TWI580912B - A Method for Predicting the Maintenance Time of Trolley Air Conditioning - Google Patents

Description

Method for predicting the maintenance time of the cold air condition of the crane

The present invention relates to a method for predicting maintenance, and more particularly to a method for predicting the maintenance schedule of a cold air condenser of a crane.

The overhead air conditioner is located above the crane. It is an air-cooled air conditioner that uses fins to dissipate heat. Its design is based on high reliability, high quality components and convenient maintenance. According to the type, it can be divided into medium-temperature and high-temperature crane air-conditioning and high-temperature crane air-conditioning. The medium temperature warm air car can be used for the environment where the ambient temperature is between normal temperature and 50 ° C (continuous operation temperature), while the high temperature crane air cooling can be used for the ambient temperature between normal temperature and 65 ° C (continuous operation temperature) environment of. Although the design of the overhead air conditioner is more difficult than the general commercial unit, it needs to meet the requirements of high temperature and vibration. However, the air conditioning cycle is a work of heat transfer. It needs enough external air to help the heat transfer in the room to be removed. Reduce the indoor temperature. The cranes in steel plants are usually exposed to high temperatures or even high dust, while dust and high temperatures are risk factors for heat transfer. The accumulation of dust on the fins hinders heat transfer, and the amount accumulated will not be accurately estimated as the process and line yields change.

When the condenser of the air conditioner obstructs heat exchange due to excessive ambient temperature or excessive dust accumulation, the pressure of the refrigerant vapor in the condenser will rise. When the pressure is too high, the condensation temperature of the refrigerant liquefaction cannot be reached, and liquid refrigerant cannot be produced. The latent heat of vaporization of the liquid state transition is provided, so that the temperature inside the crane cannot be lowered. When the heat transfer cannot be carried out smoothly, the unit will be damaged or even severely burned to the compressor. If it is small, the crane will be reimbursed for cold air. In severe cases, the crane cannot operate smoothly, resulting in loss of the production line. How to provide correct maintenance before the unit is damaged is the most important issue in the current use of the cold air.

In the conventional maintenance operation, it is judged whether there is dust accumulation in the fins of the condenser, and it is generally judged whether the visual fins are blocked or not, and the advanced technician can observe whether the pressure gauge is out of the normal operating range. However, because the crane is driven to a cooler area during maintenance, the pressure value is judged to be distorted. Therefore, it is often found that there is no abnormality in the maintenance area, but when the vehicle enters the high temperature furnace area, there is already a dust accumulation fin. The sheet will be in the high temperature zone, so that the heat transfer will not proceed smoothly, and the refrigerant vapor pressure will be out of the normal operating range and the unit will be damaged. Furthermore, the condenser fins used in each type of air-conditioner are different in size, the fin spacing is not the same, and the type of refrigerant may be different, which makes it quite difficult to judge.

The object of the present invention is to provide a method for predicting the maintenance time of the cold air maintenance of the crane, which simulates the pressure value of the cold air in the external state in advance, and calculates and estimates the operating point and dust of each temperature in the actual application. The equation of the relationship between the accumulation and the pressure value is used as the control limit to provide the correct time point for the condenser to predict the maintenance.

In order to achieve the above objective, a method for predicting the cooling air maintenance time course of a crane according to an embodiment of the present invention comprises: placing a cold air of a crane in an air-conditioning laboratory for running test, and simulating the temperature of the laboratory as the highest temperature of the crane. Operating outdoor temperature; at the highest operating outdoor temperature, simulating the difference in the heat exchange of the condenser for the cold air of the crane; at the maximum operating outdoor temperature, the pressure of the refrigerant in the condenser is at the limit of the system, and the corresponding condenser heat exchange The difference amount is used as the simulation point; the operating frequency of the condensing windmill motor of the crane cold air is maintained at the frequency conversion value of the simulation point, and the temperature of the air conditioning laboratory is changed to simulate the cold air of the crane to operate at different outdoor temperatures, and recorded in each The high pressure value of the refrigerant vapor pressure of the crane cooling air under simulated temperature; at the same analog point frequency conversion value, the recorded outdoor temperature versus the high pressure value of the refrigerant vapor pressure is used to fit a control curve; and the use of regulation The curve is divided into a danger zone and a safety zone, wherein the upper part of the control curve is defined as a danger zone, and the lower part of the control curve is defined as safety. .

