Cooling systems and methods using two circuits with water flow in series and counter flow arrangement

Abstract

A cooling system is provided including a first evaporator coil in thermal communication with an air intake flow to a heat load, a first liquid refrigerant distribution unit in fluid communication with the first evaporator coil to form a first fluid circuit, a second evaporator coil disposed in series with the first evaporator coil in the air intake flow and in the thermal communication with the air intake flow to the heat load, a second liquid refrigerant distribution unit in fluid communication with the second evaporator coil to form a second fluid circuit, a water loop in thermal communication with the first fluid circuit and second fluid circuit, and a chiller loop in thermal communication with the water loop.

Claims

1. A cooling system comprising: a first refrigerant circuit including a first evaporator coil in thermal communication with an air outtake flow to a heat load in a first condenser in fluid communication with the first evaporator coil; a second refrigerant circuit including a second evaporator coil in thermal communication with an air intake flow from the heat load and a second condenser in fluid communication with the second evaporator coil, the second evaporator coil disposed in air flow series with the first evaporator coil so that the air intake flow is fluidly coupled to the air outtake flow, the second condenser arranged in series with the first condenser so that the second condenser is in direct fluid communication with the first condenser; a single water loop in fluid communication with a free-cooling fluid cooler and in fluid communication with the first condenser and the second condenser so that water output from the free-cooling fluid cooler flows to the second condenser directly from the first condenser; a single chiller loop in thermal communication with the water loop and each of the first and second condensers, the chiller loop including a trim condenser in fluid communication with the chiller loop at a first fluid path of the trim condenser and the water loop at a second fluid path of the trim condenser; and a single air conditioning system evaporator in thermal communication with each of the first and second condensers, the single air conditioning system evaporator having a first fluid path and a second fluid path, the first fluid path of the air conditioning system evaporator being in fluid communication with an outlet of the first fluid path of the trim condenser and the second fluid path of the air conditioning system evaporator being in fluid communication with the water loop, wherein the second fluid path of the air conditioning system evaporator is in fluid communication with the second fluid path of the trim condenser via the first condenser and the second condenser, and wherein the fluid flowing through the chiller loop and a fluid flowing through the water loop flow in opposite directions through the trim condenser.

2. The cooling system according to claim 1, wherein the first and second evaporator coils are microchannel evaporator coils.

3. The cooling system according to claim 1, wherein the chiller loop includes a compressor in fluid communication with a fluid output of the first fluid path of the air conditioning system evaporator and with a fluid input of the first fluid path of the trim condenser.

4. The cooling system according to claim 3, wherein chilled water from the air conditioning system evaporator is in thermal communication with the first and second fluid circuits; and wherein the chiller water and the refrigerant flowing through the first and second fluid circuits are in thermal counter flow.

5. The cooling system according to claim 3, wherein water flow through the trim condenser is in a series or in a parallel arrangement with water flow through the air conditioning system evaporator, the first condenser, and the second condenser.

6. A cooling system, comprising: a first refrigerant circuit including a first evaporator coil in thermal communication with an air outtake flow to a heat load and a first condenser in fluid communication with the first evaporator coil; a second refrigerant circuit including a second evaporator coil in thermal communication with an air intake flow from the heat load and a second condenser in fluid communication with the second evaporator coil, the second evaporator coil disposed in air flow series with the first evaporator coil so that the air intake flow is fluidly coupled to the air outtake flow, the second condenser arranged in series with the first condenser so that the second condenser is in direct fluid communication with the first condenser; a single water loop in fluid communication with a free-cooling fluid cooler and in fluid communication with the first condenser and the second condenser so that water output from the free-cooling fluid cooler flows to the second condenser via the first condenser; a single chiller loop in thermal communication with the water loop and each of the first and second condensers, the chiller loop including: a single trim condenser having a first fluid path and a second fluid path; a single air conditioning system evaporator in thermal communication with each of the first and second condensers, the single air conditioning system evaporator having a first fluid path and a second fluid path, the first fluid path of the air conditioning system evaporator being in fluid communication with the first fluid path of the trim condenser; and a compressor in fluid communication with a fluid output of the first fluid path of the air conditioning system evaporator and with a fluid input of the first fluid path of the trim condenser, wherein the first refrigerant circuit includes the first condenser having a first fluid path and a second fluid path, a first fluid receiver in fluid communication with the first fluid path of the first condenser, and a first refrigerant pump in fluid communication with the first fluid receiver, the second fluid path of the first condenser being in fluid communication with the second fluid path of the air conditioning system evaporator, wherein the second refrigerant circuit includes the second condenser having a first fluid path and a second fluid path, a second fluid receiver in fluid communication with the first fluid path of the second condenser, a second refrigerant pump in fluid communication with the second fluid receiver, the second fluid path of the second condenser being in fluid communication with the second fluid path of the first condenser and the water loop, wherein the water loop is in fluid communication with the second fluid path of the trim condenser, wherein water flows through the air conditioning system evaporator to the trim condenser via the first condenser and the second condenser, and wherein a fluid flowing through the chiller loop and a fluid flowing through the water loop flow in opposite directions through the trim condenser.

