GB2125159A

GB2125159A - Dehumidifier

Info

Publication number: GB2125159A
Application number: GB08319162A
Authority: GB
Inventors: William Armond Dunne
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-07-16
Filing date: 1983-07-15
Publication date: 1984-02-29
Also published as: GB8319162D0

Abstract

A dehumidifier provides ducted dry air at a specific location, the air passing only once through the dehumidifier which comprises a cabinet (1) defining an airtight plenum chamber and containing a refrigeration compressor (3), an evaporator (4) co-operating with an air inlet aperture, a condenser (5) co- operating with an air outlet aperture and a fan (6) to draw air into the plenum chamber through the inlet aperture and to expel air through the outlet aperture. The dehumidifier may include a damper (20) at the air outlet aperture to permit the performance to be increased in hot and/or humid ambient atmospheres. The dehumidifier may also include a refrigerant to fluid heat exchanger (22) to extract heat from the refrigerant gas flowing in a tube (9) leading the gas from the compressor (3) to the condenser (5), thereby to allow the dehumidifier to supply air at a very low dew point and at a low temperature. <IMAGE>

Description

SPECIFICATION Dehumidifier The invention relates to a dehumidifier.

Packaged mechanical dehumidifiers have been previously proposed for removing, or at least reducing, the water vapour content of air usually in an enclosed space, in which space for example a piece of machinery may operate or goods may be stored, such machinery or goods being sensitive to humid air. Previously proposed dehumidifiers have thus acted repeatedly on the same air which is drawn therethrough, the humidity of the air dropping from an initial high level to a final low level and the load on the dehumidifier being generally proportional to the existing humidity, that is to say a high load at the start of operation tailing off to a low load.

Generally, mechanical dehumidifiers operate on a refrigeration principle, that is to say air is drawn through an evaporator coil which chills the air to a dew point thus condensing water vapour in the air into water which is drained away, the cold dryer air then being passed through a condenser to be reheated.

According to the invention there is provided a dehumidifier from which relatively dry air can be ducted to a specific location, the air passing only once through the dehumidifier, wherein the dehumidifier comprises a cabinet defining an airtight plenum chamber and containing a refrigeration compressor, an evaporator Co- operating with an air inlet aperture, a condenser co-operating with an air outlet aperture and a fan to draw air into the plenum chamber through the inlet aperture and to expel the air through the outlet aperture.

The fan, in operation, draws air in through the inlet aperture of the cabinet so that it passes around finned tubes of the evaporator which is preferably constructed with the finned tubes having relatively widely spaced fins thereon whereby the evaporator can operate close to the freezing point of water without undue frosting up.

A drain, preferably a drain pan, is provided to collect water condensed by the evaporator out of the air drawn in by the fan.

The condenser, to which saturated or nearly saturated air is passed from the evaporator, is preferably constructed from thin tubes with the fins thereon relatively closely spaced and with the condenser so sized as to obtain high re-heat of the air thereby to reduce the relative humidity of the air.

The refrigation compressor discharges hot refrigerant gas into the condenser, the refrigerant gas being condensed in the condenser to a liquid by the cold air passing thereover.

An expansion valve is preferably provided to meter the flow of liquid refrigerant into the evaporator, in which evaporator the refrigerant is vaporised by heat absorbed from the air passed over the evaporator by the fan.

The flow of refrigerant to the compressor may, on certain applications, be further controlled by a suction pressure regulator. In the compressor, the low pressure refrigerant gas is compressed to a high pressure and temperature before it is discharged to the condenser for a further cycle of operation.

Advantageously the evaporator and the condenser are designed to take the total fan output, that is to say the same air flow over both, to give a maximum dehumidification. The performance of the dehumidifier with regard to low humidity will thus improve with an increase in load. Increase in the evaporator load will increase the power absorbed by the compressor and the temperature of the discharged refrigerant. With the same air flow, this increases the temperature of the discharged air thereby further lowering its relative humidity.

Means for sensing and indicating the pressure of the refrigerant in the system can be provided and indicating means for air temperature may also be provided and/or a manually or automatically operated air damper can be operated to allow air drawn into the cabinet to bypass the evaporator.

Thus, the evaporator has a resistance to air flow and opening the air damper will allow ambient air to be drawn in thereby reducing the amount of air drawn through the evaporator and thus the load on the compressor to prevent unacceptable operating pressures or temperatures developing.

In such dehumidifiers it may be advantageous to include the facility to increase the amount of air flowing therethrough and the performance of the machine in certain operating conditions.

In such dehumidifiers an output damper may be provided at the air output side of the evaporator to provide a resistance to air flow under normal operating conditions, which output damper can be opened to increase the performance of the dehumidifier in hot and/or humid ambient atmospheres.

Automatic temperature, pressure or humidity sensing means may be provided and coupled to output damper operating means to effect adjustments in the position of the output damper.

