In the field of refrigeration technology, we deal with physical quantities such as temperature, pressure, flow rate, power and cooling capacity every day. Whether it is equipment nameplates, calculating system performance, conducting fault diagnosis or communicating with international counterparts, accurately understanding and proficiently applying various units and their conversion relationships are essential basic skills for every refrigeration technician.
Temperature
Temperature is one of the most crucial parameters in a refrigeration system, used to describe the degree of coldness or heat. Common temperature scales include Celsius (°C), Fahrenheit (°F), and Kelvin (K).
Celsius (°C) : A commonly used unit in the International System of Units (SI).
Fahrenheit (°F) : Mainly used in North America or commonly found on nameplates of American equipment.
Kelvin (K) : The fundamental unit of temperature in the International System of Units (SI), used in scientific calculations and thermodynamic analysis. 0K represents absolute zero.
Conversion formula
°C and °F:
°F = (°C × 9/5) + 32
°C = (°F - 32) × 5/9
Example: 25°C = (25 × 9/5) + 32 = 77°F; 68°F = (68 - 32) × 5/9 ≈ 20°C
°C and K:
K = °C + 273.15
°C = K - 273.15
Example: 0°C = 273.15K 300K ≈ 26.85°C
°F and K:
K = (°F - 32) × 5/9 + 273.15
Example: 68°F ≈ (68-32) × 5/9 + 273.15 ≈ 293.15K
Application Tip: In refrigeration cycle calculations (such as COP, EER), absolute temperature (K) is typically used. In daily operation and debugging, °C and °F are more commonly used. Attention should be paid to the units of equipment parameter tables or sensor readings.
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