SOLAS Refrigeration cheat sheet

Refrigeration and Air Conditioning - SOLAS Refrigeration

• Refrigeration moves heat from a lower-temperature region to a higher-temperature region; it does not create cold, it removes heat.

• The refrigeration cycle has four stages: compression, condensation, expansion, and evaporation. The evaporator absorbs heat; the condenser rejects it.

• Pressure-enthalpy (p-h) diagram: the compressor work is the enthalpy rise across compression (h2 − h1); refrigerating effect is h1 − h4.

• The coefficient of performance (COP) is refrigerating effect divided by compressor work: COP = (h1 − h4) / (h2 − h1).

• Superheat is the temperature of vapour above its saturation temperature at the same pressure; subcooling is liquid below its saturation temperature.

• Saturation temperature and pressure rise and fall together: for a given refrigerant, a higher condensing pressure means a higher condensing temperature.

• The expansion valve (or capillary tube) maintains the pressure difference between the high side and low side and meters refrigerant into the evaporator.

• Air conditioning conditions air for temperature, humidity, cleanliness, and movement; sensible heat changes dry-bulb temperature, latent heat changes moisture content.

• A refrigerant leak on the low-pressure side draws air and moisture into the system; non-condensable gases raise head pressure and reduce capacity.