Two kilograms of air is stored in a rigid volume of 2 m3 with the temperature initially at 300°C. Heat is transferred from the air until the pressure reaches 120 kPa. Calculate the entropy change of (a) the air and (b) the universe if the surroundings are at 27°C.

Find the general solution for the following ODEs. If initial condition is given, solve the initial value problem.

3) (D^4 − 13D^2 + 36I)y = 12e^x

4) (D^3 − D^2 − D + I)y = 0, y(0) = 0, Dy(0) = 1, D^2y(0) = 0

Q.3) Suppose (y, z) plane forms the boundary between a nonconducting linear
medium (1) and a conducting medium (2). A monochromatic plane wave traveling
in the x direction and polarized in the y direction approaches the interface from the
left direction.
i) Draw the diagram for this case by indicating the directions for incident, reflected
and transmitted electric and magnetic fields along with the propagation direction.
ii) Calculate the reflection coefficient R and transmission coefficient T and
show that R+T=1?

A straight cylindrical pipe (içi boş boru) lying along the x axis has a length of L and inner diameter of R1 and outer diameter R2. It is made of a material with a resistivity of ρ. Assume that a potential of Vo is applied at x = L, and the potential V = 0 at x = 0. Find (a) the electric field E in the wire as a vector, show the current direction. (b) find the current density J in the wire c) Calculate the magnetic field everywhere. Show and explain every step by using Ampere’s Law. d) Calculate the amplitude of Poynting vector in the wire.

Acetylene gas (C2H2) with 20% excess air, fully in continuous regime
incinerated. Air and fuel, separate to the combustion chamber, separate temperature of 250C and 1 atm
under pressure and under reaction, 300,000 to the environment at 250C
kJ / kmol C2H2 is experiencing heat transfer. Combustion end products, combustion chamber 1 atm
leaves the pressure.
a) The end of combustion here means the temperature,
b) Total entropy change for 1 kmol of C2H2,
c) this reaction exergy destruction (usability loss)
You calculate.

The net power of a steam power plant operating according to the simple ideal Rankine cycle is 30.5 MW. Water vapor enters the turbine at 7 MPa pressure and 500 ° C, expands to 10 kPa condenser pressure in the turbine. The steam is condensed in the condenser by cooling it with water from a lake. The flow rate of the lake water is 1950 kg / h. Get the pump and turbine adiabatic efficiency of 87%. Show the cycle in the T-s diagram.

C_water=4.18 kJ/kg°C

a) Calculate the thermal efficiency of the cycle,

b) Flow rate of the steam circulating in the cycle,

c) Calculate the temperature rise of the coolant.

Refrigerant R-134a enters the compressor of a refrigeration machine at 140 kPa pressure and -10 ° C temperature and exits at 1 MPa pressure. The volumetric flow of the refrigerant entering the compressor is 0.23 m3 / minute. The refrigerant enters the throttling valve at 0.95 MPa pressure and 30 ° C, exiting the evaporator as saturated steam at -18 ° C. The adiabatic efficiency of the compressor is 78%. Show the cycle in the T-s diagram. In addition,

a) the power required to start the compressor,
b) Heat drawn from the cooled medium per unit time, COP_SM =?

c) Calculate between the evaporator and the compressor, how much the pressure of the refrigerant drops and how much the heat gain is.

The pressure ratio of a Brayton cycle with air operated regenerator is 8. The lowest and highest temperatures of the cycle are 310 K and 1150 K. The adiabatic efficiency of the compressor and turbine is 75% and 82%, respectively, and the efficiency of the regenerator is 65%. Show the cycle in the T-s diagram. Consider the variation of specific temperatures with temperature.

a) Calculate the temperature of the air at the turbine outlet,

b) Net work of the cycle,

c) Calculate the thermal efficiency of the cycle.

a=2 b=1

A bullet is to be tested in the laboratory to determine the drag force on it. Dependent parameter the drag force D (Newton) depends on the velocity of the bullet V(m/s), the length of the bullet L(m), sound velocity c(m/s), density of fluid ρ (kg/m³) and dynamic viscosity µ(kg/ms).

Solve the problem by making the necessary assumptions and drawing the schematic figure

I-Determine the nondimensional p parameters using repeating variables

ii-a bullet with a speed of 9a,b m/s in air may be modelled in a water tunnel with a test section velocity of 2ab cm/s. Determine the length of the model, if the length of the bullet is 5a,b mm. The air and water temperature is 20 ^oC degree at 1 atm.

iii- if the drag force on the model is measured to be 2,ab N, then determine the expected drag force on the bullet. Comment on dynamic similarity equivalence?

The compression ratio of an ideal air-powered Diesel cycle is 20. At the beginning of the compression process, the pressure of the air is 100 kPa, the temperature is 20 ° C, and the highest temperature of the cycle is required not to exceed 2250 K. Show the cycle in the P-v diagram. Accept specific temperatures constant at room temperature.

k=1.4 CP=1.005 kJ/kgK CV=0.718 kJ/kgK R=0.287 kJ/kgK

a) Calculate the temperatures entering and leaving the cycle, the thermal efficiency of the cycle,

b) Calculate the average effective pressure of the cycle.

Vibration absorbers are used in railroad cars to protect sensitive loads from large acceleration due to periodic excitation given by rail links. For certain trains, the rail connection is 5 m. The car, when empty, has a mass of 25,000 kg. Two vibration absorbers are used, each having a mass of 12,000 kg. Absorbers for certain cars are designed to remove vibrations from the main mass when the car is loaded with 12,000 kg of cargo and moves at 100 m / s. The personal frequency of the uncarried carriage is 165 rad / s.

(a) At what speed will resonance occur in cars with a load of 12,000 kg?

(b) What is the best speed for carriages when loaded with 25,000 kg of cargo?

You are invited to give a talk to SPM students who wish to choose their future career in engineering field. As a young engineer graduated from UPNM, you are being selected to give a short introductory speech on the profession of Mechanical Engineer to the students. Write a short outline of the speech which should cover the following topics; explanation of engineering, mechanical engineering, profession, professionalism, attributes and their roles to the society.

A 6.2-mm-diameter electrical transmission line is exposed to windy air. Determine the drag force exerted on a 165-m-long section of the wire during a windy day when the air is at 1 atm and 15°C and the wind is blowing across the transmission line at 65 km/h.

The density and kinematic viscosity of air at 1 atm and 15°C are ρ = 1.225 kg/m³ and ν = 1.470×10^-5 m²/s.

_____ N

Course : Heat Transfer

question 3

a-) In heat transfer by radiation, describe the swallowing,reflection, passing coefficients, write down the relation between them.

b-)Write the expression radiative heat transfer between two surfaces with different areas in a closed volume.

Show that 2D potential flows satisfy Euler’s equations even if μ ≠ 0.