JP4338592B2 - Heater unit - Google Patents

Description

The present invention relates to a heat exchanger used in the cooling cycle of the vehicle air conditioner, and more particularly relates to a heater unit for heating the refrigerant pressure on the high pressure side is applied to a supercritical refrigeration cycle equal to or greater than the critical pressure of the refrigerant .

  Some vehicle air conditioners have an independent temperature control function that allows an occupant to individually control the temperature. For example, in Patent Literature 1, two left and right ventilation paths are formed in the heater unit, a heater core using engine cooling water as a heating medium, and a partition plate that divides the cooler into two are provided, and two ventilation paths are connected to each ventilation path. By adjusting the opening degree of the mix door, the ratio of the air passing through the heater core and the air flowing through the bypass path (the region not passing through the heater core) is adjusted to be able to independently control the temperature ( Hereinafter, the above configuration is referred to as an independent temperature control heater unit).

In the heater core using engine cooling water as the heating medium, the temperature difference between the inlet and outlet of the engine cooling water is about 10 ° C., so that the two mix doors in the heater unit as described above have the same opening and are separated by the partition plate. Even when air of the same air volume is passed to the left and right of the heater core, there is almost no air outlet temperature difference between the left and right of the heater core.
Japanese Patent Laid-Open No. 9-328011

  Conventionally, chlorofluorocarbon refrigerants have been mainly used in the cooling cycle of a vehicle air conditioner. However, if they are released into the atmosphere, environmental problems such as global warming due to destruction of the ozone layer are a concern. As a countermeasure, a cooling cycle using carbon dioxide, ethylene, ethane nitric oxide or the like (hereinafter, carbon dioxide is a representative example) has been proposed (for example, Japanese Patent Application Laid-Open No. 2002-130849).

  Such a cooling cycle using carbon dioxide as a refrigerant is in principle the same as a conventional cooling cycle using chlorofluorocarbon. However, since the critical temperature of carbon dioxide is about 31 ° C., which is significantly lower than the critical temperature of conventional chlorofluorocarbon (for example, R-12 is 112 ° C.), the carbon dioxide temperature on the radiator side is higher than the critical temperature of carbon dioxide. However, the difference is that the temperature of carbon dioxide, which is a refrigerant, decreases from the inlet to the outlet in a gas state.

  On the other hand, the heating cycle of a vehicle air conditioner uses engine cooling water as a heating medium in an engine vehicle, but there is no engine cooling water in an electric vehicle or the like. Instead, a cooling cycle radiator is used as a heater core. Heating is considered. Even when such a cooling cycle radiator using carbon dioxide as a refrigerant (hereinafter referred to as a heater core) is incorporated into an independent temperature control heater unit for heating, the air outlet temperature difference between the left and right of the heater core There is almost no need for it.

  However, since the refrigerant pressure of carbon dioxide is higher than the critical pressure on the high-pressure side, the refrigerant inlet / outlet temperature difference is increased to about 100 ° C. in the heater core. For this reason, even if air of the same air volume is allowed to pass to the left and right of the heater core divided by the partition plate, the difference in the amount of heat exchange between the left and right of the heater core becomes large. ) Will increase the air outlet temperature difference. That is, if you want the same temperature on the left and right with the independent temperature control heater unit, even if you let the two mix doors have the same opening and let the same amount of air pass to the left and right of the heater core divided by the partition plate, At each outlet of the heater core, there will be a difference in temperature between the left and right air outlets.

  Even when the heater unit is not an independent temperature control system (no partition plate and one mix door), if the temperature difference between the left and right of the heater core is large, a difference in temperature between the left and right air outlets occurs at each outlet of the heater core. It will end up.

  In addition, it supplements that the prior art document which incorporated the heater core of the cooling cycle which used the carbon dioxide as the refrigerant | coolant in the heater unit of an independent temperature control system and was made to perform heating is not detected within the search range by the applicant.

An object of the present invention is a heat exchanger used as a heater core in a cooling cycle using carbon dioxide as a refrigerant, and even if air conditioned air of the same air volume is passed to the left and right of the heater core, an air outlet temperature difference hardly occurs. It is to provide a heater unit .

