Refrigeration and Air Conditioning Practice Flashcards

This set of vocabulary flashcards covers the fundamental components, safety devices, operational procedures, and environmental regulations associated with marine refrigeration and air conditioning systems.

Compressor

A single stage, reciprocating component that compresses refrigerant to a pressure dependent on the cooling water temperature and volume of gas.

Condenser

A water cooled tube cooler where sensible and latent heat are removed to convert refrigerant into a high pressure undercooled liquid.

Expansion Valve

A component that drops refrigerant pressure by passing it through a variable orifice, resulting in an associated drop in temperature through constant enthalpy.

Evaporator

A coil where low pressure liquid/gas refrigerant absorbs heat from the air and evaporates, becoming a low pressure superheated gas.

Specific Enthalpy ($h$)

Measured in $kJ/kg$, it represents the total heat content of the refrigerant at various stages of the cycle.

High Pressure Cut-out

A safety component that shuts down the compressor during overpressure; it is adjusted via a spring and must be manually reset.

Oil pressure safety cut-out

A differential control that stops the compressor if the difference between oil pressure and suction pressure falls below a minimum value.

Solenoid Valve

An electrically controlled valve in the liquid line that opens or closes to regulate refrigerant flow to the expansion valve based on thermostat signals.

Oil Separator

A device in the compressor discharge line that uses tangential entry and a wire wool demister to return entrained oil to the compressor sump.

Liquid Receiver

A reservoir below the condenser used to gauge refrigerant levels and provide space for liquid when the system is pumped down.

Sight Glass

A bulls eye indicator used to ensure only liquid enters the expansion valve, often featuring a colored ring that changes color if water is detected.

Filter Drier

A unit containing a desiccant cartridge or bags used to remove moisture, which can freeze or form acids, and fine particles from the refrigerant.

Thermostatic Expansion Valve

A valve where the top of the bellows responds to superheat temperature and the underside responds to evaporator outlet pressure to regulate flow.

Undercooling

Cooling the liquid refrigerant in the condenser below its saturation temperature to increase plant efficiency and prevent flash off.

Pumped down

The process of evacuating refrigerant gas into the condenser to allow for system maintenance without the loss of refrigerant.

Comfort Zone

The temperature and Relative Humidity zone suitable for human occupancy, typically ranging from $20^{\circ}C$ at $70\%$ RH to $29^{\circ}C$ at $40\%$ RH.

Legionella

A bacteria found naturally in freshwater that can spread in human-made water systems; prevented by design, weekly filter cleaning, and $50\,ppm$ chlorine solution.

Montreal Protocol

An international agreement that stopped the production of CFCs such as $R12$ and $R11$ to protect the ozone layer.

HFC (HydroFluoroCarbons)

Refrigerants like $R134a$ that contain no chlorine and do not attack the ozone layer, but are potent greenhouse gases.

GWP

Global Warming Potential; regulations cap and phase-down HFCs with a GWP of $2500$ and above through equipment and maintenance bans.

ODS Record Book

A mandatory log for ozone-depleting substances where charging, recovery (quantified by weight), inspections, and leak detections must be recorded.