Patent CA-1269520-A (CA)
Inventor: MACCRACKEN CALVIN D
IPC: F28F9/013
Filed: 1985-06-28
Granted: 1990-05-29
Abstract: TITLE:  SUPERDENSITY ASSEMBLY METHOD AND         SYSTEM FOR PLASTIC HEAT EXCHANGER RESISTS LARGE BUOYANCY FORCES AND PROVIDES FAST MELT DOWN IN PHASE CHANGE THERMAL STORAGE     ABSTRACT OF THE DISCLOSURE     Superdensity assembly method and system for coiled tubing bundle plastic heat exchangers resists the large buoy-ancy forces occurring due to ice build-up on the multiple tubes and provides fast melt down in phase change thermal storage tanks.  Changes in predetermined horizontal and ver-tical tube spacings (tubing density throughout various tanks) are accomplished easily and reliably for meeting the require-ments of various applications while maintaining excellent overall performance and durability.  Tubing densities through the range from 5% to 32% or even more are readily accomplished in phase change material in tanks for meeting various require-ments of different applications.  The fast melt down capability achieved by the superdensity tube spacing in the upper portion of this range is desirable for meeting severe requirements for sudden surges of cooling over relatively brief spans of time, in a compact, economical tank installation.  The coiled tubing bundle heat exchanger in the tank is assembled from numerous vertical slippery plastic strips, for example, high density polyethylene or ultra high molecular weight polypropylene, 1/8th inch to 1/4th inch thick having keyhole-shaped slots of predetermined uniform spacing extending inwardly from the front edge of each strip.  Each slot terminates in a rounded seat opening spaced inwardly a predetermined distance from the rear edge of the strip.  These rounded seat openings have a diameter slightly smaller than the outside diameter (O.D.) of the indi-vidual tubes which are made of similar slippery plastic and have an O.D. in the range from 9/32nds to one inch.          The tubes are forced into the keyhole slots to become firmly seated and captured in these rounded seat openings for advan-tageously holding the tubes extending horizontally parallel with each other and uniformly spaced apart vertically by the predetermined center-to-center spacing of the rounded seat openings in each strip.  The assembly of parallel tubes is coiled into a tight spiral coil, as seen in plan view, having a vertical axis parallel with the length "L" of the strips so that the successive coil convolutions rest against the rear edges of neighboring strips for being uniformly spaced apart horizontally by the predetermined location of the rounded seat opening with respect to the rear edge of each strip.  The length L of all of the vertical strips equals the internal height of the tank so that the upper ends of all of the strips press up against the underside of the cover for resisting the large buoyancy forces developed by these superdensity heat exchangers during ice build-up on their numerous tubes.  The slippery tube and support strip components avoid undue de-formation during freezing, because the ice does not stick to their surfaces too strongly and they can resiliently deform and act to provide escape routes for melted PCM trapped with-in encircling freezing PCM during freeze up.