Dehumidifying and re-humidifying air cooling for an electronics rack

1. An apparatus for facilitating cooling of an electronics rack, the apparatus comprising:

a dehumidifying air-to-liquid heat exchanger configured to reside at an air inlet side of the electronics rack, wherein the electronics rack comprises the air inlet side and an air outlet side, the air inlet side and the air outlet side respectively enabling ingress and egress of air through the electronics rack, and wherein the dehumidifying air-to-liquid heat exchanger is positioned for ingressing air to pass thereacross before passing through the electronics rack, the dehumidifying air-to-liquid heat exchanger being in fluid communication with a coolant loop for passing chilled coolant therethrough, and the dehumidifying air-to-liquid heat exchanger with chilled coolant passing therethrough dehumidifying ingressing air to the electronics rack to lower a dew point temperature of air flowing through the electronics rack;

a condensate collector disposed at the air inlet side of the electronics rack for collecting liquid condensate from the dehumidifying air-to-liquid heat exchanger's dehumidifying of ingressing air to the electronics rack; and

a condensate evaporation system disposed at the air outlet side of the electronics rack and humidifying air egressing from the electronics rack, the condensate evaporation system being coupled in fluid communication with the condensate collector at the air inlet side of the electronics rack and evaporating liquid condensate received therefrom, the condensate evaporation system comprising a re-humidifying air-to-liquid heat exchanger configured to reside at the air outlet side of the electronics rack so that air egressing from the air outlet side of the electronics rack passes across the re-humidifying air-to-liquid heat exchanger, and a condensate delivery mechanism delivering liquid condensate from the condensate collector disposed at the air inlet side of the electronics rack to the re-humidifying air-to-liquid heat exchanger disposed at the air outlet side of the electronics rack, the re-humidifying air-to-liquid heat exchanger re-humidifying and cooling air egressing from the air outlet side of the electronics rack.

2. The apparatus of claim 1 , further comprising a pumped-feed line coupling the condensate collector and the condensate evaporation system in fluid communication, and transferring liquid condensate from the condensate collector at the air inlet side of the electronics rack to the condensate evaporation system at the air outlet side of the electronics rack.

3. The apparatus of claim 1 , further comprising a modular refrigeration unit disposed within the electronics rack and at least one refrigerant evaporator coupled in fluid communication therewith via a refrigerant loop for passing refrigerant through the at least one refrigerant evaporator for cooling at least one electronic component within the electronics rack coupled thereto, the at least one refrigerant evaporator, the at least one electronic component coupled thereto, or the refrigerant loop comprising a surface cooled to a temperature below a dew point temperature of the ingressing air prior to dehumidifying thereof by the dehumidifying air-to-liquid heat exchanger.

4. The apparatus of claim 3 , further comprising a liquid-to-liquid heat exchanger coupled to the coolant loop and to the refrigerant loop for facilitating cooling of coolant flowing through the coolant loop via refrigerant flowing through the refrigerant loop, and a pump in fluid communication with the coolant loop for pumping coolant through the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger.

5. The apparatus of claim 4 , further comprising a controller coupled to the pump, the controller controlling coolant flow rate through the coolant loop as a function of a determined dew point temperature of air exiting the dehumidifying air-to-liquid heat exchanger and a determined coolest surface temperature of at least one surface of (or coupled to) the at least one refrigerant evaporator, the at least one electronic component coupled thereto, or the refrigerant loop, and the controller at least one of determines whether a difference in temperature between the determined coolest surface temperature and the determined dew point temperature of air exiting the dehumidifying air-to-liquid heat exchanger is less than a first predetermined threshold, and if so, the controller automatically increases pump speed to increase the flow of coolant through the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger, or determines whether the difference between the coolest surface temperature and the determined dew point temperature of air exiting the dehumidifying air-to-liquid heat exchanger is greater than a second predefined threshold, and if so, the controller automatically reduces pump speed to reduce the flow of coolant through the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger.

6. The apparatus of claim 3 , wherein the coolant loop is coupled in fluid communication with the refrigerant loop and the coolant flowing through the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger is the refrigerant.

7. The apparatus of claim 3 , wherein the coolant loop is coupled to a coolant distribution unit external to the electronics rack, the coolant loop providing chilled coolant to the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger and expelling heat from the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger to a facility coolant loop passing through the coolant distribution unit, and wherein the apparatus further comprises a controller for controlling an amount of dehumidifying of ingressing air to the electronics rack to control the dew point temperature of the air flowing through the electronics rack.

