Friday, December 14, 2012

Useful Engineering Verbs for resumes, engineering manuals, presentations and documentation


Although this list is not exhaustive, these engineering verbs are helpful and handy when preparing job application resumes, engineering manuals, work or training instructions, writing textbooks and other documentation materials, and specially during presentations, safety briefs, meetings, and seminars where you audience might have little or no background in engineering. I have listed these verbs alphabetically and it is my recommendation to choose the appropriate verbs depending on you audience. For example, when doing and engineering presentation to a general audience, it is recommended to use verbs such as produces, delivers, draws, enters, receives, transmits, etc. which are easily understood by listeners which have varies background knowledge. If you have select audience with engineering backgrounds, then use the appropriate engineering technical terminologies.

A
abide
abolish
abort
accelerate
access
acclimatize
achieve
acknowledge
acquire
act
action
actuate
add
adjust
adopt
advance
advocate
affect
aggravate
agitate
aid
alarm
align
allocate
ally
alter
amalgamate
amass
amplify
analyze
angle
anneal
anodize
antifoul
apply
appropriate
approximate
arc
arrange
ascertain
asphyxiate
assemble
assist
assume
atomise
attack
attenuate
attract
authorize
automate
average
avoid

B
backlash
backup
balance
ballast
bar
beam
bear
become
become
begin
bend
benefit
blast
block
blow
board
boil
bond
boost
border
bore
braze
break
brew
brief
brine
brinell
brood
build
burn
burr
bypass

C
calculate
calibrate
cancel
cap
carburize
carry
carry out
cast
categorize
cause
center
centralize
centrifuge
chain
change
char
characterize
charge
check
choke
choose
circle
circulate
circumscribe
class
classify
close
coal
coalesce
coat
coincide
collaborate
collapse
collect
collide
colonize
combat
combine
commence
compare
compass
compensate
compile
complete
comply
compost
compound
compute
concentrate
conclude
concuct
conduct
confer
configure
conserve
consist
consolidate
constitute
constrain
constrict
construct
consume
contact
contaminate
contract
convert
cook
cool
cooperate
coordinate
copy
correct
corrode
cost
counter
counteract
counterpunch
couple
cover
crack
crest
critique
crystalize
cube
culture
curve
cushion
cut
cycle

D
damage
date
debrief
decay
decelerate
decentralize
decode
decrease
deduce
defer
defuel
de-gas
degauss
degrade
degrease
dehumidify
de-install
de-ionize
delegate
delete
delineate
demobilize
demodulate
demulsify
deny
depend
deplete
deploy
depopulate
depress
depressurize
derive
desalinate
describe
de-sensitize
design
dessicate
destroy
destruct
detail
deter
deteriorate
determine
develop
deviate
dewater
diagnose
die cast
differentiate
diffuse
dilute
diminish
dip
disable
discharge
disconnect
disembark
disjoin
dismantle
displace
display
dispose
disrupt
dissipate
dissolve
distill
distort
distribute
disturb
dive
divide
download
drag
drain
draw
drill
drop
drop forge
dry
dry run
duplicate

E
eat
economize
educate
effect
elaborate
element
eliminate
embark
embed
emerge
emphasize
employ
empty
emulsify
enable
encircle
encode
end
enforce
engine
engineer
engulf
enhance
enrich
ensure
entail
enter
entrain
enumerate
equalize
escalate
escape
establish
estimate
evacuate
evaluate
exacerbate
excavate
exceed
exchange
exclude
execute
exempt
exhaust
exit
expatriate
expel
experiment
expire
explain
explode
export
expose
extend
exterminate
extinguish
extract
extrapolate
extrude

F
factor
fail
feel
figure
fill
fillet
find
fine tune
fire
fit
flake
flange
flank
flash
float
flow
flush
focus
follow
forge
form 
form cut
formalize
formulate
foul
freeze
fuel
funnel

G
gage
gain
gas
gather
gear
generalize
generate
germinate
give
give off
go
govern
grade
graduate
graph
grease
grind
ground
group
grow
guide

H
hammer
harden
harvest
hear
heat
heave
heel
help
hob
hog
hoist
hold
hold down
hone
hub
humidify

I
identify
ignite
illuminate
imagine
impart
impede
implement
implode
imply
import
impose
impregnate
improve
in-charge
incinerate
incline
include
increase
incubate
indent
induce
infer
influence
inform
ingress
inhibit
initialize
initiate
inject
input
inscribe
inspect
inspire
install
insulate
integrate
intensify
interact
interchange
interface
interpolate
interrogate
intersect
intersperse
invalidate
invent
invert
investigate
involve
ionize
isolate

J
journey
justify

K
know

L
leave
level
liaise
life test
lift
light
limit
line
liquefy
list
listen
load
locate
lock
lock
log
loll
look
loosen
lose
lower
lubricate

M
machine
magnetize
make
manage
manufacture
margin
marginalize
mass
match
materialize
maximize
measure
meet
meld
melt
memorize
merge
mesh
mesh out
meter
minimize
mist
mist spray
mitigate
mix
mobilize
mock run
model
modify
modularize
modulate
module
moisturize
mold
moment
monitor
move
multiply
multitask

N
name
narrow
narrow down
necessitate
negate
network
neutralize
nitride
node
note
notice
nourish
nullify

