JP6605366B2 - Oil free air compressor - Google Patents

Description

  The present invention relates to an oil-free air compressor.

  An air compressor produces compressed air by sucking and compressing the atmosphere. Normally, the atmosphere contains water vapor, and the air that has been compressed to a high temperature is then cooled, so that the water vapor is condensed and drain water is generated. This drain water needs to be discharged outside the compressor. In particular, since the drain water in the air compressor is handled as industrial wastewater, the drain water is temporarily stored in a container and artificially discarded, or additional equipment such as a discharge line is required. In any case, the drainage of the drain water is a factor in complicating the device configuration and increasing costs.

  Patent Document 1 and Patent Document 2 disclose an evaporator that evaporates drain water without discarding it in order to solve the above-described problem of discarding drain water.

JP 2011-145041 A JP 2009-186044 A

  The evaporators of Patent Document 1 and Patent Document 2 are both open types. When a large amount of drain water is evaporated using an open type evaporator, the drain water may be scattered or leaked to the outside of the evaporator.

  An object of the present invention is to provide an oil-free air compressor that does not require additional equipment for disposal of drain water and can prevent the drain water from scattering or leaking to the outside.

The oil-free air compressor of the present invention includes a compressor main body that sucks and compresses and discharges air, a cooling unit that cools the compressed air discharged from the compressor main body, and generates drain water during cooling, An airtight container type evaporator that is fluidly connected to the cooling unit and evaporates the drain water , wherein the cooling unit cools the compressed air discharged from the first-stage compressor body, and A first cooler fluidly connected via a first solenoid valve and the compressor, and the compressed air discharged from the second stage compressor body is cooled, and the fluid is passed through the evaporator and the second solenoid valve. A second cooler connected to each other, a dehumidifier that removes moisture from the compressed air flowing out of the second cooler, and is fluidly connected via the evaporator and a third electromagnetic valve, The oil-free air compressor includes the first solenoid valve and the second solenoid valve. Serial addition Ru comprising a controller for controlling such that the third and an electromagnetic valve respectively shifting the timing of valve opening.

According to this configuration, labor costs for manually and periodically draining drain water and additional equipment such as a drain water discharge line are not required, and the running cost of the oil-free air compressor is greatly improved. Further, since the evaporator is a closed container type, even when a large amount of drain water is evaporated, it is possible to prevent the drain water from being scattered or leaked outside the evaporator. Further, the drain water is usually intermittently discharged, and the compressed air is also discharged along with the drain water. Therefore, when drain water is simultaneously supplied to the evaporator from a plurality of locations, the flow velocity at the vapor side outlet of the evaporator is increased by the compressed air supplied together with the drain water, and the droplets may be scattered outside. However, by controlling as described above, the timing for supplying the drain water to the evaporator can be shifted and the timing can be fixed, so that it is possible to prevent the drain water from flowing into the evaporator from a plurality of locations at the same time. Thereby, it can prevent that the flow velocity of the vapor | steam side exit of an evaporator increases, and can prevent that a droplet disperses outside.

  The control device controls the time for opening the first electromagnetic valve, the second electromagnetic valve, and the third electromagnetic valve to be equal to or less than the time tc represented by the following expression (1). It is preferable.

Ｓ：前記蒸発器に溜められた前記ドレン水の水面より上側の密閉容器の伝熱面積
ｔｗ：密閉容器に付着できる水の平均水膜厚さ
Ｑ：蒸発器への単位時間当たりのドレン噴射量
ρ：水の密度

S: Heat transfer area of the sealed container above the surface of the drain water stored in the evaporator tw: Average water film thickness of water that can adhere to the sealed container Q: Drain injection amount per unit time to the evaporator ρ: Water density

