JP2006138545A - Air conditioner, and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air conditioner not causing cost increase, and capable of carrying out wet heating against microorganisms adhered to and growing on an indoor heat exchanger surface during a stopped state of the air conditioner or during heating cycle operation without requiring a humidifying means in an indoor unit casing. <P>SOLUTION: During the stopped state of the air conditioner, or when carrying out the heating cycle operation, when an instruction for inactivation operation is outputted, dehumidification cycle operation is carried out, and it is confirmed by a dew formation sensor whether the indoor heat exchanger surface is covered by dew water. If it is covered by dew water, high temperature heating cycle operation with a higher heat dissipation temperature than the normal heating cycle operation is carried out, and a temperature of an indoor heat exchanger is raised. A surface temperature of the indoor heat exchanger is measured by a temperature sensor, and when the temperature arrives at a protein denaturation temperature of the microorganisms, the indoor heat exchanger is maintained at the temperature or more for a predetermined time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an air conditioner and a method for operating the same, and more particularly to inactivation to reduce the number of microorganisms that adhere to and grow on the indoor heat exchanger surface of the air conditioner.

  As a method for inactivating microorganisms, there is a heat treatment, but the inactivation effect is greatly different between when the microorganisms are heated by dry heat using heated air and when the microorganisms are heated by wet heat using steam or hot water. That is, it is known that wet heat heating has a greater inactivation effect than dry heat heating (for example, Non-Patent Document 1). The reason for this is considered that as the amount of water in the growth medium of the microorganism increases, the amount of heat transfer to the microorganism increases and the heating effect increases, and the proteins and nucleic acids constituting the microorganism are more likely to be thermally denatured.

Therefore, as a method for inactivating microorganisms that adhere to and grow in the indoor unit of an air conditioner, a method using wet heat heating is disclosed (for example, Patent Document 1). This is a method of supplying moisture to the inside of the indoor unit casing of the air conditioner with a humidifier and heating with an indoor heat exchanger.
JP-A-9-229456 "Handbook for sterilization and sterilization" supervised by Isao Shibazaki, Science Forum, September 25, 1985, p22-25

  As described above, the conventional method for inactivating microorganisms that adhere to and grow on the indoor unit of an air conditioner humidifies and heats up the entire interior of the indoor unit casing. This is because the conventional air conditioner has a slow rate of heating the entire interior of the indoor unit casing, and the moisture in the indoor unit casing evaporates before the temperature rises to the temperature required for inactivation. Needed to be humidified. As a result, there has been a problem that the humidifying means increases the cost of the air conditioner.

  Therefore, the present invention has been made in order to solve such a conventional problem, and it is possible to prevent microorganisms that adhere to and grow on the surface of the indoor heat exchanger when the air conditioner is stopped or during a heating cycle operation. It is an object of the present invention to provide an air conditioner that can perform wet heat heating without requiring humidification means in the machine casing and does not cause an increase in cost.

  The present invention relates to a heating cycle in which carbon dioxide is used as a refrigerant, the refrigerant is radiated by an indoor heat exchanger, evaporated by an outdoor heat exchanger, and indoor air heated by the indoor heat exchanger is blown from the indoor unit outlet into the room by a fan. An air conditioner equipped with a control unit that switches between operation and dehumidification cycle operation that evaporates refrigerant in an indoor heat exchanger and dissipates heat in an outdoor heat exchanger to generate condensed water on the surface of the indoor heat exchanger. Switch from the air conditioner stopped state or heating cycle operation to dehumidification cycle operation to attach dew condensation water to the surface of the indoor heat exchanger, and the heat release temperature in the indoor heat exchanger from the dehumidification cycle operation to the heating cycle operation. Switch to high-temperature heating cycle operation to raise the temperature to bring the indoor heat exchanger surface above the microbial protein denaturation temperature and hold the indoor heat exchanger surface above the microbial protein denaturation temperature for a predetermined time. It is.