O
obscure
occur
offer
oil
open
oppose
order
output
overcurrent
overheat
overload
overvoltage

P
paint
pair
parameter
pass
paste
penetrate
perceive
percolate
perforate
period
permeate
phase
phase in
phase out
pick up
picture
piece
pit
pitch
place
plan
plane
plot
point
poll
pollute
populate
position
pour
power
pre-amplify
preclude
precoat
predict
prefer
pre-filter
prepare
present
preserve
press
pressure
pressurize
prewet
prioritize
probe
proceed
procure
produce
program
progress
prohibit
project
promote
promulgate
propel
protect
prove
provide
pull
pull out
pump
pump out
punch
purge
purify
purpose
push

Q
qualify
quantify
quantisize
quench

R
radiate
raise
range
rate
reach
react
ready
realize
rebuild
recall
recharge
reciprocate
recode
recognize
recoil
recommend
reconfigure
reconnect
record
recover
rectify
recycle
redesign
reengineer
reenter
refer
refill
refit
refract
refresh
refrigerate
refuel
refurbish
regain
regulate
rehearse
reinforce
relate
relegate
relieve
remain
remind
remove
renew
repair
repeat
repel
replace
repopulate
report
reprocess
reproduce
request
require
rescue
research
reserve
reset
resist
resize
respond
response
restore
restrain
restrict
result
retail
retain
retard
return
reverse engineer
revert
review
revise
revolve
rework
rig
rim
rinse
rivet
roll
rotate
round  
round off
rule
rust

S
sag
sample
saturate
save
saw
scale
scour
screen
screw
scrub
scuff
search
sector
secure
select
sense
sensitize
separate
service
settle
setup
shake
shape
sharpen
shine
ship
shove
shut down
sight
sign
simulate
situate
sketch
slope
slow
smell
smoothen
snug
soak
soap
soften
solder
solidify
solve
source
spark
speak
specialize
specify
speed
spell
spill
spray
square
stabilize
stagnate
standardize
start up
state
store
straighten
stream
strengthen
stress
stretch
strike
strip
strive
stroke
study
sub-contract
subject
sublimate
submerge
subtend
subtract
succeed
sum
supersede
supervise
supply
support
suppose
surface
surge
suspect
suspend
swell
switch
switch off

T
table
tabulate
tag
tag out
take
tangent
taper
task
taste
temper
tender
term
terminate
test
thaw
thrive
throw
thrust
tick
tighten
time
tip
tolerate
tone
tow
trace
train
transfer
transform
transition
transpire
trap
travel
treat
treble
triangulate
trigger
trim
trip
tube
tune
turn
turn off
twist

U
universalize
unload
update
upgrade
upload
use
utilize

V
vacate
vacuum
validate
vaporize
verify
vibrate
view
violate
visualize

W
warm
wash
watch
water
wax
weaken
wear
weld
wet
winch
wipe
work
wrench

X
x-axis
x-ray
x-section

Y
yard
yaw
y-axis

Z
z-axis
zero
zero in

Wednesday, December 5, 2012

MATHEMATICS and ELECTRICAL ENGINEERING: Joint and Combined Variation - Wire resistance, length, area


WIRE RESISTANCE is directly proportional to LENGTH and inversely proportional to AREA


R = k L/A


where:

R = wire resistance

k = constant

L = length of wire

A = cross-sectional area of wire



1. If 700 meters of a 4 mm-diameter wire has a resistance of 28 ohms, find the length of a 7 mm-dia wire of same resistance.


given:

L1 = 700 m

d1 = 4 mm

R1 = 28 ohms

d2 = 7 mm

R2 = 28 ohms = R1


find:

L2 = length of wire with 7 mm diameter having same resistance of 28 ohms


solution:


R = k L/A

k = R * A/L

R1 * A1/L1 = R2 * A2/L2

28 * (4^2 * pi/4)/700 = 28 * (7^2 * pi/4)/L2

16/700 = 49/L2

L2 = 700 * 49/16

L2 = 2144 m




2. By what factor will the wire resistance change if both the wire length and diameter are increased by 200% (doubled)?


given:

L1 = L

d1 = d

L2 = 2L

d2 = 2d


find:

change factor of wire resistance when wire length and wire diameter are both doubled


solution:


R = k L/A

k = R * A/L

R1 * A1/L1 = R2 * A2/L2

R1 * (d^2 * pi/4)/L = R2 * [(2d)^2 * pi/4]/2L

R1 * d^2 = R2 * (4 * d^2)/2

R1 = R2 * 2

R2 = (R1)/2

R2 = 0.5 R1  ---> the final wire resistance (R2) is REDUCED to HALF of the initial wire resistance (R1)

Tuesday, December 4, 2012

CHEMISTRY, CHEMICAL, MECHANICAL ENGINEERING FUELS & COMBUSTION: Latin, Greek ROOTS, PREFIXES, SUFFIXES



A

a-, an- = not, without [anhydrous, amorphous, atrophy]

acid = sour, sharp [hydrochloric acid, sulfuric acid]

alkali = soda ash, [alkali, alkaline]

allo, -io = other, different [allotrope, alloy]

alpha = 1st letter of Greek alphabet [alpha particle, alpha rays]

amin = ammonia amine [amino acid, ammonia, amine]

amph, -i, -o = double, on both sides [amphoteric, amphibian]