In order to achieve the above object, the invention of claim 1 comprises a core portion in which a refrigerant passage through which a refrigerant flows and cooling fins are stacked, and a pair of tank portions respectively communicating with both end portions of each refrigerant passage. The core section is divided into a plurality of paths each having a predetermined number of refrigerant passages as one path, and is configured such that the refrigerant is folded in each tank section and circulates through each path in turn, and the pair of tank sections either the inlet pipe and the outlet pipe in which the refrigerant flows in and out is provided at one of the front Symbol first direction the refrigerant is distributed in the core section (hereinafter, forward) to the refrigerant passage number of paths through which the refrigerant flows in the same direction as the On the other hand, the number of refrigerant passages in the path through which the refrigerant flows in the direction opposite to the forward direction (hereinafter referred to as the reverse direction) is increased, and the downstream side of the conditioned air of the heater core is orthogonal to the refrigerant passage of the core portion. So that the partition plate is provided Conditioned air which has passed through the core portion is characterized in that it is configured to flow in separate passages.

  According to a second aspect of the present invention, in the first aspect, the tank portion has a separator for partitioning a flow passage formed therein, and the number of refrigerant passages in the path is set by the position of the separator. Features.

  According to the invention of claim 1, the heat exchange amount in the path through which the refrigerant flows in the reverse direction is increased, and the heat exchange amount in the path through which the refrigerant flows in the forward direction and the heat exchange amount in the path through which the refrigerant flows in the reverse direction Can be made substantially equal to each other, when the conditioned air having the same air volume is passed to the left and right of the heat exchanger, the difference in temperature between the left and right air outlets can be made substantially zero at the outlet of the heat exchanger.

  According to the invention of claim 2, the number of tubes for each pass can be easily changed by changing the position of the separator.

Hereinafter, the heater unit that involved in the present invention dioxide carbonate described embodiment when applied to the heater core of the cooling cycle that the refrigerant.

  FIG. 1 is a perspective view showing an overall configuration of a heater core according to the present embodiment. The heater core 10 includes a core portion 20 and header tanks 30 and 40 disposed at both ends of the core portion 20.

  The core portion 20 is formed by alternately stacking tubes 21 as refrigerant passages through which refrigerant flows and cooling fins 22 formed in a corrugated shape. The tubes 21 are stacked in parallel with each other in a state where a gap through which conditioned air (air) flows is secured between adjacent ones, and fins 22 are disposed in the respective gaps.

  The header tanks 30 and 40 are tank units that distribute the refrigerant supplied from the outside to the respective tubes 21, join the conditioned air and the refrigerant after heat exchange, and discharge the refrigerant to the outside. The header tanks 30 and 40 are joined to both ends of the core portion 20, that is, both end portions in the longitudinal direction of the plurality of tubes 21, and a refrigerant flow path provided inside the header tanks 30 and 40 and the inside of each tube 21. The passage is configured to communicate with each other.

  The header tanks 30 and 40 incorporate separators 23 to 25 for partitioning a flow passage formed inside. By incorporating this separator, the plurality of tubes 21 constituting the core portion 20 are divided into a plurality of passes each having a predetermined number of tubes 21 as one pass. In the core part 20 of a present Example, it is divided into a path | pass (1)-a path | pass (4) from the top, and is comprised by 3 turns (number of folds back) and 4 paths. The number of tubes for each pass can be easily changed by changing the positions of the separators 23 to 25 in the header tanks 30 and 40.

  A refrigerant inlet pipe 31 is provided above the separator 23 of the header tank 30, and a refrigerant outlet pipe 32 is provided below the separator 24 of the header tank 30.

  The refrigerant supplied from the inlet pipe 31 to the header tank 30 is distributed to each tube 21 of the path (1), flows through each tube, and flows into the header tank 40. This refrigerant is folded back in the header tank 40, distributed to the tubes 21 of the path (2), flows through the respective tubes, and flows into the header tank 30. Similarly, the refrigerant circulates in the core portion 20 in order of the header tank 30 → pass (3) → header tank 40 → pass (4) → header tank 30 and is partitioned by the separator 24. After being merged in the header tank 30, it is discharged from the outlet pipe 32. During this time, every time the refrigerant flows through each path, heat exchange is performed with the conditioned air 50 flowing into the core portion 20.

