Review of thermodynamics applied to flow — first law for open systems: Foundations

3.1.1 · D1 · Physics › Compressible Flow & Aerodynamics › Review of thermodynamics applied to flow — first law for ope

Is page pe assume kiya gaya hai ki aapne parent note ki koi bhi notation pehle nahi dekhi. Hum har symbol ek picture se build karenge, ek aisa order follow karte hue jahan har symbol sirf unhi symbols pe depend karta hai jo pehle aaye hain.

1 — Stage: kya "flows" karta hai aur kahan

Boundary draw karne ke do tarike hain, aur poora topic unhi ke difference ke baare mein hai.

Figure — Review of thermodynamics applied to flow — first law for open systems

Yeh topic kyun zaroori hai: energy ka reliable law jo hamare paas hai woh closed systems (fixed matter) ke liye likha gaya hai. Lekin nozzle ek open system hai. Parent note ka poora trick yeh hai ki ek closed lump ko open region ke through follow karo, phir translate karo. Derivation ko samjhe bina dono pictures ek saath hold nahi kar sakte. Closed version ke liye jo hum se start karte hain, Closed-system first law of thermodynamics dekho.

2 — Mass aur woh kitni tez flow karti hai

3 — Pressure, volume, aur "volume" ke do flavours

4 — Energies jo ek fluid parcel carry karta hai

Har travelling parcel ek "backpack" mein teen pockets mein energy laata hai. Hum har cheez per kilogram measure karte hain (yahi "specific" ka matlab hai) taaki kisi bhi size ke parcels fairly compare ho sakein.

5 — Gift-wrap: enthalpy

Yeh hai woh punchline jiske around poora topic built hai.

6 — Heat aur work jo boundary cross karte hain

7 — Steadiness aur stopped-flow idea

8 — Perfect-gas shortcut

Prerequisite map

Ise bottom-right se padho: pressure aur volume flow work banate hain; flow work plus internal energy enthalpy banate hain; enthalpy plus moving/lifting energies, steady flow ke andar closed-system law mein feed hokar, SFEE banti hain; ise specialise karo aur stagnation relation bahar aata hai.

Equipment checklist

Khud ko test karo — right side cover karo aur reveal karne se pehle jawab do.

Kisi symbol pe dot (jaise

\overset{m}{˙}

mein) ka kya matlab hai?

"Per second" — ek rate of flow, e.g. kilograms jo har second ek face cross karte hain.

Closed aur open system mein kya difference hai?

Closed = matter ka fixed lump, boundary uske saath move karti hai (koi mass cross nahi karta); open = space ka fixed region, mass boundary ke through stream karta hai.

Specific volume

v

kya hai?

Fluid ke ek kilogram ke by occupied volume (m

^{3}

/kg); density ka reciprocal.

V

aur

v

mein distinguish karo.

Capital

V

= bulk flow speed (m/s); lowercase

v

= specific volume (m

^{3}

/kg). Unrelated quantities.

Flow work

p v

geometrically kahan se aata hai?

Force

p A

times distance

L

— volume

v = A L

ke ek kilogram-slug ko ek face ke across push karne ke liye — deta hai

p v

Enthalpy kya hai aur ise kyun define kiya jaata hai?

h = u + p v

; yeh internal energy ko boundary pe unavoidable flow work ke saath glue karta hai, taaki open-system energy balances clean rahein.

q

aur

w_{s}

ke liye sign convention kya hai?

q > 0

= heat added;

w_{s} > 0

= shaft work out (turbine positive, compressor negative).

Ek parcel ke energy backpack mein teen pockets kaunse hain?

Internal

u

, kinetic

\frac{1}{2} V^{2}

, potential

g z

Stagnation enthalpy

h_{0}

kya represent karta hai?

Woh enthalpy jo flow ke paas hoti agar use adiabatically rest pe laaya jaaye:

h_{0} = h + \frac{1}{2} V^{2}

Perfect gas ke liye enthalpy aur temperature ka kya relation hai?

h = c_{p} T

, toh temperature enthalpy ki direct read-out hai.

Connections

Closed-system first law of thermodynamics
Conservation of mass — continuity equation
Stagnation properties & isentropic relations
Speed of sound and Mach number
Bernoulli equation as low-speed limit of SFEE
Nozzles and diffusers