Computer Room Air Conditioner With Pre-Cooler
A computer room air conditioner (“CRAC”) has a cabinet having an air inlet through which return air from an area is drawn and an air outlet through which air cooled by the CRAC is exhausted. An air moving unit is disposed in the cabinet as are a plurality of cooling coils, which are in separate cooling circuits. The cooling coils are arranged so that the air passes through the cooling coils in serial fashion, that is, first through an upstream cooling coil and then through a downstream cooling cool. The upstream cooling coil acts as a pre-cooler to the subsequent downstream cooling coil. The CRAC includes a controller that controls the cooling provided by the cooling circuits. The controller controls the cooling provided by the upstream cooling circuit so that when it is being used to provide cooling, it provides only sensible cooling.
1 . A computer room air conditioner, comprising:
a cabinet having an air inlet and an air outlet;
an air moving unit disposed in the cabinet;
a plurality of separate cooling circuits including an upstream cooling circuit and a downstream cooling circuit;
the upstream cooling circuit including a cooling coil (upstream cooling coil) and the downstream cooling circuit including a cooling coil (downstream cooling coil) wherein the cooling coils are arranged so that air to be cooled passes through them in serial fashion, first through the upstream cooling coil and then through the downstream cooling coil wherein the upstream cooling cool is a pre-cooler to the downstream cooling coil; and
a controller that controls the cooling circuits, the controller controlling the upstream cooling circuit when the upstream cooling circuit is being used to provide cooling to provide only sensible cooling.
2 . The computer room air conditioner of claim 1 , wherein the controller controls the downstream cooling circuit to provide any latent cooling that is required and any sensible cooling that is required in addition to the sensible cooling provided by the upstream cooling circuit.
3 . The computer room air conditioner of claim 1 wherein the controller controls the downstream cooling circuit to provide sensible cooling and any latent cooling that is required and controls the upstream cooling circuit so that it is not providing any cooling.
4 . The computer room air conditioner of claim 1 wherein the upstream cooling cool is a microchannel cooling coil and the downstream cooling coil is a fin-and-tube cooling coil.
5 . The computer room air conditioner of claim 1 wherein the upstream cooling coil and the downstream cooling coil are both microchannel cooling coils.
6 . The computer room air conditioner of claim 1 wherein the upstream cooling coil and the downstream cooling coils are both fin-and-tube cooling coils.
7 . The computer room air conditioner of claim 1 wherein the upstream cooling circuit is a pumped refrigerant cooling circuit having the upstream cooling coil, a flow regulator, a condenser and a pump arranged in the pumped refrigerant cooling circuit, and the downstream cooling circuit is a direct expansion cooling circuit having the downstream cooling coil, an expansion valve, a condenser and a compressor arranged in the direct expansion cooling circuit.
8 . The computer room air conditioner of claim 1 wherein the upstream cooling coil is disposed at the air inlet of the cabinet.
9 . The computer room air conditioner of claim 1 wherein the upstream cooling coil is disposed at an air inlet of the downstream cooling coil.
10 . The computer room air conditioner of claim 1 including at least three cooling circuits, the controller controlling all but a most downstream cooling circuit to provide only sensible cooling when these cooling circuits are being used to provide cooling.
11 . The computer room air conditioner of claim 10 wherein the controller controls controlling the most downstream cooling circuit to provide any latent cooling that is required and any sensible cooling that is required in addition to the sensible cooling provided by the cooling circuits upstream of the most downstream cooling circuit.
12 . The computer room air conditioner of claim 10 wherein the controller controls the downstream cooling circuit to provide sensible cooling and any latent cooling that is required and controls the upstream cooling circuit so that it is not providing any cooling.
13 . The computer room air conditioner of claim 1 wherein the upstream and downstream cooling coils are disposed in the cabinet.
14 . The computer room air conditioner of claim 1 wherein the downstream cooling coil is disposed in the cabinet and the upstream cooling coil is in an air inlet plenum outside the cabinet which is coupled to the air inlet of the cabinet.
15 . The computer room air conditioner of claim 14 wherein the upstream cooling circuit cools air passing through the upstream cooling coil sufficiently so that a cooling capacity of the downstream cooling circuit is sufficient to reduce a temperature of the air passing through the downstream cooling to below a dew point of the air to provide latent cooling.
16 . The computer room air conditioner of claim 1 wherein the upstream cooling circuit increases a temperature delta across the computer room air conditioner by at least ten degrees Fahrenheit.