-ane = single covalent bond [alkane, hexane, butane, propane]


anti = against, opposite [antiseptic, antibiotic]

-ate = used to indicate a salt of an acid ending in -ic [sulfate, nitrate]

aqua = water [aqueous, aquatic, aquamarine]



B

baro = pressure [barometer, barometric]

beta = second letter of Greek alphabet [beta particle, beta rays]

bi = two [binary, bipolar]

bio = life [biology, biochemistry, biometrics]



C

carb, -o, -on = coal, carbon [carbohydrate, carbonic, carbon dioxide]

chem = chemistry, chemical [chemical, chemotherapy]

co, -l, m, -n = with, together [covalent, coefficient, colligative, concuction]

com = with, together [composition, combination]

conjug = joined together [conjugate acid, conjugal acid]

cosm,-o = the world or universe [cosmic rays, cosmology]

cry, -mo, -o = cold crystal [cryogenics]



D

de = down, without, from [decomposition, denatured, dehydrated]

dens = thick, dense [dense, density]

di = separate, double, across [diatomic, divalent, disaccharide]

dis = separate, apart [dissociation, dissolved]

duc, -t = lead [ductile, induction]



E

e = out, without, from [evaporation, eradication]

ef = out, from, away [effervescence, effluent]

electr, -i, -o = electrode, electric [electrolyte, electrochemical, electrical, electromechanical]

elem = basic [elements, elementary]

empir, -o = experienced [empirical formula]

en = in, into [endothermic, endocrine]

-ene = double covalent [alkene, acetylene, toluene, propylene]

equ = equal [equilibrium, equivalent]

erg = work, energy [erg, energy, ergonomic]

exo = out, outside, without [exothermic, exocrine, exothermal]



F

ferr, -o = iron [ferromagnetism, ferric, ferrous]

fiss, -i, -ur = cleft, split [fission, fissure]

flu = flow [fluids, confluent]

fract = break, broken [fraction, refraction, fracture]



G

gamma = 3rd letter of Greek alphabet [gamma rays, gamma]

gen = bear, produce, beginning [gene, genetic]

glyc, -er, -o = sweet [glycogen, glycolysis, glycose, glycolipid, glycol, glycerine]

graph, -o, -y = write, writing [graphite, graphical, graphics]



H

halo- = salt [halogens]

hetero- = other, different [heterogeneous]

hom, eo, -o = same, alike [homogeneous]

hybrid = combination [hybrid orbital]

hydr, -a, -i, -o = water [hydrolysis, hydroelectric]

hyper = over, above, excessive [(hy)perchloric acid, hyperactive, hypertension]

hypo = under, beneath [hypochlorous acid, hypothetical, hypothermic]



I

-ic = show the higher of two valences, having some characteristics of [ferric, metallic]

-ide = group of related chemical compounds [monosaccharide]; binary compound [sodium chloride, hydrogen cyanide]; chemical element with properties similar to another [lanthanide series]

im = not [immiscible, impenetrable]

in = in, into [intrinsic, internal]

-ine = of or pertaining to, of the nature of, made of, like [crystalline, marine]; halogen [bromine]; basic compound [amine]; alkaloid [quinine]; amino acid [glycine]; mixture of compounds [gasoline]; commercial material [glassine]

-ion = process [fusion, fission, evaporation]

iso = equal [isomers, isometric, isochoric]

-ite = salt or ester of an acid named with an adjective ending in -ous [sulfite]; rock, mineral [graphite]; fossil [trilobite]; product [metabolite]; commercial product [ebonite]



K

kilo = thousand [kilogram, kilojoule]

kine = move, moving, movement [kinetic energy]



L

lip, -o = fat [lipoprotein, lipid]

liqu, -e, -i = fluid, liquid [liquefy, liquor]

lys, -io, -is, -io = loose, loosening, breaking [hydrolysis]



M

macr, -o = large, long [macromolecule, macroscopic]

malle, -o, -us = hammer [malleable, malleability]

mer, -e, -i, -o = part [dimer, polymer, isomer]

met, -a = between [metabolism, metamorphosis]

-meter = measure [calorimeter, thermometer]

mill -e, -i, -o = one thousand [milliliter, milligram, millimeter]

misc = mix [miscible, miscellaneous]

mon -a, -er, -o = single, one [monomer, monovalent, monoxide]

morph, -a, -o = form [amorphous, metamorphic, polymorphic]




N

neo = new [neoprene]

neutr = neither [neutral, neutron]

nom, -en, -in = name [nominal, nomenclature]

non = not, ninth [nonpolar, non-reactive]

nuc, -ell, -i = nut, center [nucleus, nuclear]



O

oct, -i, -o = eight [octet, octane]

-oid = like, form [metalloid, colloid]

orbi, -t = circle [orbital, orbit]

-ous = possessing, full of, lower of two possible valences [aqueous, porous, ferrous, ferrous sulfide]

oxid = oxygen [oxide, oxidation]



P

photo = light [photochemical, photosynthesis]

polar, -i = of the pole [polarity, polar]

poly = many [polymer]

pro = forward, positive, for, in front of [proton, projectile, projection]