  Since the drain water discharge cycle is shortened, when drain water is supplied to the evaporator, it increases the rate of evaporation that adheres to the inner surface of the high-temperature evaporator and is stored in the evaporator without adhering. The rate at which the drain water falls on the water surface can be reduced. As a result, the heat transfer surface (high temperature evaporator inner surface) above the water surface of the evaporator can be used more effectively, and the performance of the evaporator is improved. Specifically, if the amount of drain water Q × tc [kg] discharged at one time is less than the amount of water S × tw × ρ [kg] that can adhere to the heat transfer surface, the drain water supplied to the evaporator is Since it can adhere to the upper heat transfer surface and evaporate, the heat transfer surface can be used effectively. Therefore, S × tw × ρ ≧ Q × tc, that is, as shown in the equation (1), tc is preferably (S × tw × ρ) / Q or less.

  The controller estimates the drain water generation amount D based on the following equation (2), and discharges the drain water by the amount of the drain water generation amount D. It is preferable to minimize the total valve opening time by controlling the time for opening the second solenoid valve and the third solenoid valve. However, in the following equation (2), when D is a negative value, the calculation is made with D as zero.

Ｍ：周囲温度および周囲湿度から推定された絶対重量湿度［kg/kg(DA)］
Ａ： 前記冷却部の最終段において、冷却された直後の空気の最低温度および圧力から推定された最終段での冷却直後の空気の飽和状態における絶対重量湿度［kg/kg(DA)］
Ｖ： 前記圧縮機本体の回転数および周囲温度、周囲湿度から推定される単位時間あたりの吸込空気中の乾き空気質量［kg(DA)/min］

M: Absolute weight / humidity estimated from ambient temperature and humidity [kg / kg (DA)]
A: Absolute weight humidity [kg / kg (DA)] in the saturated state of the air immediately after cooling in the final stage of the cooling unit, estimated from the minimum temperature and pressure of the air immediately after cooling.
V: Dry air mass [kg (DA) / min] in the intake air per unit time estimated from the rotation speed, ambient temperature and ambient humidity of the compressor body

  By optimizing the amount of drain water discharged from the cooling unit, the loss of compressed air discharged from the cooling unit can be minimized.

  The drain water inlet to the evaporator is preferably provided at the top of the evaporator.

  Normally, drain water is accumulated in the evaporator, and the water level in the evaporator is maintained at a position where the amount of drain water evaporated on the heat transfer surface balances the amount of drain water supplied to the evaporator. . Since the drain water inlet is provided above the water level, it is possible to prevent the drain water stored in the evaporator from being blown out of the evaporator by the compressed air supplied together with the drain water.

  It is preferable that an atomization nozzle is provided at the inlet of the drain water to the evaporator.

  By spraying the drain water into the evaporator as fine water droplets using the atomization nozzle, the drain water can be adhered widely to the above heat transfer surface, and the heat transfer surface above the water surface in the evaporator is It can be used effectively and evaporation is promoted.

  It is preferable that the inlet is arranged in a direction within a range of −90 degrees to +90 degrees in a plan view with respect to the outlet of the evaporator.

  Since no discharge port is provided in the drain water injection direction, the drain water injected into the evaporator can be prevented from being directly discharged to the outside air through the discharge port without being evaporated.

  According to the present invention, in an oil-free air compressor, it is not necessary to add equipment for disposal of drain water, and further, it is possible to prevent the drain water from scattering or leaking to the outside.

1 is a schematic configuration diagram of an oil-free air compressor according to a first embodiment of the present invention. FIG. 2 is a partial longitudinal sectional view of the evaporator of FIG. 1. The figure which shows the modification of the evaporator of FIG. 2A. FIG. 2B is an enlarged cross-sectional view of the nozzle portion of FIG. 2A. The top view of the evaporator of FIG. The schematic block diagram of the oil-free air compressor which concerns on 2nd Embodiment of this invention. The schematic block diagram of the oil-free air compressor which concerns on 3rd Embodiment of this invention. The schematic block diagram of the 1st modification of the oil-free air compressor of FIG. The schematic block diagram of the 2nd modification of the oil-free air compressor of FIG. The schematic block diagram of the 3rd modification of the oil-free air compressor of FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
As shown in FIG. 1, the oil-free air compressor 1 of the present embodiment (hereinafter sometimes simply referred to as a compressor) includes a compressor body 10, an evaporator 20, and a cooling unit 30. First, these components will be described.

