THIS INVENTION relates to air-conditioning. In particular, the invention relates to a method of providing air-conditioning underground in a mine, and to a mobile air-conditioning unit. The invention also relates to an air-conditioning system for delivering cooled air at a plurality of workstations in an underground mine.

The invention provides a method of providing air-conditioning underground in a mine, which method includes: moving a mobile air-conditioning unit to a position underground in the mine adjacent a workstation where the provision of cooled air is required; using the mobile air-conditioning unit to cool air adjacent the workstation by evaporation of a refrigerant in an evaporator and condensing of the refrigerant in a condenser; and cooling the refrigerant after or during condensing thereof by passing water through the air-conditioning unit in heat exchange relationship with the refrigerant.

By mobile air-conditioning unit is meant a unit which is shaped and sized to permit transportation thereof to a desired location underground in a mine, and which is designed for temporary installation at a point of use, thus being designed for regular connection and disconnection from water- and electricity supplies.

Cooling of the refrigerant may comprise passing water through a water-cooled condenser forming part of the air-conditioning unit. In a preferred embodiment of the invention, cooling of the refrigerant comprises passing water through a plate heat exchanger in which heat exchange between the water and the refrigerant occurs.

The method may include connecting the air-conditioning unitto a resident underground water supply system for passing water through the air-conditioning system, to cool the refrigerant.

By resident underground water supply system is meant a water distribution or reticulation system installed underground for purposes not exclusively related to the cooling of air-conditioning units, for instance serving as a service water supply system underground in the mine.

Connection of the air-conditioning unit to the water supply system may be by means of an elongated flexible connection which permits movement of the air-conditioning unit relative to the water supply system. In the case of the workstation being adjacent a mining face, the method may include advancing the air-conditioning unit together with the mining face, the air-conditioning unit being moved with the face while being connected to the water supply system.

The method may include drawing air over the evaporator forming part of the air-conditioning unit, to provide moving cooled air to the workstation. Optionally, the method includes connecting a delivery duct to an air outlet of the air-conditioning unit, to deliver moving cooled air at an outlet end of the delivery duct, spaced from the air-conditioning unit. An air-filter may be installed to remove impurities from the air which is drawn over the evaporator.

Moving of the air-conditioning unit to a desired position in the mine may include supporting the air-conditioning unit on a dedicated rail vehicle, and moving the rail vehicle to the desired location on rails.

The method may include temporarily installing the air- conditioning unit at the workstation by suspending the air-conditioning unit from a hanging wall in a mine stope or tunnel, suspension of the air- conditioning unit from the hanging wall conveniently comprising connecting the unit to anchor bolts set in the hanging wall.

The method may include locating a plurality of the air- conditioning systems at distributed workstations throughout the mine, each air-conditioning unit supplying cooled air to a respective workstation.

The invention also provides a mobile air-conditioning unit which includes: air-conditioning equipment forming a refrigeration cycle for the circulation of a refrigerant fluid, the air-conditioning equipment including an evaporator and a condenser; a heat exchanger for cooling the refrigerant fluid during or after condensing thereof, the heat exchanger having a water inlet and a water outlet for passing water therethrough in heat exchange relationship with the refrigerant fluid; and a housing which houses the air-conditioning equipment, the housing being sized and shaped to facilitate transportation of the air-conditioning unit to a rock workface under ground a mine.

The housing of the air-conditioning unit typically has a maximum length of 1.5 m - 1.8 m, a maximum width of 0.7 m - 0.9 m, and a maximum height of 0.7 m - 0.9 m. Preferably, the maximum length is 1.5 m, the maximum width is 0.85 m, and the maximum height is 0.75 m. The mobility of the air-conditioning unit is enhanced by limiting its gross weight to less than 400 kg.

The unit may include a connector for connecting the inlet of the heat exchanger to a resident water supply underground in the mine, the connector being configured for regular connection to and disconnection from the water supply. The unit typically includes a flexible hose which is connectable in-line between the inlet of the heat exchanger and the water supply, to place the heat exchanger in liquid flow connection with the water supply. The heat exchanger may be provided by a water cooled condenser forming part of the air-conditioning equipment. In one embodiment of the invention, the heat exchanger is a plate heat exchanger.

