Air Cooling Unit For Data Centers
An air handling unit utilizing a humidifier in conjunction with a heat exchanger to provide a means for free cooling recirculating return air with evaporatively cooled outside air. A first air stream comprising outside air can be circulated through the evaporative humidifier and a first portion of the energy recovery heat exchanger, while a second air stream comprising recirculated inside air can be circulated through a second portion of the heat exchanger. The outside air will be humidified as it circulates through the humidifier, thereby cooling the outside air to its adiabatic saturation temperature. The heat exchanger will cool the recirculating inside air with the evaporatively cooled outside air.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/491,057 filed May 27, 2012.
II. BACK GROUNDData centers—facilities that primarily contain electronic equipment used for data processing, data storage, and communications networking—have become common and essential to the functioning of nearly every sector of the economy to aid business processes, information management, and communications functions. Increasing demand for computer resources has led to significant growth in the number of data center servers, along with a considerable increase in the energy used by these servers and the cooling infrastructure that supports them. The cooling infrastructure for data centers is estimated to account for 50 percent of the total energy consumption of data centers. See U.S. EPA Report to Congress on Server and Data Center Energy Efficiency, Public Law 109-431 (August 2007).
The continuous operation of the electronic equipment generates a significant amount of heat. The role of data center air-conditioning systems is to remove this heat from the data center to keep the components of the electronic equipment within the manufacturers' specified temperature and humidity ranges. Cooling in data centers is often provided by computer room air conditioning units, where the entire air handling unit is situated on the data center floor. The air handling unit contains fans, filters, and cooling coils and is responsible for conditioning and distributing air throughout the data center. In most cases, air enters the top of the air conditioning unit and is conditioned as air passes across coils containing chilled water pumped from a chiller located outside of the data center room. The conditioned air is then supplied to the electronic equipment (primarily servers), typically through a raised floor area. Fans within the servers pull the conditioned air through the servers. The warmed air then stratifies toward the ceiling and eventually makes its way back to the air conditioning unit intake. Most air circulation in data centers is internal to the data center zone. To maintain a controlled environment, the majority of data centers are designed so that only a small amount of outside air enters.
Due the increased energy and capital costs associated with the expanded use of computer resources, there has been mounting interest in opportunities for energy efficiency in the information technology (IT) industry. Air-side economizers are increasingly being considered as a viable option for lowering the energy usage of a data center's cooling infrastructure. An air-side economizer is a type of air handling unit which takes advantage of cold outside temperatures to provide “free cooling” cycles that reduce or eliminate the need for the mechanical air cooling (i.e., cooling via compressors, chillers, cooling media pumps, etc.) employed by traditional data center air-conditioning systems.
Given that a data center must run continuously for a total of 8,760 hours per year, significant energy savings can be achieved with a typical air-side economizer when the outside air conditions fall within the allowable ranges. However, the operating hours of an air-side economizer are dependent on the outside air conditions—namely, the air temperature and air humidity. An air-side economizer can provide free cooling any time the outside temperature is below the required supply temperature and below the required supply dew point for the controlled environment. The economizer cycle can provide partial free cooling by reducing the mechanical cooling load when the outdoor temperature is higher than the required supply temperature but the outdoor air dew point is less than the dew point of the return air. In the context of data centers, the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) has provided the following recommended and allowable temperature and humidity ranges for data centers:
Air-side economizers typically are integrated with a mechanical cooling system in order to assure the environmental integrity of the controlled environment regardless of the outside air conditions. A typical air-side economizer unit is shown in
Air-side economizers have proven to be an effective tool in reducing energy usage in cool climates and mild climates having low humidity. However, the efficiencies provided by current-generation air-side economizers are significantly reduced or altogether eliminated in humid climates. Humidity control is a concern for conditioned spaces, particularly in data centers containing electronic equipment. Exposing electronic equipment to overly humid outside air can cause condensation to form on the equipment, thereby negatively affecting the equipment's performance and/or causing premature equipment failure. In cool, humid climates, air-side economizer units can utilize dehumidifiers to remove moisture from the outside air before introducing the air to the conditioned space. However, dehumidifiers consume a considerable amount of energy themselves, thus diminishing the overall efficiencies achievable with the economizer unit. In warm, humid climates, dehumidification is not a viable option. The dehumidification of the outside air in the air handling unit is an adiabatic process. As latent heat is removed from the outside air, the sensible heat of the outside air will rise. Thus, the dehumidification of the warm outside air will increase the temperature of the outside air, thereby reducing or eliminating the free cooling potential of the outside air.
