HVAC and Refrigeration Fundamentals

Vocabulary practice flashcards covering fundamental thermodynamics, refrigeration principles, system calculations, and servicing procedures.

BTU

The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

Evaporation

The change of state from a liquid to a vapor absorbing heat.

Condensing

The change of state from a vapor to a liquid rejecting heat.

Latent Heat

Heat that changes the state of a liquid but not its temperature.

Sensible Heat

Heat that can be measured with a thermometer.

Temperature, Pressure, and Saturation Relationship

When temperature goes up, pressure goes up and saturation goes up; when temperature goes down, pressure goes down and saturation goes down.

Saturation (Number One Definition)

PSIG converted to temperature.

Superheat

Sensible heat added to a vapor above its saturation point.

Formula for Superheat

$$\text{Actual suction line temperature} - \text{Suction saturated temperature} = \text{Superheated (Vapor)}$$

Subcooling

Sensible heat removed from a liquid below its saturation point.

Formula for Subcooling

$$\text{Liquid saturated temp} - \text{Liquid line temp} = \text{SUB COOLING LIQUID}$$

Target Superheat for a Fixed Orifice

Found by using the formula $\text{Target SH} = \frac{[(\text{IDWB} \times 3) - \text{ODT} - 80]}{2}$, or by measuring indoor wet bulb temperature and outdoor dry bulb temperature and using a chart or an app.

Target Superheat for a TXV

$$8\text{--}18^\circ\text{F}$$

TEV System: Good Superheat and High Subcooling

A condition in a system with proper airflow indicating that it is overcharged, requiring recovery of refrigerant.

First Law of Thermodynamics

Energy cannot be created or destroyed but can be converted from one form to another.

Second Law of Thermodynamics

Heat travels from a warmer location to a cooler location (heat seeks "cold").

Refrigeration

Moving heat from a place that is unwanted to a place that is Insignificant.

Recovery

Moving refrigerant from a unit in any condition and putting it into a recovery tank.

Charging Procedure

Adding refrigerant to a system by throttling it in through the low side.

Timing for Refrigerant Recovery

Refrigerant is recovered when the unit is overcharged or needs to be opened for repair.