Derive the expressions for maximum rate of climb, (?? ?? ?
)?????? and the velocity at maximum rate of climb, ??(?? /C )??????
for propeller-driven and jet-propelled A/C.
In: Mechanical Engineering
A Carnot-cycle refrigerator rejects heat at the pressure of 1000 kPa during which the working fluid R -134a changes from saturated vapor to saturated liquid. The heat is added to the cycle at the pressure of 320 kPa. Show the cycle in a T-s diagram and determine the coefficient of performance of the cycle using a) the first law of thermodynamics b) the Carnot cycle efficiency equation and c) the T-s diagram.
In: Mechanical Engineering
A spherical shell of wood with thermal conductivity of 0.13 W/m.K and an inner and outer radius of 10 cm and 20 cm respectively contains a mixture of water and water vapor(100 C) inside the shell which is undergoing a phase change at atmospheric pressure. The shell is suspended in a large room with an ambient air temperature of 25 C Determine the temperature on the outer surface of the spherical shell and rate of heat loss from the fluid undergoing phase change. The thermal conductivity of air is 0.024 W/m.K Assume negligible flow of air inside the room.
In: Mechanical Engineering
The following system is a small power generating plant which contains a boiler, a superheater, a turbine and a condenser. Describe each part of the system with reference to the equations required in terms of heat transfer and work transfer. The feed water flows at 1 tonne/hr at 50°C. The output pressure is 6 bar with a dryness fraction is 0.9 and the efficiency of the boiler is 75%. The calorific value of the fuel is 38MJ/kg. Determine the fuel flow rate.
The superheater adds 300°C of super heat, determine the energy input to the superheater assuming no heat loss.
The turbine is 70% efficient and the output steam is at 0.2 bar and 0.8 dryness fraction. Determine the output power of the turbine.
In: Mechanical Engineering
Case Study
In Francisco Automotive Manufacturing Plant, a large number of engineering activities are carried out in a wide range of areas. These activities include design, production of parts, assembly, testing, and quality assurance.
Many of the manufacturing processes in the plant are performed using automated technologies and equipment. People also perform some of the manufacturing tasks and the plant employs over 400 workers. The decision on whether people or machines will be used for a particular task is dependent on many factors, including costs, time, quality and worker health and safety.
The plant considered here produces a many parts for vehicles and assembles them. Among the parts produced are engine materials and parts, pumps, fans, some exterior parts, and electronics components. The plant normally operates three shifts per day and has production lines including machining equipment, conveyers and overhead cranes, punch presses, and paint-spray booths. The plant utilizes electricity and natural gas extensively.
A number of workers at the plant have over the last six months been subject to several different health problems. The following information has been received by the head engineer at the plant.
a) In an assembly area that was installed recently, workers have to bend to the ground throughout the day to attach several small parts onto a large and heavy vehicle component. Some workers have begun to develop lower back pain, likely due to the repetitive bending. The problem has become so severe for one of the workers that he has been told by his doctor to stay off work for two weeks so his back can recover. The manufacturing engineers who designed the assembly operation had wanted to use an automated system, but that option was deemed not to be economic. So they used a manual operation, but did not take into account industrial ergonomics, as they had no expertise in that discipline.
b) An increased incidence of respiratory illnesses has been reported over the last month by workers operating near the paint-spray booths. Many of the substances used in the booths (paints, solvents, etc.) are known to be causes of the observed respiratory illnesses. But the workers are not supposed to come into contact with any of the substances because the paint-spray booths are designed to ensure that all materials exit the plant through a high capacity ventilation system and that no materials can leak back into the plant. No tests had been carried out on the ventilation system, or on the air quality around the paint spray booths, so it is uncertain whether or not there have been any leaks into the plant from the paint-spray booths.
c) In an area of the plant where metal cutting occurs and workers use protective eyewear, workers have reported minor eye injuries. The area in question is one where it is common knowledge that the workers do not routinely use the protective eyewear. It is often observed to be hanging on nearby hooks or to be loosely hanging around the necks of workers. Workers complain that they find the protective eyewear uncomfortable and do not think it is needed or important. The plant manager knows of this behaviour but overlooks it, since enforcing the use of the protective eyewear seems may make the workers unhappy and, consequently, less productive. That, he feels, could render the plant non-competitive.
Questions:
1) Which of the unsafe conditions and acts identified in part b are (a) of a technical nature,
or (b) related to human behaviour or management?
