1. Relative Humidity (RH)

It is ratio of partial pressure of water vapor to equilibrium vapor pressure water. Simply it is measure of water vapor in air.

$$\begin {aligned}RH=\frac{P_{H_2 O }} {P^*_{H_2O }} \end{aligned}$$

2. Ton of refrigeration

One ton of refrigeration is equivalent to a refrigeration rate of 12660 kJ/hr in SI units.

3. Point Temperature

1. Bubble point Temperature : The bubble-point temperature is the one at which the first bubble of vapour is produced from the liquid on heating at constant pressure.

2. Dew point Temperature : The dew-point temperature is the one at which the first drop of condensate is formed on cooling a vapour at constant pressure.

4. Degree of Saturation ($\mu $)

It is the ratio of the humidity ratio of moist air ($x $) to the humidity ratio of saturated moist air ($x_s$) at the same temperature and pressure.

$$\begin {aligned}\mu = \frac{x}{x_s} \end{aligned}$$

5. Coefficient of Performance (COP)

The efficiency or coefficient of performance (COP) of a refrigerator is defined as the quantity of heat absorbed at the low temperature per unit of work.

$$ \begin {aligned} COP=\frac{Q_2}{W}=\frac{Q_2}{Q_1-Q_2}\end{aligned}$$