1. Mechanical Engineering Case study 3 Student’s Name C

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Mechanical Engineering
Case study 3
Student’s Name
Course
Professor’s Name
Institution’s Name
Institution’s Location
Date

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Case study 3
Part a: Measuring the height of a building
Barometer reading at the top of building is 665mmHg while bottom of building 695mmHg.
Density of air 1.17kgm-3 while density of mercury is 13600kgm-3
Therefore,
Height of building=Pressure difference∗Relative density
Relative density = Density of Mercury
Density of air
Height= ( 695−665 )∗13600
1.17
Height =348.7 m
Part b: Heat transfer
Heat transfer in cooling a cup of coffee
The cooling process entails the transfer of heat from the mug and coffee to the surrounding. The
lower temperatures of the surrounding, in essence, the temperature difference makes the kinetic
energy of the particles in the coffee and those of the mug to decrease, as it is lost to the
surrounding until an equilibrium in temperatures is attained in a process referred to as conduction
(Lohajinda, Pathumsara, and Teeka, 2019, p.16)
Heating a room by an electric fan heater
When the heater in a room is switched on, the air particles near the coils warm up and rises. The
cold air, which is denser than the warm air, replaces the space left by the warm light air near the
coils of the heater. The process goes on as the colder air particles keep replacing the warm air

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thus forming convection currents. During the movement of these waves, the air particles keep
gaining energy from the coils of the heater thus warming up the room in a process called
convection heater transfer (Lança, Coelho, and Viegas, 2019, pp.653-667).
Part c: Power output of a piston engine
Steam pressure = 1.8 atm.
Length of a single stroke = 30mm.
Piston cross sectional area = 10 cm2.
Revolutions per second = 8.
Power output =piston areas∗Length of Stroke∗Mean effective pressure∗revs
second
Mean effective pressure = 1.8 atm which is equivalent to 182385 N/m2
Therefore,
Power output =0.0 0 1∗0.01∗182385∗8
power output =14.5908Watts
Power output =0 . 01957 Mechanical horsepower

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References
Lança, M., Coelho, P.J. and Viegas, J., 2019. Enhancement of heat transfer in office buildings
during night cooling− reduced scale experimentation. Building and Environment, 148, pp.653-
667.
Lohajinda, N., Pathumsara, K. and Teeka, C., 2019, March. Teaching specific heat using
learning by laboratory activity. In AIP Conference Proceedings (Vol. 2081, No. 1, p.16). AIP
Publishing.