2) What are some steps can be taken to rectify the health problems observed?
In: Mechanical Engineering
Case Study
In Francisco Automotive Manufacturing Plant, a large number of engineering activities are carried out in a wide range of areas. These activities include design, production of parts, assembly, testing, and quality assurance.
Many of the manufacturing processes in the plant are performed using automated technologies and equipment. People also perform some of the manufacturing tasks and the plant employs over 400 workers. The decision on whether people or machines will be used for a particular task is dependent on many factors, including costs, time, quality and worker health and safety.
The plant considered here produces a many parts for vehicles and assembles them. Among the parts produced are engine materials and parts, pumps, fans, some exterior parts, and electronics components. The plant normally operates three shifts per day and has production lines including machining equipment, conveyers and overhead cranes, punch presses, and paint-spray booths. The plant utilizes electricity and natural gas extensively.
A number of workers at the plant have over the last six months been subject to several different health problems. The following information has been received by the head engineer at the plant.
a) In an assembly area that was installed recently, workers have to bend to the ground throughout the day to attach several small parts onto a large and heavy vehicle component. Some workers have begun to develop lower back pain, likely due to the repetitive bending. The problem has become so severe for one of the workers that he has been told by his doctor to stay off work for two weeks so his back can recover. The manufacturing engineers who designed the assembly operation had wanted to use an automated system, but that option was deemed not to be economic. So they used a manual operation, but did not take into account industrial ergonomics, as they had no expertise in that discipline.
b) An increased incidence of respiratory illnesses has been reported over the last month by workers operating near the paint-spray booths. Many of the substances used in the booths (paints, solvents, etc.) are known to be causes of the observed respiratory illnesses. But the workers are not supposed to come into contact with any of the substances because the paint-spray booths are designed to ensure that all materials exit the plant through a high capacity ventilation system and that no materials can leak back into the plant. No tests had been carried out on the ventilation system, or on the air quality around the paint spray booths, so it is uncertain whether or not there have been any leaks into the plant from the paint-spray booths.
c) In an area of the plant where metal cutting occurs and workers use protective eyewear, workers have reported minor eye injuries. The area in question is one where it is common knowledge that the workers do not routinely use the protective eyewear. It is often observed to be hanging on nearby hooks or to be loosely hanging around the necks of workers. Workers complain that they find the protective eyewear uncomfortable and do not think it is needed or important. The plant manager knows of this behaviour but overlooks it, since enforcing the use of the protective eyewear seems may make the workers unhappy and, consequently, less productive. That, he feels, could render the plant non-competitive.
Questions:
1) How would you go about investigating the causes of the observed health problems?
2) What are the unsafe conditions and acts in the plant?
In: Mechanical Engineering
CASE STUDY
In the Appliances Manufacturing Plant, a large number of engineering activities are carried out in a wide range of areas. These activities include design, production of parts, assembly, testing, and quality assurance.
Many of the manufacturing processes in the plant are performed using automated technologies and equipment. People also perform some of the manufacturing tasks and the plant employs over 400 workers. The decision on whether people or machines will be used for a particular task is dependent on many factors, including costs, time, quality and worker health and safety.
The plant considered here produces a many part for appliances and assembles them. Among the parts produced are door and housing materials and parts, compressors, motors, fans, some exterior parts, and electronics components. The plant normally operates three shifts per day and has production lines including machining equipment, conveyers and overhead cranes, punch presses, and paint-spray booths. The plant utilizes electricity and natural gas extensively.
A number of workers at the plant have over the last six months been subject to several different health problems. The following information has been received by the head engineer at the plant.
The head engineer at the plant wants to ensure that the plant provides a safe and healthy environment. So, she decides to ask an engineering health and safety consulting company to do a health and safety audit of the plant. The report provided by the consulting company lists the following safety problems:
a) An expert on fires and explosions notes that the extensive use of natural gas in the plant could lead to an explosion in the plant in some circumstances. The force of such an explosion could lead to severe injuries or deaths of workers and, possibly, cause the building to be damaged or to collapse. The potential for an explosion could develop if a sufficient natural gas leak occurs or the plant ventilation system fails to perform properly or certain controls or sensors fail. But, the expert further notes, there is insufficient
information available on the concentration of natural gas in the plant air, as only one natural gas sensor is in place at the plant, but it is not located in the main area where an accumulation of natural gas is likely to occur. Thus, the potential for an explosion could exist, yet not be detected or acted upon. In addition, the expert is concerned because the natural gas sensor is connected neither to an automated shut-off system for the natural gas supply nor to an alarm, thus increasing the likelihood of an incident and its potential severity.