Another method for predicting the cooling air maintenance time course of the crane according to another embodiment of the present invention comprises: placing the crane cold air in an air conditioning laboratory for running test, and simulating the temperature of the laboratory as different outdoor temperatures; at different temperatures Simulate the difference of the heat exchange of the condenser in the cold air of the crane; at the maximum operating outdoor temperature, the pressure of the refrigerant in the condenser is at the limit of the system, and the corresponding heat exchange difference of the condenser is used as the simulation point; in the same simulation At the operating frequency of the condensing windmill motor, the recorded outdoor temperature is recorded at a high pressure value of the refrigerant vapor pressure to fit a control curve; and the control curve is used to distinguish the dangerous zone from the safe zone, wherein the control curve The upper part is defined as the danger zone, and the lower part of the control curve is defined as the safety zone.

The above and other objects, features, and advantages of the present invention will become more apparent from the accompanying drawings. In the description of the present invention, the same components are denoted by the same reference numerals and will be described.

The present invention is a method for predicting the maintenance time of the cold air maintenance of the crane. Referring to the preferred embodiment shown in the flow chart of FIG. 1, the pressure value of the cold air in the external state is measured in advance, and the calculation is performed. Estimate the relationship between the operating point of each temperature and the dust accumulation and pressure value in actual application, and use the relational equation as the control limit to provide the correct time point for the condenser to predict the maintenance. The specific steps are as follows:

1. Place the overhead air conditioner in the air conditioning laboratory for operation test (110). The temperature of the laboratory is simulated as the highest operating outdoor temperature at which the overhead cooling air is located, for example, 65 ° C, and is raised from the normal temperature to the highest operating outdoor temperature.

2. At this maximum operating outdoor temperature, simulate the difference in the heat exchange of the condenser that records the cooling air of the crane (120). Specifically, it is the cooling fin of the condenser that sprays the cold air of the crane with different air volume at the highest operating outdoor temperature, and observes the change of the pressure value of the refrigerant in the condenser.

Specifically, the frequency converter can be used to change the operating frequency of the condensing windmill motor, for example, to 30, 40, 50, and 60 Hz to generate different air volumes to blow the fins, thereby simulating different amounts of dust accumulating in the condensation. The heat sink fins of the device cause a state of reduced heat transfer. The lower the frequency at which the condensing windmill motor operates, the smaller the rotational speed of the windmill, and the smaller the amount of air blown to the condenser, indicating that the fins accumulate a large amount of dust, and the heat transfer efficiency is also low.

After the condensing windmill motor blows out a fixed air volume for a period of time at the same operating frequency, for example, at 30 Hz, the condenser is also operated for a considerable period of time, and the refrigerant vapor pressure in the condenser has stabilized, and the high pressure of the refrigerant vapor pressure is at this time. The value (ie, the refrigerant vapor pressure at the condenser end of the crane) is recorded. The operating frequency of the condensing windmill motor is then changed, for example to 40, 50 and 60 Hz, and the above steps are repeated to record the high pressure value of the refrigerant vapor pressure at different operating frequencies of the condensing windmill motor.

The above is to change the frequency of the condensing windmill motor to simulate the accumulation of different amounts of dust on the fins to reduce the heat transfer. We can also use damper control or shotcreting to simulate different amounts of dust accumulation. The above-mentioned cumulative state of simulating different amounts of dust by means of frequency reduction, damper control or shotcreting may be different from the actual dust accumulation state. Therefore, the correction coefficient can be used to approximate the heat exchange difference of the actual dust accumulation condenser. .

3. At the maximum operating outdoor temperature, the refrigerant pressure in the condenser is at the limit of the system, and the corresponding condenser heat exchange difference is used as the simulation point (130). For example, the maximum operating outdoor temperature of the high-temperature crane air conditioner is 65 ° C, and the limit value of the refrigerant pressure in the condenser is 19 kgf / cm ² , which is in accordance with the value recorded in the above step (120). The frequency conversion value of the inverter corresponding to the pressure is taken as the analog point, that is, the intersection of the temperature of 65 ° C and the pressure of 19 kgf / cm ² , and the frequency conversion value of the corresponding inverter is used as the simulation point.

