JP4860267B2 - Heat pump equipment - Google Patents

Description

  The present invention relates to a heat pump device.

  In a heat pump apparatus having a refrigerant circulation passage having a compressor, a condenser, an expansion valve, and an evaporator, as described in Patent Documents 1 and 2, for example, the condenser is ventilated with a cooling fan for condensation. An apparatus using an air-cooled condenser for cooling the refrigerant in the container is known.

Conventional heat pump devices generally have means for increasing or decreasing the rotational speed of the compressor in accordance with the load. On the other hand, the action of the condenser is left to the ambient temperature and is not usually controlled. For this reason, the cooling fan of the condenser has a problem that it keeps passing the air volume according to the maximum load even at low load and consumes more energy than necessary.
Japanese Unexamined Patent Publication No. 7-63427 Japanese Patent Laid-Open No. 7-120086

  Then, in view of the said problem, this invention makes it a subject to provide the heat pump apparatus with which the cooling fan of a condenser does not consume useless energy.

In order to solve the above problems, a heat pump device according to the present invention includes a refrigerant, a compressor, a condenser, an expansion valve, and an evaporator that exchanges heat between the refrigerant and a medium to be cooled. An installed refrigerant circulation passage, a cooling fan for passing through the condenser, a temperature sensor for detecting the temperature of the cooled medium at the evaporator inlet, and the temperature of the cooled medium at the evaporator outlet. The compressor is controlled in rotation speed so as to keep the temperature constant based on the temperature at the outlet of the evaporator , and determines the rotation speed of the cooling fan according to the load factor. Therefore, the difference between the temperature at the evaporator inlet and the temperature at the evaporator outlet is used as a value indicating the load factor, and the rotation speed of the cooling fan is decreased as the difference decreases .

  According to this configuration, the cooling fan is a condenser by increasing or decreasing the number of rotations of the cooling fan according to the load factor of the heat pump device, that is, the amount of heat to be exchanged between the refrigerant and the medium to be cooled in the evaporator. It is possible to prevent excessive air flow. In this way, the efficiency of the entire heat pump can be maintained high by preventing the cooling fan from consuming unnecessary energy.

In the heat pump apparatus of the present invention, the temperature at the evaporator outlet of the medium to be cooled is kept constant by controlling the rotation speed of a general compressor, and the temperature at the evaporator inlet of the medium to be cooled and the temperature at the evaporator outlet are maintained. The load factor of the heat pump device can be directly measured by the difference, and the energy consumption of the cooling fan can be controlled to the minimum necessary level.

  Further, in the heat pump device of the present invention, when the measured outside air temperature is low with an outside air temperature sensor that measures the outside air temperature, the degree of lowering the rotation speed of the cooling fan may be increased.

  According to this configuration, the energy consumption of the cooling fan can be controlled to the minimum necessary regardless of the outside air temperature.

  As described above, according to the present invention, since the amount of ventilation of the condenser by the cooling fan is optimized according to the load factor of the heat pump device, the efficiency of the entire heat pump device can be maintained high.

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows a heat pump apparatus 1 according to the first embodiment of the present invention. The heat pump device 1 includes a refrigerant compressor 7, a condenser 3, a receiver 4, an evaporation valve 5, and an evaporator 6, and has a refrigerant circulation flow 7 in which a refrigerant is enclosed. In the heat pump apparatus 1, the refrigerant removes heat from a medium to be cooled such as cooling water or brine in the evaporator 6, and releases heat into the air in the condenser 3.

  The screw compressor 2 is driven by a compressor motor 8, and the rotation speed of the compressor motor 8 is controlled by a compressor inverter 9.

  Further, the heat pump device 1 is provided with a cooling fan 10 that allows the outside air to flow through the condenser 3, and the fan motor 11 that rotates the cooling fan 10 can control the rotation speed by a fan inverter 12.

  The heat pump device 1 further includes a control device 13 that controls the frequencies of the compressor inverter 9 and the fan inverter 12, and a temperature sensor 14 that measures the temperature of the medium to be cooled at the outlet of the evaporator 6.

