The main attraction of sculptor Nancy Holt’s eagerly awaited exhibition is a functioning hot water system called “Flow Ace Heating.” Improbable as that may sound, the piece is uncommonly interesting, both visually and conceptually. In the way of all art, it extracts the essence of a form and presents it anew for fresh consideration; in the way of contemporary conceptual and environmental sculpture, it mines the territory of the real world and runs it through an aesthetic sensibility.

“Flow Ace Heating” begins with a pipe that cuts through a gallery wall near the ceiling and grows into a complex configuration of linear form, punctuated by radiators, valve wheels, gauges and other instruments. The pipes (all warm to the touch) wrap around walls of two rooms and extend into their centers where they blossom into large rectangles and loops. Seen through two doorways, from the plumbing’s inception, the pipes appear as an elegant abstraction. Observation from the inside, during a room-by-room inspection, renews Modernism’s appreciation for the forms of technology. The appeal of Holt’s work is partly the stunning fact of its being presented as art in a gallery, but it settles into memory as a trenchant testament to the marriage of aesthetics and science.

The remainder of the exhibition consists of table-top models, color photographs and drawings of Holt’s outdoor projects done during the last five years. To her credit, this dreaded “documentation” (a term we’ve come to associate with deadly dull recapitulations) conveys the life and presence of such massive installations as a “Waterwork” plumbing and draining system at Gallaudet College in Washington and “Rock Rings,” a circular, open-topped architectural structure at Western Washington University.

Some of Holt’s most intriguing projects incorporate celestial events and perceptual phenomena with earth-bound sculptures. People who climb a grassy mound and peer through a cylindrical tunnel inserted through it see an oval pool that appears to be circular, in an Ohio installation called “Star-Crossed.” Shadows cast by concrete spheres and poles in “Dark Star Park,” line up precisely at 9:23 a.m. on Aug. 1, in memory of the day when the site of the piece was acquired in Arlington, Va. (Flow Ace Gallery, 8373 Melrose Ave., to Feb. 9.)