  By using carbon dioxide as the refrigerant, a high refrigerant temperature can be easily obtained, so that the temperature of the indoor heat exchanger surface can be rapidly increased. As a result, when the dehumidification cycle operation is switched to the high-temperature heating cycle operation, the surface of the indoor heat exchanger can be made higher than the protein denaturation temperature of the microorganisms before the condensed water evaporates. Here, in order to inactivate microorganisms, a short time is sufficient at a high heating temperature, but a long time heating is necessary at a low temperature. Moreover, in order to inactivate microorganisms, it is necessary to denature the protein which comprises microorganisms. Therefore, the heating temperature for inactivating the microorganism needs to be equal to or higher than the protein denaturation temperature of the microorganism, and the microorganism can be inactivated by maintaining the temperature at the temperature or higher for a predetermined time. In this way, for microorganisms growing on the surface of the indoor heat exchanger, it is possible to heat and heat the surface of the indoor heat exchanger without requiring a humidifying means, which may lead to an increase in the cost of the air conditioner. Absent.

  Moreover, the air conditioner of this invention is good also as a structure provided with the temperature sensor and the dew condensation sensor in contact with the surface of an indoor heat exchanger. With such a configuration, the temperature of the indoor heat exchanger surface and whether condensed water has evaporated can be confirmed more reliably, and microorganisms can be inactivated more reliably.

  The operation method of the air conditioner according to the present invention is such that the indoor air heated by the indoor heat exchanger is heated from the indoor unit outlet through the fan by using carbon dioxide as a refrigerant, radiating the refrigerant with the indoor heat exchanger, evaporating with the outdoor heat exchanger. Between the heating cycle operation that blows the air in the room and the dehumidification cycle operation that causes the refrigerant to evaporate in the indoor heat exchanger and dissipate heat in the outdoor heat exchanger to generate condensed water on the surface of the indoor heat exchanger. The first step of switching from the condition where the conditioner is stopped or from the heating cycle operation to the dehumidification cycle operation to attach condensed water to the surface of the indoor heat exchanger, and the heat radiation temperature in the indoor heat exchanger from the dehumidification cycle operation to the heating cycle operation Switch to high temperature heating cycle operation to raise the temperature, and before the condensed water evaporates, the second step to bring the surface of the indoor heat exchanger above the protein denaturation temperature of the microorganism, and the surface of the indoor heat exchanger It is to perform the inactivation operation and a third step of holding a predetermined time at the protein denaturation temperature or more microorganisms. By such an operation method, the microorganisms on the surface of the indoor heat exchanger can be inactivated without requiring humidification means in the indoor unit.

  In addition, the temperature of the indoor heat exchanger surface and the predetermined time in the third step of the operation method of the air conditioner of the present invention may be 75 ° C. or more and 5 minutes or more. Under such temperature and time conditions, airborne bacteria and fungi can be inactivated.

  Further, the temperature of the indoor heat exchanger surface and the predetermined time in the third step of the operation method of the air conditioner of the present invention may be 85 ° C. or more and 10 minutes or more. Such temperature and time conditions can inactivate C. perfringens.

  According to the air conditioner of the present invention and the operation method thereof, humidifying means for heating the microorganisms that adhere to and grow on the surface of the indoor heat exchanger when the air conditioner is stopped or in the heating cycle operation is humidified in the indoor unit of the air conditioner. Therefore, the cost of the air conditioner is not increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1 is a schematic configuration diagram of an air conditioner according to an embodiment of the present invention. The air conditioner includes an indoor unit 10 and an outdoor unit 20. The indoor unit 10 includes an indoor heat exchanger 14 and an indoor control unit 16. The indoor heat exchanger 14 includes a dew condensation sensor 12 that detects whether moisture is attached to the surface of the indoor heat exchanger 14, and a temperature sensor 13 that detects the surface temperature of the indoor heat exchanger 14. The outdoor unit 20 includes an outdoor heat exchanger 22, an expansion valve 24, a compressor 26, a four-way valve 28, and an outdoor control unit 30. Further, as shown in FIG. 1, the indoor heat exchanger 14, the expansion valve 24, the outdoor heat exchanger 22, the four-way valve 28, and the compressor 26 are connected by a refrigerant pipe 34 to constitute a refrigeration cycle. Carbon dioxide is filled as the refrigerant.

