JPS5814931A - Apparatus for dehumidifying compressed air - Google Patents

Abstract

PURPOSE:To contrive to shorten the operation time of a compressor, to reduce starting power and to save an operation cost, by a method wherein the compressor is started and stopped according to the load of compressed air and, when the operation is started, the solenoid valve of a cooling medium arranged piping is opened only for a predetermined time. CONSTITUTION:In a compressed air dehumidifying apparatus, a cooling medium high pressure arranged piping 31 and a cooling medium low pressure arranged piping 32 are connected through a generally closed solenoid opening and closing valve 33. The cooling medium temp. at the outlet part of an evaporator 24 and the air temp. at the outlet part of a cooling tank 23 are detectd by each sensors 34, 35. According to this detected values, control circuits 36, 37 are operated to start or stop a motor driving a compressor 25 as well as to control the opening and the closing of the solenoid opening and closing valve 33. In this control, the solenoid opening and closing valve 33 is opened for a predetermined time through a timer 38 when the compressor is started. By this mechanism, compressed air is cooled by melting heat of frost adhered to the evaporator 24 after the compressor 25 is stopped and, therefore, cooling and dehumidifying capacities are maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compressed air dehumidifier that dehumidifies compressed air by cooling it to a temperature below the total dew point.

As shown in FIG. 1, for example, a conventional device of this type has an evaporator 2 housed in a cooling tank 1 that forms a flow path for compressed air, and a refrigerant connected to the evaporator 2 installed outside the tank. By connecting the compressor 3, condenser 4, all capillary tubes 5, and accumulator 6 for circulation to form a refrigeration cycle, the compressed air is cooled to a temperature below the total dew point using the heat of evaporation of the refrigerant and dehumidified. There is something I did.

However, in such a dehumidifying device, the flow rate of compressed air,
When the compressor 3 is completely started and stopped in response to temperature changes, the frequency of starting and stopping of the compressor 8 increases, and when the pressure difference between the discharge (high pressure) side and the suction (low pressure) side is large, the compressor 3 There is a risk that the system will be activated and overloaded, or that the cooling and dehumidifying temperature may not be able to keep up with the sudden increase in the compressed air load.

Therefore, conventionally, as shown in FIG. 1, the high-pressure refrigerant piping 7 and low-pressure piping 8 are connected through the full capacity control valve 9, and the high-pressure refrigerant flowing to the low-pressure side via the control valve 9'If: The flow rate was controlled to maintain the cooling temperature of the compressed air at a predetermined value. 10 is a compressed air inlet, 11 is a compressed air outlet, and 12 is a drain trap.

However, continuously operating the compressor 8 by fully adjusting the opening degree of the capacity control valve 9 to adjust the cooling capacity leads to waste of electrical energy, and is uneconomical. When operated with the dehumidifier open, the evaporation pressure of the refrigerant increases, so the specific volume of the suction gas refrigerant increases, and even in partial load operation, the shaft power of the compressor increases significantly, making the operating cost of this type of dehumidifier high. There was a drawback.

The present invention has been made in view of the above, and has an object to reduce operating costs of this type of dehumidifier by completely starting and stopping a refrigerant compressor in response to changes in compressed air flow rate, temperature, etc. With the goal.

The present invention will be explained in detail below based on an embodiment shown in FIG.

Cooling tank 2 provided with an inlet 21 and an outlet 22 for compressed air
A refrigerant evaporator 24 is installed in the tank 28.
Similar to the conventional method, a refrigerant compressor 25 and a condenser 26 installed outside the evaporator are connected to the evaporator 24 through a capillary tube 27 and an accumulator 28 to form a refrigeration cycle. 29 is a cooling fin, 3° is a drain trap.

Here, in the present invention, a first temperature sensor is provided which is connected to the refrigerant high/pressure pipe 31 and the refrigerant low pressure pipe 32 via a fully normally closed electromagnetic on-off valve 33, and which detects the entire refrigerant temperature at the outlet of the evaporator 24. 84 and a second temperature sensor 35 for detecting the air temperature at the outlet of the cooling tank 23. The output from the control circuit 86, 87 is connected to the control terminal of the driving motor (not shown), and the output blade end of the circuit/path 86, 870 and the electromagnetic on-off valve 38 are connected via the timer 88i. The compressor 25 is started and stopped by the control signal, and the electromagnetic on-off valve 33 is fully opened and closed.