  In this embodiment, the compressor main body 10 is an oil-free and two-stage screw type, and includes a first-stage compressor main body 11 and a second-stage compressor main body 12. The first-stage compressor body 11 and the second-stage compressor body 12 are fluidly connected via an evaporator 20 and an intercooler (first cooler) 31 that constitutes a part of the cooling unit 30. Yes. The first-stage compressor main body 11 and the second-stage compressor main body 12 take in air from the intake ports 11a and 12a, compress them with internal screws (not shown), and discharge the air from the discharge ports 11b and 12b. The rotation speeds of the screws inside the first-stage compressor body 11 and the second-stage compressor body 12 are measured by rotation speed sensors 41a and 41b, respectively. The measured rotation speed is used for calculating the discharge air amount as will be described later. The humidity and temperature of the air taken in by the first stage compressor body 11 can be measured by the humidity sensor 42 and the temperature sensor 43a. In addition, you may convert the rotation speed of such a screw from the frequency of the inverter which is not shown in figure.

  As shown in detail in FIG. 2A, the evaporator 20 is a sealed container type including a sealed container 21. The sealed container 21 has a shape closed by an upper header 21a, a lower header 21b, and a side wall 21c. The sealed container 21 is provided with an inlet 21d through which drain water is injected at the upper part of the side wall 21c. Normally, drain water is accumulated in the evaporator 20, and the evaporation is performed at a position where the amount of drain water evaporated on the heat transfer surface, which is the inner surface of the evaporator 20, and the amount of drain water supplied to the evaporator 20 are balanced. The water level in the vessel 20 is maintained. Since the drain water inlet 21d is provided above the water level, the drain water stored in the evaporator 20 is jetted out of the evaporator 20 by the compressed air supplied together with the drain water. Can be prevented.

  Drain water is stored in the lower part of the airtight container 21 of the evaporator 20. In the evaporator 20, a plurality of (for example, 20 to 30) tubes 24 extending in the vertical direction in the figure are provided. One end of each of the plurality of tubes 24 is connected to the lower header 21b, and the other end is connected. It is connected to the upper header 21a. Accordingly, the upper header 21a is provided with an air outlet 21g connected to the tube 24, and the lower header 21b is provided with an air inlet 21f connected to the tube 24. The number of air inlets 21g and air outlets 21f is provided corresponding to the number of tubes 24. Therefore, the high-temperature compressed air supplied from the first-stage compressor body 11 and the second-stage compressor body 12 flows inside the plurality of tubes 24 so as not to be mixed. Thus, the compressed air before being cooled by the cooling unit 30 after being discharged from the compressor body 10 is used as the heat source of the evaporator 20.

  As shown in FIG. 2B, the air inlet 21g and the air outlet 21f do not necessarily have to be provided corresponding to the number of tubes 24. When the supply source of the compressed air to the evaporator 20 is one place as in the second embodiment to be described later, one air inlet 21g and one air outlet 21f may be provided.

  As shown in FIG. 3, the atomization nozzle 22 is provided in the injection port 21d. The atomization nozzle 22 is for spraying drain water into the evaporator 20 as fine water droplets. By spraying the drain water into the evaporator 20 as fine water droplets using the atomization nozzle 22, the drain water can be widely adhered to the above-described heat transfer surface, and the transfer of water above the water surface in the evaporator 20 can be performed. The hot surface can be used effectively and evaporation is promoted.

  Further, the evaporator 20 is provided with a steam discharge chimney 23 for discharging steam. Therefore, the sealed container 21 is provided with a connection port (discharge port) 21 e that is in fluid communication with the steam discharge chimney 23. Therefore, the sealed container 21 is a closed container except for the injection port 21d and the connection port 21e.