4. Adjust the inverter's inverter value to the analog point so that the operating frequency of the condensing windmill motor is maintained at the analog point's variable frequency value (140). The temperature of the laboratory was then changed to simulate the overhead cooling of the crane at different outdoor temperatures, for example to 35, 45 and 55 ° C, and the high pressure value (150) of the refrigerant vapor pressure at each simulated temperature was recorded. In general, the higher the outdoor temperature, the more dust is deposited, and the worse the heat exchange between the condenser refrigerant and the outdoor air will be.

5. In each of the values recorded in the above steps, at the same conversion value of the analog point, the recorded point of the recorded outdoor temperature versus the high pressure value of the refrigerant vapor pressure is used to fit a control curve and a The governing equation (160), in which the governing equation is a temperature versus pressure curve.

6. Use the control curve to distinguish between hazardous areas and safe areas (170). When the vehicle is repaired, it will usually stay in the cold zone (outside the furnace zone). At this time, the actual outdoor outdoor air temperature is measured and the pressure in the refrigerant pressure gauge of the condenser on the cold air of the crane (ie the high pressure of the refrigerant vapor pressure) is observed. Value), against the control zone line. If it is above the control curve, it means that in the danger zone, the maintenance of the condenser cleaning and maintenance should be carried out as soon as possible.

7. A pressure monitoring point and a temperature monitoring point can be set in the cold air of the crane. The pressure monitoring point monitors the high pressure value of the refrigerant vapor pressure in the condenser and records it as P1, while the temperature monitoring point monitors the outside of the crane. Gas temperature value, recorded as T2. Provides the information needed to prevent maintenance by continuously calculating the equations online.

The foregoing embodiment discloses that, after determining the simulation point, the high pressure value change of the refrigerant vapor pressure of the crane cold air at other simulated outdoor temperatures is made according to the simulation point. However, the present invention can also make a change in the high pressure value of the refrigerant vapor pressure caused by different frequency conversion values of the inverter under all simulated outdoor temperatures before determining the simulation point, that is, the difference in the heat exchange of the condenser. That is, after the simulation point is determined, the previously made data is enough to fit the control curve, and it is not necessary to simulate recording other data after determining the simulation point.

In actual implementation, the condensing windmill motor is down-converted to 60, 50, 40, and 30 Hz by a frequency converter to generate different air volumes to blow the heat-dissipating fins, thereby simulating the dust accumulation phenomenon on the heat-dissipating fins. The wind volume of the windmill is small, and the simulated dust accumulation is large; when the wind volume of the windmill is large, the simulated dust accumulation amount is small. The temperature of the real room is simulated as the outdoor outdoor air temperature, which is raised from normal temperature to high temperature, and the temperature sections of 35, 45, 55 and 65 °C are designed. In the above different simulated outdoor outdoor air temperature and different air volume (corresponding to different frequency conversion values of the inverter), record the vapor pressure of the refrigerant in the condenser, and find the outdoor temperature 65 ° C and the upper limit pressure 19 kgf / cm The intersection of ² . As shown in Fig. 2, according to the measured results, the frequency conversion value corresponding to the inverter of the intersection is 30 Hz, so the corresponding frequency conversion value of the dust to be cleaned is estimated to be 30 Hz, and the fitting curve is y = 0.0023x ² + 0.0732. x + 4.1863, where y is the high pressure value of the refrigerant vapor pressure and x is the outside air temperature value as a process control. It should be understood that the control curve does not have to be fitted with a quadratic curve, and other higher-order curves can also fit the control curve. Of course, the more analog data is required to fit with a higher degree of curve.

The actual verification is shown in Fig. 3. The outdoor air temperature is x: 35 °C, and the measured high pressure value of the refrigerant vapor pressure is y: 11.95 kgf/cm ² . Although the high-speed tripper did not occur in the cold air of the crane at this time, when the crane moved to a high temperature zone of about 57 °C, the measured high pressure value of the refrigerant vapor pressure has exceeded the upper limit of the high pressure, causing the machine to trip.

The final control curve is shown in Figure 4. The governing equation is as follows:

P1>0.0023(T2) ² +0.0732(T2)+4.1863, where P1 is the high pressure monitoring value of the refrigerant vapor pressure, and T2 is the outside air temperature value.

According to the method for predicting the cooling air maintenance time of the crane, a pressure monitoring point and a temperature monitoring point can be set in the cold air of the crane to monitor the high pressure value P1 of the refrigerant vapor pressure in the condenser and monitor the outside of the crane. External air temperature value T2. Provides the information needed for preventive maintenance by continuously monitoring the calculation equations online.