  The control device 13 performs PID control on the frequency of the compressor inverter 9, that is, the rotational speed of the screw compressor 2 so as to keep the temperature detected by the temperature sensor 14 at a preset temperature, similarly to the conventional heat pump device. . According to this control, the control device 13 increases the rotational speed of the screw compressor 2 as the amount of heat exchanged between the refrigerant and the medium to be cooled in the evaporator 6 and, as a result, the load factor of the heat pump device 1 increases.

  Further, the control device 13 changes the set frequency of the fan inverter 12 according to the set frequency of the compressor inverter 9 by the above control. That is, the control device 13 controls the rotation speed of the cooling fan 10 according to the load factor of the heat pump device 1.

  Here, in order to explain the rotational speed control of the cooling fan 10, the coefficient of performance (COP), which is the overall efficiency of the heat pump device 1, is changed in FIG. 2 when the rotational speed ratio with respect to the rating of the cooling fan 10 is changed. The graph shows how the change depends on the load factor. In the present embodiment, the load factor is a value obtained by dividing the rotational speed of the screw compressor 2 determined based on the PID control described above by a predetermined rotational speed, for example, 3675 rpm.

  As shown in the figure, the maximum efficiency is shown at a certain rotation speed ratio at any load factor, but it can be seen that the lower the load factor, the lower the rotation speed ratio of the fan 10 showing the maximum efficiency. Specifically, at an outside air temperature of 25 ° C., the rotation speed ratio of the cooling fan 10 showing the maximum efficiency is 0.8 when the load factor is 80%, 0.75 when the load factor is 50%, and 35% of the load factor. When the load factor is 25%, it is 0.65. In addition, at the outside air temperature of 15 ° C., the rotational speed ratio of the fan 10 exhibiting the maximum efficiency is about 0.55 when the load factor is 25%. As described above, the lower the load factor is, the lower the cooling fan 10 that exhibits the maximum efficiency is. However, when the outside air temperature is 25 degrees, the rotation speed ratio of the cooling fan 10 that exhibits the maximum efficiency is approximately below the load factor 25%. It is constant.

  Based on the above efficiency change, the heat pump device 1 determines the rotation speed of the cooling fan 10 according to the load factor as shown in FIG. 3 based on the data of the outside air temperature of 25 ° C. Specifically, the heat pump device 1 sets the rotational speed ratio with respect to the rating of the cooling fan 10 to 0.65 when the load factor is 35% or less, and the cooling fan 10 when the load factor exceeds 35% and is 50% or less. When the load ratio exceeds 50% and the load ratio exceeds 80%, the rotation speed ratio of the cooling fan 10 is set to 0.8, and when the load ratio exceeds 80%. The rotation speed ratio of the cooling fan 10 is set to 1.0.

  The optimum rotation speed ratio corresponding to the load factor of the cooling fan 10 continuously changes as shown by the broken line. However, in the heat pump apparatus 1, the above-described steps are taken into consideration in consideration of the stability of control. Rotational speed control is performed. In actual control, since the load factor is substantially proportional to the rotational speed of the screw compressor 2, the control device 13 determines the set frequency of the fan inverter 12 according to the set frequency of the compressor inverter 9.

  Thus, the heat pump apparatus 1 of this embodiment can maintain the whole efficiency high by changing the rotation speed of the cooling fan 10 according to the fluctuation | variation of a load factor.

Further, different embodiments of the present invention will be described.
FIG. 4 shows a heat pump apparatus 1a according to the second embodiment of the present invention. The heat pump device 1a has the same configuration as the heat pump device 1 of the first embodiment, but further includes a temperature sensor 15 that measures the temperature of the medium to be cooled at the inlet of the evaporator 6.

  As with the conventional heat pump device, the control device 13, as with the heat pump device 1, the frequency of the compressor inverter 9 is maintained so that the temperature of the medium to be cooled detected by the temperature sensor 14 is maintained at a preset temperature. That is, the rotational speed of the screw compressor 2 is PID controlled. Further, the control device 13 determines the difference between the temperature of the cooled medium at the inlet of the evaporator 6 detected by the temperature sensor 15 and the temperature of the cooled medium at the outlet of the evaporator 6 detected by the temperature sensor 14. Accordingly, the rotational speed of the cooling fan 10 is controlled.

