Sub-wet bulb evaporative water chiller with gradient chilling and air-to-air heat exchange

Abstract

An evaporative chiller cooling water to below ambient wet bulb temperature. Sub-wet bulb chilling is achieved by pre-cooling incoming air upstream of the saturator. The incoming air is ambient air at ambient air temperature that is cooled using the coolness of the lower temperature outgoing air exiting the saturator. The pre-cooling lowers the temperature of the incoming air and lowers its wet bulb temperature below that of ambient air. The saturator water is chilled to below the ambient wet bulb temperature. The air in the saturator flows across the water as it gravity drips or flows from the top to the bottom of the saturator. The pre-cooled air flows across the saturator with the coolest air directed across the bottom of the saturator where the coldest water is flowing and with the hottest air directed across the top where the hottest water is flowing to provide gradient chilling.

1 . An evaporative water chiller, comprising:
 a saturator with a liquid inlet and a liquid outlet, wherein water to be cooled enters the saturator through the liquid inlet and drains by gravity through the saturator and exits through the liquid outlet; and   an air delivery assembly delivering a volume of air to the saturator at temperatures below a temperature of ambient air entering the chiller,   wherein the air delivered to the saturator has a first temperature near the liquid inlet of the saturator and a second temperature near the liquid outlet of the saturator that is lower than the first temperature,   wherein the air delivery assembly comprises an air-to-air heat exchanger including plates defining a plurality of incoming passageways for the air delivered to the saturator and a plurality of outgoing passageways interposed between adjacent pairs of the incoming passageways for the delivered air to exit the chiller after passing through the saturator, and   wherein the air-to-air heat exchanger defines the incoming and outgoing passageways to maintain a vertical chilling gradient in the air delivered to the saturator and the air exiting the chiller after passing through the saturator.   
     
     
         2 . The chiller of  claim 1 , wherein the air delivered to the saturator is directed to flow through the saturator transverse to a direction of flow of the liquid in the saturator. 
     
     
         3 . The chiller of  claim 1 , wherein the plates are positioned to extend parallel and vertically within the chiller. 
     
     
         4 . The chiller of  claim 3 , wherein the heat exchanger further comprises spacers defining at least two separate flow levels in which the air delivered to the saturator is forced to flow in horizontal channels without mixing with air in other ones of the horizontal channels or with the air exiting the chiller. 
     
     
         5 . The chiller of  claim 1 , wherein the plates are positioned to extend horizontally and in a parallel manner within the chiller. 
     
     
         6 . The chiller of  claim 5 , wherein side-by-side pairs of the plates have a W-shaped cross sectional shape or an S-shaped cross sectional shape to enhance heat transfer. 
     
     
         7 . The chiller of  claim 1 , wherein the air-to-air heat exchanger defines the incoming and outgoing passageways such that the air delivered to the saturator flows in a first direction and the air exiting the chiller after passing through the saturator flows in a second direction counter to the first direction. 
     
     
         8 . The chiller of  claim 1 , wherein the plates are formed of plastic sheets. 
     
     
         9 . An evaporative chiller for cooling water to a temperature below the ambient air wet-bulb temperature, comprising:
 a saturator in which water is able to flow from a top portion to a bottom portion, the saturator extending vertically within the chiller with a first side and a second side both permeable to air flow;   a fan for drawing ambient air into the chiller as incoming air to flow through the first and second sides of the saturator; and   a heat exchanger at least partially positioned upstream of the first side of the saturator for first cooling the incoming air to a range of temperatures below ambient temperature and for second directing the cooled incoming air into the saturator along the first side with portions at a higher end of the range of temperature provided near the top portion and portions at a lower end of the range of temperature provided near the bottom portion of the saturator.   
     
     
         10 . The chiller of  claim 9 , wherein the heat exchanger comprises a plurality of spaced apart sheets defining flow passageways for the incoming air and flow passageways for outgoing air exiting the saturator with each of the incoming air flow passageways being adjacent at least one of the outgoing air flow passageways. 
     
     
         11 . The chiller of  claim 10 , wherein the spaced apart sheets are arranged to control air mixing to at least partially maintain temperature stratification within the incoming air and within the outgoing air. 
     
     
         12 . The chiller of  claim 10 , wherein the heat exchanger controls air flow to provide counter flow between the incoming air and the outgoing air. 
     
     
         13 . The chiller of  claim 10 , wherein the spaced apart sheets are parallel and extend horizontally within the heat exchanger. 
     
     
         14 . The chiller of  claim 13 , wherein the incoming air flows in a cross flow pattern through the saturator and then reverses direction and flows through the heat exchanger as the output air. 
     
     
         15 . The chiller of  claim 10 , wherein the spaced apart sheets are parallel and extend vertically within the heat exchanger. 
     
     
         16 . The chiller of  claim 9 , wherein the water flowing near the bottom portion is at a temperature below the wet-bulb temperature of the ambient air. 
     
     
         17 . An evaporative cooling system, comprising:
 a chiller comprising a saturator and an air-to-air heat exchanger generating a stream of pre-cooled air at an air inlet to the saturator by cooling ambient air to temperatures below ambient air temperature by transferring heat from the ambient air to air exiting the saturator through an air outlet, wherein the pre-cooled air temperatures range from a higher temperature proximate to a top of the saturator and a lower temperature proximate to a bottom of the saturator;   a space cooling system including a heat exchanger with a liquid side; and   a water circulation system pumping water exiting the bottom of the saturator through the liquid side of the space cooling system heat exchanger.   
     
     
         18 . The system of  claim 17 , wherein the heat exchanger comprises a plurality of sheets defining flow channels for the pre-cooled air and for the air exiting the saturator such that no mixing of the pre-cooled air and the air exiting the saturator occurs and such that the pre-cooled air is input into the saturator to flow transversely across water flowing downward through the saturator. 
     
     
         19 . The system of  claim 18 , wherein the sheets are arranged to extend horizontally within the heat exchanger and are substantially planar or have a W-shaped or S-shaped cross sectional shape and wherein the water exiting the bottom of the saturator is at a temperature at least about 5° F. lower than a wet-bulb temperature of the ambient air. 
     
     
         20 . The system of  claim 17 , wherein the air-to-air heat exchanger is configured for counter current flow between incoming flow of the ambient air and flow of the air exiting the air outlet of the saturator.