A cylinder contains ethylene, C2H4, at 1.536 MPa, -13oC. It is now compressed in a reversible isobaric (constant pressure) process to saturated liquid. Find the specific work, heat transfer and entropy generated.
In: Mechanical Engineering
A strip of elastomer 1 cm×1 cm×10 cm is stretched to 25 cm length at T =25C, a stress of 1.5 MPa being required
(a) Assuming a tetrafunctional crosslinking mode, how many moles of network chains are there per cubic centimeter?
(b) What stress is required to stretch the sample to only 15 cm at T = 25C?
(c) What stress is required to stretch the sample to 25 cm length at 100C?
In: Mechanical Engineering
The theory of rubber elasticity and the theory of ideal gas dynamics show that the two equations, G = nRT and PV = n'RT, share certain common thermodynamic ideas.
What are they?
In: Mechanical Engineering
a) Define the following terms:
i) Calorific Value
ii) Volumetric Percentage with respect to air composition
iii) Gravimetric percentage with respect to air composition
iv) Stoichiometric Ratio
b) In combustion chemistry, state why the usage of excess oxygen is often desirable.
c) Consider the combustion of pentane. Determine:
i) The stoichiometric air to fuel ratio
ii) The excess air supplied, if 8% CO2 (by vol) is found in the dry product. ( Take air to be 21% Oxygen,and 79% Nitrogen)
In: Mechanical Engineering
. A disposable coffee cup (including a lid) may be regarded as a polystyrene cylinder, diameter 50mm, height 80mm and thickness 2.5mm. The base and lid may be regarded as 2.5mm thick disks. When being held using finger tips (having a very small area) the heat transfer coefficient from the outside of the cup is 20W/m2K and from the coffee to the inner wall is 100W/m2K. Estimate the rate of heat loss from the cup when the coffee is at 65oC and ambient temperature is 18oC. The conductivity of the polystyrene is 0.04W/mK.
Ans = 6.33W
In: Mechanical Engineering
In: Mechanical Engineering
In: Mechanical Engineering
An ideal four stroke Otto cycle engine has 6 cylinders and a displacement of 4 Liters. It has a compression ratio of 8.5:1. If the mean effective pressure is 4000 kPa when operating at 3000 rpm, what will be the indicated power and what is the required heat transfer to the engine from a combusting fuel?
In: Mechanical Engineering
A ½” diameter UNC, SAE Grade 8, bolt with rolled threads is preloaded to 70% of its proof strength when clamping a 2.75” thick sandwich of solid steel. Find the safety factors against static yielding, fatigue failure and joint separation when am external fatigue load having Fmax=1000 lbf and R=0 load is applied.
In: Mechanical Engineering
In: Mechanical Engineering
In: Mechanical Engineering
A .05 wide journal bearing supporting the loads on a 1 inch shaft just meets the Trumpler’s design criteria for a FACTOR OF SAFTY OF 2.05. The bearing satisfies all the other Trumpler’s design criteria by much larger margin. Your colleague suggests that increasing the bushing width to 0.75 inches would be an adequate design and you would not need to conduct another journal bearing analysis because the greater width would result in a bearing which satisfy all of Trumpler’s design criteria.
Do you agree with your colleague that you can state that the 0.75 inch wide journal bearing would exceed Trumplers Design criteria and that no additional analysis is required? Justify your answer.
In: Mechanical Engineering
3. Assume an annulus of inner radius r1 and outer radius r2. The inner surface is at T1, the outer surface at T2, T1 > T2. Assume heat transfer between the surfaces by conduction, with a variable conductivity, k = a + bT, develop an expression for the temperature in the material of the annulus.
In: Mechanical Engineering
an undulated surface that is designed to reduce friction by eliminating wear particles from the sliding interface. The interface is subjected to normal force N. The sliding speed is so low that the interfacial temperature rise is negligible relative to the melting point of the material. We are planning to use metals for the sliders.
a. Determine the optimum dimensions of the undulated topography.
b. Discuss the consequence of deviating from the optimum geometry.
In: Mechanical Engineering
A piston cylinder device containing 0.5 kg of water has initial volume of 0.5L. The device starts and goes through a Carnot cycle and generates 500.3 kJ work. If the maximum temperature that water will reach is 1.5 times the minimum temperature of water and during heat rejection process, water goes from saturated vapor to saturated liquid phase. Find:
1. QH & QL for this cycle .
2. TH & TL for this cycle.
3. Maximum and minimum pressures that the cycle will reach.
4. Show this process on a T-v diagram and label temperature, pressures and specific volumes.
In: Mechanical Engineering