High efficiency cooling system

Patent metadata

Field	Value
Publication number	US-9980413-B2
Application number	US-201514693478-A
Country	US
Kind code	B2
Filing date	Apr 22, 2015
Priority date	Apr 19, 2011
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

A cooling system has a cabinet and a plurality of separate cooling stages including an upstream cooling stage and a downstream cooling stage. At least the upstream cooling state is a variable capacity cooling stage. Each cooling stage has a cooling circuit. Evaporators of the cooling circuits are arranged in the cabinet so that air passes over them in serial fashion. A controller when a Call for Cooling first reaches a point where cooling is needed, operating the upstream cooling circuit to provide cooling and not the downstream cooling circuit. When the Call for Cooling has increased to a second point, the controller additionally operates the downstream cooling circuit to provide cooling. The cooling capacity at which the upstream cooling circuit is being operated is less than its full capacity when the Call for Cooling reaches the second point.

First claim

What is claimed is:

1. A cooling system, comprising:
a cabinet having an air inlet and an air outlet;
an air moving unit disposed in the cabinet;
a plurality of separate cooling stages including an upstream cooling stage and a downstream cooling stage, at least the upstream cooling stage having a variable capacity cooling circuit;
each cooling stage including a cooling circuit having an evaporator, a condenser, a compressor and an expansion device;
at least the cooling circuit of the upstream cooling stage having a pumped refrigerant economizer mode and a direct expansion mode wherein each cooling circuit that has both the pumped refrigerant economizer mode and the direct expansion mode also has a liquid pump wherein when that cooling circuit is operated in the direct expansion mode a compressor of that cooling circuit is on and compresses a refrigerant in a vapor phase to raise pressure of the refrigerant and thus condensing temperature of the refrigerant and the refrigerant is circulated around the cooling circuit by the compressor of that cooling circuit and wherein when that cooling circuit is operated in the pumped refrigerant economizer mode the compressor of that cooling circuit is off and the liquid pump of that cooling circuit is on and pumps the refrigerant in a liquid phase and refrigerant is circulated around that cooling circuit by the liquid pump of that cooling circuit and without compressing the refrigerant in its vapor phase;
the evaporator of the cooling circuit of the upstream cooling stage and the evaporator of the cooling circuit of the downstream cooling stage arranged in the cabinet so that air to be cooled passes over the evaporator of the cooling circuit of the upstream cooling state and the evaporator of the cooling circuit of the downstream cooling stage in serial fashion, first over the evaporator of the cooling circuit of the upstream cooling stage and then over the evaporator of the cooling circuit of the downstream cooling stage;
a controller that determines which of the cooling circuits to operate to provide cooling and for each of the cooling circuits to be operated to provide cooling that has both the pumped refrigerant economizer mode and direct expansion mode, determining whether to operate each such cooling circuit in the pumped refrigerant economizer mode or the direct expansion mode;
the controller operating each cooling circuit having both the pumped refrigerant economizer mode and the direct expansion mode in the pumped refrigerant economizer mode when an outside air temperature is low enough to provide sufficient heat rejection from the refrigerant flowing through the condenser to the outside air without compressing the refrigerant and when the outside air temperature is not low enough to provide such sufficient heat rejection operating that cooling circuit in the direct expansion mode;
the controller when a Call for Cooling first reaches a point where cooling is needed, operating the upstream cooling circuit to provide cooling and not operating the downstream cooling circuit to provide cooling and when the Call for Cooling has increased to a second point, additionally operating the downstream cooling circuit to provide cooling, wherein the cooling capacity at which the upstream cooling circuit is being operated to provide is less than the full cooling capacity of the upstream cooling circuit when the Call for Cooling reaches the second point; and
each expansion device is an electronic expansion valve, the controller when any of the cooling circuits are being operated in the direct expansion mode controlling the electronic expansion valve of that cooling circuit to control a suction superheat of the evaporator of that cooling circuit and the controller when any of the cooling circuits being operated in the pumped refrigerant economizer mode controlling the electronic expansion valve of that cooling circuit to maintain a minimum differential pressure across the liquid pump of that cooling circuit.