Q

quant = how much [quantum, quanta, quantity]



R

radi, -a, -o = spoke, ray [radius, radioactive, radial, radiation]



S

sacchar, -o = sugar [monosaccharide, saccharine]

sal, -i = salt [salinity, saline]

solu- = dissolve [solubility, soluble, solution]

spect = see, look [spectator, speculate, spectacle]

super = above, over [superheated, supersonic]

syn = together, with [photosynthesis, synthetic]



T

therm, -o = heat [thermodynamics, thermochemistry, thermal conductivity]

thesis = arranging, statement [hypothesis, antithesis]

tran, -s = across, through [transition, transfer, transfusion]



U

un = not [unsaturated, unstable]



V

vapor, -i = steam, vapor [vaporization, vaporizer, vapor pressure]

vulcan = fire [vulcanized, vulcanization]



Y

-yl = wood, matter; organic acid radical [carbonyl]; chemical names of organic compounds when they are radicals [alkyl, ethyl, phenyl]

-yne = triple covalent bond [alkyne, ethyne]

Monday, November 19, 2012

CHEMISTRY, CHEMICAL ENGINEERING: Periodic Table Elements - Roots, Origin, Etymology of Names


A

Actinium Ac - aktis = ray

Aluminum Al - alumen = substance with astringent taste

Americium Am - America (country or continent)

Antimony Sb - antimonos = opposite to solitude

Argon Ar - argos = inactive

Arsenic As - arsenikon = valiant

Astatine At - astatos = unstable



B

Barium Ba - barys = heavy

Berkelium Bk - Berkeley (University of California)

Beryllium Be - beryllos = a mineral

Bismuth Bi - bisemutum = white mass

Boron B - bawraq = white, borax

Bromine Br - bromos = stink, stench



C

Cadmium Cd - cadmia = calamine, a zinc ore

Calcium Ca - calcis = lime

Californium Cf - State and University of California

Carbon C - carbo = coal

Cerium Ce - Ceres = the asteriod

Cesium Cs - caesius = sky blue

Chlorine Cl - chloros = grass green

Chromium Cr - chroma = color

Cobalt Co - kobolos = a goblin

Copper Cu - cuprum = copper

Curium Cm - Marie & Pierre Curie (French physicists)



D

Dysprosium Dy - dysprositos = hard to get at, difficult to access, hard to obtain, rare earth



E

Einsteinium Es - Albert Einstein (German theoretical physicist)

Erbium Er - Ytterby = town in Sweden where it was discovered

Europium Eu - Europe (continent)



F

Fermium Fm - Enrico Fermi (Italian physicist)

Fluorine F - fluere = to flow

Francium Fr - France (country)



G

Gadolinium Gd - Johan Gadolin (Finnish chemist)

Gallium Ga - Gaul (historic France)

Germanium Ge - Germany (country)

Gold Au - aurum (Anglo-Saxon, Latin "gold")



H

Hafnium Hf - Hafnia (city of Copenhagen, Denmark)

Helium He - helios = sun

Holmium Ho - Holmia (city of Stockholm, Sweden)

Hydrogen H - "hydro genes" = water former



I

Indium In - indicum = indigo spectrum line

Iodine I - iodes = violet spectrum line

Iridium Ir - iridis = rainbow

Iron Fe - Anglo Saxon "iren", Latin "ferrum"



K

Krypton Kr - kryptos = hidden



L

Lanthanum La - lanthanien = to be concealed

Lawrencium Lw - Earnest Lawrence (American nuclear physicist, writer, inventor of cyclotron)

Lead Pb - Anglo Saxon lead, Latin plumbum

Lithium Li - lithos = stone

Lutetium Lu - Lutetia = ancient name of Paris, France



M

Magnesium Mg - magnes = magnet

Mendelevium Md - Dmitri Mendeleev (Russian chemist and inventor, devised periodic table)

Mercury Hg - Mercury, messenger of the gods (mythology) ; "hydrarygus" = liquid silver

Molybdenum Mo - molybdos = lead



N

Neodymium Nd - from two Greek words: neos = new; didymos = twin

Neon Ne - neos = new

Neptunium Np - named after the planet Neptune

Nickel Ni - from German "kupfernickel", false copper

Niobium Nb - Niobe = mythological daughter of Tantalus (Greek mythology)

Nitrogen N - from two Latin words: nitro = native soda; gen = born

Nobelium No - Alfred Nobel (Swedish chemist, engineer, innovator, armaments manufacturer and the inventor of dynamite)



O

Osmium Os - Greek: osme = odor of volatile tetroxide

Oxygen O - from two Greek words: "oxys" = sharp; "gen" = born



P

Palladium Pd - named after the planetoid Pallas

Phosphorus P - phosphoros = light bringer

Platinum Pt - from Spanish "plata", meaning silver

Plutonium Pu - named after the planet Pluto

Polonium Po - Poland (country of Marie Curie, co-discoverer of the element)

Potassium K - Latin "kalium", English potash

Praseodymium Pr - from Greek: Praseos = leek green; didymos = twin

Promethium Pm - Prometheus = fire bringer (Greek mythology)

Protactinium Pa - protos = first



R

Radium Ra - Latin "radius" = ray

Radon Rn - from Radium (the element Radon is formed by radioactive decay of radium)