In such dehumidifiers it may be advantageous to enable the dehumidifier to be used in applications where air at as low a dew point as previously described is required, but with a dry bulb temperature at or below the ambient dry temperature. Such an application could be in a plastics processing factory when air at a very low dew point is required but where because of site conditions or other reasons, full reheat through the condenser is not required.

Advantageously heat generated in the dehumidifier and contained in the refrigerant circuit thereof is partly or wholly transferred to a fluid to be discharged externally of the cabinet of the dehumidifier.

If desired the heat can be discharged externally of a building in which the cabinet is situated.

Discharge of the heat can be effected by fitting a refrigerant to fluid heat exchanger in the refrigerant circuit between the compressor discharge and the condenser inlet. The heat exchanger may be of any suitable kind for example of a shell and tube kind or of a coaxial tube kind of any suitable configuration.

The invention is diagrammatically illustrated by way of example in the accompanying drawing, in which Figure 1 is a schematic elevation of a dehumidifier according to the invention with a front wall removed to show inner details; Figure 2 is a side view showing the lefthand end of the dehumidifier as viewed in Figure 1; and Figure 3 is a side view showing the righthand end of the dehumidifier as viewed in Figure 1.

Figure 4 shows a view similar to Figure 1 of a modified dehumidifier according to the invention including an output damper; Figures 5 and 6 are end views of the dehumidifier shown in Figure 4; and Figure 7 shows a further modified dehumidifier according to the invention including a refrigerant to fluid heat exchanger.

Referring to Figures 1 to 3, a dehumidifier has an outer casing 1 mounted on wheels 2. Mounted within the cabinet 1 are a refrigeration compressor 3, an evaporator 4, a condenser 5 and a fan 6. The evaporator 4 is in communication with an inlet aperture 7 such that operation of the fan 6 draws air in through the inlet aperture 7 to pass through the evaporator 4 into the cabinet 1 and expel the air through an outlet aperture 8 into a duct (not shown) after the air passes through the condenser 5. Apart from the apertures 7 and 8, the cabinet 1 is closed and forms a plenum chamber.

The refrigeration compressor 3 discharges hot refrigerant gas through a pipe 9 to the condenser 5 and condensed refrigerant passes from the condenser 5 through a pipe 10 to the evaporator 4 by way of an expansion valve 11. Refrigerant vapour passes from the evaporator 4 through a pipe 12 back to the refrigeration compressor 3 by way of a suction pressure regulator 13. A pan 14 with a drain pipe 1 5 is provided below the evaporator 4.

Thus, humid air drawn in through the inlet aperture 7, by the action of the fan 6, is cooled to below its dew point whereby the moisture in the air condenses and drips from the widely spaced fins of the evaporator 4 into the drip tray 14 to pass from the cabinet 1 through the drain pipe 1 5.

The cold, saturated or nearly saturated air is then drawn into the fan 6 and forced by the fan 6 through the condenser 5 whereby it is warmed before leaving the cabinet 1 through the outlet aperture 8 and passing into the duct. A suction pressure regulator 13 can be used, in certain applications, to control the return flow of refrigerant through the pipe 12 to the refrigeration compressor 3. The expansion valve 11 meters the flow of liquid refrigerant into the evaporator 4.

Gauges 1 6 indicate the pressure in the refrigerant system and, if the air temperature increases to a level which results in unacceptable pressures in the system, the pressure sensed may be used automatically to open, or a manual control may be provided to open, an air damper 1 7 which allows a leak of ambient air into the cabinet 1 thereby reducing the amount of air drawn through the evaporator 4 and consequently the load on the compressor 3 so as to reduce operating pressures and temperatures. Electrical control gear is provided within a housing 1 8.

The ducting (not shown) leading from the outlet aperture 8 of the cabinet 1 permits dehumidified air to be ducted to a specific area or areas to give a constant supply of dehumidified air. The dehumidifier is designed so that it can operate on maximum load at all times and is intended to pass air only once through the cabinet 1 , that is to say it is not provided within a space to dehumidify the air within the space by recirculating it through the cabinet 1 but rather is intended to draw in humid air and provide a supply of dehumidified air. Thus, it must in one operation reduce the relative humidity of the air to a very low level, preferably to a relative humidity of less than 10%.

Referring to Figures 4 to 6, means for indicating the air pressure within the air tight plenum chamber can be provided such as an inclined manometer 19. The air pressure within the plenum chamber is relative to the air flow and a variation of the fluid level in the manometer therefore indicates a variation in the air flow.

The fan 6 is selected to give an air flow greater than that normally required tq operate on a duct system connected to the dehumidifier with a resistance to air flow no greater than that specified.

A damper 20 at the air outlet aperture of the condenser 5 can be adjusted to give the required system resistance to achieve the required air flow through the evaporator 4 and the condenser 5.

The damper 20 can be either manually or automatically operated.

For manual operation the damper can be adjusted according to a scale marked on the manometer 19 or a reading can be taken of the temperature and/or humidity of the air entering the evaporator 4.

