Thermodynamics Sta. Maria 2nd Edition

1 dyne force (cgs system)

accelerate 1 gram mass at 1 cm/s²

1 newton force (mks system)

accelerates 1 kg mass at 1 m/s²

1 lb force (fps system)

accelerates 1 slug mass at 1 ft/s²

1 lb force

accelerates 1 lb mass at 32.174 ft/s²

1 g force

accelerates 1 gm mass at 980.66 cm/s²

1 kg force

accelerates 1 kg mass at 9.8066 m/s²

1 kgf

9.8066N

1 slug

32.174 lbm

1 gmf

980.66 dynes

mass

the absolute quantity of matter in a body

weight

the force of gravity acting on a body

density

mass per unit volume

specific volume

volume per unit mass

specific weight

the force of gravity on a unit volume

pressure

the normal force exerted by the system per unit area

1 atm to mm Hg

760 mm Hg

1 atm to in Hg

29.92 in Hg

1 atm to psia

14.696 lbf

open-type manometer

used to measure pressure in flow lines or vessels

equation for open-type manometer where Pabs>Patm

P= Po + yh

equation for open-type manometer where Pabs<Patm

P= Po - yh

closed-type manometer

used to measure the pressure difference between two flow lines or vessels

equation for closed-type manometer is pressure at vessel x is greater than pressure y

yh = Px - Py

equation for closed-type manometer is pressure at vessel y is greater than pressure x

yh = Py - Px

gage pressure

the defect or excess of absolute pressure over the barometric pressure

vacuum pressure

is the defect or excess of atmospheric pressure over the absolute pressure

barometer

used to measure the atmospheric pressure

absolute temperature

the temperature measured from absolute zero

absolute zero temperature

the temperature at which all molecular motion ceases

formula for C to F

F=9C/5+ 32

formula for F to C

C = 5/9 (F-32)

formula for F to R

R = F+460

formula for C to K

K = C + 273

law of conservation of mass

states that mass is indestructible

volume flow rate

Q = Av

mass flow rate

m = pAv

Einstein’s Theory of Relativity

states that mass can be converted into energy and energy into mass

Relativity Equation

E = mc²

gravitational potential energy

energy due to position or elevation

kinetic energy

energy stored or stored capacity for performing work possessed by a moving body by virtue of its momentum

GPE

mgh

KE

½ mv²

Internal Energy

energy stored within a body or substance by virtue of the activity and configuration of its molecules and of the vibration of the atoms within the molecules

heat

energy in transit from one body to another solely because of temperature difference

flow work (flow energy)

work done in pushing a fluid across a boundary, usually into or out of a system

equation for Flow Work

W_f= FL = pAL = pV

enthalpy

a composite property applicable to all fluids defined by:

h = u + pV or h = u + W_f 

Work

product of the displacement of the body and the component of the force in the direction of the displacement, it is a work in transition

closed system

mass does not cross its boundaries

open system

mass crosses its boundaries

Work Non-Flow Equation

W_NF = pdV

Work Non-Flow

the work done as the piston moves in a closed system,

work done during a non-flow reversible process

area under the curve of the process on the pV plane

expansion work

when work is done by the pressure force of a gas on the face of a piston (positive)

compression work

when work is done by piston on a gas (negative)

Work Non-flow by General Energy Equation

W_NF = Q - U

work steady-flow or work done for an open system

the area behind (to the left) of the curve of the process on the pV plane

Work Steady-Flow Equation

W_SF= VdP

conservation of energy

states that energy is neither created nor destroyed

First Law of Thermodynamics

states that “if energy cannot be created nor destroyed, then it can be transformed from one form to another”

ideal gas

ideal only in the sense that it conforms to the simple perfect gas laws

Boyle’s Law

“if the temperature of a given quantity of gas is held constant, the volume of gas varies inversely with the absolute pressure during a change of state”

Boyle’s Law equation

V₂/V₁=P₁/P₂

Charle’s Law 1

“if the pressure on a particular gas is held constant, then with any change of state, the volume will vary directly as the absolute temperature”

Charle’s Law 1 equation

V₂/V₁=T₂/T₁

Charle’s Law 2

“if the volume of a particular quantity of gas is held constant, then with any change of state, the pressure will vary directly as the absolute temperature of the gas”

Charle’s Law 2 equation

P₂/P₁=T₂/T₁

equation for ideal gas

pV=mRT

combined gas laws

PV/T= c

specific heat

defined as the quantity of heat required to change the temperature of unit mass by one degree

constant specific heat equation

Q = mcdT

Constant Volume Specific Heat equation

Q = mc_vdT

constant pressure specific heat equation

Q_v= mc_pdT

ratio of specific heats (k)

C_p/C_v>1

Joule’s Law

states that “the change of internal energy of an ideal gas is a function of only the temperature change”

Joule’s Law equation / Internal Energy of an Ideal Gas

dU = mc_vdT

Enthalpy of Ideal Gas

dH = mc_pdT

Mayer’s Rule

C_p + C_v = R

C_v equation

C_v = R/(k-1)

C_p equation

C_p = kR/(k-1)

entropy (S)

a property of a substance which remains constant if no heat enters or leaves the substance, while it does work or alters its volume, but which increases or diminishes should a small amount of heat enter or leave

entropy equation

dS = dQ/T

entropy equation for constant specific heat

dS = mcln(T₂/T₁)

heat transferred during the process

represented by the area under the curve of the process on the TS plane

reversible process

any process that can be made to go in reverse direction by an infinitesimal change in the conditions

W_SF when change in KE = 0 or the KE when W_SF=0

represented by the area behind the curve of the process on the pV planes

irreversible process

any process that is not reversible

isometric or isochoric

a reversible constant volume process, in this process the working substance is contained in a rigid vessel

isomer or isochore

the curve for an isometric process

relation between T and P when isometric

P₂/P₁=T₂/T₁

work non-flow when isometric

W_NF=0

change in internal energy when isometric

dU = mc_vdT

heat transferred when isometric

Q_v = mc_vdT

change in enthalpy when isometric

dH = mc_pdT

change of entropy when isometric

dS = mc_vln(T₂/T₁)

reversible steady flow when isometric

W_SF=V(P₁ - P₂)

irreversible nonflow when isometric

W_NF=0

isobaric or isopiestic

an internally reversible process of a substance during which a pressure remains constant

isobar

the curve for an isobaric process

relation between V and T when isobaric

V₂/V₁=T₂/T₁