  As virtually indicated by a broken line in FIG. 4, the positional relationship between the injection port 21d and the connection port 21e is such that the injection port 21d is arranged within a range of −90 ° to + 90 ° with respect to the connection port 21e in plan view. Preferably it is. In the present embodiment shown in FIG. 4, the connection port 21e is arranged at a position of −90 degrees from the injection port 21d. As described above, since the discharge port 21e is not provided in the drain water injection direction, it is possible to prevent the drain water injected into the evaporator 20 from being directly discharged to the outside air through the discharge port 21e without being evaporated. .

  By configuring the evaporator 20 in this way, it is not necessary to use a high-temperature compressed air discharged from the compressor body 10 as a heat source of the evaporator 20 and to prepare another heat source such as a heater, that is, energy efficiency. Can be improved. Moreover, in the evaporator 20, since the temperature of compressed air falls by heat exchange with drain water, the load of the cooling part 30 which cools compressed air after that decreases, and the cooling part 30 can be reduced in size.

  Furthermore, since the compressed air discharged from both the first-stage compressor body 11 and the second-stage compressor body 12 is used as a heat source for the evaporator 20, the heat source of the evaporator 20 increases, and the evaporator 20 The evaporation performance of the evaporator is improved, and the evaporator 20 can be downsized. In addition, by setting the compressor body 10 to a two-stage type, the discharge pressure can be adjusted over a wide range compared to the one-stage type.

  In the evaporator 20, heat exchange is performed between the compressed air flowing in the tube 24 and the drain water, the compressed air is cooled, and the drain water is heated and evaporated. The evaporated drain water is discharged to the outside through the steam discharge chimney 23. By providing the evaporator 20 in this way, labor costs for manually discarding drain water and additional equipment such as a drain water discharge line are unnecessary, and the running cost of the compressor 1 is reduced. Greatly improved. Moreover, since the evaporator 20 is a closed container type, even when a large amount of drain water is evaporated, the drain water can be prevented from scattering or leaking outside the evaporator 20.

  The steam exhaust chimney 23 is installed upward at the top of the oil-free air compressor 1, and a duct 25 is provided around the steam exhaust chimney 23. A fan 26 for causing the air around the steam discharge chimney 23 to flow is provided at the lower part of the duct 25.

  Since the steam discharge chimney 23 is provided, the steam discharge port 21 e can be installed far from the compressor 1. Therefore, it can suppress that the discharged | emitted vapor | steam is again sucked into the compressor main body 10, and can suppress the air volume fall accompanying it. Further, the steam discharge chimney 23 can keep the discharged steam away from an electric system (not shown), and can prevent leakage due to condensation of steam. In addition, since the steam exhaust chimney 23 is provided upwards, it is possible to prevent the discharged high-temperature steam from flowing in the horizontal direction where humans may exist due to ambient winds, etc., improving safety To do. Further, since the duct 25 is provided, the steam can be reliably discharged upward, and the safety is further improved.

  As shown in FIG. 1, the cooling unit 30 includes an intercooler (first cooler) 31, an aftercooler (second cooler) 32, and a dryer (dehumidifier) 33. The intercooler 31 and the aftercooler 32 are provided for cooling the compressed air. The dryer 33 is provided to remove moisture from the compressed air cooled by the aftercooler 32. In the intercooler 31, the aftercooler 32, and the dryer 33, drain water is generated. The intercooler 31 is fluidly connected to the inlet 21d of the evaporator 20 via the first electromagnetic valve 34, and the aftercooler 32 is fluidly connected to the inlet 21d of the evaporator 20 via the second electromagnetic valve 35. The dryer 33 is fluidly connected to the inlet 21 d of the evaporator 20 via the third electromagnetic valve 36. The drain water generated by these is supplied to the evaporator 20 together with the compressed air. The temperature and pressure of the compressed air that has passed through the cooling unit 30 are measured by temperature sensors 43b to 43d and pressure sensors 44a to 44c, respectively. The mode of the cooling unit is not particularly limited. For example, an air-cooled heat exchanger can be used for the intercooler 31 and the aftercooler 32, and a refrigeration dryer can be used for the dryer 33.