For automatic operation the damper 20 may be operated by air and/or fluid pressure and/or motor drive, actuated and controlled by a device sensing the air pressure in the plenum chamber and/or the temperature and/or the humidity of the air entering the evaporator 4.

Figure 5 shows a duct adaptor or 'take off' with two dampers 21 to which can be connected rigid or flexible ducting. By using similar adaptors with multiple connections with or without specially shaped air outlets at the ends of the ducting and by adjusting or varying if necessary the setting of the damper on each duct and/or varying the position of the outlets a space of very dry air of steplessly variable pattern can be created.

Figure 7 shows a view similar to Figure 4 but including a refrigerant to fluid heat exchanger 22 in the form of a coaxial tube of a circular configuration. The tube 9 through which hot refrigerant gas passes from the compressor 3 is diverted through the heat exchanger 22 in which heat from the hot refrigerant gas is transferred to fluid flowing in a tube 23. Flow of fluid through the tube 23 can be adjusted so as partially or wholly to de-superheat the refrigerant gas and partially or wholly to condense the refrigerant to a liquid. The fluid flow may be manually regulated or automatically controlled by a valve 24 responding to temperature or pressure fluctuations within the system and normally a fluid inlet shut off valve 25 and outlet valve 26 would be provided on the tube 23. The heat gained by the fluid flowing through the tube 23 can be extracted therefrom, externally of the cabinet.

The possibility of the adverse effect of liquid refrigerant passing to the compressor is increased by the fitting of the refrigerant to fluid heat exchanger 22 and in consequence the provision of a suction accumulator 27 is desirable.

The description given has referred only to the major components of dehumidifiers which are either necessary or desirable but the dehumidifiers should follow normal good refrigeration practice and include such items as a refrigerant stainer/dryer, a refrigerant charge/moisture indicator and a liquid receiver. These have been omitted from the drawings for clarity.

Claims

1. A dehumidifier from which relatively dry air can be ducted to a specific location, the air passing only once through the dehumidifier, wherein the dehumidifier comprises a cabinet defining an airtight plenum chamber and containing a refrigeration compressor, an evaporator co-operating with an air inlet aperture, a condenser co-operating with an air outlet aperture and a fan to draw air into the plenum chamber through the inlet aperture and to expel the air through the outlet aperture.

2. A dehumidifier according to claim 1, in which the fan, in operation, draws air in through the inlet aperture of the cabinet so that it passes around finned tubes of the evaporator.

3. A dehumidifier according to claim 2.

including a drain to collect water condensed by the evaporator out of the air drawn in by the fan.

4. A dehumidifier according to any one of claims 1 to 3, in which the refrigeration compressor discharges hot refrigerant gas into the condenser, the refrigerant gas being condensed in the condenser to a liquid by the cold air passing thereover.

5. A dehumidifier according to any one of claims 1 to 4, including an expansion valve to meter flow of liquid refrigerant into the evaporator, in which evaporator the refrigerant is vaporised by heat absorbed from the air passed over the evaporator by the fan.

6. A dehumidifier according to any one of the preceding claims, including a suction pressure regulator to further control the flow of refrigerant to the compressor.

7. A dehumidifier according to any one of the preceding claims, in which the evaporator and the condenser are designed to take the total fan output, that is to say the same air flow over both, to give maximum dehumidification whereby the performance of the dehumidifier with regard to low humidity will improve with an increase in load, increase in the evaporator load will increase the power absorbed by the compressor and the temperature of the discharged refrigerant, and, with the same air flow, the temperature of the discharged air will increase thereby further lowering its relative humidity.

8. A dehumidifier according to any one of claims 1 to 6, including means for sensing and indicating the pressure of the refrigerant in the system, indicating means for air temperature and/or a manually or automatically operated air damper operable to allow air drawn into the cabinet to bypass the evaporator.

9. A dehumidifier according to any one of the preceding claims, including an output damper at the air output side of the evaporator to provide a resistance to air flow under normal operating conditions, which output damper can be opened to increase the performance of the dehumidifier in hot and/or humid ambient atmospheres.

10. A dehumidifier according to claim 9, including automatic temperature, pressure or humidity sensing means coupled to operating means for the output damper to effect adjustments in the position of the output damper.

11. A dehumidifier according to any one of the preceding claims, in which heat generated in a dehumidifier and contained in the refrigerant circuit thereof is partly or wholly transferred to a fluid to be discharged externally of the cabinet of the dehumidifier.

12. A dehumidifier according to claim 11, in which the heat is discharged externally of a building in which the cabinet is situated.

13. A dehumidifier according to claim 12, in which discharge of the heat is effected by fitting a refrigerant to fluid heat exchanger in the refrigerant circuit between the compressor discharge and the condenser inlet.

1 4. A dehumidifier substantially as hereinbefore described and illustrated with reference to the accompanying drawings.