Evaporative Cooling Using Hollow Fiber Membranes
Scope
A typical evaporative cooler or "swamp" cooler utilizes wetting pad allowing for direct contact between water and air. The current project seeks to investigate using hollow-fiber membranes as wetting media in evaporative cooling applications. The membrane seperates the air from water and eliminates direct air-water contact and as such offers some unique advantages including sanitary operation and elimination of re-circulation pump.
Experimental Setup
Groups of 96 fibers of 0.53 (21 in.) exposed length were bundled together and epoxied into 5.1-cm.-long (2 in.), 0.635 cm. (0.25 in.) outside diameter, stainless steel tubes on both ends. The potted ends were joined to a water-distribution maifold through holes within a metal frame as shown in figure 1 and 2.
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Figure 1. Photo of module within frame
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Figure 2. Side and front sketch of modules within frame
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A centrifugal fan forced air through a square duct into which fiber modules were placed downstream. Fiber modules were housed within an aluminum frame positioned within the duct to allow cross flow. Distilled water was gravity fed from a vessel resting on a mass balance above the duct. A guillotine
damper allowed for varying the airflow rate.
Figure 3. Experimental Setup
Preliminary Findings
Preliminary results indicate evaporative cooling is possible using hollow-fiber membranes. For the current configuration, effectiveness values of up to ~7% were realized; however, substantially more fibers could be packed per unit volume in order to increase effectiveness.
Current Status
Presently, work is being done to publish preliminary findings.
Work Yet to be Done
Future investigations will involve the use of hollow-fiber membrane sheets, not bundled modules, to ensure more regular fiber spacing and maximum surface area density. A variety of flow types will be investigated with the membrane sheets. In addition, the number of sheets will be varied in order to determine the optimum configuration for evaporative cooling.