  Next, the flow of fluid in the oil-free air compressor 1 will be described. The flow of fluid described here is for air and drain water, but first the flow of air will be described.

  As shown in FIG. 1, the first-stage compressor main body 11 draws in air at about 20 ° C. from the intake port 11a (point P1), compresses the intake air inside, and discharges it from the discharge port 11b. The discharged air has a high temperature of about 200 ° C. due to the compression heat generated during compression (point P2). The discharge port 11 b of the first stage compressor body 11 is fluidly connected to the evaporator 20, and high-temperature compressed air discharged from the discharge port 11 b is supplied to the evaporator 20.

  The compressed air supplied from the first stage compressor body 11 to the evaporator 20 flows through the tube 24 in the evaporator 20 (see FIG. 2A), and heat exchange with the drain water in the evaporator 20 is about 110 ° C. (Point P3). The evaporator 20 is fluidly connected to the intercooler 31, and the compressed air cooled here is supplied to the intercooler 31.

  The compressed air supplied to the intercooler 31 is cooled to about 40 ° C. by the intercooler 31 (point P4). The intercooler 31 is fluidly connected to the intake port 12 a of the second stage compressor body 12, and the compressed air cooled here is supplied to the second stage compressor body 12.

  The second-stage compressor main body 12 sucks compressed air cooled by the intercooler 31 from the intake port 12a, compresses the intake air inside, and discharges it from the discharge port 12b. The discharged air has a high temperature of about 200 ° C. due to the compression heat generated during compression (point P5). The discharge port 12 b of the second stage compressor body 12 is fluidly connected to the evaporator 20, and high-temperature compressed air discharged from the discharge port 12 b is supplied to the evaporator 20.

  The compressed air supplied from the second stage compressor body 12 to the evaporator 20 is cooled to about 110 ° C. by exchanging heat with drain water in the evaporator 20 (point P6). The evaporator 20 is fluidly connected to the aftercooler 32, and the compressed air cooled here is supplied to the aftercooler 32.

  The compressed air supplied to the after cooler 32 is cooled to about 40 ° C. by the after cooler 32 (point P7). The aftercooler 32 is fluidly connected to the dryer 33, and the compressed air cooled here is supplied to the dryer 33.

  The compressed air supplied to the dryer 33 is cooled to about 30 ° C. in the internal cooling mechanism, moisture is removed (point P8), heated by the internal heating mechanism, and then supplied to the supply destination according to the application. (Point P9). The supply destination is, for example, a factory line.

  Next, the flow of drain water will be described.

  Drain water is generated from the intercooler 31, the aftercooler 32, and the dryer 33. The temperature of the generated drain water is about 20 ° C. to 30 ° C. (point P10). The drain water generated by the intercooler 31, the aftercooler 32, and the dryer 33 is supplied to the evaporator 20.

  The drain water sprayed into the evaporator 20 from the inlet 21d of the evaporator 20 through the atomization nozzle 22 is heated to about 102 ° C. to evaporate, and is discharged from the steam discharge chimney 23 (point P10).

  In addition, the oil-free air compressor 1 of the present embodiment includes a control device 40. The control device 40 receives measurement values from the various sensors 41a to 44c described above, and performs three controls based on these measurement values.

  First, the control device 40 performs control so as to shift the timings at which the first electromagnetic valve 34, the second electromagnetic valve 35, and the third electromagnetic valve 36 are opened. For example, the first solenoid valve 34 is opened every t1 seconds for td1 seconds, the second solenoid valve 35 is opened every t2 seconds for td2 seconds, the third solenoid valve 36 is opened every t3 seconds for td3 seconds, These times are set so that the valve opening timings do not overlap, and the valves are opened at intervals.

