Thermodynamics Fundamentals and Units Flashcards

Flashcards covering the fundamental laws of thermodynamics, unit conversions, system definitions, and fluid properties based on lecture notes.

Zeroth Law of Thermodynamics

If two thermodynamic systems are each in thermal equilibrium with a third one, then they are in thermal equilibrium with each other.

First Law of Thermodynamics

The Law of Conservation of Energy, which states that energy can neither be created nor destroyed, only transformed into other forms.

Second Law of Thermodynamics (Entropy)

States that the direction of heat energy flow is from a higher temperature body to a lower temperature body and that the total entropy of an isolated system always increases over time.

Third Law of Thermodynamics

As the temperature of a system approaches absolute zero ($0\,K$, $0\,R$, $-273.15^{\circ} C$, or $-459.67^{\circ} F$), the entropy of a pure crystalline substance approaches zero (a constant minimum).

Positive Work ($+W$)

Work done BY the system on its surroundings, such as when a gas expands and pushes a piston upward, resulting in a loss of internal energy.

Negative Work ($-W$)

Work done ON the system by an external force, such as compressing gas in a cylinder, which forces energy into the system.

Dimensional Homogeneity

The principle using proportionality constant "k" to maneuver between different unit systems, ensuring units like $N$ and $kg \cdot m / s^2$ are compatible.

CGS System

A unit system where $1\,\text{dyne}$ force accelerates $1\,\text{gram}$ mass at $1\,cm/s^2$, with $k = 1\,gm \cdot cm / (dyne \cdot s^2)$.

MKS System

A unit system where $1\,\text{Newton}$ force accelerates $1\,kg$ mass at $1\,m/s^2$, with $k = 1\,kg \cdot m / (N \cdot s^2)$.

FPS System

A unit system where $1\,lbf$ accelerates $1\,\text{slug}$ mass at $1\,fps^2$, with $k = 1\,slug \cdot ft / (lbf \cdot s^2)$.

1 Statute Mile

A linear unit equivalent to $5280\,\text{feet}$ or $1760\,\text{yards}$.

1 Nautical Mile

A linear unit equivalent to $6080\,\text{feet}$.

1 US Gallon

A volume unit equivalent to $231\,cu.\,\text{inches}$, $3.7854\,\text{liters}$, or $4\,\text{quarts}$.

1 BTU (British Thermal Unit)

A unit of work or energy equivalent to $778\,ft \cdot lb$, $252\,cal$, or $1055\,J$.

1 Horsepower (hp)

A unit of power equivalent to $550\,ft \cdot lb/s$, $33000\,ft \cdot lb/min$, $2545\,BTU/hr$, or $746\,\text{watts}$.

Atmospheric Pressure (1 atm)

Standard pressure equivalent to $101.325\,kPa$, $14.7\,psi$, $760\,mm\,Hg$, or $29.92\,in\,Hg$.

Thermodynamics

The study of energy, specifically how thermal energy interacts with matter and transforms into and out of other types of energy.

Working Substance

A fluid that receives, transports, and transfers energy, or a fluid in which energy can be stored and removed.

Thermodynamic State

The exact, measurable reality of a system at a specific moment, defined by numerical properties like $200\,kPa$ and $50^{\circ} C$.

Thermodynamic Condition

The general environment or physical constraint applied to a system, such as "constant pressure" or "adiabatic" (qualitative/situational).

Closed System (Controlled Mass System)

A system where the working substance does not cross boundaries but energy does; mass remains constant while energy is variable.

Open System (Controlled Volume System)

A system where both the working substance and energy cross boundaries; both mass and energy are variable.

Isolated System

A thermodynamic system where neither mass nor energy crosses boundaries, remaining completely unaffected by surrounding conditions.

Intensive Property

System characteristics that are independent of mass, such as temperature, pressure, density, and voltage.

Extensive Property

System characteristics that depend on the mass of the system, such as total volume and total internal energy.

Density ($\rho$)

The mass per unit volume of a substance, typically measured in $kg/m^3$ ($\rho = m/V$).

Specific Volume ($\nu$)

The volume occupied by a unit mass ($\nu = V/m$); it is the reciprocal of density ($1/\rho$).

Specific Weight ($\gamma$)

Defined as the weight per unit volume ($\gamma = W/V$), measuring the gravitational force exerted by matter per unit of space.

Specific Gravity (Relative Density)

The dimensionless ratio of the density of a fluid to the density of water (usually $1000\,kg/m^3$).

Absolute Pressure ($P_{abs}$)

Pressure measured starting from a perfect vacuum (absolute zero pressure); it can never be negative.

Gauge Pressure ($P_{gauge}$)

Pressure measured relative to the local atmospheric pressure, treating ambient air as "zero."

Hydrostatic Law

States that pressure within a static fluid increases linearly with depth: $P = P_0 + \rho gh$.