The unit may include a fan drawing air over the evaporator, to discharge moving cooled air from an air outlet. A flexible delivery duct may be provided for releasable connection to the air outlet, to deliver moving cooled air at an outlet end of the delivery duct, said outlet end being spaced from the housing.

The unit typically includes an electrical connection arrangement for connecting electrically powered air-conditioning equipment forming part of the unit to an electrical network, the electrical connection arrangement being connectable to a supply of three-phase electrical power.

The unit may include suspension means fast with the housing for permitting suspension of the housing from a hanging wall. The suspension means may include a plurality of connectors fast with the housing, each connector being for connection to a tensile element which is connected to an anchored support set in the hanging wall.

The invention extends to an air-conditioning system for delivering cooled air at a plurality of workstations in an underground mine, the system including a plurality of air-conditioning units as defined above, each air-conditioning unit being positioned adjacent a respective workstation where the delivery of cooled air is required.

The system may include a transportation system for facilitating transportation of the air-conditioning units to their respective workstations, the transportation system including a plurality of rail vehicles on which the respective air-conditioning units are supportable.

The system preferably includes a water supply system distributed through the mine for supplying water to the respective air- conditioning units for cooling thereof. The water supply system may be a resident service water supply system in the mine.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic drawing of an air-conditioning system which includes an air-conditioning unit, in accordance with the invention, at a workplace under ground a mine; and Figure 2 is a schematic block-diagram of air-conditioning equipment forming part of the air-conditioning unit of Figure 1.

In the drawings, reference numeral 10 generally indicates an air-conditioning system, in accordance with the invention. The air- conditioning system 10 includes a mobile air-conditioning unit 18, the air- conditioning components (shown in Figure 2) of which are housed inside a housing, generally indicated by reference numeral 12. The air-conditioning unit 18 can be a direct-expansion-type air-conditioning unit.

The housing arrangement 12 includes a sheet metal box 14 having an air outlet opening 16 through which cooled air is blown by a fan 19 which is installed inside the box 14 near an evaporator 20 of the air- conditioning unit 18. The box 14 is shaped and dimensioned to permit transportation thereof down a mine shaft to a site where air-conditioning is required underground, such as near an advancing stope face 22. The box 14 includes a flat base 25 in the form of a skid-frame for firmly standing on a flat bed rail vehicle 26, to permit transportation of the box 14 along a mine tunnel by the rail vehicle 26. In this example, the box 14 is 0.75 metres high, 0.85 metres wide, and 1.5 metres long. The width and the length of the box 14 are thus selected to permit use of an existing rail transport system. The unit 18 weighs about 380 kilograms.

In other embodiments of the invention, the unit 18 can be mounted on a dedicated wheeled trolley or undercarriage, to permit movement of the trolley in the mine to positions where localised air conditioning is required.

Connectors in the form of eye-bolts 27 are fitted to an upper surface or roof of the box 14 and to the skid-frame 25. The eye-bolts 27 can be used to suspend the box 14 from anchored supports in a hanging wall 29.

In this embodiment of the invention, the air-conditioning unit 18 includes components required to perform a complete air-conditioning or refrigeration cycle, and thus includes a compressor 28, the evaporator 20, an expansion valve 30, and a condenser 32. The condenser is a water-cooled condenser, being a condenser which includes a water-cooled plate heat exchanger. The water-cooled condenser 32 has a water inlet 24 connectable to a water supply 36 underground in the mine. To this end, the inlet 24 includes a quick release connector for ready connection and disconnection of the inlet 24. A water filter 60 is provided for removing impurities from the cooling water before entering the water-cooled condenser 32. The components also include, in conventional fashion, a refrigerant drier 54, an in-line sight glass 56, and a suction accumulator 58.

The system 10 includes a flexible hose 38 which is connected at one end to the inlet 24, the other end of the flexible hose 38 being connectable to a complementary valve 40 which is installed in-line the water supply pipe 36. In this example the water supply 36 is a service water supply pipeline which runs to the stope face 22.

Similarly, the unit 18 includes a water outlet 42 of the water- cooled condenser 32, the outlet 42 presenting an outlet port on the exterior of the box 14 for connection to the service water supply 36. Instead, the outlet 42 can be connected directly to equipment used underground which normally utilises service water, e.g a jackhammer drill or a dust suppression sprayer. Alternatively, the outlet water can be directed to a drainage system leading to an underground pump station.