In the above configuration, when the compressor 25 is operated and the refrigerant evaporates in the evaporator 24, the compressed air passing through the cooling tank 23 is cooled to a temperature below the dew point by the heat of evaporation and dehumidified. When the air temperature at the outlet of the cooling tank 23 drops to a predetermined value, the contact point of the first control circuit 87 is opened. Also, the flow rate of compressed air decreases, or
When the temperature, humidity, etc. of the supplied compressed air decrease and the heat load decreases, moisture freezes in the cooling fins 29 of the evaporator 24, and the temperature of the refrigerant at the outlet of the voice generator 24 decreases. When the temperature of the refrigerant decreases to a temperature at which frost adheres to some extent in this manner, the contacts of the first control circuit 36 are opened by the output of the second sensor 34. Then, 1. Since no operation signal is output from any of the control circuits 86, 87751, the compressor 25 is stopped.

After the compressor 25 is stopped in this manner, the refrigerant no longer evaporates, but the compressed air is cooled by the heat of melting the frost adhering to the evaporator 24, so the cooling and dehumidifying functions are maintained.

When the frost completely melts and the air temperature at the outlet of the cooling tank 23 becomes higher than the set value, a signal from the second sensor 25 closes the contacts of the second control circuit 37, and the refrigerant Since the temperature is also 1, the contacts of the first control circuit 36 are also closed. Therefore, after the frost melts, the compressor 25 is started and operated again, but the first control circuit 8
At the same time as the contact point 6 closes, the timer 38 operates and causes the electromagnetic on-off valve 88 to open for a predetermined period of time, so when the compressor 25 is started, there is almost no pressure difference between the high pressure side and the low pressure side. ing. For this purpose, °compressor'25
The load at startup can be reduced, and the total startup power can be reduced.

Note that during normal operation, a certain amount of frost adheres to the evaporator 24, so the flow rate of compressed air increases negatively.
Alternatively, even if the temperature of the compressed air or air suddenly rises, the cooling effect by melting the frost is performed in addition to the cooling effect by the evaporator 24, so that even if the load of the compressed air suddenly increases, the desired dehumidification performance can be maintained.

In the above embodiment, the temperature of the refrigerant at the outlet of the evaporator and the temperature of the air at the outlet of the cooling tank? Although the compressor and the electromagnetic on-off valve are all controlled by detection, either of them may be omitted.

Also, in the embodiment, the condenser is completely cooled with external air, but is it possible to cool the condenser with cooled and dehumidified compressed air? By cooling, dry compressed air at room temperature can be obtained.

As explained above, according to the present invention, the compressor is fully started or stopped depending on the compressed air load, and the heat of melting of the frost attached to the evaporator during partial load is used as cooling energy during overload or stop. Since the compressor is designed to be used, the operating time of the compressor can be shortened and operating costs can be reduced entirely.

In addition, at startup, the solenoid on-off valve is fully opened to equalize the pressure on both the high and low pressure sides, reducing the starting power of the compressor, and during normal operation, the solenoid on-off valve is fully closed to reduce the evaporation pressure. Since the specific volume of the refrigerant sucked into the compressor is reduced, the compressor shaft power can be completely reduced, which greatly reduces the operating cost of the compressor, which accounts for the majority of the equipment operating cost, and saves electricity and other energy. Can be used effectively.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a conventional example, and FIG. 2 is a system diagram of an embodiment of the present invention. 23...Cooling tank 24...Evaporator 25.
...Compressor 26...Condenser 27,...
Capillary tube 28...Accumulator 31...Refrigerant high pressure piping 32...Refrigerant low pressure piping 33...Solenoid on-off valve 8
4.85...Temperature sensor 36.87...Control circuit 38...Timer patent applicant Orion Machinery Co., Ltd.

Claims (1)

[Claims] A refrigeration cycle is constructed by connecting a refrigerant compressor, a condenser, a capillary tube, an evaporator, and an accumulator, and the evaporator is completely installed in a cooling tank that constitutes a flow path for compressed air. In a compressed air dehumidifier configured to cool and dehumidify all flowing air to a temperature below the total dew point, the high-pressure refrigerant piping and low-pressure refrigerant piping are connected via a normally closed electromagnetic shut-off valve, and the evaporator outlet section The system is equipped with seven sensors that detect the compressed air load through the refrigerant temperature and/or the air temperature at the outlet of the cooling tank and start and stop the compressor, and the solenoid valve is opened for a predetermined period of time when the compressor is started. A compressed air dehumidifier that features a valve-operated timer and all features.