Question

a) A vertical plate of 700 mm wide
and 120 cm height is maintained at a temperature of 95^{o}C
in a room at 25^{o}C with an air conditioning with velocity
of 36000 cm/min. Calculate the heat transfer coefficient and
convective heat transfer rate.

(b) Two concentric cylinders are
located in a large room. Determine the view factors for the two
cylinders when the length is 20 cm, the inner radius
(r_{1}) is 5 cm and the outer radius (r_{2}) 10 cm.
The whole system is in thermal equilibrium.

(c) A heat exchanger uses oil
(c_{p} = 1880 J kg^{-1} K^{-1}) at an
initial temperature of 205°C to heat up water with heat capacity of
1 kcal kg^{-1} K^{-1}, and density = 0.998 g
cm^{-3}, flowing at 0.00376 m^{3} min^{-1}
from 16°C to 44°C. The configuration of the heat exchanger is in
countercurrent. The oil mass flow rate is 270 kg
h^{-1}.

(1 cal = 4.18 J)

(i) What is the heat
transfer area required for an overall heat transfer coefficient of
0.34 kW m^{-2}
K^{-1})?

(ii) Determine the number of transfer units (NTU).

(iii) Calculate the effectiveness of the heat exchanger

Answer #1

b). Consider the following figure;

Then by summation law, i.e., Now, by law of reciprocity, i.e., Now, again by the law of summation,

c). Given: And, since mass flow rate = volume flow rate X Density, we have -

Then, Now, for counter flow,

A thin-walled double pipe counter flow heat exchanger is to be
used to cool oil (cp = 2200 j/kg*K) from 150 ℃ to 30 ℃ at a rate of
2.1 kg/s by water (cp= 4180 J/kg*K) that enters at 20 ℃ at a rate
of 1.2 kg/s. The diameter of the tube is 2.5 cm, and its length is
10 m.
Using Excel (a) Determine the overall heat transfer coefficient
of this heat exchanger. (b) Investigate the effects of oil...

water at the rate of 225 kg/hours is to be heated from
350C to 950C by means of a concentric tube
heat exchanger. Oil at a rate of 225kg/hr with specific heat of
2095 J/kg.K and temperature of 2100C is to be used as
the hot fluid. If the overall heat transfer coefficient based on
the outer diameter of the inner tube is 550 W/m2.K,
determine the length of heat exchanger if the outer diameter of the
tube is 100...

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 process fluid having a specific heat of 3500 J/kg?K and
flowing at 2 kg/s is to be cooled from 80 °C to 40 °C with chilled
water, which is supplied at a temperature of 15 °C and a flow rate
of 2.5 kg/s. Assuming an overall heat transfer coefficient of 2000
W/m2?K, calculate the required heat transfer areas for the
following exchanger configurations: (a) Parallel flow; (b) Counter
flow; (c) a 1-2 shell and tube exchanger with the water...

A freshly baked loaf of bread (30cm long, 15cm high, 10 cm wide)
is removed from an oven and set on the counter (assumed insulated)
to cool. The bread is at 125°C initially (assume uniform) and the
room is at 25°C. Thermal conductivity and diffusivity for bread are
k=0.05 W/m•K and α=5x10-7 m2/s, and the convective heat
transfer coefficient is h=10 W/m2K.
(a) Write down the governing differential equation in
three-dimension representing this problem.
(b) Write down the boundary conditions...

Adrian is trying to heat up a sphere (radius = 0.05 m) of
unknown material in a furnace. She wants to know how long it will
take for the object to heat up to 300°C when moved from room
temperature (25°C) to a 600°C furnace. Use the following
information to determine the time (in minutes) it will take for the
sphere to reach 300°C after transfer to the furnace.
Make sure to show validation for any equations that you
use....

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....

Water at 15°C enters a tube of 2 cm of diameter with flow rate
3953 kg/h. Assume the ratio L/D>10, and the wall temperature is
constant at 80-C. The outlet temperature is 50°C The properties of
water at the film temperature are density rho = p = 985 kg/m3,
specific heat Cp = 4180 J/kgk, conductivity k = 0.651 W/mK, dynamic
viscosity mu= u = 4.71 × 10- kg/ms, At the wall temperature of 80°C
we have dynamic viscosity muw=...

Question 3
Part A
An aluminium saucepan containing 1 kg of water is heated by a
hot plate as shown in the figure below. The pan has a cylindrical
shape, with a radius of 15 cm. The thickness of the aluminium
section at the bottom is 10 mm. The air temperature is 25 degrees
celsius, and water temperature in the pan is uniform at 100 degrees
celsius.
a. Calculate the heat transfer rate via convection at the water
surface.
b....

Homework-9
Due:
Q) A fuel plate is fabricated from 0.3 cm thick 1.5% enriched
uranium. The cladding is 0.25 mm 304 stainless steel. The coolant
saturation temperature is 260 oC. The
average thermal neutron flux is 2.5 X
1014
neutrons/cm2 /s. The surface
temperature of the clad is 350 oC.
Assume any missing data to answer the following questions:.
1) Write an expression of the heat generated per unit volume
2 What is the heat flux at the surface of...

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 12 minutes ago

asked 14 minutes ago

asked 27 minutes ago

asked 41 minutes ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 2 hours ago

asked 2 hours ago

asked 3 hours ago

asked 3 hours ago

asked 3 hours ago