A urethane elastomer is selected as an artificial heart valve material. You wish to calculate the maximum theoretical strain (strain endurance limit) the material can withstand forever. This material has a threshold fracture resistance of 50 J/m^2 based upon its crosslink density, its intrinsic flaw size is 50 micron, and its tensile modulus is 1 MPa.

Q4. State whether the following are true or false with a brief explanation (1-2 sentences).

(i) Given a control volume with one inlet and two exits, the two exits must have identical mass flow rates.

(ii) You are given a control volume with one inlet and one exit such that more ‘mechanical energy’ is coming in than going out (‘mechanical energy’ is the sum of enthalpy, kinetic energy and potential energy per unit mass), but are given no information on the work or heat interactions. The total energy (Ecv) within the control volume must increase with time.

(iii) You are given a control volume where the mass is changing with time but the control volume itself has no heat or work interactions with the surroundings. The total energy within this control volume must also change with time.

(iv) For a one-inlet, one-exit control volume at steady state, the volumetric flow rates must be equal at the inlet and the exit.

(v) An open control volume (i.e., with inlets and exits), by definition, always describes the same region and therefore, the specific volume of matter inside cannot change.

A shell and tube type of heat exchanger with one shell pass and two tube passes will be designed to provide the given heat transfer rate Q(kW) to cool hot water by using cold river water . The hot water flows through the shell and the cold water flows through the tubes. The inlet and outlet temperatures of the hot water and the cold water are given as Thi, The and Tci, Tce in degrees Celcius. Design the shell and tube heat exchanger by making necessary assumptions to calculate the dimensions of the heat exchanger. Q= 10 KW Hot Fluid( Water) Thi= 70 Celcius The= 40 Celcius Cold Fluid ( Water) Tci= 5 Celcius Tce= 15 Celcius 1) Assume the tube diameter and tube length . 2) Assume fouling coefficient based on inside and outside tubes, hdi and hdo . 3) Select the material of construction for the tubes to determine the thermal coefficient. 4) Find the Log Mean Temperature Difference (LMTD) . 5) Obtain the Correction Factor F. 6) Calculate the Mean Temperature Difference. 7) Assume the Overall Heat Transfer Coefficient “U” as initial guess according to type of heat exchanger. 8) Calculate the provisional area. 9) Calculate the number of tubes based on the assumed tube diameter, thickness of the pipe and tube length L. 10) Calculate the tube pitch and bundle diameter.

A fuel consists of a mixture of gases the composition of which is CO -20%, C2H2 - 35%, H2 45 % by volume. Determine the stoichiometric air-to-fuel ratio by mass. (10.6)

In a vertical high temperature wall with high prandtl number,write down the governing equation for natural convection outside the wall. Using scale analysis of the governing equations, estimate the ratio of hydrodynamic and thermal boundary layer thickness?

bending moment of 4 kN m is found to cause elastic failure of a solid circular shaft. An exactly similar shaft is now subjected to a torque T. Determine the value of T which will cause failure of the shaft according to the following theories:
(a) Maximum principal stress;
(b) Maximum principal strain;
(c) Maximum shear strain energy. ?= 0.3.)
Which of these values would you expect to be the most reliable and why?

A horizontal shaft of 75mm diameter projects from a bearing and, in addition to the torque transmitted, the shaft carries a vertical load of 8 kN at 300 mm from the bearing. If the safe stress for the material, as determined in a simple tension test, is 135 MN/m2 find the safe torque to which the shaft may be subjected using as a criterion
(a) The maximum shearing, stress,
(b) The maximum strain energy per unit volume.
Poisson’s ratio ? = 0.29.

Describe the common characteristics and mechanical properties associated with aluminum.

A nuclear power plant is planned to be constructed near Sydney. The plant is required to have an installed capacity of 1200 MW and will be operated for 7500 hours per year. Consider providing 1200 MW of energy by two solar power plants; one in Sydney and the other in Canberra. It is required that a fixed solar module be mounted. Determine the following parameters if the overall efficiency of the module is given as 15%:

a) The peak power of the solar generator at each site.
b) The total solar generator area for each site.
c) The amount of land area required at each site.
d) Discuss any technical, environmental, operational and financial implications of using solar power modules at the two sites.

Why is the moment at leading edge(LE)=-c/4 times lift + moment at c/4=-position of center of pressure times lift? The equation shows like this MLE=-c/4*L+Mc/4=-xp*L. Because moment of leading edge and moment at center of pressure or moment at c/4 they always act on the wing but why they equal to each other but not like sum them up? Also, what is neutral point? Is neutral point always change in different situations like flying with different angle of attack? And why the derivative of moment at c/4 of time(d(Mc/4)/dt)=0? Is it because moment at c/4 always constant? Thank you so much

what will be the impact towards society, health,safety and environment if the engineer used diameter of discharge line more than the minimum diameter?

In a pharmaceutical application distilled water with a flow rate of 34560 kg/hr is to cool ethyl alcohol in a parallel flow heat exchanger. The alcohol flowing at 31320 kg/hr enters the exchanger at 75oC and is cooled to 45oC. Assuming that the water flows through the tubes and enters the exchanger at 15oC, determine, for an overall heat transfer coefficient of 0.5kW/m2K the dissipation rate, together with the required heat transfer area. The specific heat capacity of both the alcohol and water is 3.84 and 4.181kJ/kgK

a)

What are the two important physical quantities that characterize wetting and liquid repellency of a

solid surface? Name them, and explain the difference between these two quantities

b)

Peter is playing around with four different solid surfaces (labelled as A, B, C, and D) by placing

different types of liquids onto these surfaces. Peter found something very puzzling: When he

placed small drops of water and oils onto Surface

A, all of these liquids stick to the surfaces.

However, when he placed water and oils droplets onto Surface B, only water can roll off the

surface but oils remain stuck to the surface. Peter

also

found that both water and oils droplets are

highly mobile o

n Surface C, and can be rolled off from the surface. Finally, when Peter placed

both water and oils droplets onto Surface D,

oil droplets are highly mobile but the water droplets

appear to spread completely on the surface. Please provide possible

physical

explanations to all

the above scenarios. Please remember to include schematics and important physical quantities in

your explanations

Describe the procedure to determine the first modal damping. Outline the key steps and sketch the collected acceleration data.

The planet Mars has a diameter of 6772 km, and it orbits the sun at a distance of 227.9 x 10^6 km. If the sun is assumed to radiate like a blackbody at 5760 K, and Mars has an albedo of 0.15 ( reflects 15% of incident radiation back to space), estimate the average temperature of the Martian surface. Ignore the effects of the thin Martian atmosphere.