  FIG. 2 is a diagram schematically showing the relationship between the air passage and the partition plate when the heater core 10 as described above is incorporated into an independent temperature control heater unit. As shown in FIG. 2, a partition plate 60 is provided on the downstream side of the conditioned air of the heater core 10, and two independent ventilation paths F <b> 1 and F <b> 2 are formed by the partition plate 60. The conditioned air 50 that has passed through the right core portion 20a of the heater core 10 flows through the ventilation path F1, and the conditioned air 50 that has passed through the left core portion 20b of the heater core 10 flows through the ventilation path F2. That is, the heat exchange region (core portion 20) of the heater core 10 is divided into two by the ventilation paths F1 and F2.

  In addition, as an independent temperature control type heater unit to which the heater core 10 of the present embodiment is applied, for example, a vehicle air conditioner disclosed in Japanese Patent Laid-Open No. 9-328011 (FIG. 1) can be used.

  In FIG. 2, when the conditioned air 50 having the same air flow is passed to the left and right of the heater core 10, the air outlet temperature difference (T1−) between the air outlet temperature T1 of the ventilation path F1 and the air outlet temperature T2 of the ventilation path F2. If T2) is zero, the heat exchange amounts in the core portions 20a and 20b are equal. The heat exchange amount can be expressed by the following formula (1).

Heat exchange amount Q = A (heat transfer area) × K (heat passage rate) × ΔT (temperature difference) (1)
Here, ΔT is a temperature difference between the refrigerant temperature and the air outlet temperature, and ΔT increases because the refrigerant temperature is higher toward the upstream side when viewed from the direction in which the refrigerant flows. FIG. 3 shows the relationship between the refrigerant temperature and the air outlet temperature when the same volume of conditioned air is passed through the one-pass heater core. (A) shows the refrigerant flow direction, the refrigerant temperature, and the air inlet / outlet temperature. (B) is explanatory drawing which shows the difference of the heat exchange amount of right and left, (c) is the schematic which shows the heater core of 1 pass. When the refrigerant flows from the left to the right through the one-pass heater core as shown in FIG. 3 (c), as shown in FIG. 3 (a), ΔT increases toward the upstream side where the refrigerant first circulates. When the left and right core areas are compared as shown in 3 (b), the heat exchange amount of the left core on the upstream side is larger than that of the downstream right core through which the refrigerant flows.

  Therefore, in the case of a four-pass heater core as shown in FIG. 1, ΔT is given by pass (1)> pass (2)> pass (3)> pass (4). Among them, in the path (1) and the path (3), ΔT of the right core part 20a> ΔT of the left core part 20b, and in the paths (2) and (4), ΔT <right of the right core part 20a. It becomes ΔT of the left core part 20b. In this way, in the cooling cycle using carbon dioxide as the refrigerant, the refrigerant inlet / outlet temperature difference is large, so that a difference occurs in the heat exchange amount between the left and right, and the air outlet temperature difference (T1-T2) becomes large.

  Such a tendency occurs regardless of the number of paths. FIG. 4 is a characteristic diagram showing air outlet temperatures T1 and T2 for 2, 4, and 6-pass heater cores when the number of tubes per pass is equalized. As shown in FIG. 4, even if the number of passes is increased, the air outlet temperature difference (T1-T2) does not decrease. FIG. 5A shows the calculation results of the air outlet temperatures T1 and T2 when the same amount of conditioned air is passed to the left and right of the 4-pass heater core (the number of tubes in each pass is the same). As shown in the figure, the air outlet temperature difference (T1-T2) increases as the passing air volume increases, and the left and right air outlet temperature difference between the driver seat and the passenger seat increases.

  Here, the number of tubes and the passage cross-sectional area of the refrigerant will be described.

  By increasing or decreasing the number of tubes for one pass, the passage cross-sectional area of the refrigerant and the flow velocity of the refrigerant are increased or decreased, the heat transfer area on the refrigerant side / air side is increased or decreased, and the heat exchange amount for one pass is increased or decreased. A × K in the formula (1) is expressed by the following formula.