Rhenium Re - Rhenus = Rhine province of Germany

Rhodium Rh - rhodon = a rose

Rubidium Rb - rubidus = red

Ruthenium Ru - Ruthenia (Latinized form of Russia) = region of western Ukraine south of the Carpathian Mountains



S

Samarium Sm - Vasili Samarski-Bykhovets, a Russian mining engineer

Scandium Sc - Scandinavia

Selenium Se - selene = moon

Silicon Si - silex = flint

Silver Ag - Latin "argentum", Anglo-Saxon, siolful

Sodium Na - Latin "natrium"; "sodanum" = cure for headaches

Strontium Sr - town of Strontian, Scotland

Sulfur S - Latin: sulphur, sulpur, sulfur = brimstone



T

Tantalum Ta - Tantalus (Greek mythology)

Technetium Tc - technetos = artificial

Tellurium Te - tellus = the earth

Terbium Tb - Ytterby (town in Sweden)

Thallium Tl - thallos = young shoot

Thorium Th - Thor (Scandinavian mythology)

Thulium Tm - Thule = northern part of habitable world

Tin Sn - Latin "stannum", Tinia (Etruscan god)

Titanium Ti - Titans (Greek mythology: The Titans were the first sons of the earth)

Tungsten W - symbol from German "worfram"; from Swedish: "tung sten" meaning heavy stone



U

Uranium U - named from the planet Uranus



V

Vanadium V - Vanadis (goddess of Scandinavian mythology)



X

Xenon Xe - from Greek "xenos" = strange



Y

Ytterbium Yb - Scandinavian: Ytterby  (a town in Sweden)

Yttrium Y - Scandinavian: Ytterby (town in Sweden)



Z

Zinc Zn - German "zink", "zinn" meaning tin

Zirconium Zr - zircon = mineral

Saturday, November 17, 2012

Thermodynamics: PV Work: compression-expansion work


derivation of PV work formulas


1. isobaric conditions: p = c


W = F * d

F = A * p


substituting,

W = A * p * d


but:

V = area * height

dV = A * d



W = p * dV  ---> PV work for constant pressure process



2. isothermal conditions: T = c


W = S(V1 V2) p * dV


but:

pV = RT


and

p = RT/V


substituting,


W = S(V1 V2) p * dV

W = S(V1 V2) RT/V * dV


because temperature T = constant,

W = RT * S(V1 V2) 1/V * dV


but the

Integral of 1/v * dv = ln V


putting the limits (V1 V2)

W = RT * (ln V2 - ln V1)


but from logarithmic properties

ln (u/v) = ln u - ln v

ln (uv) = ln u + ln v

ln u^n = n ln u



finally getting


W = RT * ln (V2/V1)  ---> PV work for constant temperature process



where:

W = Work done by compression or expansion(- if done on the surroundings)

F = Force

d = distance

p = absolute pressure

A = area

V = volume

dV = change in volume

T = absolute temperature

V2 = volume at point2

V1 = volume at point1

R = gas constant

S(V1 V2) = integral from V1 to V2

CHEMICAL ENGINEERING: Chemistry - Molecular weight, molar mass, molecular mass, moles, Avogadro's number, molecules


Molecular Weight (also called molecular mass or molar mass)

- is the sum of the atomic weights of all the atoms in a molecule.

- it has a unit of amu. One atomic mass unit (1 amu) is 1/12 the mass of the carbon-12 isotope, which is assigned the value 12.



water: H2O

1 molecule of water H2O = 2 atoms of hydrogen + 1 atom of oxygen

components:

2 H * 1 amu = 2 amu
1 O * 16 amu = 16 amu

MW of water = sum of components

MW of water = 2 amu + 16 amu

MW of water = 18 amu



dry air:

MW of air = 29 amu



Moles

A mole (mol) of any substance is the amount of that substance that contains Avogadro's number of atoms or molecules.  Avogadro's number is defined as the number of carbon atoms in 12 g of 12C.  It has a value of 6.022 x10^23 molecules/mol.

A mole of a substance is Avogadro's number of that substance.


n = N/Na

n = m/MW

m = n * MW


where:

n = number of moles

m = mass of substance

MW = molecular weight of substance

N = number of molecules

Na = Avogadro's Number, 6.022 x10^23 molecules/mol




Avogadro's Number

- the number of atoms needed such that the number of grams of a substance equals the atomic mass of the substance, 6.022 x10^23 /mol

- an Avogadro's number of substance is called a mole.

- for example, a mole of carbon-12 atoms is 12 grams, a mole of hydrogen atoms is 1 gram, a mole of hydrogen molecules is 2 grams




Units of molar mass --> g/mol

The most common unit of molar mass is g/mol because in that unit the numerical value equals the average molecular mass in units of u.



1 mole of Water H2O


average atomic mass of Hydrogen =  1 u

average atomic mass of Oxygen = 16 u

molecular mass of water = (2 * 1 u) + 16 u = 18 u

Thus,

1 mole of water has a mass of 18 grams.