2. The cooling system of claim 1 wherein each of the condensers includes an electronically commutated fan, the controller varying the speed of the electronically commutated fan to maintain a temperature of the refrigerant leaving the condenser at a setpoint.

3. The cooling system of claim 1 wherein the condensers are air cooled condensers.

4. The cooling system of claim 1 wherein the condensers are water cooled condensers.

5. The cooling system of claim 1 wherein the air moving unit includes at least one electronically commutated fan, the controller increasing the speed of the electronically commutated fan as a cooling load on the cooling system increases and decreasing the speed of the electronically commutated fan as the cooling load decreases.

6. The cooling system of claim 1 wherein the compressor of each cooling circuit is a tandem compressor including a fixed capacity compressor and variable capacity digital scroll compressor, the controller controlling the fixed capacity compressor and variable capacity digital scroll compressor of each of the tandem compressors based on the Call for Cooling, which of a plurality of ranges that the Call for Cooling falls within and whether the Call for Cooling is ramping up or ramping down.

7. The cooling system of claim 6 wherein the controller first begins ramping the variable capacity digital scroll compressor of the upstream cooling circuit to provide cooling and when the Call for Cooling increases above a threshold, the controller also begins ramping the variable capacity digital scroll compressor of the cooling circuit of the downstream cooling stage in parallel with ramping the variable capacity digital scroll compressor of the upstream cooling circuit.

8. The cooling system of claim 1 wherein each cooling circuit has both the pumped refrigerant economizer mode and the direct expansion mode.

9. The cooling system of claim 6 wherein the controller selects which of a plurality of superheat control modes to use in operating the electronic expansion valve of each cooling circuit based on control parameters and a current operating status of each of the variable capacity digital scroll compressor and fixed capacity compressor of the tandem compressor of that control circuit.

10. A cooling system, comprising:
a cabinet having an air inlet and an air outlet;
an air moving unit disposed in the cabinet;
a plurality of separate cooling stages including an upstream cooling stage and a downstream cooling stage;
each cooling stage including a cooling circuit having an evaporator, a condenser, a tandem digital scroll compressor and an electronic expansion valve;
each tandem digital scroll compressor including a fixed capacity compressor and variable capacity digital scroll compressor;
at least the cooling circuit of the upstream cooling stage having a pumped refrigerant economizer mode and a direct expansion mode wherein each cooling circuit that has both the pumped refrigerant economizer mode and the direct expansion mode also has a liquid pump wherein when that cooling circuit is operated in the direct expansion mode the compressor is on and compresses a refrigerant in a vapor phase to raise its pressure and thus its condensing temperature and refrigerant is circulated around the cooling circuit by the compressor and wherein when that cooling circuit is operated in the pumped refrigerant economizer mode the compressor of that cooling circuit is off and the liquid pump of that cooling circuit is on and pumps the refrigerant in a liquid phase and refrigerant is circulated around that cooling circuit by the liquid pump and without compressing the refrigerant in its vapor phase;
the evaporator of the cooling circuit of the upstream cooling stage

Assignees

• Liebert Corp

Inventors

• Judge John F
• Schrader Timothy J
• Sillato Stephen
• Noll Roger
• Helmink Gary A
• Barbato Pierpaolo
• Mana Giuseppe Dalla
• Monnier Lou
• Lin Zhiyong
• Dolcich Benedict J
• Schutte Daniel J
• Haggy Greg

Classifications

• F25B45/00

  Arrangements for charging or discharging refrigerant · CPC title

• F25B41/00

  Fluid-circulation arrangements · CPC title

• F25B25/00

  Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00 · CPC title

• F25B2500/31

  Low ambient temperatures · CPC title

• F25B2400/06

  Several compression cycles arranged in parallel · CPC title