1 / KA = 1 / (αg × Ag) + 1 / (αa × Aa) (2)
Where αg: refrigerant side heat transfer coefficient
αa: Air side heat transfer coefficient
Ag: Heat transfer area on the refrigerant side
Aa: Air side heat transfer area Among these, α (heat transfer coefficient) is expressed by the following equation.

α = 0.022 × (v + D / ν) ^ 0.8 × Pr ^ 0.5 × (λ / D)
... (3)
Where v: flow velocity (= G / Ac G: flow rate, Ac: passage cross-sectional area)
D: Channel diameter
ν: Kinematic viscosity coefficient
Pr: Prandtl number
λ: Thermal conductivity of fluid Here, the increase / decrease ratio of the number of tubes to the number of reference tubes is represented by N (reference N = 1). When N = 1, if αg = 1, αa = 1, vg (refrigerant flow velocity) = 1, Ag = 1, and Aa = 1, KA = 0.5. For example, when N = 2 (twice the number of tubes with respect to the reference), the result is as follows.

vg = 0.5
αg = reference 1 × 0.57 (because v ^ 0.8 with respect to the reference from equation (3))
αa ≒ 1 (because the wind speed is the same)
Ag = standard 1 × 2
Aa = standard 1 × 2
From the above, from equation (2), when N = 2, KA = 0.7, and if the number of tubes for one pass is doubled with respect to the standard, KA is about 1.4 times, and heat exchange The amount can be increased. That is, the heat exchange amount for each pass can be increased or decreased by increasing or decreasing the number of tubes for one pass.

  Therefore, in the heater core 10 of the present embodiment, the number of tubes of the path (1) in which the refrigerant first circulates in the core portion 20 and the path (3) in which the refrigerant flows in the same direction (forward direction) as the path (1). On the other hand, the number of tubes of the paths (2) and (4) through which the refrigerant flows in the direction opposite to the forward direction (reverse direction) is increased. By adopting such a number of tubes, the heat exchange amount of the paths (2) and (4) is increased, the heat exchange amount of the paths (1) and (3) and the heat exchange amount of the paths (2) and (4) Can be made approximately equal.

  However, when N = 1, K = 0.5, and when N = 2, K = 0.35. When the number of tubes is doubled, K decreases, and N = 1 and N = 2. When compared with the same A, the heat exchange amount becomes larger when N = 1 where the number of tubes is small. That is, with the same core volume, the smaller the number of tubes per pass, the greater the heat exchange amount of the entire core. However, if the number of tubes per pass is reduced, vg increases and the pressure loss increases, so the load on the compressor increases. Therefore, the number of tubes in the paths (2) and (4) through which the refrigerant flows in the opposite direction needs to be set in consideration of the balance between the heat exchange amount of the entire core and the pressure loss.

  FIG. 6A is a characteristic diagram showing the relationship between the number of tubes and the refrigerant-side heat transfer coefficient αg, and FIG. 6B is a characteristic diagram showing the relationship between the number of tubes and the pressure loss (each line is the refrigerant temperature, Shows characteristics when calculated under different pressure conditions). As shown in FIG. 6A, the smaller the number of tubes, the higher the refrigerant-side heat transfer coefficient αg. On the other hand, the pressure loss also increases as shown in FIG. 6B, and the load on the compressor is reduced. Will increase. Therefore, the best balance between the two is in the range of 4 to 6 tubes. If the allowable value of pressure loss on the refrigerant side is large, the heat exchange amount can be increased if the number of tubes per pass is small. However, since the pressure loss increases as described above, the heat exchange amount of the entire core Considering the balance of pressure loss, it is preferable to set in the range of 4 to 6 tubes.

