycle apparatus according to claim 5, wherein any one of HFO refrigerant, HC refrigerant, carbon dioxide, ammonia, water, HFC refrigerant, or a mixed refrigerant containing these is used as the refrigerant circulating in the second refrigeration cycle.