Refrigeration Systems, Purifiers, and HVAC Components

Vocabulary flashcards covering marine refrigeration system components, pressure switches, safety devices, HVAC fundamentals, and centrifugal purifier operations.

Solenoid Valve

A two-position (open/closed) valve installed ahead of the thermostatic expansion valve that controls box temperature by starting or stopping refrigerant flow.

Thermostatic Switch

A temperature control switch connected to a sensing bulb in the box that signals the solenoid valve to open when box temperature rises above the setpoint.

Thermostatic Expansion Valve (TXV)

A throttling valve with infinite positions that regulates refrigerant flow into the evaporator to control superheat based on temperature from a bulb at the evaporator coil outlet.

Hand Expansion Valve

A manually operated bypass valve around the TXV and solenoid valve that allows manual control at a single cooling rate during control system failures.

Evaporator Back Pressure Regulator

A regulator installed at the outlet of evaporator coils on all but the coldest box in multibox systems to maintain minimum coil pressure and prevent rapid temperature cycling and moisture stripping.

Low Pressure Cut Out

A control switch installed at the compressor suction inlet that automatically cycles the compressor on or off based on suction pressure.

High Pressure Cut Out

A safety switch installed at the compressor discharge that shuts off the compressor during abnormally high pressure conditions and usually requires a manual reset.

Compressor Relief Valve

An internal safety valve in positive displacement compressors that relieves excessive discharge pressure back to the suction side to prevent damage from liquid slugging.

System Relief Valve

A safety valve located on the condenser or receiver that relieves excessive refrigerant pressure if the high pressure cut out switch fails.

Saturated Condition

A state where air reaches $100\times10^{-2}$ relative humidity ($100{\%}$) and cannot hold further water vapor; any drop in temperature causes moisture to condense.

Secondary Refrigerant

A fluid, such as chilled water, circulated in a closed loop through an HVAC system to transfer cooling capacity from a primary refrigerant loop to conditioned spaces.

Phosgene Gas

A highly toxic, dangerous gas produced when non-toxic refrigerant gas is exposed to high temperatures or direct heat from a fire.

Non-Condensable Gas

Gases like nitrogen that remain in a gas state at normal system operating temperatures (such as $-100\text{ }^\text{o}\text{F}$) and reduce the partial pressure of the refrigerant.

Evaporator

The refrigeration system component where liquid refrigerant vaporizes and absorbs heat from the surrounding space or medium.

Compressor

The mechanical component of a refrigeration system that maintains refrigerant circulation through the high and low pressure sides of the system.

One Refrigerant Ton

A unit of refrigeration equivalent to a continuous heat removal rate of $12000\text{ }\text{BTU/hr}$.

Heat Transfer Methods

The three physical processes by which heat moves from higher to lower temperatures: conduction, convection, and radiation.

Lube Oil Preheating

The process of heating contaminated lube oil prior to feeding it into a centrifuge to improve separation and purification efficiency.

Regulating Tube

The component located at the top of a disk-type centrifugal purifier through which contaminated oil enters the centrifugal bowl.

Bowl Closing Water

Water pressure applied beneath the lower sliding bowl in a centrifugal purifier to lift and seal it against the top bowl shell.