Extras din notiță
1. intro in engineering thermodynamics
1.1.Energy – measures the quantity of motion; in e.t. a great interest
is how to transform the energy from a form to another
1.1.1 Heat and Work – both are energy transfer forms; occur in an interaction;
Heat is the energy transfer form due to the interaction bet 2 bodies at dif temp.;
the driving force is Work is the energy transfer form due to the mechanical
interaction bet 2 bodiesin mechanics: displacement of the body; in thermod: p
1.2.Thermody. system – it’s an assembly of bodies that interact bet them and
the surroundings by heat, work and substance transfer Q,W,m; types: opened sys:
the exchange of Q,W,m occurs; closed sys:just Q,W; isolat adiab: W,m?, isol: none;
1.3. Equil state – the sys is in equil when there is the same pressure and temp;
thermal equil(same T);mechanical(same p);internal(inside);external (at the border)
1.4. Thermo. Parameters – characterize the energetic state of a sys in equil;
a) intensive param: don’t dep on the mass of the sys; p,T –can be measured;
b) extensive p: dep on the mass – can be measured; volume V[m3]=m[kg]v[m3/kg];
internal energy U[J]=m[kg]u[J/kg];enthalpy H[J]=m[kg]h[J/kg];
entropy S[J/K]=m[kg]s[J/kgK]1.5. Thermal eq of state – a relation bet several param;
gen we have 2 deg of freedom f(p,V,T)=0
1.6. Thermod process – the passing of the sys from several intermediary equil
states (initial -> final state); if final st=init st => closed process or cyclic one; if not =>
opened process; types: isometric process (V=ct); isobaric(p=ct) isothermal (T=ct);
adiab (´Q=0) w.r.t. keeping a param const; wrt the time: steady state regim
Law of the perfect gases
Boyle – Mariotte
At T=ct. the volume of perfect gas varies inverse prop
with its pabsolute ; T=ct. ópV=ct. or pv=ct. for m=1kg;
v=V/m [m3/kg] v=1/Á[kg/m3] isometric –
Gay - Lussac law
Isobaric p=ct. V of the p. gass
Varies prop with its T
deg-1
=> dilatation coef
other forms:
c=a+bt; c-mass specific heat
if v=0 => t=-1/±=-273.15 C;
T= [K]
V/Vo=T/To => V/T=ct. for m=1kg => v/T=ct. specific vol.
The normal state
-the technical state: po=760mmHg to=20C
-the physical state: pN=760mmHg TN=273.15K
def: 1 normal cubic meter=the quantity of gas which
occupies V=1m3 in normal state cond (1m3N)
Avocadro Law: same v of diff p.g., in same p,T cond.
Contain same no of molecules. NA=NB
Chemistry knowledge: 1.molecular mass of a subst:
Nondimensional no. which shows how many times is
the molecule’s mass wrt the 12th part of molecule
mass C12 ex: MO2=32[-]; 2.kilomol – a quantity of
subst. ginven in kg= molecular mass; ex: 1kmol O2=
32 kg O2 3.molecular mass=the equiv o a kmol in kg
MO2=32[kg/kmol]
The conseq of Avocadro: C1: molar vol of gases
Let A,B gases: nA=NA*¼A nB=NB*¼B - ¼A,¼B-molecule mas
nA/nB =NA*¼A/NB*¼B=¼A/¼B=(¼A/(¼C12/2))/(¼B/(¼C12/2))=
MA/MB=(mA/VA)/(mB/VB)=ÁA/ÁB=vB/vA=>MA vA =MBvB ó
At same p,T - Mv is the same for all perfect gases
M[kg/Kmol]v[m3/kg]=Mv[m3/Kmol]=VM- molar volume
óVMA=VMB if pA=pB TA=TB=>at same p,T - VM is the same
for all p.g.; C2: No. of Avogadro – in one kmol of gas the
no. of molecules is the same NA6.023*1026molec/kmol
C3: universal constant of gases; let A,B gases => at
Preview document
Conținut arhivă zip
- Thermodinamics
- 1.doc
- 10.doc
- 11.doc
- 12.doc
- 13.doc
- 14.doc
- 15.doc
- 16.doc
- 17.doc
- 18.doc
- 19.doc
- 2.doc
- 3.doc
- 4.doc
- 5.doc
- 6.doc
- 7.doc
- 8.doc
- 9.doc
- lab_uri.doc