LiBr

Lithium Bromide is a salt that is chemically stable, non-flammable, non-toxic, ecologically benign and ozone-friendly. Together with water (H₂O), it is the working fluid in YAZAKI absorption chiller machines.

Quasi-vacuum

Approximately 8 mbar in Absorber/Evaporator, approx. 88 mbar in Generator/Condenser. This pressure is important to maintain the evaporative condition for the refrigerant.

COP

Coefficient of Performance is the ratio of the usable (cooling) energy divided by the correspondent input energy, e.g. COPPE (usable cooling energy divided by Primary Energy input) or COPEL (usable cooling energy divided by Electric Energy input).

A typical COP for WFC series is 0.7. The COP for gas fires CH-K series range well above 1.0.

RT

Refrigeration Ton, 1 RT = 12.000 Btu/h = 3,516 kW
A Refrigeration Ton represents the heating energy absorbed when a ton of ice melts over 24 hours. The ice assumed to be solid at 0°C initially will become water at 0°C. The energy absorbed by the ice is the latent heat of ice multiplied by the total weight. A cooling machine with 1 RT is said to have an equal capacity to freeze one ton of 0°C water in 24 hours. Refrigeration Ton is a rate of removing heat, rather than a quantity of heat. This rate can be converted to Btu (British Thermal Unit) per hour or to Watt (W).

Example:
1 ton (US) = 2.000 pound, and latent heat of melting ice = 144 Btu/pound
1 RT = 2.000 pound x (144 Btu/pound) / (24 h) = 12.000 Btu/h; 1 Btu/h = 0,293 W
1 RT = 12.000 x 0,293 W = 3516 W = 3.516 kW

Latent Heat

The heat absorbed while a substance changes state from liquid to solid. The amount of latent heat is equal to the cooling energy that is needed by a substance to freeze. This substance has the same temperature before and after the state-changing process (e.g. 0°C with water).

Refrigerant

A refrigerant is a compound used in a heat cycle that undergoes a change of state from a gas to a liquid and back. Water (H₂O) is the refrigerant used in YAZAKI absorption machines.

Sorbent

A material that has the capacity to absorb another substance. In YAZAKI absorption machines the sorbent is LiBr.

Solution

A diluted or concentrated mixture of LiBr-salt and water.

Evaporation

Is the process in which the refrigerant changes state from a liquid to a gas.

Condensation

Is the process in which the refrigerant changes state from a gas to a liquid.

Single effect

The driving energy (e.g. hot water) is able to separate refrigerants from LiBr-solutions. This happens in the generator of an absorption cooling machine. WFC series feature only one heat exchanger, since driving temperatures are relatively low (70 - 95°C).

Double effect

The driving energy (e.g. gas burned in a burner) is able to separate refrigerant from a LiBr solution. This happens in the generator of an absorption cooling machine. As for the gas-fired absorption machine from YAZAKI, the driving temperatures are high enough to put two generator heat exchangers in a row. Thus the LiBr-solution gets condensed to a semi-concentrated solution in the High-Temperature-Generator during the first step. In the second step, this semi-concentrated solution is again heated in a Low-Temperature-Generator to become a concentrated solution. Because the driving energy of the gas is twice used to generate refrigerant, the COP of these machines is higher than in WFC series.