  In this embodiment, the number of tubes in each pass is set to pass (1) = 4, pass (2) = 6, pass (3) = 4, and pass (4) = 5, respectively. FIG. 5B shows the air outlet temperatures T1 and T2 when the same amount of conditioned air is passed to the left and right of the air. Compared to FIG. 5A, when the number of tubes in the paths (2) and (4) is larger than the number of tubes in the paths (1) and (3), the paths (1) and (3) Therefore, even if the passing air volume increases, the air outlet temperature difference (T1-T2) can be made substantially zero. Therefore, in the independent temperature control type heater unit, when the two mix doors have the same opening and the same amount of air is passed to the left and right of the heater core, there is a difference between the left and right air outlet temperature at each outlet of the heater core. Since it hardly occurs, the driver's seat and the passenger seat can be set to substantially the same temperature. In this case, it is not necessary to individually adjust the opening degrees of the two mix doors, and the left and right sides of the heater core can be set to substantially the same temperature by setting the same opening degree, so that temperature control is easy. .

  In addition, when the heater core 10 of the present embodiment is applied to a heater unit that is not an independent temperature control system, the difference in temperature between the left and right air outlets hardly occurs at each outlet of the heater core. The temperature can be made substantially the same, and temperature control can be made easy.

  In the present embodiment, an example is shown in which the number of tubes is set to 19 (path (1) = 4, path (2) = 6, path (3) = 4, path (4) = 5). However, the present invention can also be applied to other combinations of the number of passes and the number of tubes. In other words, by setting the number of tubes of the path through which the refrigerant flows in the reverse direction to the number of tubes of the path through which the refrigerant flows in the forward direction, the heat exchange amount of each path in the forward direction and the reverse direction can be reduced. Can be approximately equal.

The perspective view which shows the whole structure of the heater core concerning an Example. The figure which showed typically the relationship between the ventilation path and partition plate when the heater core of an Example was integrated in the heater unit of an independent temperature control system. (A) is a characteristic view showing the relationship between the refrigerant flow direction, the refrigerant temperature, and the air inlet / outlet temperature. (B) is explanatory drawing which shows the difference of the heat exchange amount of right and left. (C) is a schematic diagram showing a one-pass heater core. The characteristic view which showed the air exit temperature difference T1-T2 about the heater core of 2, 4, 6 pass at the time of equalizing the number of tubes per pass. (A) is a characteristic view showing the calculation results of air outlet temperatures T1 and T2 when the same amount of conditioned air is passed to the left and right of the 4-pass heater core. (B) is a characteristic view showing the calculation results of the air outlet temperatures T1, T2 when the number of tubes in each path is set to the number of the embodiment. (A) is a characteristic view showing the relationship between the number of tubes and the refrigerant side heat transfer coefficient αg. Fig. (B) is a characteristic diagram showing the relationship between the number of tubes and pressure loss.

Explanation of symbols

F1, F2 ... Ventilation path 10 ... Heater core 20 (20a, 20b) ... Core portion 21 ... Tube 22 ... Fins 23-25 ... Separator 30, 40 ... Header tank 31 ... Inlet pipe 32 ... Outlet pipe 50 ... Air-conditioning air 60 ... Partition Board

Claims (2)

A core portion (20) in which a refrigerant passage (21) through which refrigerant flows and a fin (22) for cooling are stacked, and a pair of tank portions (30, 40) communicating with both end portions of each refrigerant passage (21), respectively. made in heater core (10), before SL core portion and a (20) is divided into a plurality of paths to one path a predetermined number of refrigerant passages (21), the refrigerant is each tank portion (30, 40) in And configured to circulate each path in turn ,
An inlet pipe (31) and an outlet pipe (32) through which refrigerant flows in and out of one of the pair of tank parts (30, 40) are provided,
The direction opposite to the forward direction (hereinafter, reverse) with respect to the number of refrigerant passages (21) of the path through which the refrigerant flows in the same direction as the direction in which the refrigerant first flows through the core portion (20) (hereinafter, forward direction). The number of refrigerant passages (21) of the path through which the refrigerant flows in the direction) ,
On the downstream side of the conditioned air (50) of the heater core (10), a partition plate (60) is provided so as to be orthogonal to the refrigerant passage (21) of the core (20), and the air conditioning that has passed through the core (20). wind (50) heater unit you characterized in that has been configured to flow in separate passages. The tank portions (30, 40) have separators (23-25) for partitioning the flow passages formed therein, and the number of refrigerant passages (21) in the path depends on the position of the separators (23-25). The heater unit according to claim 1, wherein: is set .

Images