The unit 18 also includes a fan housing 44 fixed to the box 14, the fan 19 being installed inside the box 14 adjacent the evaporator 20 for drawing air over the evaporator 26, in heat exchange relationship to introduce cooled air into the workplace, in use. A delivery duct (not shown) can be fitted to the fan housing 44, i.e. to the cooled air outlet, to discharge cooled air at a position remote from the box 14, e.g. up travelling way tunnels into gullies, raise lines and other stoping areas.

An electrical connection terminal box46 is provided on the unit 18 for connection to an underground electricity supply network 48. Typically, an electrical cable extension 50 is provided from an electrical distribution box 52. The electrical power supply is for powering electrical components of the unit 18, such as the compressor 28 and a motor driving the fan 19.

In this example, an electrical network 48 underground supplies three-phase type power at 525V, the fan motor and the compressor 28 being configured to cooperate with the three-phase supply, and the unit including a 525V -24V transformer for supplying low-voltage power to a user interface and control arrangement. Construction and installation of the air-conditioning system 10 is done in accordance with prescribed safety regulations for mines and works.

In use, if the cooling of air at a particular location underground a mine is required, a user transports the air-conditioning unit 18 to the desired position for spot-cooling. To this end, the unit 18 can be taken to the desired level station by a mine lift or cage winder, and be transported along the necessary underground tunnels on a flat bed rail vehicle 26. The unit 18 can then be off-loaded from the flat bed rail vehicle 26 and placed on the foot wall, or it can be left on the rail vehicle 26. Instead, the unit can be suspended or hung from the hanging wall 29 by its eye-bolts 27. Since anchor bolts (not shown) are typically already connected to the hanging wall 29 for stabilization, the unit 18 can be suspended byway of tensile elements, such as chains (not shown) connecting the eye-bolts 27 and the anchor bolts. For stability, four eye-bolts 27 are provided on the box 14 adjacent respective corners of the roof of the box 14 and four eye-bolts 27 are provided near respective corners of the skid-frame 25. It should be appreciated thatthe unit 18 should preferably be level, and such suspension of the box 14 from the hanging wall facilitates levelling thereof. The unit 18 is also neatly out of the way when hung from the hanging wall, thus avoiding cluttering of cramped spaces adjacent the stope face 22. The unit 18 is then electrically connected to the electrical distribution box 52, and the water inlet 24 of the water-cooled condenser 32 is connected to the service water supply pipeline 36 by the flexible hose 28. The length of the electrical cable extension 50 and the flexible hose 38 can be chosen to have adequate slack, permitting advancement of the unit 18 together with the advancing stop face 22.

Refrigerant fluid is pumped through the air-conditioning components of Figure 2 in conventional fashion, evaporating at the evaporator 20 being for taking up heat which is released when the refrigerant condenses at the condenser 32. The fan 19 blows over the evaporator 20, to produce a stream of cooled air emanating from the unit 18, the cold air typically being directed to where spot-cooling is required.

Heat which is released at the condenser 32 is removed by service water which moves through the water cooled plate heat exchanger forming part of the condenser 32, so that heat exchange between the refrigerant fluid and the service water takes place. The service water thereafter joins the resident underground service water supply, or is fed directly to equipment where it is needed, or is directed into a drainage system, as explained above. No hot air is thus released or discharged by the unit 18 into the ambient air.

If a worker is working in a position which can not be reached directly by the stream of cooled air from the fan 19, a delivery hose or ducting (not shown) can be removably connected to the air outlet 16 of the unit 18. The delivery duct can then be positioned as desired, so that moving cooled air is discharged from an outlet of the delivery duct at the required spot.

It is an advantage of an air-conditioning system 10 in accordance with the invention that use of a plurality of air-conditioning units 18 which are transportable to desired locations underground in a mine can replace or supplement large and extensive central refrigeration plants for mines. This avoids the construction associated with installing ducting for distributing the cooled air underground a mine, advantageously reducing associated construction and maintenance costs.

Use of the water-cooled condenser 32 prevents the discharge of heated air into ambient air, as extracted heat is dissipated by the water supply to which the condenser 32 is connected.