Ethane (C2H6) is burned with air in a steady-flow combustor. The mass flow rate of fuel entering the combustor is 0.57 kg/s and the equivalence ratio is 0.64. The fuel enters at 25oC and the air enters at 500 K. Determine:
The heat release rate, in kW.
The mass flow rate of air, in kg/s.
The mole fraction of O2 in the products.
The mass fraction of CO2 in the products.
The total mass of CO2 produced per year (365 days), assuming that they system operates continuously 24 hours per day, in kg.
The adiabatic flame temperature, using 1400 and 2400 K as your guesses.
In: Mechanical Engineering
Ethane gas (C2H6) is burned with air. The fuel flow rate is 0.1 kg/s and the air flowrate is 2.2 kg/s. Ethane’s enthalpy of formation is -84,680 kJ/kmol. Determine:
The equivalence ratio
Ethane’s lower heating value by deriving it from enthalpy of formation data.
The heat release rate, in kW.
The mass fraction of oxygen in the products.
The mass of CO2 emitted per 1000 hours of operation.
The mass of fuel burned per 1000 hours of operation.
The adiabatic flame temperature, using 1400 and 2200 K as your guesses.
In: Mechanical Engineering
In: Mechanical Engineering
Q2 Write short notes on any two of the following:
a) Optimum Design. b) New Design c) Empirical Design [12 marks]
(iii) Mention two methods used in design in minimizing stress
concentration. [5 marks]
Q4 (i) Find the power transmitted by a 50mm diameter solid shaft
running at 200rpm if the shear strength of the material is 124
MN/m2 using factor of safety of 2.
What will be the power transmitted by an equivalent hollow shaft of the same cross sectional area as the solid shaft above, if the ratio of the outside to inside diameter is 3/2. [18 marks]
(ii) Explain the meaning of the answers in (i) above
In: Mechanical Engineering
Explain how tacticity (isotactic, atatic) effect the molecules crystalinnity and other characterstics.
In: Mechanical Engineering
Question 3 a)In an Electrochemical Machining process, the feedstock is made of an aluminium alloy (Ultimate Tensile Strength=572 MPa, Tensile Yield Strength=503 MPa). The desired time to machine a hole (?=10 mm) through a 20 mm-thick part is 2.1 min at a feed rate of 0.18 mm/s. What are: (i)the efficiency of the process in %, and (ii)the current requirement in amps to achieve this machining time target? [30 marks] Describe in detail the process of circular sawing with the aid of a freehand sketch. What are the two major mechanisms by which circular sawing is achieved and what materials are commonly used as circular saws of each type?
In: Mechanical Engineering
Briefly explain the following terms:
a)Exiting phenomena(drilling)
b)Sparkling out process(grinding)
c)Six point rules
In: Mechanical Engineering
1045 Steel (quenched specimen)
Draw a picture of what you think the microstructure would look like and label the constituents (martensite, ferrite, cementite or whatever you expect to find in this quenched specimen). Include the figure number.
In: Mechanical Engineering
Capillary number is proportional to { (viscous force) / (surface tension force) } and is used in momentum transfer in general and atomization and 2-phase flow in beds of solids calculations in particular. It is equivalent to (We/Re).
___________ Which is the friction factor for ReD = 600 and e/D = 0.002 in pipe flow?
___________ What is the friction factor for ReD= 3 x 105 and D/e = 5000 in pipe flow?
In: Mechanical Engineering
Iron ores found in Ireland and Britain are not suitable for production of high-quality steel because they contain too much of which one of the following elements:
(a) Sulphur
(b) Carbon
(c) Nitrogen
(d) Phosphorus?
The inside of the stack of a blast furnace is usually lined with:
(a) Steel sheets
(b) Ceramic refractories (c) Asbestos
(d) Water-cooled copper?
To improve the fuel-efficiency of the modern blast furnace, which one of the following may be added to the blast:
(a) O2 (b) N2 (c) H2 (d) CO2?
In steelmaking, basic slags are necessary for the removal of which element:
(a) Carbon
(b) Silicon
(c) Phosphorus (d) Oxygen?
In: Mechanical Engineering
Give three examples of materials properties, and indicate where they are used in engineering product development. Compare any one of the listed properties for Metals, Ceramics, and Polymers materials on the same scale graphically
In: Mechanical Engineering
A circumferential aluminum fin is attached to an electronic resistor having 1/4 inch diameter. The fin is 1/8 inch long and .001 inches thick. The convective heat transfer coefficient to the surrounding media, air at 60oF, is 10 Btu/h ft2 oF when the fin is at 120oF. Estimate the fin efficiency and the heat transfer from the fin.
In: Mechanical Engineering
A two-pass shell and tube heat exchanger has an overall conductance of 450 W/m2 oC when used as a condenser for a large air conditioning system. Refrigerant R-134a enters thecondenser at 20 kg/ s as a saturated vapor at 70oC and leaves as a saturated liquid. If cooling water enters at a rate of 60 L/s, 10oC, determine the outlet temperature of the cooling water and the effective area of the condenser.
In: Mechanical Engineering
Explain the principle of a critical radius when adding isolation to pipes
In: Mechanical Engineering
Sailplanes use updrafts to stay aloft for hours at a time. Near one particular airfield, a stone quarry (with very dark rocks) surrounded by a wooden area provides a particularly regular source for updrafts on hot days. With your knowledge of heat transfer, explain the processes that create the updraft
In: Mechanical Engineering