JPH0248782Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a natural circulation type cooling device that performs air cooling using a refrigerant natural circulation cycle.

(Prior Art) In this type of cooling device, when controlling the cooling capacity, the refrigerant flow rate control method (for example, Japanese Patent Laid-Open No. 48-1999
101640) or an air volume control method that controls the fan rotation speed (for example, see Utility Model Application Publication No. 49-40043), but both require control valves and control circuits. This increases the complexity of the device and reduces its reliability. Particularly in devices that are used in places where dust and the like should not be generated, such as electronic equipment rooms, it is necessary to minimize the number of movable parts that can cause failures.

(Purpose of the invention) The present invention was made in view of the above problems, and uses a non-azeotropic mixed refrigerant as a circulating refrigerant in a natural circulation type cooling device, and uses a non-azeotropic mixed refrigerant whose dew point temperature is lower than the set air temperature. The purpose is to control the cooling capacity by setting the temperature to be slightly lower than the set air temperature so that when the indoor air temperature falls below the set air temperature, the cooling capacity can be reduced as much as possible. .

(Structure of the invention) The present invention connects a condenser located at a higher level and an evaporator located at a lower level through a liquid pipe and a gas pipe to form a refrigerant natural circulation circuit, and also includes a non-azeotropic A mixed refrigerant is sealed so that its dew point temperature is slightly lower than the set temperature of the air to be cooled under the operating pressure of the device, and a gas-liquid separation mechanism is provided on the gas pipe side that is the outlet side of the evaporator. As a result, the cooling capacity is rapidly reduced below the set air temperature, thereby controlling the cooling capacity.

(Example) Hereinafter, a natural circulation type cooling device according to an example of the present invention will be described with reference to the accompanying drawings.

This cooling device consists of a condenser 1 on the outdoor side, evaporators 2 and 2 on the indoor side, a liquid pipe 3 and a gas pipe 4 that cyclically connect the two, and a gas-liquid separator that acts as a gas-liquid separation mechanism. The condenser 1 is located at a higher position than the evaporators 2, 2, and a liquid pipe 3 is connected between the lower connection ports of the condenser 1 and the evaporators 2, 2.
The upper connection ports are connected by gas pipes 4 to allow natural flow of the refrigerant without resisting gravity, and the gas pipes 4 are connected to the evaporators 2 and 2.
A refrigerant natural circulation circuit 6 is constructed by interposing a gas-liquid separator 5 on the outlet side of the refrigerant. Incidentally, as shown in FIG. 2, the gas pipe 4 may be appropriately thickened to have a gas-liquid separation function without providing a special gas-liquid separator 5.

Therefore, although a non-azeotropic mixed refrigerant (for example, R22 and R12, R22 and R11, or R22 and R114, etc.) is circulated in the refrigerant natural circulation circuit 6, the mixing ratio of the non-azeotropic mixed refrigerant (i.e. , mixing ratio of low boiling point refrigerant and high boiling point refrigerant) x
The pressure in the refrigerant natural circulation circuit 6 is set by controlling the pressure so that the dew point temperature of the non-azeotropic mixed refrigerant is slightly lower than the set temperature of the air to be cooled (ie, indoor air). Reference numeral 7 is a refrigerant cooling device.

This natural circulation type cooling device works as follows.

In the natural circulation type cooling device, the non-azeotropic mixed refrigerant is liquefied by heat radiation in the condenser 1, and then flows down the liquid pipe 3 toward the evaporators 2 and 2 according to gravity, and flows into the evaporator 2. , 2 to cool the indoor air by exchanging heat with the indoor air, and at the same time absorbs heat, evaporates into gas, and returns to the condenser 1 via the gas pipe 4. At this time, the refrigerant liquid that has not been evaporated in each evaporator 2 is stored in each gas-liquid separator 5 .

Next, the state change of the non-azeotropic mixed refrigerant in the evaporator 2 will be described in further detail with reference to the concentration diagram shown in FIG.

In FIG. 3, the symbol T is the temperature, and x is a high boiling point refrigerant in a non-azeotropic mixed refrigerant, for example, R12, R1
1, R114, etc., and the rightmost position in Figure 3 shows high boiling point refrigerants such as R114.
12, R11, R114, etc. are shown, and the leftmost position shows a case where only a low boiling point refrigerant such as R22 is used.