According to the method of the present invention for predicting the maintenance time of the cold air maintenance of the overhead crane, the control curve can be used to distinguish between a dangerous zone and a safe zone. When the vehicle is repaired, it will usually stay in the maintenance area. At this time, by measuring the actual outdoor outdoor air temperature and observing the pressure in the refrigerant pressure gauge of the condenser on the air conditioner, the control area line should be as fast as possible above the curve. Perform maintenance on the cleaning and maintenance of the condenser to avoid damage when the air-conditioning unit continues to operate.

While the present invention has been disclosed by the foregoing examples, it is not intended to be construed as limiting the scope of the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

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BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram showing the steps of a preferred embodiment of the present invention. Figure 2 is a graph showing the high pressure value of the outside air temperature - refrigerant vapor pressure in accordance with a preferred embodiment of the present invention. Figure 3 shows a graph of actual verification using the preferred embodiment of the present invention. Figure 4 is a graph showing the coordinates of a control curve in accordance with a preferred embodiment of the present invention.

Claims (6)

A method for predicting the maintenance time of the cold air maintenance of the crane comprises: placing the cold air of the crane in the air conditioning laboratory for running test, and simulating the temperature of the laboratory as the highest operating outdoor temperature at which the cold air of the crane is located; Next, simulate the difference of the heat exchange of the condenser of the cold air of the crane; at the maximum operating outdoor temperature, the pressure of the refrigerant in the condenser is at the limit of the system, and the difference of the heat exchange of the condenser corresponding to the condenser is used as a simulation point; The operating frequency of the condensing windmill motor of the car air conditioner is kept at the frequency conversion value of the simulation point, the temperature of the air conditioning laboratory is changed to simulate the cold air of the crane to operate at different outdoor temperatures, and the refrigerant vapor of the cold air of the crane is recorded at each simulated temperature. The high pressure value of the pressure; at the same analog point frequency conversion value, the recorded outdoor temperature versus the high pressure value of the refrigerant vapor pressure is used to fit a control curve; and the control curve is used to distinguish the dangerous zone from the safe zone. Where the upper of the control curve is defined as the danger zone and the lower of the control curve is defined as the safe zone. The method for predicting the cold air maintenance time course of the crane according to claim 1, wherein the step of simulating the difference in the heat exchange of the condenser of the cold air of the crane comprises changing the operating frequency of the condensing windmill motor to generate a difference. The air volume is used to blow the fins of the condenser, thereby simulating a state in which different amounts of dust accumulate on the fins, resulting in a decrease in heat transfer. For example, the method for predicting the cold air maintenance time course of the crane according to claim 1 is to set a pressure monitoring point and a temperature monitoring point in the cold air of the crane to monitor the high pressure of the refrigerant vapor pressure in the condenser. The value and the value of the outside air temperature outside the crane. A method for predicting the maintenance time of a cold air maintenance of a crane comprises: placing a cold air of the crane in an air conditioning laboratory for running test, and simulating the temperature of the laboratory as a different outdoor temperature; simulating the cold air of the crane at different temperatures The difference in the heat exchange of the condenser; the pressure of the refrigerant in the condenser at the maximum operating outdoor temperature is the limit value of the system, and the corresponding difference in the heat exchange of the condenser is taken as the analog point; the condensing windmill motor at the same analog point At the operating frequency, the recorded outdoor temperature versus the high pressure value of the refrigerant vapor pressure is used to fit a control curve; and the control curve is used to distinguish between the hazardous area and the safe area, wherein the upper part of the control curve is defined as the dangerous area. The lower part of the control curve is defined as a safe area. The method for predicting the cold air maintenance time course of the crane according to claim 4, wherein the step of simulating the difference in the heat exchange of the condenser of the cold air of the crane comprises changing the operating frequency of the condensing windmill motor to generate a difference. The air volume is used to blow the fins of the condenser, thereby simulating a state in which different amounts of dust accumulate on the fins, resulting in a decrease in heat transfer. The method for predicting the cold air maintenance time course of the crane according to the fourth aspect of the patent application, wherein a pressure monitoring point and a temperature monitoring point are set in the cold air of the crane to monitor the high pressure of the refrigerant vapor pressure in the condenser. The value and the value of the outside air temperature outside the crane.