Systems and methods for managing conditions in enclosed space
Systems and methods for controlling temperature in an enclosed space can include an air-to-air heat exchanger (AAHX) and a direct evaporative cooler (DEC). The DEC can be located in a scavenger or outdoor air stream such that the DEC cools the outdoor air, which is then used to cool or reject heat from a process air stream passing through the AAHX. In an example, the AAHX can be a sensible wheel. In another example, the AAHX can be a counter-flow flat plate. The system can operate in various modes, including an economizer mode and an evaporation mode, depending, in part, on the outdoor air conditions and a load on the system. In some examples, the system can include a DX coil to provide additional cooling to the process air in another operating mode.
1. A system for controlling temperature in an enclosed space, the system comprising:
an air-to-air heat exchanger (AAHX) arranged in a flow path of process air between a process air inlet and outlet and in a flow path of scavenger air between a scavenger air inlet and outlet, the AAHX comprising at least one of a counter-flow flat-plate heat exchanger and a sensible wheel;
a direct evaporative cooler (DEC) arranged in the flow path of scavenger air between the AAHX and the scavenger air inlet; and
a direct expansion (DX) system to provide additional cooling to the process air exiting the AAHX, the DX system comprising:
a DX coil arranged in the flow path of process air between the AAHX and the process air outlet; and
a liquid-to-liquid heat exchanger arranged in the flow path of scavenger air between the scavenger air inlet and the AAHX.
2. The system of claim 1 , wherein water from the DEC flows through the liquid-to-liquid heat exchanger and conditions refrigerant flowing from the DX coil through the liquid-to-liquid heat exchanger.
3. The system of claim 1 wherein the flow path of scavenger air is through a top portion of the system and the flow path of process air is through a bottom portion of the system, and the system is configured for use on a rooftop of a building containing the enclosed space.
4. The system of claim 3 further comprising a partition separating the top and bottom portions of the system, and wherein the flow path of scavenger air and the flow path of process air remain separate from one another in the system.
5. The system of claim 4 wherein the AAHX is disposed in both the top and bottom portions of the system.
6. The system of claim 1 wherein the enclosed space is a data center.
7. The system of claim 1 wherein the AAHX is a counter-flow flat plate heat exchanger configured for counter-parallel flow such that the flow path of scavenger air is in an opposite direction of the flow path of process air.
8. A system for controlling temperature in an enclosed space using multiple modes of operation, the system comprising:
a sensible wheel arranged in a first flow path of process air between a process air inlet and outlet and in a second flow path of scavenger air between a scavenger air inlet and outlet;
a direct evaporative cooler (DEC) arranged in the second flow path upstream of the sensible wheel to selectively provide evaporative cooling to the scavenger air in the second flow path in a second mode of operation and a third mode of operation; and
a direct expansion (DX) coil configured to selectively provide additional cooling to the process air in the first flow path in the third mode of operation,
wherein the system is configured to selectively operate in a first mode of operation when the sensible wheel sufficiently conditions the process air without the DEC and DX coil, and wherein the system switches to the second and third modes as additional cooling is required to condition the process air.
9. The system of claim 8 , further comprising one or more bypass features for operating the system in the first or second mode.
10. A method of conditioning air in an enclosed space, the method comprising:
passing scavenger air through a first portion of a conditioning system, the scavenger air entering the first portion at a scavenger air inlet and exiting the first portion at a scavenger air outlet;
passing process air through a second portion of the conditioning system, the process air entering the second portion at a process air inlet and exiting the second portion at a process air outlet;
passing the scavenger air through a direct evaporative cooler (DEC) arranged in the first portion of the conditioning system to cool the scavenger air;
passing the cooled scavenger air and the process air through an air-to-air heat exchanger (AAHX) arranged in the conditioning system downstream of the direct evaporative cooler, wherein the cooled scavenger air sensibly cools the process air in the AAHX, wherein the AAHX is arranged partially in the first portion of the conditioning system and partially in the second portion of the conditioning system, and wherein the AAHX comprises at least one of a counter-flow flat-plate heat exchanger and a sensible wheel; and
bypassing the DEC in an economizer mode by closing the scavenger air inlet and directing the scavenger air to enter the first portion at a location downstream of the DEC.
11. The method of claim 10 further comprising:
passing the process air through a direct expansion cooling device arranged in the second portion of the conditioning system downstream of the AAHX, wherein the direct expansion cooling device provides additional cooling to the process air exiting the AAHX.
12. The method of claim 11 further comprising:
passing the scavenger air through a condenser coil arranged in the first portion of the conditioning system downstream of the AAHX, wherein the condenser coil cools a refrigerant from the direct expansion cooling device, using the scavenger air.
13. A method of conditioning air in an enclosed space using multiple modes of operation, the method comprising:
passing scavenger air through a first portion of a conditioning system, the scavenger air entering the first portion at a scavenger air inlet and exiting the first portion at a scavenger air outlet;
passing process air through a second portion of the conditioning system, the process air entering the second portion at a process air inlet and exiting the second portion at a process air outlet;
passing the scavenger air and the process air through an air-to-air heat exchanger (AAHX) arranged partially in the first portion of the conditioning system and partially in the second portion of the conditioning system such that the scavenger air sensibly cools the process air in the AAHX; selectively using a direct evaporative cooler (DEC) arranged in the first portion of the conditioning system upstream of the AAHX to cool the scavenger air in a second or third operating mode in which the AAHX is not sufficient to condition the process air without the DEC;
selectively using a direct expansion cooling device arranged in the second portion of the conditioning system downstream of the AAHX to provide additional cooling to the process air exiting the AAHX in in the third operating mode in which the AAHX and DEC are not sufficient to condition the process air without the direct expansion cooling device, a first operating mode excludes the DEC and direct expansion cooling device; and
operating the system at the lowest operating mode, among the first, second and third operating modes, sufficient to adequately cool the process air.