b) Although maintenance is supposed to be done quarterly on the natural gas lines and equipment, no evidence is found that maintenance has ever been performed since they were first installed four years ago. Such maintenance typically involves checking for and fixing gas leaks. Also, no training has been provided to workers on either understanding the potential for explosion, or the steps to take to avoid an explosion. In fact, most workers did not even realize the potential for an explosion existed. Furthermore, no written procedures relating explosions exist within the plant.
c) The plant contains toxic materials that can harm people and animals. The way this material is stored in the plant, it could, in the event of a plant explosion, be released and impact an area within one kilometer of the plant. Such an incident could lead to illnesses or deaths among members of the public and could harm animals in the environment.
Questions:
1) If the head engineer at the plant decides that measures must be taken to protect health and
safety, but the plant manager refuses to approve the measures, what are the obligations of
the head engineer?
2) Do any of the problems cited demonstrate that it is best to address health and safety
comprehensively in the early stages of an engineering activity, preferably within the
design process and not as an afterthought? For instance, can you indicate some measures
that will likely be more expensive to implement to fix the problem compared to the cost
that would have been incurred during the design process to resolve the problem then?
In: Mechanical Engineering
CASE STUDY
In the Appliances Manufacturing Plant, a large number of engineering activities are carried out in a wide range of areas. These activities include design, production of parts, assembly, testing, and quality assurance.
Many of the manufacturing processes in the plant are performed using automated technologies and equipment. People also perform some of the manufacturing tasks and the plant employs over 400 workers. The decision on whether people or machines will be used for a particular task is dependent on many factors, including costs, time, quality and worker health and safety.
The plant considered here produces a many part for appliances and assembles them. Among the parts produced are door and housing materials and parts, compressors, motors, fans, some exterior parts, and electronics components. The plant normally operates three shifts per day and has production lines including machining equipment, conveyers and overhead cranes, punch presses, and paint-spray booths. The plant utilizes electricity and natural gas extensively.
A number of workers at the plant have over the last six months been subject to several different health problems. The following information has been received by the head engineer at the plant.
The head engineer at the plant wants to ensure that the plant provides a safe and healthy environment. So, she decides to ask an engineering health and safety consulting company to do a health and safety audit of the plant. The report provided by the consulting company lists the following safety problems:
a) An expert on fires and explosions notes that the extensive use of natural gas in the plant could lead to an explosion in the plant in some circumstances. The force of such an explosion could lead to severe injuries or deaths of workers and, possibly, cause the building to be damaged or to collapse. The potential for an explosion could develop if a sufficient natural gas leak occurs or the plant ventilation system fails to perform properly or certain controls or sensors fail. But, the expert further notes, there is insufficient
information available on the concentration of natural gas in the plant air, as only one natural gas sensor is in place at the plant, but it is not located in the main area where an accumulation of natural gas is likely to occur. Thus, the potential for an explosion could exist, yet not be detected or acted upon. In addition, the expert is concerned because the natural gas sensor is connected neither to an automated shut-off system for the natural gas supply nor to an alarm, thus increasing the likelihood of an incident and its potential severity.
b) Although maintenance is supposed to be done quarterly on the natural gas lines and equipment, no evidence is found that maintenance has ever been performed since they were first installed four years ago. Such maintenance typically involves checking for and fixing gas leaks. Also, no training has been provided to workers on either understanding the potential for explosion, or the steps to take to avoid an explosion. In fact, most workers did not even realize the potential for an explosion existed. Furthermore, no written procedures relating explosions exist within the plant.
c) The plant contains toxic materials that can harm people and animals. The way this material is stored in the plant, it could, in the event of a plant explosion, be released and impact an area within one kilometer of the plant. Such an incident could lead to illnesses or deaths among members of the public and could harm animals in the environment.
Questions:
1) What are the unsafe conditions and acts in the plant?
2) What are some steps can be taken to rectify the noted safety concerns?
