Evaporative cooling system and device

An evaporative cooling system includes an indirect cooling coil containing a cooling fluid to be circulated and a blower assembly configured to generate an inlet air stream through the indirect cooling coil. The cooling fluid in the indirect cooling coil is a slurry of water and phase change material.

FIELD OF THE INVENTION

The present invention relates generally to evaporative cooling and, more particularly, to an indirect evaporative cooling system and device containing a slurry of phase change material.

BACKGROUND OF THE INVENTION

An evaporative cooler is a device that cools air through the evaporation of water. Existing evaporative cooling devices are typically rectangular in shape and have a shallow water reservoir which is supplied by the plumbing of the structure being cooled. A pump pulls water from the reservoir and pumps it through tubing to the top of the unit, where it flows down the sides and through pads that line the sides of the unit. An electric motor powers a fan in the center of the device, which serves to draw outside air through the pads and into the unit.

As the warm, outside air is drawn in through the porous pads by the fan, the latent heat in the air causes water flowing through the pads to evaporate. This evaporation is caused by a transfer of heat from the air to the water. This results in a net loss of heat in the air or, in other words, cooling. The now cooled air is then forced through an exit duct and into the area to be cooled.

Various types of evaporating cooling devices exist, including direct evaporative coolers, indirect evaporative coolers, and two-stage evaporative coolers, also known as indirect-direct evaporative coolers.

Direct evaporative coolers force outside air through a moist evaporative pad to produce cooled air prior to distributing the cool air to a target area. As discussed above, direct evaporative coolers typically have a blower or centrifugal fan that forces the outside air in through the evaporative pad to cool the air, and then out of the device into the target area.

Indirect evaporative coolers are similar to direct evaporative coolers, but instead utilize some type of heat exchanger. For example, in one type of indirect evaporative cooler, processing air is drawn into the device where heat in the air is absorbed by water in an air-to-water heat exchanger to produce cooled air. The heat in the water is then rejected in a cooling tower where the evaporation occurs. In this sense, indirect evaporative closed systems in that the water in the heat exchange absorbs heat from the air, rejects heat to atmosphere in a cooling tower, and recirculates to absorb more heat from the air. Typically, rather than distributing the cooled air into the target area directly, however, the device secondarily performs a heat exchanging process of reducing the temperature of inlet air by the cooled processing air, thus indirectly cooling the inlet air prior to distributing the air to the target room. Accordingly, the cooled, moist processing air never comes in direct contact with the cooled air entering the target area.

Lastly, indirect-direct evaporative coolers use both direct and indirect evaporative cooling in a two-stage process. In the first stage, warm air is pre-cooled indirectly without adding humidity (such as, for example, by passing inside a heat exchange that is cooled by evaporation on the outside). In the direct stage, the pre-cooled air passes through a water-soaked pad and picks up humidity as it cools. Since the air supply is pre-cooled in the first stage, less humidity is transferred in the direct stage, to reach the desired cooling temperatures. This results in cooler air with a relative humidity between 50-70%, depending on the climate, compared to a traditional system that produces about 70-80% relative humidity in the conditioned air.

As will be readily appreciated, water is a critical natural resource. As the available supply of water is becoming outstripped by demand, the cost of potable water may increase to the point where using it for air conditioning purposes, such is in evaporative coolers, could become prohibitive.

Accordingly, there is a need for an evaporative cooling device that requires less water to cool air than is typically required for existing devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an evaporative cooling device.

It is another object of the present invention to provide an evaporative cooling device of the indirect type.

It is another object of the present invention to provide an indirect evaporative cooling device that utilizes a lesser amount of water as compared to existing indirect cooling devices.

It is another object of the present invention to provide an indirect evaporative cooling device that utilizes a slurry of phase change material.

It is another object of the present invention to provide an indirect evaporative cooling device having a thermal battery bank utilized to cool inlet air.

According to the present invention an evaporative cooling system is provided. The evaporative cooling system includes an indirect cooling coil containing a cooling fluid to be circulated and a blower assembly configured to generate an inlet air stream through the indirect cooling coil. The cooling fluid is a slurry of water and phase change material.

In an embodiment of the present invention a cooling system is provided. The cooling system includes a cooling coil containing a cooling fluid to be circulated, a fan configured to generate an inlet air stream through the cooling coil, and a thermal battery bank arranged downstream from the indirect cooling coil and configured to absorb heat from said inlet air stream.

In another embodiment, an evaporative cooling device is provided. The evaporative cooling device includes a housing, a first heat exchanger containing a first cooling fluid to be circulated through the heat exchanger, and a fan configured to generate an inlet air stream through the first heat exchanger. The first cooling fluid includes a slurry of water and a phase change material.

According to the present invention, a method of cooling a target area includes initiating a flow of inlet air, cooling the inlet air by passing the inlet air through a thermal battery bank having a plurality of thermal battery pods containing a cooling fluid, and cooling the inlet air by passing the inlet air through a first heat exchanger containing a circulated cooling fluid when a cooling capability of the thermal battery bank is substantially exhausted.

These and other objects, features, and advantages of the present invention will become apparent in light of the detailed description of the best mode embodiment thereof, as illustrated in the accompanying drawings.

