JPS6214073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a defrosting operation control device for a cooling coil in an air conditioner that cools a room such as a test room.

[Conventional technology]

Conventionally, this type of device has been equipped with a timer to perform defrosting operation at regular intervals, as disclosed in Japanese Patent Laid-Open No. 51-36656. It is also known to install a differential pressure detector communicating with the air inlet and outlet sides of the cooling coil (Japanese Utility Model Publication No. 52-166158).

[Problem that the invention seeks to solve]

However, the frost formation on the cooling coil of an air conditioner is
The amount of frost is not necessarily constant and does not increase, depending on the temperature conditions of the room, the amount of moisture generated in the room, and the state of moisture intrusion into the room (outside air conditions). Therefore, in the former case, the defrosting operation may be performed even though there is almost no frost formation, or the defrosting operation may not be performed even though there is a lot of frost formation. In other words, defrosting was not carried out at an appropriate time, making it inconvenient to use the room.

In the latter case, when frost forms, it becomes difficult for air to flow, so the differential pressure between the air inflow and outflow sides of the cooling coil becomes large, and the frost state can be detected.

However, even if the amount of frost is the same, the magnitude of the differential pressure will change if the flow rate of circulating air in the cooling coil changes. There is a problem that defrosting operation cannot be performed at certain times of the year.

SUMMARY OF THE INVENTION An object of the present invention is to provide a defrosting operation control device that can perform defrosting operation at an appropriate time in a device in which the circulation flow rate of a cooling coil is variable.

[Means for solving problems]

A feature of the present invention is that at least one of a differential pressure detector communicating with both the air inlet side and the air outlet side of the cooling coil and a wind speed detector installed on the air outlet side of the cooling coil is provided. an operating flow rate signal generator that generates a signal corresponding to the operating flow rate, and a defrost control device electrically coupled to the detector and the operating flow signal generator, the defrost control device having a limit differential pressure. a means for forming a signal or a means for forming a critical wind speed signal, the signal and the differential pressure detector, or
and a means for comparing the signal with the signal of the wind speed detector,
A limit differential pressure corresponding to the operating flow rate is formed based on a signal from an operating flow rate signal generator, and the differential pressure detected by the differential pressure detector exceeds the limit differential pressure corresponding to the operating flow rate. or based on a signal from the operating flow rate signal generator, a critical wind speed corresponding to the operating flow rate is formed, and the wind speed detected by the wind speed detector is lower than the critical wind speed corresponding to the operating flow rate. When at least one of the following conditions is satisfied, a defrosting start signal is generated.

[Effect]

As described above, since the threshold differential pressure for generating the defrosting start signal is changed in response to changes in the operating flow rate, defrosting operation can be performed at an appropriate time even when the operating flow rate changes.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In Figure 1, 1 is a room that should be kept at a low temperature (hereinafter referred to as the cold room), 2 is the cold room 1 and the suction side duct 1
0 and a discharge side duct 11, this air conditioner 2 includes a cooling coil 3 for cooling circulating air, a fan 4 driven via a motor 5, and an air volume adjustment mechanism (vane damper) 7. It is equipped with 6 is a control panel for the motor 5, 8 is an actuator that adjusts the opening degree of the vane damper 7 according to the required amount of circulating air, and 9 is an actuator 8.
12 is a temperature detector installed on the inlet side of the air conditioner 2, 13 is a differential pressure detector connected to both sides of the cooling coil 3, 14 and 15 are the inlet side of the cold room 1 (the air conditioner A wind speed detector and a temperature detector are installed on the discharge side of the pump.

16 and 17 are an inflow path and an outflow path for a cooling cold medium connected to the cooling coil 3; 18 and 19 are an inflow path and an outflow path for a defrosting hot medium connected to the inflow path 16 and outflow path 17, respectively; 2
0, 22 and 21, 23 are the inflow passages 16, 1
8 and an on-off valve provided in each of the outflow passages 17 and 19, 24 a flow control valve provided in the outflow passage 17, and 25 a drain drain pipe of the air conditioner 2.

26 is a known microcomputer consisting of a signal converter 27, an arithmetic unit 28, a signal generator 29, a storage device 30, and a comparator 31; Detector 13, wind speed detector 14 and temperature detector 15
It is connected to the. On the other hand, the signal transmitter 29 is connected to the above-mentioned motor control panel 6, actuator 8, switching valves 20 to 23, and flow rate control valve 24.

Next, the operation of this embodiment configured as described above will be explained.

The relationship between the opening degree θ of the vane damper 7 and the discharge air volume, that is, the discharge outlet wind speed v of the discharge duct 11 is as shown by a curve 32 shown in FIG. As the frost formation on the cooling coil 3 increases, the above relationship changes as shown by the curve 33, so even if the opening degree of the vane damper 7 remains the same, the wind speed decreases.

Therefore, the curve 33 expresses the wind speed v at which defrosting should be performed depending on the opening degree Θ of the vane tamper 7, or in other words, for each operating flow (air) amount of the air volume adjustment mechanism.
It can be said to be a defrost limit curve related to wind speed.

