A coolant flows through a rectangular channel (gallery) within the body of a mold used to form metal injection parts. The gallery dimensions are a = 90 mm and b = 9 .5 mm , and the fluid flow rate is 1.3 × 10 − 3 m 3 / s . The coolant temperature is 15 ° C , and the mold wall is al an approximately uniform temperature of 14 0 ° C . To minimize corrosion damage to the expensive mold, it is customary to use a heat transfer fluid such as ethylene glycol, rather than process water. Compare the convection coefficients of water and ethylene glycol for this application. What is the tradeoff between thermal performance and minimizing corrosion?
A coolant flows through a rectangular channel (gallery) within the body of a mold used to form metal injection parts. The gallery dimensions are a = 90 mm and b = 9 .5 mm , and the fluid flow rate is 1.3 × 10 − 3 m 3 / s . The coolant temperature is 15 ° C , and the mold wall is al an approximately uniform temperature of 14 0 ° C . To minimize corrosion damage to the expensive mold, it is customary to use a heat transfer fluid such as ethylene glycol, rather than process water. Compare the convection coefficients of water and ethylene glycol for this application. What is the tradeoff between thermal performance and minimizing corrosion?
A coolant flows through a rectangular channel (gallery) within the body of a mold used to form metal injection parts. The gallery dimensions are
a
= 90 mm and
b
=
9
.5 mm
, and the fluid flow rate is
1.3
×
10
−
3
m
3
/
s
. The coolant temperature is
15
°
C
, and the mold wall is al an approximately uniform temperature of
14
0
°
C
.
To minimize corrosion damage to the expensive mold, it is customary to use a heat transfer fluid such as ethylene glycol, rather than process water. Compare the convection coefficients of water and ethylene glycol for this application. What is the tradeoff between thermal performance and minimizing corrosion?
Pure aluminium is poured into a sand mold. The metal level in the pouring basin is 203.2mm above the metal level in the mold, and the runner is circular with a 7.62 mm diameter.What is the velocity and the rate of flow of the metal into the mold? Is the flow turbulent orlaminar? Note that pure aluminum has a density of 2700 kg/m3and a viscosity of 0.004Ns/m
3.
Dye for our new line of blue jeans is being blended in a mixing tank. The desired color of
blue is produced using a concentration of 1500 ppm blue dye, with a minimum acceptable
concentration of 1400 ppm. At 9 A.M. today the dye injector plugged, and the dye flow was
interrupted for 10 min, until we realized the problem and unclogged the nozzle. For how
many minutes was the flow leaving the mixer off-specification (< 1400 ppm)? How many
gallons of off-spec dye were made? See Fig. P5-15.
Water
20 gal/min
20 gal/min aqueous dye for jeans
(1500 ppm blue dye)
Concentrated
dye injector
V= 100 gal
FIGURE PS-15
4.
A thermocouple junction of area A, mass m, heat capacity C, and emissivity e is located in
a furnace that normally is at T C. At these temperatures convective and conductive heat
transfer to the junction is negligible compared with radiative heat transfer. Determine the
linearized transfer function between the furnace temperature T, and the junction temperature
To. For the case
m…
10
Assuming that the interstices in a clay are of size equal to one tenth the mean
diameter of the grain, estimate the height to which water will rise in a clay soil of average grain
diameter of 0.048 mm. Assume surface tension at air-water interface as 0.074 N/m.
11
Calculate the work done in blowing a soap bubble of diameter 100 mm. Assume
the surface tension of soap solution = 0.038 N/m.
12
Determine the minimum size of glass tubing that can be used to measure water
level, if the capillary rise in the tube is not to exceed 0.3 mm. Take surface tension of water in contact
with air as 0.0735 N/m.
13
A U-tube is made up of two capillaries of bores 1.2 m and 2.4 mm respectively.
The tube is held vertical and partially filled with liquid of surface tension 0.06 N/m and zero contact
angle. If the estimated difference in the level of two menisci is 15 mm, determine the mass density of
the liquid.
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