Other features and advantages of the present disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principals of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS. 1 and 2, an indirect evaporative cooling system10according to an embodiment of the present invention is shown. As will be readily appreciated, the configuration of the cooling system10is generally similar to existing indirect evaporative cooling systems/devices. The system10includes a first heat exchanger, namely a cooling coil12, a cooling tower14, a blower assembly16and an electric motor (not shown) electrically coupled to the blower. The blower assembly16is configured to draw inlet (outside) air into the system and pull the air through a face of the cooling coil12. As warm inlet air passes through the cooling coil12, heat from the air is transferred to a cooling fluid circulating within the cooling coil12. The now-cooled inlet air may then be forced into a structure to provide cooling, as desired.

As best shown inFIG. 2, a portion of the cooling coil12is located within the cooling tower14. A pump (not shown) continuously circulates the cooling fluid in the cooling coil12between the face of the cooling coil12adjacent to the blower16and the cooling tower14. In particular, in operation, as heat is transferred from the inlet air to the cooling fluid to cool the inlet air, the cooling fluid is circulated through the coiling coil12and to the cooling tower14. As also shown inFIG. 2, the cooling tower14includes a secondary heat exchanger18, such as a liquid-to-liquid heat exchanger, fluidly isolated from the cooling coil12. The secondary heat exchanger18serves to remove heat from the cooling fluid in the cooling coil12as it passes through the cooling tower14, allowing the cooling fluid to “recharge.”

In an embodiment, the cooling fluid is a slurry that includes water and a phase-change material entrained in the water. Preferably, the phase change material is encapsulated in a plurality of small plastic balls20, such as those shown inFIG. 3. In an embodiment, the phase change material has a latent heat absorption capacity that is roughly five (5) times that of water alone. In an embodiment, the phase change material is Micronal® DS 5008 X or Micronal® DS 5045 X, available from BASF, although other phase change materials having a latent heat absorption capacity approximately five times that of water may also be utilized without departing from the broader aspects of the present invention.

The slurry of water and encapsulated phase change material is continuously circulated between the indirect cooling coil12and the cooling tower14. While in the indirect cooling coil12the slurry absorbs heat from the outside air, thereby cooling the air before the air enters a structure, as discussed above. Upon the slurry's return to the cooling tower14, the absorbed heat from the slurry is removed, by heat transfer, in the secondary heat exchanger18, to allow the cooling fluid and, in particular the phase change material, to recharge. In an embodiment, the heat transferred in the secondary heat exchanger from the cooling fluid can then be rejected to atmosphere.

Due to the significantly greater heat absorption of the cooling fluid slurry, the slurry allows the same degree of cooling effect to occur from an indirect evaporative cooling unit of a correspondingly smaller size. Thus, importantly, the amount of water used by the system is reduced.

With reference toFIGS. 4 and 5, an alternative embodiment of an indirect evaporative cooling system50is shown. The system50is substantially similar to the system10shown inFIGS. 1 and 2. In particular, the system50may include a cooling coil52, a cooling tower54, a blower assembly56and an electric motor (not shown) electrically coupled to the blower. The cooling tower54additional may include a secondary heat exchanger158. The system50may also include a pump for circulating a fluid within the coil52and the secondary heat exchanger58, respectively. As will be readily appreciated, the indirect cooling coil52may include water or a slurry of water and phase change material as discussed above.

As with the system10, described above, blower56pulls inlet air through the cooling coil52, whereby heat from the air is transferred to the cooling fluid within the cooling coil52. The cooling fluid is circulated through the cooling coil52and to the cooling tower, where it enters the secondary heat exchanger58. In the secondary heat exchanger58, heat from the cooling fluid is rejected such that the cooling fluid can recharge and be circulated for cooling once again.

Importantly, however, the system50also includes a thermal battery bank60positioned in behind the indirect cooling coil52between the cooling coil52and the blower56. The thermal battery bank60includes a plurality of individual thermal battery pods62containing a cooling fluid. In an embodiment, the thermal battery pods62are generally rectangular in shape, as shown inFIG. 6, and are arranged in stacks in the thermal battery bank60. In an embodiment, the cooling fluid is a slurry of water and encapsulated phase change material. In an embodiment, the phase change material has a latent heat absorption capacity that is roughly five (5) times that of water alone.

After the inlet air is cooled by passing through the face of the indirect cooling coil52, as discussed above, it is pulled through the thermal battery bank60for further cooling. In particular, as the air is pulled through the thermal battery bank60, the cooling fluid within the pod absorbs additional heat from the air to further cooling the air before it enters a structure.

Importantly, the pods62are removably inserted into the thermal battery bank60to charge the thermal battery bank60with cooling during the night or at times of low ambient temperatures. Once charged, the thermal battery bank60servers to further cool the incoming building air until the pods62are completely discharged (whereby they can't absorb any more heat from the air). The pods62could then be recharged at night or at times of low ambient temperature.

Importantly, the thermal battery bank60may also be utilized in combination with known indirect evaporative cooling devices that are water driven. In particular, the thermal battery bank60may be utilized to cool the inlet air until the pods62have been exhausted of their cooling capability, at which time standard evaporative cooling through water evaporation may be utilized. As will be readily appreciated, this allows the evaporative cooling equipment to stay off-line for extended periods, thus, reducing the annual water consumption of the evaporative cooling equipment.

In an embodiment, either of the above-described systems10,50and their components may be integrated into a housing so as to form an evaporative cooling device that may be installed in an opening in a structure.

One significant advantage of the thermal battery bank60is that the pods62are designed for installation in other types of equipment where it functions much like a traditional thermal storage system to shed electrical load during peak hours.