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 15 terms in this directory beginning with the letter K.

**k-factor (thermal conductivity)**

time rate of steady-state heat flow through a unit area of a homogeneous material, induced by a unit temperature gradient in a direction perpendicular to that unit area. Units are Btu in./h·ft2·°F or Btu/h·ft·°F [W/(m·K)].

**kata thermometer**

alcohol thermometer used to measure low velocities in air circulation by heating the large bulb of the thermometer above 100°F (38°C) and noting the time it takes to cool from 100°F to 95°F (38°C to 35°C) or some other interval above ambient temperature with the time interval being a measure of the air current at that location.

**katharometer (katherometer)**

instrument for measuring the CO2 concentration in a cold storage atmosphere working on the principle that CO2 has a thermal conductivity different from other gases. Concentrations of other gases can also be measured using this principle.

**Kelvin temperature**

SI absolute temperature scale on which the triple point of water is 273.16 K and the boiling point is approximately 373.15 K (1 K = 1°C). The Kelvin is the fraction 1/273.16 of the temperature of the thermodynamic triple point of water. See [[triple point]].

**Kepler’s laws**

three laws describing the motions of planets in their orbits: (1) the orbits of planets are ellipses with the sun at the common focus; (2) the line joining a planet and the sun sweeps over equal areas during equal intervals of time; (3) the squares of the periods of revolution of any two planets are proportional to the cubes of their mean distances from the sun.

**kerf**

The width of a cut used to create wafers from silicon ingots, often resulting in the loss of semiconductor material.

**kilovolt ampere (kVA)**

the product of the line current (amperes) times the nominal system voltage (kilovolts) times 1.732 for three-phase currents. For single-phase applications, kVa is the product of the line current (amperes) times the nominal system voltage (kilovolts).

**kilowatt (kW)**

A standard unit of electrical power equal to 1000 watts, or to the energy consumption at a rate of 1000 joules per second.

**kilowatt-hour (kWh)**

1,000 thousand watts acting over a period of 1 hour. The kWh is a unit of energy. 1 kWh=3600 kJ.

**kinematic viscosity**

ratio of absolute viscosity to density of a fluid. A measure of a fluid’s resistance to flow in units of centistokes.

**king valve (master valve)**

(1) stop valve between receiver and liquid main in a refrigeration system. (2) stop valve on boiler head.

**Kirchoff’s law**

ratio of the emissivity of a heat radiator to the absorptivity of the same radiator is the same for all bodies, depending on frequency and temperature alone, and is equal to the emissivity of a blackbody.

**Kohlrausch’s law**

when ionization is complete, the conductivity of an electrolyte is equal to the sum of the conductivities of the ions into which the substance dissociates.