  Specifically, the temperature of the medium to be cooled at the inlet of the evaporator 6 (temperature detected by the temperature sensor 15) is Ts, and the temperature of the medium to be cooled at the outlet of the evaporator 6 (detected by the temperature sensor 14). When the load factor is L and the load factor is L, the control device 13 sets the load factor L to L = (Ts−Td) / (Tth−) within a range where Ts does not become higher than the predetermined temperature Tth. Calculated as Td) × 100%.

  For example, when the temperature of the medium to be cooled at the outlet of the evaporator 6 is set to be kept constant at 7 ° C. in the PID control, and the predetermined temperature Tth is 12 ° C., Td is ideal. Therefore, if Ts is 12 ° C. in the ideal state, the load factor L is calculated as 100%. Similarly, if Ts is 11 ° C., the load factor L is 80%, if Ts is 10 ° C., the load factor L is 60%, and if Ts is 9 ° C., the load factor L is 40% and Ts is 8 If it is ° C., the load factor L is calculated as 20%. If the load factor L is calculated, the heat pump device 1a determines the number of rotations of the cooling fan 10 according to the load factor L, as shown in FIG.

Furthermore, a third embodiment of the present invention will be described.
FIG. 5 shows a heat pump device 1b according to a third embodiment of the present invention. The heat pump device 1b has the same configuration as the heat pump device 1 of the first embodiment, but further includes an outside air temperature sensor 16 that measures the outside air temperature around the condenser 3.

  As with the conventional heat pump device, the control device 13, as with the heat pump device 1, the frequency of the compressor inverter 9 is maintained so that the temperature of the medium to be cooled detected by the temperature sensor 14 is maintained at a preset temperature. That is, the rotational speed of the screw compressor 2 is PID controlled.

  By the way, as can be seen from the above-described curve when the outside air temperature is 25 ° C. and the load factor is 25% shown in FIG. 2 and when the outside air temperature is 15 ° C. and the load factor is 15%, as the outside air temperature decreases, the maximum The rotational speed ratio of the fan 10 showing the efficiency also decreases. Specifically, as described above, the “rotational speed ratio of the cooling fan 10 exhibiting the maximum efficiency”, which was about 0.65 when the load factor was 25% at the outside air temperature of 25 ° C., was the same load at the outside air temperature of 15 ° C. When the rate is 25%, it decreases to about 0.55.

  Note that the present inventors have found that even when the load factor is other than 25%, the “rotational speed ratio of the cooling fan 10 exhibiting the maximum efficiency” decreases as the outside air temperature decreases. This is because when the outside air temperature is lowered, the ratio of the power of the cooling fan 10 is increased in the overall power mainly composed of the power of the screw compressor 2 and the power of the cooling fan 10. The performance change at the time of the wind force change of the fan 10 is large, which means that the optimum air volume shifts to the low air volume side.

  The heat pump device 1b of the present embodiment measures the outside air temperature with the outside air temperature sensor 16 based on the above-described knowledge, and when the measured outside air temperature falls below a “predetermined temperature” (when the outside air temperature is low). On the contrary, when the outside air temperature rises above the “predetermined temperature” so as to increase the degree of lowering the number of revolutions of the cooling fan 10 when the number of revolutions of the screw compressor 2 is low (the outside air temperature is When the rotational speed of the screw compressor 2 is low, the degree of lowering the rotational speed of the cooling fan 10 is reduced. Here, the former “predetermined temperature” may be equal to or lower than the latter “predetermined temperature”, and it is not essential that the two are the same.

Specifically, for example, it is as follows.
In advance, data of a plurality of “graphs showing the relationship between the load factor and the cooling fan rotational speed” that are different in accordance with the above-described FIG. The control device 13 holds the data shown in FIG. When the outside air temperature is higher than 15 ° C. and lower than 35 ° C., the control device 13 is based on FIG. 3 described above. When the outside air temperature is 15 ° C. or lower, based on FIG. Determines the number of revolutions of the cooling fan 10 based on FIG.