  The drain water is normally intermittently discharged, and the compressed air is also discharged along with the drain water. For this reason, when drain water is supplied to the evaporator 20 from a plurality of locations at the same time, the flow rate of the outlet 21e of the evaporator 20 increases due to the compressed air supplied together with the drain water, and the droplets are scattered outside. It is done. However, by controlling as described above, the timing for supplying the drain water to the evaporator 20 can be shifted and the timing can be fixed, so that it is possible to prevent the drain water from being simultaneously supplied to the evaporator 20 from a plurality of locations. Thereby, it can prevent that the flow velocity of the discharge port 21e of the evaporator 20 increases, and can prevent that a droplet splashes outside.

  Second, the controller 40 opens the first electromagnetic valve 34, the second electromagnetic valve 35, and the third electromagnetic valve 36, respectively, for a time tc or less expressed by the following equation (1). To control.

Ｓ：前記蒸発器に溜められた前記ドレン水の水面より上側の前記密閉容器の伝熱面積
ｔｗ：蒸発器の密閉容器に付着できる水の平均水膜厚さ
Ｑ：蒸発器への単位時間当たりのドレン噴射量
ρ：水の密度

S: Heat transfer area of the closed container above the water surface of the drain water stored in the evaporator tw: Average water film thickness of water that can adhere to the closed container of the evaporator Q: Per unit time to the evaporator Drain injection amount ρ: Water density

  Since the drain water discharge cycle is shortened, when the drain water is supplied to the evaporator 20, the rate at which the drain water adheres to the high temperature inner surface of the evaporator 20 and evaporates is increased. The rate at which the drain water accumulated in the water drops to the water surface can be reduced. Thereby, the heat transfer surface (high-temperature evaporator inner surface) above the water surface of the evaporator 20 can be used more effectively, and the performance of the evaporator 20 is improved. Specifically, if the amount of drain water Q × tc [kg] discharged at one time is less than the amount of water S × tw × ρ [kg] that can adhere to the heat transfer surface, the drain water supplied to the evaporator 20 is Since it can adhere to the heat transfer surface above the water surface and evaporate, the heat transfer surface can be used effectively. Therefore, S × tw × ρ ≧ Q × tc, that is, as shown in the equation (1), tc is preferably (S × tw × ρ) / Q or less.

  Thirdly, the control device 40 estimates the amount D of drain water generated based on the following equation (2), and the first electromagnetic valve 34 and the first electromagnetic valve 34 discharge the drain water by the amount D generated. The total valve opening time is minimized by controlling the time for opening the second electromagnetic valve 35 and the third electromagnetic valve 36.

Ｍ：周囲温度および周囲湿度から推定された絶対重量湿度［kg/kg(DA)］
Ａ： 前記冷却部の最終段において、冷却された直後の空気の最低温度および圧力から推定された最終段での冷却直後の空気の飽和状態における絶対重量湿度［kg/kg(DA)］
Ｖ： 前記圧縮機本体の回転数および周囲温度、周囲湿度から推定される単位時間あたりの吸込空気中の乾き空気質量［kg(DA)/min］

M: Absolute weight / humidity estimated from ambient temperature and humidity [kg / kg (DA)]
A: Absolute weight humidity [kg / kg (DA)] in the saturated state of the air immediately after cooling in the final stage of the cooling unit, estimated from the minimum temperature and pressure of the air immediately after cooling.
V: Dry air mass [kg (DA) / min] in the intake air per unit time estimated from the rotation speed, ambient temperature and ambient humidity of the compressor body

  Thus, by optimizing the amount of drain water discharged from the cooling unit, the loss of compressed air discharged from the cooling unit can be minimized.

(Second Embodiment)
In the oil-free air compressor 1 according to the second embodiment shown in FIG. 5, the compressor body 10 is a single stage type. Except for this point, the present embodiment is substantially the same as the first embodiment of FIG. Therefore, the description of the same parts as those shown in FIG. 1 is omitted.