  Next, the operation | movement in the refrigerating cycle of such an air conditioner is demonstrated. In the dehumidification cycle operation in FIG. 1, the refrigerant flows as indicated by a solid arrow A, evaporates in the indoor heat exchanger 14, and lowers the surface of the indoor heat exchanger 14. Then, the indoor air is condensed on the surface of the indoor heat exchanger 14 to dehumidify, and the outdoor heat exchanger 22 radiates heat. Further, in the heating cycle operation and the high-temperature heating cycle operation, the refrigerant flows as indicated by a broken line arrow B, evaporates in the outdoor heat exchanger 22, and dissipates heat in the indoor heat exchanger 14. The switching of the refrigerant flow is performed by the four-way valve 28. The compressor 26 makes it easy to dissipate heat by setting the refrigerant to a high temperature and high pressure, and the expansion valve 24 reduces the refrigerant pressure to facilitate evaporation. Yes.

  FIG. 2 is a perspective view of the indoor heat exchanger in the air conditioner according to the embodiment of the present invention. The indoor heat exchanger 14 is, for example, a fin tube type composed of a copper pipe 36 through which a refrigerant passes and aluminum fins 38, and the condensation sensor 12 and the temperature sensor 13 are provided on the surface thereof. The temperature sensor 13 is preferably attached at the center of the edges of the copper pipe 36 and the fin 38 so that the average temperature of the surface of the indoor heat exchanger 14 can be measured.

  As described above, in the dehumidification cycle operation, the refrigerant evaporates in the indoor heat exchanger 14 and the surface thereof is at a low temperature, so that condensation occurs and the dew condensation water 40 covers the surface. Here, the surface of the fin 38 is uniformly covered with a water film, but water droplets are formed from the upper end to the lower end of the fin 38 and flow down to the drain pan 44. Accordingly, the lower end of the fin 38 is most wet. Therefore, as shown in FIG. 2, when the high-temperature refrigerant from the compressor during the high-temperature heating cycle operation is circulated from the lower part to the upper part of the indoor heat exchanger 14, it can be heated at a high temperature from the place where the microorganisms 42 are most likely to grow. It is effective.

  Next, the inactivation operation in which the air conditioner inactivates microorganisms on the indoor heat exchanger 14 covered with the condensed water 40 through the dehumidification cycle operation from the stopped state or the heating cycle operation will be described. In addition, the control part which memorize | stores this inactivation driving | operation is comprised by the indoor control part 16 and the outdoor control part 30 which were connected by the signal wire | line 32 of FIG.

  FIG. 3 is a flowchart of the inactivation operation of microorganisms, which is an operation method of the air conditioner according to the embodiment of the present invention. When the air conditioner is in a stopped state or performing a heating cycle operation, if an inactivation operation instruction is issued, the dehumidification cycle operation is performed in the first step, and the surface of the indoor heat exchanger is covered with dew condensation water by the dew condensation sensor. Make sure that If it is not covered with condensed water, the dehumidification cycle operation is continued until the indoor heat exchanger surface is covered with condensed water. When covered with dew condensation water, the fan may be stopped and the indoor unit outlet may be closed in order to quickly raise the temperature of the indoor heat exchanger. In the second step, a high-temperature heating cycle operation is performed to raise the temperature of the indoor heat exchanger. Then, the surface temperature of the indoor heat exchanger is measured with a temperature sensor to check whether the protein denaturation temperature of the microorganism has been reached. If the protein denaturation temperature of the microorganism is not reached, the high-temperature heating cycle operation is continued. In the third step, when the temperature of the surface of the indoor heat exchanger reaches the protein denaturation temperature of the microorganism, the indoor heat exchanger is held at the temperature or higher for a predetermined time.