  As can be seen from FIGS. 3, 6, and 7, the rotation speed ratio with respect to the rating of the cooling fan 10 is decreased step by step as the load factor decreases regardless of the outside air temperature. However, the step on the drawing is larger in FIG. 3 than in FIG. 7 and in FIG. 6 than in FIG. As can be seen from the above, when the rotational speed ratio with respect to the rating of the cooling fan 10 is reduced, the degree of reduction is increased as the outside air temperature is lower. That is, here, when the outside air temperature is lowered to 15 ° C. or less, the outside air temperature is conversely increased so that the degree of lowering the number of revolutions of the cooling fan 10 is increased when the number of revolutions of the screw compressor 2 is low. When the temperature rises to 35 ° C. or higher, the degree of lowering the rotational speed of the cooling fan 10 is reduced when the rotational speed of the screw compressor 2 is low.

  Thus, by grasping | ascertaining the change of external temperature and utilizing it for control of the cooling fan 10, there exists an advantage that the whole efficiency can be maintained irrespective of the change of external temperature.

  Note that an outside air temperature sensor for measuring the outside air temperature may be added to the heat pump device 1a of the second embodiment, and the outside air temperature may be used for controlling the cooling fan 10 as in the above-described third embodiment. Good.

  Of course, the “graph showing the relationship between the load factor and the cooling fan rotation speed” is not limited to the above three, and the control device 13 may hold more data. Further, instead of changing the rotation speed of the cooling fan 10 stepwise, it may be changed continuously as a function of the load factor and the outside air temperature by, for example, PID control.

  In addition, the heat pump apparatus said to this invention is not restricted to the above-mentioned thing. Although what has been described above has a function of exchanging heat between the refrigerant and the medium to be cooled in the evaporator 6 and utilizing the cooled medium to be cooled, the heat pump device according to the present invention has only that function. It is not limited to the above, and a so-called cooling / heating function may be switched. For example, the heat pump device according to the present invention further includes a switching channel such as a four-way valve in addition to the one shown in FIG. 1 described above. 1, the condenser 3 in FIG. 1 plays a role of an evaporator, and the evaporator 6 in FIG. 1 plays a role of a condenser to cool a medium called a medium to be cooled. It may be configured so that it can be warmed as well.

1 is a schematic view of a heat pump device according to a first embodiment of the present invention. The graph which shows the relationship between the rotation speed ratio of a cooling fan and the coefficient of performance ratio in the heat pump of FIG. 1 for every load factor. The graph which shows the relationship between the load factor and cooling fan rotation speed in the heat pump of FIG. Schematic of the heat pump apparatus of 2nd Embodiment of this invention. Schematic of the heat pump apparatus of 3rd Embodiment of this invention. The graph which shows the relationship between a load factor and the cooling fan rotation speed in the outside temperature of 15 degrees C or less of the heat pump of FIG. The graph which shows the relationship between a load factor and the cooling fan rotation speed in the external air temperature of 35 degreeC or more of the heat pump of FIG.

Explanation of symbols

1, 1a, 1b Heat pump device 2 Screw compressor 3 Condenser 5 Expansion valve 6 Evaporator 7 Refrigerant circulation channel 9 Compressor inverter 10 Cooling fan 12 Fan inverter 13 Control device 14 Temperature sensor 15 Temperature sensor 16 Outside air temperature sensor 16

Claims (2)

A refrigerant circulation passage in which refrigerant is enclosed, and a compressor, a condenser, an expansion valve, and an evaporator for exchanging heat between the refrigerant and the medium to be cooled are interposed;
A cooling fan that ventilates the condenser;
A temperature sensor for detecting the temperature of the cooled medium at the evaporator inlet;
A temperature sensor for detecting the temperature of the cooled medium at the outlet of the evaporator;
Based on the temperature at the evaporator outlet , the compressor is rotationally controlled to keep the temperature constant,
Depending on the load factor, the number of revolutions of the cooling fan constant because,
As a value indicating the load factor, using the difference between the temperature at the evaporator inlet and the temperature at the evaporator outlet,
The heat pump device characterized in that the number of rotations of the cooling fan is lowered as the difference becomes smaller . It has an outside temperature sensor that measures outside temperature,
When the measured outside air temperature is low, the heat pump apparatus according to claim 1, characterized in that to increase the degree of lowering the rotational speed of the cooling fan when the difference is smaller.

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