Dehumidification system and method
The present invention relates to a dehumidification system and method and, in particular, to a system and method for controlling the humidity of air in a process or location using a desiccant-coated fluid-air heat exchanger. The desiccant material adsorbs water at or above ambient temperatures during an adsorption cycle, and the resultant air stream is of a reduced humidity compared with the humidity of the supply air. The desiccant material may then be dried during a regeneration cycle through addition of heating fluid through the heat exchanger, driving water back into the vapor state with addition of latent energy of vaporization. The desiccant material may be cooled, during the adsorption cycle, through addition of cooling fluid through the heat exchanger to maintain the temperature within a range sufficient for water vapor to be removed from the stream of air.
1. A dehumidification system for providing dehumidified air to an evaporative cooling process, the dehumidification system including:
a fluid-air heat exchanger including an external, air-side surface coated with desiccant material, wherein during an adsorption cycle fluid is passed through the heat exchanger at a temperature which causes water vapour to be removed from a stream of air permitted or forced across the heat exchanger;
a means for permitting or forcing the stream of air across said heat exchanger during the adsorption cycle;
a means of heating the desiccant material during a regeneration cycle to cause adsorbed water to be removed from the desiccant material by vaporisation, thereby regenerating the desiccant material to a state which will allow the desiccant material to remove water vapour from a stream of air in a subsequent adsorption cycle;
a means for cooling the desiccant material during the adsorption cycle in order to maintain said temperature within a range sufficient for water vapour to be removed from the stream of air, wherein the means of cooling the desiccant material is the fluid-air heat exchanger wherein cooling is achieved by passing a cooling fluid through the fluid-air heat exchanger;
an evaporative means that includes a volume of fluid; wherein an evaporative cooling process includes permitting or forcing a volume of desiccated air across a surface area of the volume of fluid in the evaporative means, whereby the volume of air causes the temperature of said fluid to be lowered by evaporation; and wherein the volume of fluid, having had its temperature reduced by the evaporative cooling process in the evaporative means, is supplied to the fluid-air heat exchanger as cooling fluid and is used to cool the desiccant material during the adsorption cycle.
2. The dehumidification system according to claim 1 , wherein the means of heating the desiccant material is the fluid-air heat exchanger, wherein heating is achieved by passing heating fluid through the fluid-air heat exchanger.
3. The dehumidification system according to claim 2 , further including a 2-way valve at an entry into said heat exchanger which is operable to switch between heating and cooling fluid supply to the fluid-air heat exchanger.
4. The dehumidification system according to claim 2 , wherein the heating and cooling fluid is fluid from a common sourced heated or cooled prior to entry into the fluid-air heat exchanger according to whether the fluid-air heat exchanger is operating the adsorption cycle or the regeneration cycle.
5. The dehumidification system according to claim 1 , wherein the means of permitting or forcing the stream of air is one or more fans.
6. The dehumidification system according to claim 1 , wherein the fluid-air heat exchanger is in the form of a fin radiator including a fluid flow pipe and associated heating cooling fins which are coated in said desiccant material.
7. The dehumidification system according to claim 1 , wherein the fluid-air heat exchanger and the means for permitting or forcing the stream of air is disposed in ductwork used to transport ambient air into a location.
8. The dehumidification system according to claim 1 , wherein the fluid-air heat exchanger and the means for permitting or forcing the stream of air forms part of a module which is attachable to ductwork used to transport ambient air into a location.
9. The dehumidification system according to claim 7 , wherein the location is a building interior.
10. The dehumidification system according to claim 7 , wherein the means of permitting or forcing the stream of air across the fluid-air heat exchanger is operated alternately in an air supply mode to permit or force the stream of air to the location via the fluid-air heat exchanger, and an air return mode to draw the stream of air out from the location.
11. The dehumidification system according to claim 10 , wherein return air is supplied to the evaporative cooling process.
12. The dehumidification system according to claim 7 , further including:
a second fluid-air heat exchanger operating in parallel to said fluid-air heat exchanger, wherein when the fluid-air heat exchanger is operating said adsorption cycle, the second fluid-air heat exchanger is operating said regeneration cycle, and vice versa, to ensure a continuous supply of dehumidified air to said location;
a means of switching the operation of each of the fluid-air heat exchanger and the second fluid-air heat exchanger between adsorption and regeneration cycles; and
air handing means which provide that air passing through the fluid-air heat exchanger or the second fluid-air heat exchanger operating in said regeneration cycle is not provided to the location and air passing through the fluid-air heat exchanger or the second fluid-air heat exchanger operating in said adsorption cycle is provided to the location.
13. The dehumidification system according to claim 1 , wherein the volume of fluid is held in a tank and the volume of air is permitted or forced across a top surface area of a body of fluid in the tank.
14. The dehumidification system according to claim 1 , wherein the volume of fluid is in the form of droplets in a cooling tower and the volume of air is permitted or forced across a surface area of each droplet.
15. The dehumidification system according to claim 1 , wherein the evaporative cooling process is used to cool or re-humidify desiccated air prior to entry into a location or a further process.
16. The dehumidification system according to claim 1 , further including:
a second fluid-air heat exchanger operating downstream of the process, wherein when the fluid-air heat exchanger is operating said adsorption cycle, the second fluid-air heat exchanger is operating said regeneration cycle, and vice versa;
a means of switching the operation of each of the fluid-air heat exchanger and the second fluid-air heat exchanger between adsorption and regeneration cycles;
a means of switching a mode of operation of the means of permitting or forcing a stream of air across the heat exchanger to ensure continuous supply of dehumidified air to the process such that when the fluid-air heat exchanger is operating the adsorption cycle, a stream of air is drawn across the fluid-air heat exchanger to provide dehumidified air to the process whilst the second fluid-air heat exchanger is operating the regeneration cycle, and when the second fluid-air heat exchanger is operating said adsorption cycle, a stream of air is drawn across the second fluid-air heat exchanger to provide dehumidified air to the process whilst the fluid-air heat exchanger is operating the regeneration cycle.