  In the present embodiment, since the compressor body 10 is a single stage type, the second stage compressor body 12, the rotation speed sensor 41b, the intercooler 31, the first electromagnetic valve 34, the temperature sensor 43b, the pressure The sensor 44a is omitted from the compressor 1 of the first embodiment shown in FIG.

  As described above, the present invention can be applied not only to the two-stage type but also to the single-stage type compressor 1. Of course, the present invention can also be applied to a compressor 1 having three or more stages.

(Third embodiment)
In the oil-free air compressor 1 according to the third embodiment shown in FIG. 6, a preheating unit 50 is provided. Except for this point, the present embodiment is substantially the same as the first embodiment of FIG. Therefore, the description of the same parts as those shown in FIG. 1 is omitted.

  The preheating unit 50 of the present embodiment heats the drain water generated in the cooling unit 30 before supplying it to the evaporator 20. The preheating unit 50 is a heat exchanger, and exchanges heat between drain water supplied from the cooling unit 30 to the evaporator 20 and compressed air supplied from the evaporator 20 to the intercooler 31, and drain water. Is heating and cooling the compressed air.

  Thus, since it heats with the preheating part 50, the temperature of the drain water which flows into the evaporator 20 rises, the load of the evaporator 20 reduces by the sensible heat part, and the evaporator 20 can be reduced in size. Moreover, it is not necessary to supply electric power to the preheating part 50 from the outside, and the heat (compression heat) generated inside the compressor 1 can be used effectively. Also, since the compressed air is cooled in advance by the preheating unit 50 before being supplied to the cooling unit 30, the load on the cooling unit 30 is reduced, and the cooling unit 30 can be downsized.

  In the oil-free air compressor 1 of the first modification of the third embodiment shown in FIG. 7, the aspect of the preheating unit 50 is changed. The preheating unit 50 of the present modification is a heat exchanger, and includes drain water supplied from the cooling unit 30 to the evaporator 20 and compressed air supplied from the first stage compressor body 11 to the intercooler 31. Heat is exchanged between them, the drain water is heated, and the compressed air is cooled.

  In this modification, only the second stage compressor body 12 is fluidly connected to the evaporator 20, and the first stage compressor body 11 is not fluidly connected to the evaporator 20. Therefore, the evaporator 20 uses only high-temperature compressed air discharged from the second stage compressor body 12 as a heating source. Even when the high-temperature compressed air discharged from the first-stage compressor main body 11 is not cooled by the evaporator 20, it is supplied to the preheating unit 50, so that the drain water can be heated by the preheating unit 50. Therefore, the temperature of the drain water flowing into the evaporator 20 rises, the load on the evaporator 20 decreases by the amount of sensible heat, and the evaporator 20 can be downsized. Furthermore, since the high-temperature compressed air discharged from the first-stage compressor body 11 is cooled before being supplied to the intercooler 31 in the preheating unit 50, the load on the intercooler 31 can be reduced. Contributes to downsizing.

  In this modification, compressed air discharged from the first stage compressor body 11 is supplied to the preheating unit 50, and compressed air discharged from the second stage compressor body 12 is supplied to the evaporator 20, This relationship may be interchanged. That is, the compressed air discharged from the first stage compressor body 11 is supplied to the evaporator 20, the compressed air discharged from the second stage compressor body 12 is supplied to the preheating unit 50, and each is used as a heating source. May be.

  Moreover, in the oil-free air compressor 1 of the 2nd modification of 3rd Embodiment shown in FIG. 8, the preheating part 50 is changed into another aspect. The preheating part 50 of this modification is a heat exchanger which has the fan 51 attached to the intercooler 31 like the part shown with the dashed-two dotted line. The preheating unit 50 heats the drain water by exchanging heat between the drain water supplied from the cooling unit 30 to the evaporator 20 and the air that is sent out by the fan 51 and cooled by the intercooler 31. And the compressed air is cooled. In addition, you may use the air after cooling compressed air with the aftercooler 32 for the heating of the drain water in the preheating part 50 of this modification.

