GB2085571A

GB2085571A - De-humidifier for Compressed Gas

Info

Publication number: GB2085571A
Application number: GB8123922A
Authority: GB
Original assignee: Orion Machinery Co Ltd
Current assignee: Orion Machinery Co Ltd
Priority date: 1980-09-19
Filing date: 1981-08-05
Publication date: 1982-04-28
Also published as: JPS5758428U; GB2085571B; DE3133452A1; FR2490795A1

Abstract

Air from a compressor 11 passes into a de-humidifier through an inlet 12 and then flows through a heat- exchange passage 10 defined between inner and outer shells 8 and 9. From the passage 10, the air flows through a cooling passage 7 within the inner shell 8 where it is cooled by an evaporator 3 of a refrigerating system, and the resultant cooled and de-humidified air passes through pipes 15 in the passage 10 where heat-exchange takes place between this air and the compressed air entering through the inlet 12. From the pipes 15, the air flows through a chamber 14 and out through an outlet 16. In order to reduce the temperature difference between inside and outside the outer shell 9, high-pressure side piping 18 between a compressor 1 and a condenser 2 of the refrigerating system passes through the bottom 10a of the heat-exchange passage 10 and the chamber 14, so that the high temperature refrigerant therein heats up the air in these parts of the de- humidifier. Condensate is discharged through ports 17. <IMAGE>

Description

SPECIFICATION De-Humidifier for Compressed Gas The present invention relates to a de-humidifier which de-dumidifies compressed gas by cooling it.

Compressed air discharged from a compressor has a relatively high temperature and humidity compared to normal air (such as air in a room), and when such compressed air is cooled to room temperature, the moisture entrained therein becomes condensed into water in the compressor piping. When the cooled air is passed into various air operating devices, the condensed water adversely affects the operation of the devices and reduces their durability.

In order to avoid these disadvantages, there has been proposed a de-humidifier as shown in schematic cross-section in Figure 1 of the accompanying drawings. In this de-humidifier, a refrigerating cycle or system is formed by connecting a condenser 2 and an evaporator 3 through a refrigerating compressor 1. A cooling fan 4 sends cooled air to the condenser 2, and a capillary tube 5 and a capacity control pipe 6 are also provided. The de-humidifier proper comprises an outer shell 9 mounted outside an inner shell 8.

The inner shell 8 forms a cooling passage 7 which houses the evaporator 3, and a heat-exchange passage 10 is formed between the inner and outer shells 8 and 9. At the left-hand end of the heat-exchange passage 10 as viewed in Figure 1 there is formed an air inlet 12 connected to an outlet of an air compressor 1 while at the righthand end thereof the heat-exchange passage is connected to the cooling passage 7 through a hole 13 provided in the inner shell 8. In the heatexchange passage 10 there are provided heatexchange pipes 15 which connect an outlet (lefthand end) of the cooling passage 7 to an chamber 1 4 formed at the right-hand end of the outer shell 9.These pipes 15 perform heat-exchange between air at low temperature which is cooled and de-humidified in the cooling passage 7 and air at high temperature which is passed into the cooling passage 7 through the heat-exchange passage 10, thereby pre-cooling said air at high temperature and at the same time heating said air at low temperature and sending it out from an air outlet 16 provided in the air chamber 14 to air piping (not shown). At the bottom of the cooling passage 7 and the heat-exchange passage 10 water discharge ports 17 are provided.

In this compressed air de-humidifier, condensed water which has been moistureseparated in the heat-exchange passage 10 is gathered at a bottom 1 Oa of the passage 10 and is discharged to outside the de-humidifer through the discharge ports 17. However, when the temperature of the surroundings is high, the difference between this temperature and that of the condensed water, i.e. the temperature difference between inside and outside the outer shell 9, may cause dew to form on the outer surface of the bottom, thereby resulting in corrosion.

Also, compressed air, like other regular gases, contracts in volume when cooled. Thus, if cooled and de-humidified compressed air is passed out from the outlet 16 before being fully re-heated, there is a possibility that it may be subjected to heating action from the outer air in the midst of piping, causing its volume to expand and resulting in an unusual increase of pressure in the piping.

Simultaneously, there is another disadvantage that the load on the air compressor 11 is increased as the quantity of compressed air supplied from the compressor 11 to the dehumidifier increases.

In order to overcome these disadvantages, the heat-exchange efficiency in the passage 10 or the reheating rate of the cooled and de-humidified compressed air can be improved by adding a heat exchanger to the de-humidifier. However, the first of these alternatives is defective in that it is difficult to perform full re-heating due to the overall composition of the device, as well as due to the limitations of heat source caused by the quantity of flow of compressed air discharged from the compressor 11. The second alternative is also defective in that the provision of a heat exchanger for re-heating results in enlargement and complication of the device and an increase in cost. Thus, neither alternative is practical.

The present invention is designed in view of these problems and aims to prevent dew from forming on the outer surface of the de-humidifier without adding a special heat exchanger, and also aims to decrease the operational cost of this type of de-humidifier by lowering the load on the compressor of the refrigerating system and on the air compressor.

According to the present invention, there is provided a de-humidifier for compressed air, comprising a cooling passage which houses an evaporator of a refrigerating system and in which said compressed air is cooled and de-humidified, a heat-exchange passage provided at the outer periphery of the cooling passage and in which heat-exchange is effected between said compressed air and the cooled and de-humidified air from the cooling passage, and an air chamber connected to an exit from the heat-exchange passage and in which an outler of the dehumidifier is provided, wherein at least a part of piping on the high-pressure side of the refrigerating system from a compressor to a condenser thereof passes through the bottom of the heat-exchange passage and the air chamber.

