# The Common knowledge of refrigeration basics and refrigeration cycle

## The common refrigeration basics

1）Refrigeration: It is the process of removing heat from a low-temperature reservoir and transferring it to a high-temperature reservoir.

2) Type of refrigeration: divided into thermoelectric refrigeration, semiconductor refrigeration, magnetic refrigeration, nuclear refrigeration, etc. We usually use liquid gasification refrigeration.

3) Major terms: temperature, heat, specific heat, sensible heat, latent heat, pressure, evaporation, boiling, thermal conductivity, convective heat transfer coefficient, heat transfer coefficient, heat emission coefficient, density, humidity, enthalpy, entropy, and diagram of pressure enthalpy.

4) Temperature: It is divided into centigrade temperature ℃, Fahrenheit temperature ℉, thermodynamic temperature K. The thermodynamic temperature is the absolute measure of temperature and it selects the triple point of water at 273.16K as the fundamental fixing.

5) Heat: the unit is cal (also said calorie) and J(Joule). 1cal=4.1868J

6) Specific heat: it is the heat of unit material absorbed and release while temperature up or down to one degree C. This is the fixed nature of the material.

7) Sensible heat: Both heat and temperature are changed. The state of matter does not change. Whatever it is solid-state, liquid state, gas state, just temperature change.

8) Latent heat: Heat and the state of matter are changed. But, its temperature does not change.

9) Pressure: the unit of pressure has atm, mmHg, Pa, KPa, Mpa, bar, kgf/cm2, psi and etc.

1 atm=760 mmHg=1.01325×10^5Pa=100KPa=0.1 Mpa=1bar=1 kgf/cm2=14.7 psi.

10) Gauge pressure and absolute pressure: Gauge pressure is the visible pressure on a pressure gauge. Absolute pressure is the pressure calculated from absolute zero pressure.

Absolute pressure MPa（A）=Gauge pressure MPa（G）+0.1MPa

11) Evaporation: Evaporation is the phenomenon of vaporization occurring on the surface of the liquid. It occurs anytime and anywhere. As long as it absorbs heat, it will evaporate.

## The Refrigeration Cycle

### Refrigeration system fundamental components:

1. The compressor
2. The condenser
3. The metering device
4. The evaporator