7. The cooling system according to claim 4, wherein a refrigerant saturation temperature of the first fluid circuit is less than a refrigerant saturation temperature of the second fluid circuit.

8. The cooling system according to claim 3, wherein the first refrigerant circuit further includes a first fluid receiver in fluid communication with a first fluid path of the first condenser, wherein the first refrigerant pump is in fluid communication with the first fluid receiver, and wherein a second fluid path of the first condenser is in fluid communication with the second fluid path of the air conditioning system evaporator.

9. The cooling system according to claim 3, wherein the second refrigerant circuit further includes a second fluid receiver in fluid communication with a first fluid path of the second condenser, wherein the second refrigerant pump is in fluid communication with the second fluid receiver, and wherein a second fluid path of the second condenser is in fluid communication with the second fluid path of the first condenser and the water loop.

10. The cooling system according to claim 6, wherein the first and second evaporator coils are microchannel evaporator coils.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic flow diagram of a cooling system in accordance with embodiments of the present disclosure.

(2) FIG. 2 is a schematic flow diagram of an alternative embodiment of the cooling system of FIG. 1.

DETAILED DESCRIPTION

(3) The present disclosure features a cooling system for data centers or for any other applications that have high heat rejection temperature and high sensible heat ratio compared to general air conditioning or refrigeration applications.

(4) Some systems for data center cooling use two separate liquid refrigerant pump systems. Each pump system has its own water-cooled condenser, along with a chiller loop. The chiller loop includes a fluid cooler, a compressor, a trim condenser, and an air conditioning system (ACS) evaporator. When the outdoor ambient temperature is high, the chiller loop cools water from the outdoor fluid cooler. Further, if one of the two chiller loops fails to operate, the other is used as a backup. If both chiller loops are operable, the two of them can run in parallel for normal operation to obtain higher cooling capacity and energy efficiency.

(5) The cooling systems and methods according to the present disclosure connect the water flow of the two chiller loop systems in a series, counter-flow arrangement. This design, together with optimal flow rate selection and control, significantly improves the system energy efficiency and reduces water flow rate and pipe size.

(6) Some cooling systems use two circuits, each of which has a refrigerant pump loop and a water (or glycol) loop to condense the refrigerant. The water can be chilled (or “trimmed”) by a compressor/chiller loop when the outdoor wet bulb temperature is high. The two circuits have parallel water flow. In normal operation, the two circuits work simultaneously, and the evaporators for air cooling of the two circuits are in series, and air from the high temperature circuit enters the evaporator of the low temperature circuit to be cooled further.

(7) If one of the two circuits fails to operate, the system operates in “failure mode” or “backup mode” with only one circuit in operation. The cooling system of the present disclosure employs two circuits, but the water (or glycol) flows through the two circuits in series and counter flow pattern, resulting in higher energy efficiency, lower water flow rate, and a broader operating range, e.g., it can run with a higher outdoor wet bulb temperature.

