Question

A food product will be frozen and placed in a can with 80% water content and 6 cm in diameter. product density of 800 Kg / m3, thermal conductivity of 0.1 W / (m K), and initial freezing temperature of -2 degrees Celsius. After 10 hours frozen at -15 degrees Celsius (freezing medium), the product temperature becomes -10 degrees Celsius. determine the convective heat transfer coefficient on the freezing medium .... (W / [m2 K])

Answer #1

a food product will be frozen and placed in a can with
80% moisture content and 6cm in diameter. product density 500 kg /
m3, thermal conductivity 0.1W / (mK) and initial freezing
temperature of -2 degrees Celsius. after 10 hours it has been
frozen at -15 degrees Celsius (freezing medium) the temperature of
the product becomes -10 degrees Celsius. determine the convective
heat transfer coefficient on the freezing medium .. (W / [m2
K])

A long cylinder 11 cm in diameter is initially at a uniform
temperature of 427 C and has a density of 7250 kg/m3, thermal
conductivity of 16.7 W/m-K, and a specific heat of 540
J/kg-K. The cylinder is suddenly plunged into water with a
temperature of 27 C, giving a convective heat transfer coefficient
of 380 W/m2-K.
a) Determine the surface and centerline temperatures of the
cylinder 12 minutes after immersion.
b) Calculate the heat transferred from the cylinder during this...

A 2.5 cm inside diameter pipe is being used to convey a liquid
food at 80ºC. The inside convective heat transfer coefficient is
10W/(m2ºC). The pipe (0.5 cm thick) is made of steel (thermal
conductivity = 43W/mºC). The outside ambient temperature is 20ºC.
The outside convective heat-transfer coefficient is 100 /(m2ºC).
Calculate the overall heat transfer coefficient and the heat loss
from 1 m length of the pipe.

Consider a cube of density, specific heat, and thermal
conductivity of 2700 kg/m3, 0.896 kJ/kg-K, and 204 W/m-K,
respectively. The cube is 5 cm in length, and is initially at a
temperature of 20 oC. For t>0, two of the boundary surfaces are
insulated, two are subjected to uniform heating at a rate of 10,000
W/m2, and two dissipate heat by convection to an ambient
temperature of 20 oC, with a heat transfer coefficient of 50
W/m2-K.
Assuming lumped capacitance...

Fresh food product is held in cold storage at 278K. It is packed
in a container in the shape of a slab with all facesinsulated
except for the top flat surface, which is exposed to airat 278oK.
The slab is 154.2 mm thick and the exposedsurface area is 0.18m2.
The density of the foodstuff is 641 kg/m3. The heat of respiration
is 0.070 kJ/kg-hr.and the thermal conductivity is 0.346 W/mK.

A thin metallic wall may be constructed using copper (properties
are given in the table). The piping is required
to have a radius r = 0.008 m and carries steam at 385 K. The wall
is inside a room surrounded by air at a temperature
of 298 K. The wall is insulated with a material (properties are
given in the table).
Properties
Copper
Insulation material
Thermal Conductivity (W/m per ˚C)
385
0.071
Density (kg/m3)
8940
453
i. If the external...

A 0.6 m thick plate's temperature distribution is being
estimated using finite difference methods. Initial temperature
distribution is uniform at 30 C. A 70 C medium submerges the plate
on both sides. The medum has a heat transfer coeffficient (h) = 50
W/m2K. The thermal diffusivity of the plate material is 2.7 x 10-4
m2/s., and the thermal conductivity (k) = 0.34 W/m K.
What are the proper values of M, N, Δx and Δt used in the finite
difference...

1. In an industrial process, a tank containing 200 liters of
water at 372 K at a constant pressure is used as a thermal energy
storage device. The device is used to heat a residential space that
is maintained 293 K. There is a negligible change in the volume of
the water. The water is stirred during this process to maintain a
uniformly distributed temperature. During the process, the
convective heat transfer coefficient between the water and the
space is...

A can of soft drink, 12-cm high and 6-cm diameter, is initially
at 20°C. It is placed in a refrigerator where the air is at 0°C.
The convective heat transfer coefficient associated with the outer
surface of the can is 10 W/m2 °C. Assuming the properties of the
drink to be those of water and that the heat capacity of the
container is negligible, estimate the time taken for the
temperature of the drink to reach 5°C.
USING EES PLEASE

A block of tofu (5 cm × 2.5 cm × 1.25 cm) needs to be
sterilized to make it shelf stable. Typically holding this product
at 120 C for 2.5 minute is adequate to sterilize this product. This
is accomplished by keeping the product in high pressure retort
containing steam at 121 °C. Calculate the process time for this
operation if the convective heat transfer coefficient of steam is
200 W/m2, and thermal conductivity of the tofu is 2 W/m2....

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