8. The apparatus of claim 1 , further comprising a modular cooling unit associated with the electronics rack for facilitating liquid cooling of at least one electronic component of the electronics rack, the modular cooling unit receiving facility coolant from a source via a facility coolant loop and expelling heat in a liquid-to-liquid heat exchanger from the at least one electronic component to the facility coolant in the facility coolant loop, wherein the coolant loop is coupled to the liquid-to-liquid heat exchanger for cooling coolant passing therethrough, the coolant loop passing the chilled coolant in parallel to at least one cold plate coupled to the at least one electronic component to be cooled by the modular cooling unit, the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger.

9. The apparatus of claim 1 , wherein the condensate delivery mechanism sprays liquid condensate from the condensate collector onto the re-humidifying air-to-liquid heat exchanger for re-humidifying air passing across the re-humidifying air-to-liquid heat exchanger.

10. The apparatus of claim 1 , wherein the condensate delivery mechanism provides a gravity drip of liquid condensate from the condensate collector onto the re-humidifying air-to-liquid heat exchanger for re-humidifying air passing across the re-humidifying air-to-liquid heat exchanger.

11. A cooled electronic system comprising:

an electronics rack, the electronics rack comprising:

an air inlet side and an air outlet side, the air inlet and air outlet sides respectively enabling ingress and egress of air;

at least one electronic component requiring cooling;

at least one air-moving device, the at least one air-moving device causing air to flow from the air inlet side of the electronics rack through the electronics rack, to the air outlet side thereof; and

a dehumidifying and re-humidifying cooling apparatus for the electronics rack, the dehumidifying and re-humidifying cooling apparatus comprising:

a dehumidifying air-to-liquid heat exchanger disposed at the air inlet side of the electronics rack, the dehumidifying air-to-liquid heat exchanger being positioned for ingressing air to pass thereacross before passing through the electronics rack, and being in fluid communication with a coolant loop for passing chilled coolant therethrough, and wherein the dehumidifying air-to-liquid heat exchanger with chilled coolant passing therethrough dehumidifies ingressing air to the electronics rack to lower a dew point temperature of air flowing through the electronics rack;

a condensate collector disposed at the air inlet side of the electronics rack and collecting liquid condensate from the dehumidifying air-to-liquid heat exchanger's dehumidifying of ingressing air to the electronics rack; and

a condensate evaporation system disposed at the air outlet side of the electronics rack and humidifying air egressing from the electronics rack, the condensate evaporation system being coupled in fluid communication with the condensate collector at the air inlet side of the electronics rack and evaporating liquid condensate received therefrom, the condensate evaporation system comprising a re-humidifying air-to-liquid heat exchanger disposed at the air outlet side of the electronics rack so that air egressing from the air outlet side of the electronics rack passes across the re-humidifying air-to-liquid heat exchanger, and a condensate delivery mechanism delivering liquid condensate from the condensate collector disposed at the air inlet side of the electronics rack to the re-humidifying air-to-liquid heat exchanger disposed at the air outlet side of the electronics rack, the re-humidifying air-to-liquid heat exchanger re-humidifying and cooling air egressing from the air outlet side of the electronics rack.

12. The cooled electronic system of claim 11 , wherein the dehumidifying and re-humidifying cooling apparatus further comprises a pumped-feed line coupling the condensate collector and the condensate evaporation system in fluid communication, and transferring liquid condensate from the condensate collector at the air inlet side of the electronics rack to the condensate evaporation system at the air outlet side of the electronics rack.

13. The cooled electronic system of claim 11 , wherein the condensate delivery mechanism sprays liquid condensate from the condensate collector onto the re-humidifying air-to-liquid heat exchanger for re-humidifying air passing across the re-humidifying air-to-liquid heat exchanger.

14. The cooled electronic system of claim 11 , wherein the condensate delivery mechanism provides a gravity drip of liquid condensate from the condensate collector onto the re-humidifying air-to-liquid heat exchanger for re-humidifying air passing across the re-humidifying air-to-liquid heat exchanger.

15. The cooled electronic system of claim 11 , further comprising a modular refrigeration unit disposed within the electronics rack and at least one refrigerant evaporator coupled in fluid communication therewith via a refrigerant loop for passing refrigerant through the at least one refrigerant evaporator for cooling at least one electronic component within the electronics rack coupled thereto, the refrigerant evaporator, the at least one electronic component coupled thereto or the refrigerant loop comprising a surface cooled to a temperature below a dew point temperature of the ingressing air prior to dehumidifying thereof by the dehumidifying air-to-liquid heat exchanger, wherein the dehumidifying avoids formation of condensation on the surface cooled below dew point of the ingressing air prior to dehumidifying thereof.