  Here, the evaporation capacity of the dew condensation water on the surface of the indoor heat exchanger is the difference between the saturated vapor pressure and the absolute humidity at the temperature of the air around the indoor heat exchanger. When high-temperature refrigerant flows into the indoor heat exchanger and is heated, the temperature on the surface of the indoor heat exchanger rises rapidly, but heat transfer to the surrounding air is delayed, so evaporation of condensed water is also delayed. Promoted. Therefore, before the condensed water on the surface of the indoor heat exchanger evaporates, the surface temperature can be made higher than the protein denaturation temperature of the microorganism, and moist heat heating can be performed for a predetermined time above that temperature, and the surface of the indoor heat exchanger is Microbes that attach and grow can be inactivated.

  Thus, since the microorganisms adhering to the indoor unit of the air conditioner can be efficiently inactivated by wet heat heating, an apparatus for humidifying the entire interior of the indoor unit is not necessary, and the cost is not increased.

  Next, an example of operating conditions when switching from dehumidification cycle operation to high-temperature heating cycle operation using carbon dioxide as a refrigerant will be described. As shown in FIG. 1, the flow of the refrigerant from the dehumidification cycle operation is switched from the arrow A to the arrow B by the four-way valve 28, and for example, the inverter type compressor 26 is operated at a maximum frequency of 100 Hz. FIG. 4 is a Mollier diagram showing the refrigeration cycle at this time. The surface pressure of the indoor heat exchanger was 90 ° C. or higher with a high pressure of 11 MPa for releasing heat from the refrigerant and a low pressure of 3.5 MPa for evaporating. Thus, if carbon dioxide is used as the refrigerant, the surface temperature of the indoor heat exchanger having a compression ratio of 3.1, which is the ratio of the high pressure to the low pressure, is 90 ° C. or higher, that is, a high temperature refrigerant of 90 ° C. or higher. For R-12, which is a conventional fluorocarbon refrigerant, for example, the low pressure is 0.32 MPa when evaporated at 0 ° C., and the high pressure is 2.87 MPa even when condensed at 90 ° C., and the compression ratio is 9.0. The machine will be overloaded. However, when carbon dioxide is used as a refrigerant, a high-temperature refrigerant can be easily obtained within a range where the compression ratio is small and an excessive load is not imposed on the compressor.

  Next, an experimental method for inactivation conditions of microorganisms in the operation method of the air conditioner according to the embodiment of the present invention will be described. Switching from dehumidification cycle operation to high-temperature heating cycle operation, the condition that the surface temperature of the indoor heat exchanger to reach and the temperature held at that temperature were changed under the condition that the condensed water did not evaporate. And the number of surviving bacteria which the microorganisms on the aluminum fin of the indoor heat exchanger 14 in each combination of temperature and time remained without being killed was measured. The test method for the measurement was a bacterial transcription method, and the method for measuring the number of bacteria was a plate pour method.

  Specifically, when the surface temperature of the indoor heat exchanger, the conditions for changing the holding time at that temperature, and the surface of the indoor heat exchanger before the high-temperature heating cycle operation are 15 ° C., 5 mm from the bottom of the indoor heat exchanger Each piece of × 5 mm aluminum was cut out.

Then, the cut aluminum piece is sterilized, immersed in a test tube containing phosphate buffered saline 10 × 10 ⁻³ L (liter) prepared based on JIS Z 2801, and then shaken well to the surface. The attached bacteria were dispersed in the liquid. Next, pipette into a petri dish and take 0.1 × 10 ⁻³ L of liquid from the test tube, and keep it at 45 to 46 ° C. A normal agar medium (meat extract 5.0 g, peptone 10.0 g, sodium chloride 5.0 g, (15.0 g of agar is dissolved in 1 L of water and adjusted to pH = 7) About 15 × 10 ⁻³ L is added to the petri dish and allowed to stand at room temperature. The cells were cultured at 36 ° C. for 40 hours to 48 hours. Thereafter, the number of surviving bacteria on the aluminum piece was counted by counting the number of colonies that were a community of microorganisms per agar medium.

