SI units of Thermodynamics PDF

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SI units of Thermodynamics Mass Length Time Temperature Force Weight Density

m L t T F w ρ

(kg)

1kg = 1000g

(m)

1m=10dm=100cm=1000mm

(s)

1hr=60min=3600s

(K)

0 K= -273oC, 0oC = 273 K

0 K= absolute 0 temperature

(N)

F = m*a m => mass (kg),

1 kg*m/s2 = 1N, 1kN=1000N, 1MN = 106N

a => acceleration (m/s2)

(N)

w = m*g g => acceleration due to gravity

(kg/m ) ρ= m/v m =ρV 3

V => volume (m3)

Specific Volume Relative Density

ν s

(m3/kg) ν= 1/ρ=V/m, m = V/ν s =ρsubstance /ρwater

N = kg*m/s2 g = 9.81 m/s2 p water =1000 kg/m3 p atmospheric air = 1.2 kg/m3 volume (in m3) occupied by mass of 1kg Relative density also called

specific gravity (s.g.)

Pressure

p

(Pa)

P = F/A, F => force (N),

1 Pa = 1 N/m2, 1 bar=105Pa

A => Area (m2)

1 kPa=103Pa, 1MPa=106Pa

Energy Potential

PE

(J)

PE = m*g*z = kg*m/s2*m

J=N*m, z=vertical distance

Energy Kinetic

from the earth surface

KE

(J)

2

KE = mc /2, c=>velocity (m/s)

Energy Internal Energy

U

(J)

U = mCvT or∫Cν(t)dt

Cν=specific heat capacity at

constant volume (kJ/kgK)

Specific

u

(J/kg)

u = U/m,

Internal Energy Enthalpy

H

(J)

H=U+pV= mCpT or∫Cp(t)dt

Overall internal energy –

temperature U+pressure pV

Specific

h

(J/kg)

h=H/m, => J/kg

Enthalpy Total Energy Work

E W

(J) (J)

E=PE+KE+U (Close system) E=PE+KE+H (Open system) W=F*L, =>N*m

a means or form for energy

Heat

Q

(J)

transfer, cannot be stored Heating – heat from surrounding to the body, Cooling - heat from the body to surrounding. Energy transfer - heat naturally from hotter to colder body....