Variable refrigerant flow (VRF), also known as variable refrigerant volume (VRV), is an HVAC technology invented by Daikin Industries, Ltd. in 1982. Similar...

also invented by Daikin in 1982. Both were first sold in Japan. Variable refrigerant flow systems when compared with central plant cooling from an air handler...

A refrigerant is a working fluid used in the cooling, heating, or reverse cooling/heating cycles of air conditioning systems and heat pumps, where they...

a variable displacement compressor, its displacement; additionally, a secondary valve located on the suction side can throttle the refrigerant flow so...

controls the amount of refrigerant released into the evaporator and is intended to regulate the superheat of the refrigerant that flows out of the evaporator...

be used to control the speed of the compressor motor to drive variable refrigerant flow in a refrigeration or air conditioning system to regulate system...

surface gradients are small. Darcy's law is used for flow in porous media, and works with variables averaged over several pore-widths. In rotating systems...

by evaporation of the refrigerant, and released at the other side, by condensation of the refrigerant. Condensed refrigerant flows by gravity to the first...

helps to secure the process while providing greater efficiency. Variable refrigerant flow (VRF) VRF units are very popular cooling or reversible systems...

or refrigerant metering device (RMD) restricts the flow of the liquid refrigerant causing a pressure drop that vaporizes some of the refrigerant; this...

over-cooling. The air blower's flow rate is variable. For a single VAV air handler that serves multiple thermal zones, the flow rate to each zone must be varied...

(also called metering device) regulates the refrigerant liquid to flow at the proper rate. The liquid refrigerant is returned to another heat exchanger where...

panels A parallel all air variable-air-volume (VAV) systems Packaged unitary water source heat pumps Variable Refrigerant Flow (VRF) systems Fan coil units...

A gaseous refrigerant is compressed so its pressure and temperature rise. When operating as a heater in cold weather, the warmed gas flows to a heat exchanger...

A damper is a valve or plate that stops or regulates the flow of air inside a duct, chimney, VAV box, air handler, or other air-handling equipment. A damper...

This type of compressor can compress a wide range of gases, including refrigerant, hydrogen, and natural gas. Because of this, it finds use in a wide range...

humidity control; a ground-source heat pump system (GSHP); and variable refrigerant flow systems with heat recovery. The building also serves as a live...

the refrigerant enters the compressor as a low pressure and low temperature vapor. In heat pumps, this refrigerant is typically R32 refrigerant or R290...

narrow tube; the bubbles of refrigerant gas push the refrigerant-depleted liquid into a higher chamber, from which it will flow by gravity to the absorption...

Refrigerant reclamation is the act of processing used refrigerant gas which has previously been used in some type of refrigeration loop to meet the specifications...

use only a single fluid which is a refrigerant. In contrast, absorption heat pump requires two fluids, a refrigerant and an absorbent able to absorb it...

water and refrigerant are most common. Chilled water is supplied from a chiller that is potentially located very far away, but refrigerant must come from...

automatic. Zone dampers provide automatic control in simple systems while variable air volume (VAV) allows control in sophisticated systems. Smoke dampers...

moving parts made it more reliable; the introduction of Freon to replace refrigerant gases toxic to humans made it even less attractive commercially. The...

refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and...

nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol propellants. They include chlorofluorocarbons and hydrofluorocarbons...

space conditioning unit from the conditioned space. A refrigerant valve that reverses refrigerant flow to determine whether system is heating or cooling On...

It can also allow for cooling at higher humidity without the use of refrigerants, many of which have substantial greenhouse gas potential. Due to good...

revolving vane, or vanes used for producing currents of air. Fans produce air flows with high volume and low pressure (although higher than ambient pressure)...

variables including the working fluid, the secondary fluid, the geometry, and the material. Common secondary fluids include water, air, refrigerants,...