CHE 302

Thermodynamics I

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Molecular weights:

Molecular weights:

• 3..Find molecular weight of Aspirin:

C9H8O4

• 4..Find molecular weight of penicillin:

C16H18N2O4S

Temperature conversion

• 1.. Today is 94oF, what is it in Rankine (oR)?

• In Kelvin (K), and in Celsius (oC)?

• 2.. -195oF (at night on Mars) is how many

Kelvin? Degrees oC?

• 3..In a Carnot engine, the high temperature is

975 oC, and low temperature is 20 oC; what is

its thermal efficiency, η?

Che 302

Thermodynamics I

QUIZOJE

1. Calculate the electrical work

• 1.. Electrical work

• Formula: W = ʃ VedQe

• What work (in J) is performed when delivering

a charge Qe of 0.35 Coulomb through a

constant voltage Ve of 23 Volts?

• Note: units 1 Coulomb * 1 Volt = 1 Joule

2. Calculate the surface work

cm2

3. Converting lbm to lbf!

Calculate the work in ft-lbf!

ʃ f ds

CHE 302

Thermodynamics I

QUIZ

OJG

4. Do the same calculation as 3.

• Mass of block is now

• 909.1 kg

• Distance moved

• 16.16 m.

• Find the work in Joule.

• Convert the Joules to ft-lbf.

OJG

QUIZ: OJG

• Calculate the volume (in liter) of air (assuming

ideal gas, i.e. PV=nRT) at T= 70oF, and P = 1

atm for one lbmol.

• Calculate the temperature of nitrogen (ideal

gas) at 20 psia and 102 cuft/lbmol.

• Calculate the specific volume (m3/kmol) of

CO2 (ideal gas) at 0.012 bar and -195oF.

OJG

QUIZ• Air is contained in a vertical piston–cylinder

assembly by a piston of mass 50 kg and having

a face area of 0.01 m2. The mass of the air is 5

g, and initially the air occupies a volume of 5

liters. The atmosphere exerts a pressure of

100 kPa on the top of the piston. The volume

of the air slowly decreases to 0.002 m3 as the

specific internal energy of the air decreases by

260 kJ/kg. Neglecting friction between the

piston and the cylinder wall, determine the

heat transfer to the air, in kJ. OJG

QUIZ• (1) Read the steam tables:

• For steam at

• T = 520 oC

• P=200 bar

• Find its specific volume, v (m^3/kg),

• Enthalpy h (kJ/kg), and internal energy (kJ/kg).

• (2) Read the Mollier chart for steam at

• T= 950oF

• P= 3000 psia

• Find its enthalpy h= Btu/lbm

• (3) Convert the h from (2) to units kJ/kg)

OJL

QUIZ:

• Evaluate the heat capacity Cp (cal/(gmol.K) of

nitrogen

• At T= 298 K

• (a) using Book formula, (Table A.21, p.852) &

• (b) using new formula!

New Heat Capacity expression:(used by API*)

For N2: [ Cp* in cal/(gmol.K)]

B=6.95808, C=2.03952, D= 1681.60, E=0.506863, F=6535.68

*American Petroleum Institute

Table A.21 (p.852)

QUIZ

• For ethane at T= 922K, and volume

v=0.188m3/kmol, find its pressure P (bar).

• Use

(1) ideal gas,

• (2) van der Waals,

• (3) Redlich-kwong equations. Also

• (4) the compressibility chart!

Winnick: p.95-96 eg.4.3a

[470bar]

Tc= 305K

Pc= 48.8 bar

QUIZ

• For 2.77 kmol of CO2 at 102 atm, volume is 1

m3, find its T in Kelvin.

• Use

(1) ideal gas,

• (2) van der Waals,

• (3) Redlich-Kwong equations. Also

• (4) the compressibility chart!

OJO

Winnick: p.97-98 eg.4.4

487K.

• Use

• vR’ = v (Pc/RTc)

• And Figure A-1

Fig. A1. Generalized Z-Chart

Three equations of State

• Ideal Gas

• Van der Waals (vdW)

• Redlich-Kwong (RK)

QUIZ• For ammonia at T= 60oF, and volume v =7.9134

ft3/lbm, find its pressure in psia.

• Use (i) ideal gas, and

• (2) van der Waals, and

• (3) Redlich-Kwong

• Tc = 730oR

• Pc= 111.3 atm

• 1 lbmol NH3 = 17 lbm , 1 atm = 14.7 psia

• R = 0.7302 atm.ft3/(lbmol.oR)OJT

Ammonia

• Expt. P= 40 psia (Table A-15E) p.891

OJL

QUIZ: Calculate enthalpy

• Steam at P= 5 bar, T= 360oC, v= 0.5796 m^3/kg,

• and u = 2898.7 kJ/kg.

• Use the formula

• H = U + PV

• h = u + P v

• To calculate H (kJ/kg). OJS

From steam table:

• .h = 3188.4 (kJ/kg)

OJZ

QUIZ: Velocity of sound

• Mars atmosphere is mostly CO2. Its heat

capacity ration Cp/Cv =~ 1.3. Find its velocity

of sound, c (m/s), at 250K. (Assuming ideal

gas for CO2).

OJb

QUIZ:OKL

Find h2 (Btu/lb), also quality if P2=14.7 psia.

Quiz: Use the vdw & RK Equations of State to

calculate the entropy, S OKR

• Steam at T1 = 400 oC and P1 = 40 bar has entropy, s = 6.7690 kJ/(kg.ΔoC), find

the entropy s kJ/(kg.ΔoC), at P2 = 100 bar (at same T2=400oC).

• Note: v1= 0.07341 m3/kg, v2= 0.02641 m3/kg (Convert to molar!)

Use (a) van der Waals equation: a= 5.531, b=0.0305 (vdW),

•

(b) Redlich-Kwong equation: a= 142.59, b= 0.02111 (RK)

QUIZ: Air as Ideal Gas:

Expansion

OKR

• Air as an ideal gas expands adiabatically and

reversibly from P1= 40 psia, v1= 20 ft3/lb to P2

= 15 psia. What is its volume v2 (ft3/lb). Use

the polytropic equation with k = 1.4.

• Also calculate its initial temperature T1 (oR)

and final T2 (oR). (MW = 29).

Quiz: Otto Cycle Efficiency:

“Hot” and “Cold” Processes OKS

• For a compression ratio rc = v1/v2 =8, find the

thermal efficiency: η.

• (a) Cold process

• (b) Hot process:

• Use T1 = 300K. Find vr1 and vr2.

• Then T2.

Quiz: Otto Cycle OKWX

• (a) For an Otto cycle with compression

ratio rc = v1/v2 =8, find the temperature T2

(K) and pressure P2 (bar) after the

compression stroke using the “hot” air-

standard cycle. Also obtain h2 (kJ/kg), and

u2 (kJ/kg).

• Input: T1= 290K, P1= 1 bar, v1 = 400 cm3.

• (b) For same inputs, find T2 by the “cold”

air-standard cycle.

Quiz: Brayton Cycle in air-standard cycle OKY

• (a) For a Brayton cycle with pressure ratio

rp = P2/P1 =14, find the temperature T2

(oR) and pressure P2 (atm) after the

compressor (Stroke 1-2) using the “hot”

air-standard cycle. Also obtain h2 (Btu/lb).

• Input: T1= 520oR, P1= 1 atm, v1 = 0.015 ft3.

• (b) Calculate the amount of air in (lbm).

• (c) For the same inputs, find the

temperature T2 and the thermal efficiency

η in a “cold” air-standard cycle.

End