According to this, the temperature of the non-azeotropic mixed refrigerant having the composition x ₁ changes in the evaporator 2 from the evaporation start point temperature T ₁ to the evaporation end point temperature T ₂ (in other words, the dew point temperature).
The air is cooled by the latent heat of vaporization of the refrigerant, and the cooling capacity q [kcal/h] at this time is expressed as in the following equation.

q=Cp・G・E・ΔT ₁ (1) Here, Cp: Air specific heat [kcal/Kg°C], G: Air flow rate [Kg/h], and E and ΔT ₁ are the respective values of the evaporator 2. Temperature efficiency [-] and suction air temperature
The temperature difference between Ta ₁ [℃] and the refrigerant temperature Tr [℃], each expressed by the following formula.

E=(Ta ₁ −Ta ₂ )/(Ta ₁ −Tr) (2) ΔT ₁ =Ta ₁ −Tr (3) Here, Ta ₂ is the blowing air temperature [° C.].

In the case of a single refrigerant, the refrigerant temperature Tr is constant, and from equations (1), (2), and (3) above, q=Cp・G・E・(Ta ₁ −Tr) (4) However, in the case of a non-azeotropic mixed refrigerant, the refrigerant temperature Tr changes from T ₁ to T ₂ during the evaporation process as described above, so the temperature difference with the suction air temperature Ta ₁ changes, and the above-mentioned ΔT in equation (3) changes depending on the position of the heat exchanger tube. This is shown in Figure 5 (characteristic diagram showing changes in air temperatures Ta ₁ and Ta ₂ and refrigerant temperature Tr depending on the heat transfer tube position when using a non-azeotropic mixed refrigerant) and Figure 6 (when using a single refrigerant). Air temperature Ta ₁ , Ta ₂ when
This is also clear from the characteristic diagram showing the change in refrigerant temperature Tr depending on the position of the heat transfer tube).

Now, when the refrigerant temperature Tr changes linearly with the enthalpy of the refrigerant in a non-azeotropic mixed refrigerant, the temperature difference ΔT ₁ between the suction air temperature Ta ₁ and the refrigerant temperature Tr in the above equation (3) is expressed as: Since it is sufficient to use the logarithmic average temperature difference, ΔT=(Ta ₁ −T ₁ )−(Ta ₁ −T ₂ )/lnTa ₁ −T ₁ /Ta ₁ −T
₂ = T ₂ −T ₁ /lnTa ₁ −T ₁ /Ta ₁ −T ₂ (5) From this and equation (1), the cooling capacity q is expressed by the following equation.

q=Cp・G・E・T ₂ −T ₁ /lnTa ₁ −T ₁ /Ta ₁ −T ₂ (6) For example, as a non-azeotropic mixed refrigerant, R22 (low boiling point refrigerant) and R114 (high boiling point refrigerant) When using a mixture of 20% and 80% by weight,
The evaporation pressure-enthalpy diagram of this non-azeotropic mixed refrigerant is as shown in Fig. 7, and the pressure is controlled so that the refrigerant pressure becomes 3 kg/cm・abs by changing the cooling temperature of the refrigerant cooling device 7. In this case, the evaporation start point temperature T ₁ at the inlet of the evaporator 2 is 6°C, and the evaporation end point temperature T ₂ (in other words, the dew point temperature) is 24°C.
From the above formula (5), the average inlet temperature difference ΔT ₁ between the suction air temperature Ta ₁ and the refrigerant temperature Tr is, assuming that the suction air temperature Ta ₁ is 27°C, ΔT ₁ = 24-6/ln27-6/ 27−24=9.3. However, the suction air temperature Ta ₁ decreases,
For example, when Ta ₁ =25°C, ΔT ₁ =24-6/ln25-6/25-24=6.5. Then, as the suction air temperature Ta ₁ further decreases and approaches the evaporation end point temperature T ₂ (=24℃), the temperature difference ΔT ₁ suddenly decreases and becomes zero at Ta ₁ = 24℃. (See the solid line diagram in FIG. 4).

On the other hand, when using evaporators with the same performance with a single refrigerant, for example, if you try to obtain the same capacity at a suction air temperature Ta ₁ = 27°C, the average inlet temperature difference ΔT ₁ =
Since it is sufficient to use the refrigerant at 9.3℃, the refrigerant temperature Tr is Tr=Ta ₁ −ΔT ₁ =27−9.3=17.7, and the cooling capacity decreases linearly until the suction air temperature Ta ₁ drops to 17.7℃. Become (4th
(See the dotted line diagram in the figure).

Therefore, as shown in Figure 8, the intake air temperature
Comparing the case of a single refrigerant with the same capacity and the case of a non-azeotropic refrigerant mixture with Ta ₁ set point = 27 °C,
Since the cooling capacity rapidly decreases with a decrease in the suction air temperature Ta ₁ , for example, if the load is
When the temperature decreases from line b to line b, in the case of a non-azeotropic mixed refrigerant, the temperature is balanced at point b ₂ and the room temperature decreases less.

