A diesel engine intakes atmospheric air at 60°F and adds 800
Btu/lbm of energy. If the maximum pressure is 1200 psia,
calculate:
(a) the cutoff ratio, rc ;
(b) the thermal efficiency, ? ;
(c) the power output, in hp, for an airflow of 0.2
lbm/sec.
[Hints: Follow the Diesel cycle diagram! For ?, you will need
the compression ratio.]
8. Consider a potato being baked in an oven that is maintained
at a constant temperature. The temperature of the potato is
observed to rise by 5°C during the first minute. What will be the
temperature rise during the second minute? A. Less than 5°C B. More
than 5°C C. Equal to 5°C D. No temperature rise
Water enters a circular tube whose walls are maintained at constant temperature at a specified flow rate and temperature. To compute the rate of heat transfer between the walls and the fluid, using the flow Nusselt number the following temperature difference is used;
a. The difference between the inlet and outlet water bulk temperature
b. The difference between the inlet water bulk temperature and the tube wall temperature
c.
The log mean temperature...
Sketch and label the following thermodynamic processes on
enthalpy-temperature or internal energy-temperature diagrams (as
appropriate). Use a separate diagram for each case. Clearly label
reactant and product conditions on each diagram as well as the
direction of the process path. For each process, specify (a) what
initial conditions/inputs must be provided, (b) what resulting
reaction quantity of interest can be calculated, (c) what
thermodynamic constraints/assumptions apply, and (d) why you chose
each diagram as well as why you drew each...
Let’s consider an absolute value in real life. For example, our
internal body temperature has a range that is considered normal.
Although many people think of the normal internal body temperature
as 98.6, the temperature can vary by as much as plus or minus .5°
and still be considered normal. This can be written as an absolute
value function.
Draw a number line and graph the normal internal body
temperature. What is the minimum and maximum of our range? Label...
A refrigerator has an internal temperature of 17.52oC in a room
at temperature 30.63oC. It consumes an average of 305.26 W
electrical power while continuously removing 405.35 W thermal
(heat) from the interior to keep its insides cold. (a) What is it's
ideality factor? The ideality factor is the ratio of the actual
coefficient of performance of the refigerator to the maximum
phyically possible. (b) If it was replaced with an idealized
perfect refrigerator operating between those temperatures and still...
Based on the thermodynamic properties provided for water,
determine the energy change when the temperature of 1.45 kg of
water decreased from 109 °C to 23.0 °C.
Based on the thermodynamic properties provided for water,
determine the energy change when the temperature of 0.750 kg of
water decreased from 117 °C to 38.5 °C.
Property
Value
Units
Melting point
0
°C
Boiling point
100.0
°C
ΔHfus
6.01
kJ/mol
ΔHvap
40.67
kJ/mol
cp (s)
37.1
J/mol · °C
cp (l)
75.3
J/mol · °C
cp (g)
33.6
J/mol · °C