Also according to the present invention there is provided a de-humidifier for compressed gas, comprising an inlet and an outlet through which the compressed gas is respectively passed into and out of the de-humidifier, a refrigeration system including an evaporator, a compressor, a condenser and piping through which highpressure refrigerant flows between the compressor and the condenser, a cooling passage in which the evaporator is housed and in which the compressed gas from the inlet is cooled and de-humidified, a heat-exchange passage which is disposed on the outer periphery of the cooling passage and in which heat-exchange is effected between the compressed gas passing between the inlet and the cooling passage and the cooled and de-humidified gas from the cooling passage, and a chamber through which the cooled and dehumidified gas passes between the heatexchange passage and the outlet, wherein at least a part of said piping of the refrigerating system passes through a lowermost part of the heatexchange passage and through the chamber.

The invention will now be further described by way of example, with reference to Figure 2 of the accompanying drawings which is a schematic cross-sectional view of a de-humidifier according to the present invention. In this Figure, those parts which serve the same function as in the conventional de-humidifier described above with reference to Figure 1 are given the same reference numerals and will not be described in detail hereinafter.

As shown in Figure 2, in the present invention refrigerant gas of high temperature and pressure discharged from the compressor 1 is led to the condenser 2 through a high-pressure side piping 18 provided in the bottom 1 Oa of the heat exchange passage 10 formed between the inner and outer shells 8 and 9, and also in the air chamber 14 which connects all the outlets of the heat exchange pipes 15 to the air outlet 16. By utilizing the radiating action of the high-pressure side piping 1 8, the temperature of the condensed air gathered in the bottom of the heat-exchange passage 10 is raised while the re-heating rate of the cooled and de-humidified air temporarily gathered in the chamber 14 is also heightened so that its volume is expanded and restored to almost the same as it was immediately after being discharged from the air compressor 1 1.

Thus, even if the compressed air is drastically cooled by the evaporator 3 provided in the cooling passage 7, the temperature of the compressed air in the chamber 14 is re-heated at least up to the same degree as that of the outer air and is again fully expanded to maintain the air pressure in the de-humidifier relatively high. In this manner, an increase in the load on the compressor 11 due to the increase of quantity of the compressed air supplied is prevented. Also, as a consequence of the fact that the refrigerant gas of high temperature and pressure discharged from the compressor 1 is cooled by the high-pressure side piping 18 which passes through the bottom 1 Oa of the heat exchange passage and the chamber 14, the capacity of the condenser 2 can be decreased.Alternatively, if the size of the condenser 2 is maintained the same as in the conventional system, the condensing pressure is lowered and the load on the compressor 1 is lowered also.

In the embodiment illustrated, the refrigerant gas of high temperature and pressure directed from the compressor 1 to the condenser 2 performs heat-exchange with the air in the chamber 14 after performing heat-exchange with the condensed water in the bottom 1 Oa of the heat-exchange passage 10. This order of heatexchange may be reversed, however.

As described above, although the present invention is quite simple in structure, in that it is merely arranged that at least a part of a highpressure side piping directed from the compressor to the condenser of the refrigerating system passes through the bottom of the heat-exchange passage and the air chamber, the temperature difference between the condensed water gathered in the bottom of the heat-exchange passage and the outer air is made almost nonexistent. Thus, the formation of dew on the outer surface of the bottom of the de-humidifier is prevented. Moreover, as heat-exchange between refrigerant gas and de-humidified air is sufficiently re-heated (i.e. expanded and its volume restored) and thus the load on the air compressor is decreased. Simultaneously, the condensing pressure of the refrigerant gas is also lowered, resulting in turn in a further decrease in the load on the compressor. Thus, the present invention realizes an economical de-humidifying operation by saving on the power or energy required to drive the compressor.

Claims

1. A de-humidifier for compressed air, comprising a cooling passage which houses an evaporator of a refrigerating system and in which said compressed air is cooled and de-humidified, a heat-exchange passage provided at the outer periphery of the cooling passage and in which heat-exchange is effected between said compressed air and the cooled and de-humidified air from the cooling passage, and an air chamber connected to an exit from the heat-exchange passage and in which an outlet of the dehumidifier is provided, wherein at least a part of piping on the high-pressure side of the refrigerating system from a compressor to a condenser thereof passes through the bottom of the heat-exchange passage and the air chamber.

2. A de-humidifier for compressed gas, comprising an inlet and an outlet through which the compressed gas is respectively passed into and out of the de-humidifier, a refrigerating system including an evaporator, a compressor, a condenser and piping through which highpressure refrigerant flows between the compressor and the condenser, a cooling passage in which the evaporator is housed and in which the compressed gas from the inlet is cooled and de-humidified, a heat-exchange passage which is disposed on the outer periphery of the cooling passage and in which heat-exchange is effected between the compressed gas passing between the inlet and the cooling passage and the cooled and de-humidified gas from the cooling passage, and a chamber through which the cooled and dehumidified gas passes between the heatexchange passage and the outlet, wherein at least a part of said piping of the refrigerating system passes through a lowermost part of the heatexchange passage and through the chamber.

3. A de-humidifier for compressed gas, substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.