Problem 1:

Ten kg of Carbon dioxide has a volume of 998 L at a pressure of 200 kPa. Determine the number of moles of CO2 present. 


find:

n = number of moles of CO2


given:

m = 10 kg = 10,000 g


solution:

Mw of CO2 = 12 + 2*16

MW of CO2 = 12 + 32

MW of CO2 = 44 g/mol


n = m/MW

n = 10,000 g/44 g/mol

n = 227.3 mol




Problem 2:

How many molecules are present in 5 moles of H2O?



find:

N = number of molecules


given:

n = 5 moles


solution:

n = N/Na

5 = N/6.022 x10^23

N = 5 * 6.022 x10^23

N = 30 x10^23

N = 3.0 x10^24 molecules

MECHANICAL ENGINEERING: Thermodynamics - Closed system, piston-cylinder, Boyle's law, Constant Temperature, Parabolic curve


CLOSED SYSTEM: piston-cylinder

conditions:

Temperature is constant, T = c


Boyle's law:  Absolute pressure is inversely proportional to the volume of a gas

pV = constant

pV = k

p1V1 = p2V2


curve: Parabolic


where:

p = pressure of the gas. p1, p2 are the pressures of the gas at points 1, 2

V = Volume of the gas. V1, V2 are the volumes of the gas at points 1, 2

k = constant


1. A certain gas in a piston is compressed to a volume of 12 L. Its original volume was 21 L at 10 bar. Find the new pressure if the temperature remains constant.


find:

p2 = pressure corresponding to the compressed volume


given:

V2 = 12 L

V1 = 21 L

p1 = 10 bar


solution:

p1V1 = p2V2

10 * 21 = p2 * 12

p2 = 210/12

p2 = 17.5 bar

MECHANICAL ENGINEERING: Thermodynamics - Atmospheric, Barometric, Gage, Absolute, and Vacuum pressure


Atmospheric pressure --> Patm

= 14.7 psi

= 101.325 kPa

= 760 mmHg

= 760 torr

= 29.92 inHg

= 1013.25 millibars

= 1.01325 bar


When gage pressure is above atmospheric:


Pabs = Patm + Pgage


When gage pressure is below atmospheric (vacuum):


Pabs = Patm - Pgage


where:

Pabs = absolute pressure

Pgage =  gage pressure

Patm = atmospheric pressure


1. An oxygen cylinder has a pressure of 2400 psig at 70 F. What is the absolute pressure of the oxygen inside?


find:

Pabs = absolute pressure of oxygen inside the cylinder


given:

Pgage = 2400 psig


solution:

gage pressure is above atmospheric:

Pabs = Patm + Pgage

Pabs = 2400 + 14.7

Pabs = 2414.7 psia



2. The gauge at the vacuum pump reads 7 in. of Hg. What is the absolute pressure?


find:

Pabs = absolute pressure at the vacuum pump


given:

Pgage = 7 inHg


solution:

gage pressure is below atmospheric (vacuum):

Pabs = Patm - Pgage

Pabs = 29.92 - 7

Pabs = 22.92 inHg


Thursday, November 8, 2012

MECHANICAL ENGINEERING: Pump work - work done by a pump in lifting a fluid


Wp = F * h


where:

Wp = pump work, the work done by the pump

F = weight of fluid

h = lifting height, measured from the centroid


1. Find the work needed to pump all the water in an 8-ft radius hemispherical tank to a height of 10 ft above the top of the tank.


find:

Wp = pump work


given:

Hemispherical tank (Centroid: y = 3/8 r)

D = Water Density = 62.4 lb/cu.ft

r = 8 ft

h1 = 10 ft


solution:

V = 2/3 pi * r^3

V = 2/3 * 3.14 * 8^3

V = 1072 cu.ft


F = D * V

F = 62.4 * 1072

F = 66,893 lb


h = h1 + yCentroid

h = 10 + 3/8 r

h = 10 + 3/8 (8)

h = 10 + 3

h = 13 ft


Wp = F * h

Wp = 66,893 * 13

Wp = 869,609 lb.ft

Thermodynamics - Specific heats at constant pressure, volume, Specific heat ratio, Gas constants


Specific heat

The ratio of the amount of heat required to raise the temperature of a unit mass of a substance by one unit of temperature to the amount of heat required to raise the temperature of a similar mass of a reference material, usually water, by the same amount.


Specific heat ratio

The specific heat ratio of a gas is the ratio of the specific heat at constant pressure, Cp, to the specific heat at constant volume, Cv. It is sometimes referred to as the adiabatic index or the heat capacity ratio or the isentropic expansion factor or the adiabatic exponent or the isentropic exponent.

For an ideal gas, the heat capacity is constant with temperature.


k = Enthalpy/Internal energy

k = H/U


Enthalpy

H = Cp * T


Internal energy

U = Cv * T


Specific heat ratio (k)

k = H/U

k = Cp * T/CV * T

k = Cp/Cv


Specific heat and Gas constant R

Cp = Cv + R

R = Cp - Cv



---Derivation---

Heating a gas at constant pressure increases the internal energy of the gas and Work is done, whereas supplying the same amount of heat at constant volume only increases the internal energy, no work is done.