(Experiment 1)
The indoor heat exchanger surface temperature reached by the high-temperature heating cycle operation was 65 ° C., 75 ° C., and 85 ° C., and the holding time at each temperature was 3 minutes, 5 minutes, and 10 minutes. And the number of surviving bacteria was measured according to the above-mentioned experimental method. The results are shown in (Table 1).

  As can be seen from (Table 1), the number of surviving microorganisms in the indoor heat exchanger is 15 ° C. before the high-temperature heating cycle operation under the condition that the surface temperature of the indoor heat exchanger is 75 ° C. or higher and maintained for 5 minutes or more. The number of surviving bacteria has been reduced to less than 1/1000. Moreover, when the kind of microorganisms at this time was investigated, they were airborne bacteria and fungi. Therefore, airborne bacteria and fungi can be inactivated by maintaining the surface temperature of the indoor heat exchanger at least at 75 ° C. for 5 minutes.

  In addition, about the virus rarely discovered from airborne dust, it experimented on the same temperature and time conditions, but it was able to be inactivated when the indoor heat exchanger surface was hold | maintained at 75 degreeC or more for 5 minutes or more.

(Experiment 2)
Next, an experiment was repeated in which the surface temperature of the indoor heat exchanger, which was the inactivation condition determined in Experiment 1, was maintained at 75 ° C. for 5 minutes or more. And, with respect to the number of surviving bacteria on the surface of the indoor heat exchanger at 15 ° C before the high-temperature heating cycle operation, the ratio of the number of surviving bacteria when held at 75 ° C for 5 minutes is defined as the sterilization rate, The sterilization rate was examined in 26 cases including Example 1. The results are shown in (Table 2).

  As shown in (Table 2), among 26 cases, 20 cases are maintained at 75 ° C. for 5 minutes and the sterilization rate is less than 1/1000, but the sterilization rate is 1/100 and 1/10. There were 6 cases of less than those, and in those cases, the number of surviving bacteria was examined under the following conditions. The temperature of the surface of the indoor heat exchanger was set to 75 ° C., 85 ° C., and 95 ° C. in the high-temperature heating cycle operation, and the holding time at each temperature was set to 5 minutes, 10 minutes, and 15 minutes. Moreover, the survival cell count of the indoor heat exchanger whose surface temperature before a high-temperature heating cycle operation was 15 degreeC was investigated. And the experiment similar to Example 1 was performed, and the number of surviving bacteria per one agar medium was measured. The results are shown in (Table 3).

As can be seen from (Table 3), the number of surviving microorganisms on the condition that the indoor heat exchanger surface temperature is 85 ° C. or higher and maintained for 10 minutes or longer is 15 ° C. in the indoor heat exchanger before high-temperature heating cycle operation. The number of surviving bacteria is less than 10 ⁻³ . Further, when the type of microorganism at this time was examined, it was found to be Clostridium perfringens. Therefore, as can be seen from Table 3, when the indoor heat exchanger surface temperature is kept at at least 85 ° C. for 10 minutes, the number of surviving B. perfringens bacteria is reduced and can be inactivated. Thus, the microorganisms growing on the surface of the indoor heat exchanger can be selectively inactivated by changing the temperature and time conditions of the inactivation operation. Specifically, the temperature of the surface of the indoor heat exchanger that is reached in the high-temperature heating cycle operation may be changed to a plurality. For example, in two steps, “inactivated normal operation” inactivates airborne bacteria and fungi. Conditions for inactivating these microorganisms can be inactivated by maintaining the surface temperature of the indoor heat exchanger at 75 ° C. or more for 5 minutes or more. “Inactivated strong operation” inactivates C. perfringens. Conditions for inactivating the microorganism can be inactivated by maintaining the surface temperature of the indoor heat exchanger at 85 ° C. or higher for 10 minutes or longer.

