Refrigeration Basics 1
1. Temperature: Temperature is a measure of how hot or cold a substance is.
There are three commonly used temperature units (temperature scales): Celsius, Fahrenheit, and absolute temperature.
Celsius temperature (t, ℃): the temperature we often use. Temperature measured with a Celsius thermometer.
Fahrenheit (F, ℉): The temperature commonly used in European and American countries.
temperature conversion:
F (°F) = 9/5 * t(°C) +32 (Find the temperature in Fahrenheit from the known temperature in Celsius)
t (°C) = [F (°F)-32] * 5/9 (Find the temperature in Celsius from the known temperature in Fahrenheit)
Absolute temperature scale (T, ºK): generally used in theoretical calculations.
Absolute temperature scale and Celsius temperature conversion:
T (ºK) = t (°C) +273 (Find the absolute temperature from the known temperature in Celsius)
2. Pressure (P): In refrigeration, the pressure is the vertical force on the unit area, that is, the pressure, which is usually measured with a pressure gauge and a pressure gauge.
Common units of pressure are:
Mpa (megapascal);
Kpa (kPa);
bar(bar);
kgf/cm2 (square centimeter kilogram force);
atm (standard atmospheric pressure);
mmHg (millimeters of mercury).
Conversion relationship:
1Mpa=10bar=1000Kpa =7500.6 mmHg = 10.197 kgf/cm2
1atm=760mmHg=1.01326bar =0.101326Mpa
Generally used in engineering:
1bar = 0.1Mpa ≈1 kgf/cm2 ≈ 1atm = 760 mmHg
Several pressure representations:
Absolute pressure (Pj): In a container, the pressure exerted on the inner wall of the container by the thermal motion of the molecules. The pressure in the refrigerant thermodynamic properties table is generally absolute pressure.
Gauge pressure (Pb): The pressure measured with a pressure gauge in a refrigeration system. Gauge pressure is the difference between the gas pressure in the container and the atmospheric pressure. It is generally believed that the gauge pressure plus 1bar, or 0.1Mpa, is the absolute pressure.
Vacuum degree (H): When the gauge pressure is negative, take its absolute value and express it in vacuum degree.
See you at Refrigeration Basics 2.