Also, the opening degree θ of the vane damper 7 and the cooling coil 3
The relationship between the front and rear pressure difference △P is as shown in the curve 35 shown in Fig. 3, and the front and rear pressure difference △Po of the cooling coil 3 converted to a reference temperature of 0°C, for example, is uniquely related to the vane opening degree θ. There is a relationship. The above relationship changes as shown by the curve 34 because as the amount of frost increases, the air passage resistance increases.

Therefore, the curve 34 represents the differential pressure △ at which defrosting should be performed.
If Po is rephrased as the opening degree Θ of vane damper 7, then
It is expressed for each operating air volume of the air volume adjustment mechanism.
It can be said to be a defrost limit curve related to differential pressure.

Utilizing the above-mentioned characteristics, the defrosting operation is controlled by detecting that the amount of frosting has exceeded a specified value. That is, the signal converter 27 of the microcomputer 26 receives an opening signal (operating air volume signal) from the potentiometer 9, a differential pressure △P signal from the differential pressure detector 13, a temperature T signal from the temperature detector 12, and wind speed detection. A signal of the exit wind speed v from the device 14 and a signal of the exit temperature T from the temperature detector 15 are inputted and output to the calculator 28 . This output and the values previously stored in the storage device 30, that is, the relationship shown by the curve 33 in FIG. 2 and the relationship shown by the curve 34 in FIG. 3, are input to the calculator 28 and calculated. The result of this calculation is compared with the value stored in the storage device 30 by the comparator 31, and it is determined that at a certain opening θ of the vane damper, the wind speed v is less than or equal to the curve 33, and the differential pressure ΔPo before and after the cooling coil is
is equal to or higher than the curve 34, the detection of frost formation is output to the signal generator 29. The signal generator 29 inputting this output transmits a defrost operation signal to the motor control panel 6, the actuator 8, the switching valves 20 to 23, and the flow rate control valve 24, thereby performing the defrosting operation.

In this case, the on-off valves 20, 21 on the side of the cooling refrigerant
At the same time, the on-off valves 22 and 23 on the defrost heating medium side are opened, and the flow control valve 24 is closed.
When the bypass side is closed, the cooling coil side is opened at the same time. Furthermore, since the motor 5 is stopped by a stop signal sent to the motor control panel 6, the fan 4 is also stopped. The vane damper 7 is fully closed and stopped by a close signal to the actuator 8.

The above-mentioned operations are performed sequentially, and after a certain period of time has elapsed, the frost adhering to the outer surface of the cooling coil 3 is heated by the defrost heating medium flowing inside the cooling coil 3. Therefore, the frost melts and becomes water (drain), and this drain is discharged from the drain drain pipe 25. When the defrosting operation is completed in this way, the cooling operation is started again.

In this embodiment, the curve 33 in FIG. 2 and the curve 34 in FIG. 3 are used to detect frost formation, but the curves 32 and 35 may be used instead.

Furthermore, in the case of a fan without a vane damper, the opening degree θ can be considered to be fully open, so the value of the wind speed v in the curve 33 and the value of the differential pressure ΔPo before and after the cooling coil in the curve 34 can each be considered as one value. Furthermore, in equipment that is intended for operation when the temperature in the cold room is approximately constant, there is no need to convert the differential pressure across the cooling coil to a reference temperature, and it is sufficient to process the signal as the differential pressure across the cooling coil at that time. The system becomes simple.

Furthermore, as the air volume adjustment mechanism, one that changes the rotational speed of a blower can be used.

〔Effect of the invention〕

As described above, according to the present invention, the frosting state of the cooling coil can be accurately detected even when the operating flow rate changes, and the defrosting operation can be performed at an appropriate time.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing one embodiment of the defrosting operation control device of the present invention, and FIGS. 2 and 3 are explanatory diagrams relating to the present invention. 2... Air conditioner, 3... Cooling coil, 5... Motor control panel, 7... Vane damper, 8... Actuator, 9
...Potentiometer, 12,15...Temperature detector,
13... Differential pressure detector, 14... Wind speed detector, 26... Microcomputer, 27... Signal converter, 29... Signal generator,
20-23...Opening/closing valve, 24...Flow rate control valve.

Claims (1)

[Claims] 1. An air circulation channel connected to the room,
A cooling coil disposed in the air circulation flow path and a flow rate adjustment mechanism for varying the operating flow rate of air passing through the cooling coil, which communicates with both the air inlet side and the air outlet side of the cooling coil. At least one of a differential pressure detector and a wind speed detector installed on the air outlet side of the cooling coil, an operating flow rate signal generator corresponding to the operating flow rate, and the detector and the operating flow rate signal generator. and a defrost control device electrically connected to the differential pressure detector or the wind speed detector, and the defrost controller has a means for forming a limit differential pressure signal or a limit wind speed signal, and a means for forming a limit differential pressure signal or a limit wind speed signal, and and a means for comparing the signal with the
Based on the signal from the operating flow signal generator,
forming a limit differential pressure signal corresponding to the operating flow rate, and generating a signal from the operating flow signal generator when the differential pressure detected by the differential pressure detector exceeds the limit differential pressure corresponding to the operating flow rate; forming a critical wind speed signal corresponding to the operating flow rate based on the signal, and satisfying at least one of the conditions when the wind speed detected by the wind speed detector falls below the critical wind speed corresponding to the operating flow rate; A defrosting operation control device that generates a defrosting start signal when.