Accordingly, there is a need for a new air handling unit capable of efficient, economizer operation in humid climates.
III. SUMMARYThe invention disclosed herein is directed to an air handling unit which utilizes evaporatively cooled outside air as a cooling medium to cool return air recirculating in a conditioned space. Because the outside air is not introduced into the conditioned space, the air handling unit of the present invention is capable of economizer operation in conditions where the outside air humidity is above the targeted humidity level for the conditioned space.
An air handling unit having features of the present invention can comprise a humidifier positioned in a first air stream and a heat exchanger positioned partially in the first air stream and partially in a second air stream. The first air stream can be humidified as it circulates across the humidifier, thereby cooling the first air stream up to its adiabatic saturation temperature—the temperature that the air stream would achieve if it were allowed to become saturated adiabatically. The first air stream—which is now at its maximum free cooling potential—can then be circulated across the heat exchanger before being exhausted from the air handling unit. The heat exchanger will transmit heat energy from the recirculating second air stream to the cooled first air stream, thereby reducing the sensible heat of the second air stream. However, because the saturated first air stream does not come into contact with the recirculating second air stream, the humidity of the second air stream will not be affected.
The above summary is not intended to describe each illustrated embodiment or every possible implementation. These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.
A preferred embodiment of the air handling unit 100 of the present invention is shown in
In the preferred embodiment depicted in
Air is circulated from the air handling unit 100 to a conditioned space by means of a supply fan 150, while air is exhausted from the air handling unit 100 by means of an exhaust fan 160. In certain embodiments, the air handling unit can also feature an integrated mechanical cooling device 140 to supplement the free cooling provided by the air handling unit 100. A plurality of dampers 130, 131, 132, 133, 134 control the flow of air through the air handling unit 100. A computerized control system can be used to monitor the outside air conditions and automatically change configurations, or modes, of the air handling unit 100 to maximize the free cooling potential of the climate while maintaining the integrity of the conditioned space.
Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art having the benefit of the teaching presented in the foregoing description and associated drawings. For instance, in
Claims
1. An air handling unit for conditioning air, comprising:
- a. A humidifier positioned in a first air stream for humidifying the first air stream; and
- b. A heat exchanger positioned partially in the first air stream and partially in a second air stream, the heat exchanger capable of transferring heat from the second air stream to the first air stream.
2. The air handling unit of claim 2, wherein the first air stream comprises outside air, and wherein the second air stream comprises recirculated inside air.
3. The air handling unit of claim 2, wherein the humidifier cools the first air stream up to its adiabatic saturation temperature.
4. The air handling unit of claim 3, wherein the heat exchanger is positioned partially within a first air duct and partially within a second air duct.
5. The air handling unit of claim 4, wherein the humidifier is positioned within the first air duct.
6. The air handling unit of claim 6, wherein the humidifier is positioned within a separate air duct connected to the first air duct.
7. The air handling unit of claim 4, wherein the first air stream flows through the first air duct, and wherein the second air stream flows through the second air duct.
8. The air handling unit of claim 7, wherein the heat exchanger comprises a first portion positioned within the first air duct, and a second portion positioned within the second air duct.
9. The air handling unit of claim 8, further comprising a supply fan for circulating the cooled second air stream within a conditioned space.
10. The air handling unit of claim 9, further comprising an exhaust fan for discharging the humidified first air stream from the air handling unit.
11. The air handling unit of claim 10, further comprising a mechanical cooling device positioned in the second air stream for further cooling the second air stream before the second air stream is recirculated by the supply fan within the conditioned space.