constant pressure process:

du = dq - w

dq = du + w

w = pdV

dq = du + pdV


from ideal gas relations

pV = mRT


but at constant pressure

pdV = mRdT


thus

dq = du + mRdT ---> equation1


and

dq = m * cp * dT


equation1 becomes

m * cp * dT = du + mRdT ---> equation2





constant volume process:

du = dq - w


at constant volume, w = 0

w = pdV

w = p(v2 - v1)

but v2 = v1

w = p(0)

w = 0


du = dq + 0

du = dq

dq = m * Cv * dT

du = m * Cv * dT ---> equation3


equation3 in equation2

m * cp * dT = du + mRdT

m * cp * dT = (m * Cv * dT) + mRdT


factoring

(m * dT) (Cp) = (m * dT) (Cv + R)


(m * dT) cancels and thus leaving

Cp = Cv + R

Saturday, November 3, 2012

MECHANICAL ENGINEERING: Springs - connected in series, parallel


Hooke's law on springs:
Stretch is directly proportional to the Force

F = k S

where:

F = force applied

k = spring constant

S = stretch of spring




Springs connected in series



|
|               
|  
|-www-s1----www-s2----www-s3------> F
|               
|                
|                


S = s1 + s2 + s3



where:

S = total stretch of spring, equal to the sum of individual stretches of each spring s1, s2, s3

F = force applied 




Springs connected in parallel



|
|               
|   
|---wwww-k1----f1-|
|---wwww-k2----f2-|---> F
|---wwww-k3----f3-|
|               
|                
|                


if the springs are connected by a rigid bar, then

S = s1 = s2 = s3



sum of forces along x = 0; then 

F = f1 + f2 + f3


f1 = k1 * s1


where:

k1, k2, k3 = spring constants

S = total stretch of spring, equal to the sum of invidual stretches of each spring s1, s2, s3

F = force applied, equal to the individual forces on each springs

Thursday, October 25, 2012

Thermodynamics - Enthalpy, internal energy, pv work, saturated liquid, vapor, quality


Enthalpy
- a thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings.

- is the amount of energy in a system capable of doing mechanical work.


H = U + PV

H = m * Cp * dT

dH = dU + pdV + VdP

h = hf + (x)hfg

hfg = hg - hf


where:

H = enthalpy

U = internal energy

P = pressure

V = volume

m = mass

Cp = specific heat at constant pressure

dT = change in temperature

hf = specific enthalpy of saturated liquid

hg = specific enthalpy of saturated vapor

hfg = difference, hg - hf

x = quality



1. A steam turbine receives steam at a temperature of 500 C and pressure of 70 bar. If it expands isentropically to 0.1 bar, find the enthalpy after expansion.

find:

h2 = enthalpy after expansion


given:

at p1 = 70 bar and t1 = 500 C

we get from steam tables

h1 = 3410 KJ/kg

s1 = 6.796 KJ/kg K


at s1 = s2 (constant entropy) and 0.1 bar

sf = 0.649

sfg = 7.5


solving for x

s2 = sf + (x)sfg

6.796 = 0.649 + (x)7.5

x = 0.8196


now solve for h2

h2 = hf + (x)hfg

h2 = 192 + (0.8196)(2392)

h2 = 2152.2 KJ/kg



2. One pound of Water at 60°F is heated until it boils to 212 F. Calculate the change in enthalpy.

find:

dH = change in enthalpy


given:

m = 1 lb

t1 = 60 F

t2 = 212 F

Cp of water = 1 Btu/lb F


solution:

dH = m * Cp * dT

dH = 1 * 1 * (212 - 60)

dH = 152 Btu
 

Sunday, October 21, 2012

THERMODYNAMICS - First law of thermodynamics, conservation of energy, internal energy

First law of thermodynamics

- conservation of energy

- energy can be transformed or changed from one form to another

- energy can neither be created nor destroyed

- the increase in the internal energy of a system is equal to the amount of energy added by heating the system, minus the amount lost as a result of the work done by the system on its surroundings


dU = dQ - dW


dU = dQ - PdV


dU = TdS - PdV



where:

dQ = TdS

dW = PdV

dU = change in the internal energy of the system

dQ = heat added to the system

dW = work done by the system


sign convention of dQ and dW

(-) dQ < 0 if energy is lost from the system as heat

(+) dW > 0 if energy is lost from the system as work



1. Problem:

A cup of water (approx. 250 ml) is heated from 25 to 100 C. Find the change in internal energy for the cup of water?



find:

dU = change in internal energy of the cup of water


given:

V = 250 mL ---> a cup of water

t1 = 25 C

t2 = 100 C ---> boiling point of water


Solution:

Cp of water = 4.2 J/g C

Density of water = 1 g/mL


m = D * V

m = 1 g/ml * 250 ml

m = 250 g


dU = m * Cp * dT

dU = 250 * 4.2 * (100 - 25)

dU = 250 * 4.2 * 75

dU = 78,750 J or 78.75 kJ


Thus, to boil a cup of water,

it requires approximately

80 kJ

Monday, October 15, 2012

Thermodynamic Processes



Adiabatic process

- deflating a tire by releasing a valve and the valve stem will become quite cold during the process
- perfectly insulated containers
- thermally insulated wall
- sound propagation
- compressions and rarefactions of a sound wave
- adiabatic expansion of gas
- Hot air near the ground rises to the region of higher altitude,
where the pressure is lower, and expands. The process is adiabatic because
air is a poor heat conductor.
- events inside an engine cylinder are nearly adiabatic because the wide fluctuations in temperature take place rapidly
- fluid flow through a nozzle is fast and very little heat exchange between fluid and nozzle


isentropic process

An adiabatic process that is reversible

- air inside the tire expanding adiabatically
- rapid depressurization of gas in a cylinder

isenthalpic process

an adiabatic process that is irreversible and extracts no work

- Helium expanding across a valve in which the helium generally will increase in temperature
- air expanding across a valve
- throttling process: an ideal gas flowing through a valve in midposition
- viscous drag


Polytropic Process

a reversible process in which there is heat transfer

plot of the Log P (pressure) vs. Log V (volume) is a straight line.