  Moreover, in the oil-free air compressor 1 of the 3rd modification of 3rd Embodiment shown in FIG. 9, the preheating part 50 is changed into another aspect. The preheating part 50 of this modification is an electric heater, receives electric power from the outside, and heats drain water supplied from the cooling part 30 to the evaporator 20. Thus, aspects other than a heat exchanger may be sufficient as the preheating part 50. FIG.

  As mentioned above, although specific embodiment and its modification example of this invention were described, this invention is not limited to the said form, A various change can be implemented within the scope of this invention. For example, what combined suitably the content of each embodiment is good also as one Embodiment of this invention.

1 Oil-free air compressor (compressor)
DESCRIPTION OF SYMBOLS 10 Compressor body 11 First stage compressor body 11a Intake port 11b Discharge port 12 Second stage compressor body 12a Inlet port 12b Discharge port 20 Evaporator 21 Sealed container 21a Upper header 21b Lower header 21c Side wall 21d Inlet port 21e Connection port (Vent)
21f Air inlet 21g Air outlet 22 Atomization nozzle 23 Steam exhaust chimney 24 Tube 25 Duct 26 Fan 30 Cooling unit 31 Intercooler (first cooler)
32 Aftercooler (second cooler)
33 Dryer (Dehumidifier)
34 1st solenoid valve 35 2nd solenoid valve 36 3rd solenoid valve 40 Control device 41a, 41b Rotational speed sensor 42 Humidity sensor 43a, 43b, 43c, 43d Temperature sensor 44a, 44b, 44c Pressure sensor 50 Preheating part 51 Fan

Claims (6)

A compressor body that sucks in air, compresses it, and discharges it;
A cooling unit that cools the compressed air discharged from the compressor body and generates drain water upon cooling;
An airtight container type evaporator that is fluidly connected to the cooling section and evaporates the drain water ,
The cooling part is
A first cooler that cools the compressed air discharged from the first stage compressor body and is fluidly connected to the evaporator via a first electromagnetic valve;
A second cooler that cools the compressed air discharged from the second-stage compressor body and is fluidly connected to the evaporator via a second electromagnetic valve;
A dehumidifier that removes moisture from the compressed air flowing out of the second cooler and is fluidly connected to the evaporator via a third electromagnetic valve;
With
Further oil-free air compressor Ru a control device for controlling so as to shift the timing of opening the said first solenoid valve and the second solenoid valve and the third solenoid valve, respectively. The control device controls the time for opening the first electromagnetic valve, the second electromagnetic valve, and the third electromagnetic valve to be equal to or less than the time tc represented by the following expression (1). The oil-free air compressor according to claim 1 .

S: Heat transfer area of the sealed container above the water surface of the drain water stored in the evaporator tw: Average water film thickness of water that can adhere to the inner surface of the sealed container Q: Drain injection per unit time to the evaporator Quantity ρ: Water density The controller estimates the drain water generation amount D based on the following equation (2), and discharges the drain water by the amount of the drain water generation amount D. 2 to control the time for opening the electromagnetic valve and the third solenoid valve to minimize the valve opening amount of time, the oil-free air compressor of claim 1 or claim 2.

M: Absolute weight humidity estimated from ambient temperature and ambient humidity A: Saturation state of air immediately after cooling in the final stage estimated from minimum temperature and pressure of air immediately after cooling in the final stage of the cooling unit Absolute Weight Humidity V: Dry air mass in the intake air per unit time estimated from the rotation speed, ambient temperature and ambient humidity of the compressor body The oil-free air compressor according to any one of claims 1 to 3 , wherein an inlet for the drain water to the evaporator is provided at an upper portion of the evaporator. The oil-free air compressor according to claim 4 , wherein the injection port is provided with a atomizing nozzle. The inlet is arranged in the orientation in a range of +90 degrees from -90 degrees in plan view with respect to the evaporator outlet, oil-free air compressor of claim 4 or claim 5.

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