(8) FIG. 1 is a schematic flow diagram of a cooling system in accordance with embodiments of the present disclosure. As shown, water (or glycol) from the fluid cooler is pumped first through the ACS evaporator where it is chilled (when ambient or wetbulb temperature is high), and then through main condenser 1 and main condenser 2 of the two pumped refrigerant fluid circuits. From the main condensers, the water (or glycol/water mixture) is mixed with additional water from the outlet of the fluid cooler, and then goes through the trim condenser and finally through the fluid cooler, completing the cycle. Alternatively, the water from the main condenser 2 is mixed with the water leaving the trim condenser at the outlet of the trim condenser and returns to the fluid cooler.

(9) The two main pumped refrigerant fluid circuits are connected to evaporators at or near the heat source (e.g., mounted on the rear doors or tops of computer server cabinets or from the ceiling above the cabinets to cool the electronic equipment). Air and water flow of the two fluid circuits is in a counter flow arrangement: warm air (e.g., 40° C.) from electronic equipment is cooled in the first evaporator to a lower temperature (e.g., 32° C.), and then air leaving fluid circuit 2 enters the evaporator of fluid circuit 1 and is further cooled (e.g., to 25° C.). In other words, chilled water from the ACS evaporator is in thermal communication with the first and second fluid circuits, and the chilled water and the refrigerant flowing through the first and second fluid circuits are in thermal counter flow: the chilled water is first in thermal communication with the refrigerant with lower temperature (corresponding to lower air temperature in the evaporator) in fluid circuit 1 through the main condenser 1, with its temperature raised, and then is in thermal communication with the refrigerant with higher temperature (corresponding to higher air temperature in the evaporator) in fluid circuit 2 through the main condenser 2, with its temperature further raised. In embodiments, the evaporators may include microchannel evaporators.

(10) The refrigerant saturation temperature of fluid circuit 1 is maintained lower than fluid circuit 2 (e.g., 24° C. for fluid circuit 1 versus 31° C. for fluid circuit 2); the water (or glycol) from the fluid cooler or ACS evaporator with lower temperature flows through main condenser 1 to condense refrigerant vapor in fluid circuit 1, with its temperature raised, and then flows through main condenser 2 to condense refrigerant vapor in fluid circuit 2, with its temperature further raised, then flows to the trim condenser. This flow arrangement plus optimal water (or glycol) flow rate control can increase system energy efficiency and significantly reduce water flow rate, pipe size and pumping power.

(11) The two refrigerant fluid circuits 1 and 2 shown in FIG. 1 can also be used with a chiller plant. Chilled water from the chiller plant flows through the main condenser 1 of the fluid circuit 1, and then through the main condenser 2 of the fluid circuit 2, and then returns to the chiller plant with a higher temperature. In other words, the chiller plant may replace the water and chiller loops of FIG. 1. Thus, the output of the chiller plant is provided to the input of the water side of main condenser 1 and the output of the water side of main condenser 2 is provided to the input of the chiller plant. The chiller plant may provide chilled water to multiple refrigerant distribution units including fluid circuits 1 and 2. Compared to conventional CRAC units, this design has a lower water flow rate, and consumes much less pumping and compressor power.

(12) Although the illustrative embodiments of the present disclosure have been described herein with reference to the accompanying drawings, it is to be understood that the disclosure is not limited to those precise embodiments, and that various other changes and modification may be effected therein by one skilled in the art without departing from the scope or spirit of the disclosure.

(13) In embodiments, the water flow through the trim condenser and the water flow through the ACS evaporator, the first main condenser, and the second main condenser, may be in a series or in a parallel arrangement. FIG. 1 shows the in series arrangement. The in parallel arrangement is illustrated in FIG. 2 and may be formed by disconnecting the output of the water side of main condenser 2 from the fluid line or fluid conduit connected between the water pump and the input to the water loop side of the trim condenser, and connecting the output of the water side of main condenser 2 to the fluid line or fluid conduit connected between the output of the water loop side of the trim condenser and the input to the fluid cooler.

(14) Other applications for the cooling system of the present disclosure include turbine inlet air cooling, laboratory system cooling, and electronics cooling, among many others.