To warm up some milk for a baby, a mother pours milk into a thin-walled cylindrical container whose diameter is 6 cm. The height of the milk in the container is 7 cm. She then places the container into a large pan filled with hot water at 70°C. The milk is stirred constantly so that its temperature is uniform at all times. If the heat transfer coefficient between the water and the container is 120 W/m 2 K, determine how long it will take for the milk to warm up from 3°C to 38°C. Assume the entire surface area of the cylindrical container (including the top and bottom) is in thermal contact with the hot water. Take the properties of the milk to be the same as those of water. Can the milk in this case be treated as a lumped system? Why?
To warm up some milk for a baby, a mother pours milk into a thin-walled cylindrical container whose diameter is 6 cm. The height of the milk in the container is 7 cm. She then places the container into a large pan filled with hot water at 70°C. The milk is stirred constantly so that its temperature is uniform at all times. If the heat transfer coefficient between the water and the container is 120 W/m 2 K, determine how long it will take for the milk to warm up from 3°C to 38°C. Assume the entire surface area of the cylindrical container (including the top and bottom) is in thermal contact with the hot water. Take the properties of the milk to be the same as those of water. Can the milk in this case be treated as a lumped system? Why?
Solution Summary: The author explains that milk can be treated as a lumped system, as the temperature of the milk is assumed to remain constant every time.
To warm up some milk for a baby, a mother pours milk into a thin-walled cylindrical container whose diameter is 6 cm. The height of the milk in the container is 7 cm. She then places the container into a large pan filled with hot water at 70°C. The milk is stirred constantly so that its temperature is uniform at all times. If the heat transfer coefficient between the water and the container is 120 W/m2 K, determine how long it will take for the milk to warm up from 3°C to 38°C. Assume the entire surface area of the cylindrical container (including the top and bottom) is in thermal contact with the hot water. Take the properties of the milk to be the same as those of water. Can the milk in this case be treated as a lumped system? Why?
4. Determine which of the following flow fields represent a possible
incompressible flow?
(a) u= x²+2y+z; v=x-2y+z;w= -2xy + y² + 2z
a
(b) V=U cose
U coso 1 (9)
[1-9]
Usino |1 (4)]
[+]
V=-Usin 1+1
3. Determine the flow rate through the pipe line show in the figure in ft³/s,
and determine the pressures at A and C, in psi.
5'
B
C
12°
20'
D
6"d
2nd-
Water
A
5. A flow is field given by V = x²₁³+xy, and determine
3
·y³j-
(a) Whether this is a one, two- or three-dimensional flow
(b) Whether it is a possible incompressible flow
(c) Determine the acceleration of a fluid particle at the location (X,Y,Z)=(1,2,3)
(d) Whether the flow is rotational or irrotational flow?
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