12. The air handling unit of claim 11, wherein the first air duct comprises an outside air inlet and an exhaust air outlet, and wherein the second air duct comprises a return air inlet and a supply air outlet.
13. The air handling unit of claim 12, wherein the supply fan circulates the second air stream successively through the return air inlet, the second portion of the heat exchanger, the mechanical cooling device, and the supply air outlet.
14. The air handling unit of claim 13, wherein the exhaust fan circulates the first air stream successively through the outside air inlet, the humidifier, the first portion of the heat exchanger, and the exhaust air outlet.
15. The air handling unit of claim 15, further comprising a plurality of dampers for controlling the flow of air in the air handling unit.
16. The air handling unit of claim 7, wherein the heat exchanger is a heat pipe, the heat pipe comprising a cold deck portion and a hot deck portion, wherein the cold deck portion is positioned within the first air duct, and wherein the hot deck portion is positioned within the second air duct.
17. The air handling unit of claim 7, wherein the heat exchanger is a heat wheel.
18. The air handling unit of claim 7, wherein the humidifier is an evaporative humidifier.
19. The air handling unit of claim 3, wherein there is substantially no exchange of moisture between the first air stream and the second air stream.
20. The air handling unit of claim 3, wherein the dew point of the second air stream remains substantially unchanged.
21. An air handling unit for conditioning air, comprising:
- a. a humidifying means positioned in a first air stream for humidifying the first air stream up to its adiabatic saturation temperature; and
- b. A heat exchanger positioned partially within the first air stream and partially within a second air stream, the energy recovery heat exchanger cooling the second air stream using the humidified first air stream, wherein there is substantially no exchange of moisture between the first air stream and the second air stream.
22. The air handling unit of claim 21, wherein the humidifying means is selected from the group consisting of an evaporative humidifier, an ultrasonic humidifier, a spray mist humidifier, a steam vaporizer, a drum style humidifier, and a disc wheel style humidifier.
23. The air handling unit of claim 21, wherein the heat exchanger is selected from the group consisting of a heat pipe, a heat wheel, and a fixed-plate exchanger.
24. A data center comprising:
- a. a conditioned space housing electronic equipment;
- b. an air handling unit for conditioning the air in the conditioned space, the air handling unit comprising: i. a humidifier positioned in a first air stream, the humidifier capable of cooling the first air stream up to its adiabatic saturation temperature by humidifying the first air stream; and ii. A heat exchanger positioned partially within the first air stream and partially within a second air stream, the energy recovery heat exchanger cooling the second air stream using the humidified first air stream;
- c. an exhaust fan positioned in the first air stream for discharging the humidified first air stream from the air handling unit; and
- d. a supply fan positioned in the second air stream for circulating the second air stream within the conditioned space.
25. The data center of claim 24, wherein the heat exchanger is positioned partially within a first air duct and partially within a second air duct.
26. The data center of claim 25, wherein the first air stream flows through the first air duct, and wherein the second air stream flows through the second air duct.
27. The air handling unit of claim 26, wherein there is substantially no exchange of moisture between the first air stream and the second air stream.
28. The air handling unit of claim 26, wherein the dew point of the second air stream remains substantially unchanged.
29. A method for cooling a conditioned space, comprising:
- a. Providing an air handling unit for conditioning the air in the conditioned space, the air handling unit comprising a humidifier and a heat exchanger, the heat exchanger defining a first portion and a second portion;
- b. Circulating an outside air stream successively through the humidifier and the first portion of the heat exchanger;
- c. Circulating an inside air stream through the second portion of the heat exchanger to cool the inside air stream; and
- d. Supplying the inside air stream to the conditioned space.
30. The method of claim 29, wherein the circulated inside air is further cooled by a mechanical cooling device before the circulated inside air is supplied to the conditioned space.
Type: Application
Filed: May 16, 2012
Publication Date: Nov 29, 2012
Inventors: Stephen Madaffari (Greenwich, CT), Eric Derasse (Manhasset, NY)
Application Number: 13/472,899
International Classification: F25D 31/00 (20060101); F28F 27/00 (20060101); F28D 15/02 (20060101); F28D 15/00 (20060101);