  The inactivation operation may be instructed from the remote controller 35 as shown in FIG. In this way, the timing for performing the inactivation operation can be selected, and the inactivation operation can be performed in the room where the cooling operation is terminated and unattended, so there is no discomfort due to the high temperature air flow, and it is performed repeatedly every day. An effective driving method for inactivation can also be selected.

  In the embodiment of the present invention, the indoor air conditioner has been described. However, the same effect can be obtained even when used as an air conditioner in an automobile.

  According to the air conditioner and the operation method of the present invention, it is possible to heat and heat without having a humidifying means, and it can be applied to inactivation of microorganisms growing on the surface of an indoor heat exchanger such as indoors or in an automobile.

The schematic block diagram of the air conditioner of embodiment of this invention The perspective view of the indoor heat exchanger in the air conditioner of the embodiment Flow chart of microorganism inactivation operation of the embodiment Mollier diagram of refrigeration cycle of carbon dioxide refrigerant in the embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Indoor unit 12 Condensation sensor 13 Temperature sensor 14 Indoor heat exchanger 16 Indoor control part 20 Outdoor unit 22 Outdoor heat exchanger 24 Expansion valve 26 Compressor 28 Four-way valve 30 Outdoor control part 32 Signal line 34 Refrigerant piping 35 Remote control 36,50 Copper tube 38 Fin 40 Condensed water 42 Microorganism 44 Drain pan

Claims (5)

Heating cycle operation in which carbon dioxide is used as a refrigerant, the refrigerant is radiated by an indoor heat exchanger, evaporated by an outdoor heat exchanger, and indoor air heated by the indoor heat exchanger is blown indoors from an indoor unit outlet through a fan; ,
An air conditioner comprising a control unit that switches between a dehumidification cycle operation that evaporates the refrigerant in the indoor heat exchanger and dissipates heat in the outdoor heat exchanger to generate condensed water on the surface of the indoor heat exchanger,
The controller is
Switch from the air conditioner stopped state or the heating cycle operation to the dehumidification cycle operation to attach condensed water to the surface of the indoor heat exchanger, and from the dehumidification cycle operation to the indoor heat exchanger from the heating cycle operation Switching to a high-temperature heating cycle operation in which the heat radiation temperature of the microorganism is increased to bring the surface of the indoor heat exchanger to a temperature higher than the protein denaturation temperature of the microorganism, and holding the surface of the indoor heat exchanger at a temperature equal to or higher than the protein denaturation temperature of the microorganism for a predetermined time. Air conditioner characterized by. The air conditioner according to claim 1, further comprising a temperature sensor and a dew condensation sensor in contact with a surface of the indoor heat exchanger. Heating cycle operation in which carbon dioxide is used as a refrigerant, the refrigerant is radiated by an indoor heat exchanger, evaporated by an outdoor heat exchanger, and indoor air heated by the indoor heat exchanger is blown indoors from an indoor unit outlet through a fan; ,
Dehumidification cycle operation that evaporates the refrigerant in the indoor heat exchanger and dissipates heat in the outdoor heat exchanger to generate condensed water on the indoor heat exchanger surface can be switched,
A first step of switching the air conditioner from a stopped state or the heating cycle operation to the dehumidification cycle operation and attaching condensed water to the surface of the indoor heat exchanger;
The dehumidification cycle operation is switched from the heating cycle operation to a high-temperature heating cycle operation in which the heat radiation temperature in the indoor heat exchanger is increased, and the surface of the indoor heat exchanger is denatured before the condensed water evaporates. A second step of making the temperature or higher;
A method for operating an air conditioner, comprising performing an inactivation operation including a third step of maintaining the surface of the indoor heat exchanger at a temperature equal to or higher than a protein denaturation temperature of the microorganism for a predetermined time. The method of operating an air conditioner according to claim 3, wherein the temperature and the predetermined time of the indoor heat exchanger surface in the third step are set to 75 ° C or more and 5 minutes or more. The method of operating an air conditioner according to claim 4, wherein the temperature and the predetermined time of the indoor heat exchanger surface in the third step are set to 85 ° C or more and 10 minutes or more.

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