Glossary H
Heat pump (as used in geothermal industry) in which the refrigerant exchanges heat in a heat exchanger with a fluid circulating through an earth connection medium - ground or ground water. The fluid is contained in a variety of loop/pipes configurations depending on the temperature of the ground and the ground area available. Loops may be installed horizontally or vertically in the ground or submersed in a body of water.
Horizontal classification means a grouping of species from a similar time interval of evolution rather than those sharing a common lineage (horizontal with respect to a phylogenetic tree). Compare --->'vertical classification'.
A Handheld vacuum is a machine which is portable and sometimes cordless which make them ideal for cleaning small areas like the car. In addition to upright vacuums, it is good to use handheld vacuums because they can clean areas which an upright can not clean because they are too large.