Or stated in equation form PVn  = a constant.  


- expansion of the combustion gasses in the cylinder of a water-cooled reciprocating engine
- vapors and perfect gases in many non-flow processes


Steady flow

Fluid flow in which all the conditions at any one point are constant with respect to time.
Fluid flow without any change in composition or phase equilibria
 flow velocities do not vary with time

- groundwater and channel flows
- turbine   
- fluid heater
- orifice(throttling)
- nozzle


Non flow


- Heating at constant volume

- Adiabatic expansion in a cylinder

- Free Expansion (Joules experiment - valve is initially closed and then opened to equalize pressures)

- Heating a fluid in a cylinder at constant pressure


===========================

Important thermodynamic processes

===========================


Isobaric process

An isobaric process is a thermodynamic process in which the pressure remains constant

From the Greek isos, "equal," and barus, "heavy"


Examples of isobaric process

- movable piston in a cylinder

- boiler superheater, as the heat of the exiting steam is increased



Isochoric process

An isochoric process is a process during which volume remains constant.

From the Greek isos, "equal", and khora, "place."

An isochoric process is also known as an isometric process or an isovolumetric process.


Examples of Isochoric process

- heating air in closed tin can

- instantaneous burning of the gasoline-air mixture in an internal combustion engine

- heating a gas inside a rigid, closed box



Isothermal process

Isothermal process is a thermodynamic process in which the temperature remains constant

From the Greek words isos meaning "equal" and therme meaning. "heat" or thermos meaning "hot."


Examples of isothermal process

- system immersed in a large constant-temperature bath

- most reactions of an acid and base mixed together to form a salt

- melting and boiling

- living cell processes

- cycles of some heat engines

- sealed syringe




Adiabatic process

An adiabatic process or an isocaloric process is a thermodynamic process in which no heat is transferred to or from the working fluid.

From Greek adiabatos, impassable: a-, not; diabatos, passable


Examples of adiabatic process

- deflating a tire by releasing a valve and the valve stem will become quite cold during the process

- perfectly insulated containers

- thermally insulated wall

- sound propagation

- compressions and rarefactions of a sound wave

- adiabatic expansion of gas

- Hot air near the ground rises to the region of higher altitude,
where the pressure is lower, and expands. The process is adiabatic because
air is a poor heat conductor.

- events inside an engine cylinder are nearly adiabatic because the wide fluctuations in temperature take place rapidly

- fluid flow through a nozzle is fast and very little heat exchange between fluid and nozzle



Isentropic process

An isentropic process is one during which the entropy of working fluid remains constant. In other words there is no heat transfer with the surroudings, and no change in entropy.

An adiabatic process that is reversible

From Greek word "iso" -same and "entropia" -a turning towards (disorder)


Examples of isentropic process

- air inside the tire expanding adiabatically
- rapid depressurization of gas in a cylinder




Isenthalpic process

An isenthalpic process or isoenthalpic process is a process that proceeds without any change in enthalpy

The process will be isenthalpic if there is no transfer of heat to or from the surroundings, no work done on or by the surroundings, and no change in the kinetic energy of the fluid.

An adiabatic process that is irreversible and extracts no work

From en-, meaning "to put into" and the Greek word -thalpein, meaning "to heat"


Examples of isenthalpic process

- Helium expanding across a valve in which the helium generally will increase in temperature

- air expanding across a valve

- throttling process: an ideal gas flowing through a valve in midposition

- throttling process: the lifting of a relief valve or safety valve on a pressure vessel (the specific enthalpy of the fluid inside the pressure vessel is the same as the specific enthalpy of the fluid as it escapes from the valve)

- viscous drag




Polytropic Process

A reversible process in which there is heat transfer

The plot of the Log P (pressure) vs. Log V (volume) is a straight line

PV^n  = constant

From Greek poly = many, -tropic = bend, curve, turn

  
Examples of polytropic process

- expansion of the combustion gasses in the cylinder of a water-cooled reciprocating engine

- vapors and perfect gases in many non-flow processes

- Compression or Expansion of a Gas in a Real System such as a Turbine



Steady flow process

Fluid flow in which all the conditions at any one point are constant with respect to time

Fluid flow without any change in composition or phase equilibria

Flow velocities do not vary with time


Examples of steady flow process

- groundwater and channel flows

- turbine   

- fluid heater

- orifice(throttling)

- nozzle



Non flow process

A thermodynamic process involving no fluid flow


Examples of non-flow process

- Heating at constant volume

- Adiabatic expansion in a cylinder

- Free Expansion (Joules experiment - valve is initially closed and then opened to equalize pressures)

- Heating a fluid in a cylinder at constant pressure