A comprehensive online glossary of terms and definitions related to built environment, heating, ventilating, and air conditioning (HVAC), as well as refrigeration, building envelope, electrical, lighting, water and energy use, solar power, concentrating solar power (CSP), and measurement terms.
HVAC and Solar energy engineering Terminology
There are currently 13 terms in this directory beginning with the letter J.
jacket
(1) integral covering, sometimes fabric reinforced, that is applied over insulation. Also, the core, shield, or armor of a cable to provide mechanical or environmental protection. (2) sealed space around a piece of equipment or a storage unit, through which a thermal medium can be circulated.
jet cooling
quick chilling process using air at very high speed forced around the products, usually while those products are continuously moving on a conveyor belt. Compare to [[air-blast cooling]].
jet freezing
quick freezing process using cold air at very high speed forced onto the produce. Also called blast freezing.
Josephson effect
set of quantum mechanical phenomena occurring when a current flows through an (electrically) weak link or junction connecting two superconductors (e.g., by tunneling through a dielectric barrier or by flowing through a sufficiently narrow constriction in a superconducting material).
joule
A metric unit of energy or work; 1 joule per second equals 1 watt or 0.737 foot-pounds; 1 Btu equals 1,055 joules.
Joule-Thomson effect
ratio of temperature change to pressure change (dT/dp) of an actual gas in a process of throttling or expansion without doing work or interchanging heat.
junction
A region of transition between semiconductor layers, such as a p/n junction, which goes from a region that has a high concentration of acceptors (p-type) to one that has a high concentration of donors (n-type).
junction box
A photovoltaic (PV) generator junction box is an enclosure on the module where PV strings are electrically connected and where protection devices can be located, if necessary.