In: Mechanical Engineering
A water-to-water system is used to test the effects of changing tube length, baffle spacing, tube pitch, pitch layout, and tube diameter. Cold water at 25°C and 100,000 kg/hr is heated by hot water at 100°C , also at 100,000 kg/hr. The exchanger has a 31 in. ID shell. Perform calculations on this 1–2 shell-and-tube heat exchanger for the following conditions, as outlined in the examples, and put together an overall comparison chart. a. 3/4 in. OD tubes, 12 BWG laid out on a 1 in. triangular pitch; 3 baffles per meter of tube length. Analyze the exchanger for tube lengths of 2, 3, 4, and 5 m. b. 3/4 in. OD tubes, 12 BWG laid out on a 1 in. triangular pitch; 2 m long. Analyze for baffle placement of 1 baffle per meter of tube length, 2 baffles per meter of tube length, 3 baffles per meter of tube length, 4 baffles per meter of tube length, and 5 baffles per meter of tube length. c. 3/4 in. OD tubes, 12 BWG; 2 m long; 4 baffles per meter of tube length. Analyze the exchanger for tube layouts of 15/16 in. triangular pitch, 1 in. triangular pitch, and 1 in. square pitch. d. 1 m OD tubes, 12 BWG; 4 m long; 9 baffles. Analyze the exchanger for tube layouts of 1.25 in. triangular pitch and 1.25 in. square pitch. e. 3/4 in. OD tubes, 12 BWG laid out on a 1 in. triangular pitch; 2 m long; 4 baffles per meter of tube length. Analyze the exchanger for 2, 4, 6, and 8 tube passes, and compare to the case of true counterflow (i.e., 1 tube pass).
In: Mechanical Engineering
This is problem 5-17 from El-Wakil’s Powerplant Technology book -- consider a simple combination turbine with one Delaval impulse stage and one 60 percent reaction stage. The nozzle of impulse stage receives steam at 900 psia and 900°F and leaves it at 300 psia. The nozzle efficiency is 97 percent and its angle is 20°. The blade speed is optimum and its velocity coefficient is 0.95. The impulse stage is followed on the same shaft by the reaction stage which exhausts to 100 psia. The steam entrance angles for that stage are also 20°. The efficiency of the fixed blades (nozzles) is 90 percent. Because of different diameters of the impulse and reaction moving blades, the velocity of the reaction blade is 1.5 that of the impulse blade. (a) Determine all steam velocities and draw the velocity diagram of the combined turbine, (b) calculate the work of each stage, in Btus per pound mass, and (c) calculate the individual stage and the turbine efficiencies.
In: Mechanical Engineering
Prove that any planar F-dof (degree of freedom) linkage (contains lower pairs only) must have at least F+3 binary links.
In: Mechanical Engineering
This is problem 5-13 from El-Wakil’s Powerplant Technology book -- a 50 percent reaction stage in a steam turbine undergoes a total of 20 Btu/lbm enthalpy drop. The nozzle efficiency and angle are 88 percent and 25°, respectively. The blades move at 420 ft/s and have Vr1 = 332 ft/s, Vs2 = 386 ft/s, and ? = 22°. The steam flow is 1.08x106 lbm/h. Find (a) the work done by the stage in horsepower and megawatts, (b) the blade efficiency, (c) the stage (nozzle and blade) efficiency, and (d) the blade velocity corresponding to maximum efficiency, in feet per second.
In: Mechanical Engineering
5. A power cycle receives energy QH by heat transfer from a high temperature energy source at TH = 2000 K and rejects energy QL by heat transfer to a low temperature energy sink at TL = 400 K. For each of the following cases determine whether the cycle operate reversibly, irreversibly, or is impossible.
(a) QH = 1200 kJ, Wcycle = 1020 kJ.
(b) QH = 1200 kJ, QL = 240 kJ.
(c) Wcycle = 1400 kJ, QL = 600 kJ.
(d) efficiency = 40%.
In: Mechanical Engineering
Air at 1 atm and 27 degree C flows across a flat plate at a velocity of 14 m/s. Find the distance from the leading edge where transition to turbulent flow begins and the local heat-transfer coefficient at this point if the temperature of the plate is 77 degree C.
In: Mechanical Engineering
A piston?cylinder device initially contains 1.5?kg saturated liquid water at 120°C. Now heat is transferred to the water until the volume increases 100 times.
Determine:
a. Initial Volume of the water.
b. Final volume of water.
c. Final state of water.
d. Amount of heat added to the water
e. Draw the T?s diagram
In: Mechanical Engineering