Thermodynamics - Quiz questions

Question 1

Definition of work

Answer 1

Energy transfer due to movement

Question 2

How to calculate heat transfer in a steam closed system

Answer 2

Area under a P-V diagram

Question 3

What is the power produced by an open system without KE or PE

Answer 3

Heat input rate minus the rate of enthalpy change

Question 4

What is the first law of thermofluids

Answer 4

Heat in minus work out = change in internal energy

Question 5

What is used to calculate work in a closed system

Answer 5

Volume and pressure before and after and polytropic constant

   P1V1 - P2V2 W = -----------------
          n - 1

Question 6

Definition of heat

Answer 6

Energy transfer due to a temperature difference

Question 7

Definition of Reynolds number

Answer 7

The ratio of viscous to dynamic force

Question 8

Equation to calculate Reynolds number

Answer 8

ρ * C * d
Re = —————–
μ

Question 9

What happens to volumetric flow fate if diameter of the pipe is doubled

Answer 9

2^4 = 16 times greater

. (P2-P1)πd^4
V = ———————
128μl

Question 10

What is Newtons law of viscosity

Answer 10

du
τ = μ* ——-
dy

Question 11

Equation which describes laminar flow between parallel plates, where one is moving

Answer 11

U
u = y* ——-
Y

Question 12

If the pipe length is doubled, what happens to the volumetric flow rate

Answer 12

halved

. (P2-P1)πd^4
V = ———————
128μl

Question 13

Equation describing the volumetric flow rate between stationary plates

Answer 13

. bc^3(P2-P1)
V = ———————
12μl

Question 14

Equation describing the volumetric flow rate for laminar flow in a pipe

Answer 14

. (P2-P1)πd^4
V = ———————
128μl

Question 15

At what reynolds number does laminar turn into turbulent flow in a long straight pipe

Answer 15

2200

Question 16

At what reynolds number does laminar turn into turbulent flow over a wing

Answer 16

300,000

Question 17

What is assumed in Bernoulli’s equation

Answer 17

• Incompressible flow
• inviscid flow
• 1 direction flow
• steady state flow
• no pressure losses

Question 18

What is assumed in the continuity equation

Answer 18

• Incompressible flow
• 1 direction flow
• steady state flow

Question 19

Under which of these does Bernoulli’s equation hold:

• across a fan
• through a valve
• uphill
• when viscosity is low

Answer 19

Uphill

Question 20

Is mass flow rate, or volumetric flow rate preserved

Answer 20

mass flow rate

Question 21

If two flows at 1m/s combine into one flow. Where the second pipe is double the diameter of the first, what is C2?

Answer 21

C2 = C1 / 2 = 1/2 m/s

Question 22

Definition of minor pressure losses

Answer 22

All the loses that are not due to pipe friction

Question 23

Definition of major pressure losses

Answer 23

Pressure losses due to pipe friction

Question 24

Meaning of the reynolds equation

Answer 24

Inertia force / Viscous force

found in LBOTF

Question 25

Pressure loss coefficient for 2 sharp 90degree and 1 gradual 90degree bend

Answer 25

K = 2(1) + 1(0.2) = 2.2

found in LBOTF

Question 26

Pressure loss coefficient for sudden expansion to twice the diameter

Answer 26

K = (1 - A1/A2)^2 = (1 - 0.25)^2 = 0.5625