16. The cooled electronic system of claim 15 , further comprising a liquid-to-liquid heat exchanger coupled to the coolant loop and to the refrigerant loop for facilitating cooling of coolant flowing through the coolant loop via refrigerant flowing through the refrigerant loop, and a pump in fluid communication with the coolant loop for pumping coolant through the air-to-liquid heat exchanger.

17. The cooled electronic system of claim 11 , wherein the coolant loop of the dehumidifying and re-humidifying cooling apparatus is coupled in fluid communication with the refrigerant loop and the coolant flowing through the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger is the refrigerant.

18. The cooled electronic system of claim 11 , wherein the coolant loop of the dehumidifying and re-humidifying cooling apparatus is coupled to a coolant distribution unit external to the electronics rack, the coolant loop providing chilled coolant to the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger and expelling heat from the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger to a facility coolant loop passing through the coolant distribution unit, and wherein the dehumidifying and re-humidifying cooling apparatus further comprises a controller for controlling an amount of dehumidifying of ingressing air to the electronics rack to control the dew point temperature of the air flowing through the electronics rack.

19. The cooled electronic system of claim 11 , further comprising a modular cooling unit associated with the electronics rack for facilitating liquid cooling of at least one electronic component of the electronics rack, the modular cooling unit receiving facility coolant from a source via a facility coolant loop and expelling heat in a liquid-to-liquid heat exchanger from the at least one electronic component to the facility coolant in the facility coolant loop, wherein the coolant loop is coupled to the liquid-to-liquid heat exchanger for cooling coolant passing therethrough, the coolant loop passing the chilled coolant in parallel to at least one cold plate coupled to the at least one electronic component to be cooled by the modular cooling unit, the dehumidifying air-to-liquid heat exchanger and the re-humidifying air-to-liquid heat exchanger.

20. A method of facilitating cooling of an electronics rack, the method comprising:

disposing a dehumidifying air-to-liquid heat exchanger at an air inlet side of the electronics rack, wherein the electronics rack comprises the air inlet side and an air outlet side, the air inlet side and air outlet side respectively enabling ingress and egress of air through the electronics rack, and the dehumidifying air-to-liquid heat exchanger is positioned for ingressing air to pass thereacross before passing through the electronics rack, the dehumidifying air-to-liquid heat exchanger being in fluid communication with a coolant loop for passing chilled coolant therethrough, and the dehumidifying air-to-liquid heat exchanger with chilled coolant passing therethrough dehumidifying ingressing air to the electronics rack to lower a dew point temperature of air flowing through the electronics rack;

disposing a re-humidifying air-to-liquid heat exchanger at the air outlet side of the electronics rack so that air egressing from the air outlet side of the electronics rack passes across the re-humidifying air-to-liquid heat exchanger;

collecting liquid condensate from the dehumidifying air-to-liquid heat exchanger's dehumidifying of ingressing air to the electronics rack;

delivering the liquid condensate from the air inlet side of the electronics rack to the re-humidifying air-to-liquid heat exchanger at the air outlet side thereof; and

evaporating at the air outlet side of the electronics rack, the liquid condensate delivered to the re-humidifying air-to-liquid heat exchanger to humidify air egressing from the electronics rack.

21. The method of claim 20 , further comprising determining the dew point temperature of ingressing air to the electronics rack after dehumidifying thereof by the dehumidifying air-to-liquid heat exchanger and automatically adjusting an amount of dehumidifying by the dehumidifying air-to-liquid heat exchanger if a difference between a coolest measured surface temperature within the electronics rack and the determined dew point temperature of the dehumidified ingressing air is less than a first predetermined threshold or greater than a second predetermined threshold, wherein the automatically adjusting dehumidifying comprises automatically adjusting a coolant flow rate through the dehumidifying air-to-liquid heat exchanger.

22. The method of claim 20 , wherein the delivering comprises spraying the liquid condensate collected from the dehumidifying air-to-liquid heat exchanger's dehumidifying of ingressing air to the electronics rack onto the re-humidifying air-to-liquid heat exchanger at the air outlet side of the electronics rack to re-humidify air passing across the re-humidifying air-to-liquid heat exchanger.

23. The method of claim 20 , wherein the delivering comprises gravity-dripping liquid condensate collected from the dehumidifying air-to-liquid heat exchanger's dehumidifying of ingressing air to the electronics rack onto the re-humidifying air-to-liquid heat exchanger at the air outlet side of the electronics rack to re-humidify air passing across the re-humidifying air-to-liquid heat exchanger.