On the other hand, in the case of a single refrigerant, the temperature is balanced at point _b1 and the room temperature decreases significantly. In particular, in the case of a load that changes significantly with respect to room temperature (as shown by line b'), the load is balanced at point b ₁ ', and the drop in room temperature becomes even greater. For this reason, in the case of a single refrigerant, a special cooling capacity control device such as a refrigerant flow control valve is used, or the evaporation temperature is increased (i.e., as shown by the chain line in FIG. 9).
It is necessary to increase the size of the evaporator).

As described above, by using a non-azeotropic mixed refrigerant, it is possible to provide the evaporator 2 with favorable characteristics in terms of room temperature control. As mentioned above, the characteristic that the cooling capacity q rapidly decreases as the suction air temperature Ta ₁ approaches the dew point temperature T ₂ of the refrigerant is due to the fact that the temperature difference required to completely evaporate the refrigerant cannot be created on the exit side of the evaporator 2. However, if the outlet side of the evaporator 2 is directly connected to the gas pipe 4 and the unevaporated liquid refrigerant returns to the condenser 1 along with the refrigerant gas through the gas pipe 4, the suction air temperature Ta ₁ Even when the temperature reaches the dew point temperature T ₂ of the refrigerant, the cooling capacity q does not become completely zero, and the effect becomes weaker. Therefore, in this embodiment, a gas-liquid separator 5 is provided in the gas pipe 4 on the outlet side of the evaporator 2 to prevent unevaporated liquid refrigerant from flowing back to the condenser 1 as described above. When the suction air temperature Ta ₁ reaches the dew point temperature T ₂ of the refrigerant, the cooling capacity q becomes completely zero.

In addition, as a non-azeotropic mixed refrigerant, the dew point temperature T ₂
Any refrigerant may be used as long as it can be set appropriately, but
A mixture in which the temperature-enthalpy curve changes significantly on the gas side is preferable because the effective temperature difference can be larger than the temperature difference shown by the above formula (1).

(Effects of the invention) According to the invention, in a natural refrigerant circulation type cooling device, a non-azeotropic mixed refrigerant is used as the circulating refrigerant,
The non-azeotropic mixed refrigerant is used at a mixing ratio and pressure that makes the dew point temperature slightly lower than the set temperature of the air to be cooled, and has a structure that allows gas and liquid separation at the evaporator outlet. Since the cooling capacity is made to decrease rapidly, the cooling capacity can be adjusted without providing a special cooling capacity control device, and there is a practical effect that the apparatus can be simplified and reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a natural circulation cooling device according to an embodiment of the present invention, FIG. 2 is a system diagram of main parts of a natural circulation cooling device according to another embodiment of the present invention, and FIG. Figure 4 is a concentration diagram for explaining the state change of refrigerant in the evaporator of the cooling device shown in Figure 1.
Figure 5 is a characteristic diagram showing the change in cooling capacity with respect to the intake air temperature when using the cooling device shown in Figure 5. Figure 5 is a characteristic diagram showing the change in air temperature and refrigerant temperature depending on the position of the heat transfer tube when a non-azeotropic mixed refrigerant is used. Figure 6 is a characteristic diagram showing the changes in air temperature and refrigerant temperature depending on the heat transfer tube position when a single refrigerant is used, and Figure 7 is a characteristic diagram showing the changes in air temperature and refrigerant temperature depending on the position of the heat transfer tube when a single refrigerant is used. The evaporation pressure-enthalpy diagram when using the non-azeotropic mixed refrigerant obtained in Figure 8 shows R22 (20wt%) and R114.
Figure 9 is a characteristic diagram showing the change in cooling capacity with respect to the suction air temperature in the case of using a non-azeotropic mixed refrigerant with (80wt%) and the case of using a single refrigerant.
It is a characteristic diagram which shows the state when the case where a single refrigerant|coolant is used in the figure is corrected. 1... Condenser, 2... Evaporator, 3... Liquid pipe, 4
... Gas pipe, 5 ... Gas-liquid separation mechanism, 6 ... Refrigerant natural circulation circuit.

Claims (1)

[Scope of utility model registration request] A condenser 1 located at a high level and an evaporator 2 located at a low level are connected by a liquid pipe 3 and a gas pipe 4 to form a refrigerant natural circulation circuit 6.
, a non-azeotropic mixed refrigerant is sealed under the operating pressure of the device so that its dew point temperature is slightly lower than the set temperature of the air to be cooled, and is placed on the gas pipe 4 side which is the outlet side of the evaporator 2. is a natural circulation type cooling device characterized by being provided with a gas-liquid separation mechanism 5.