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ME4331
Pre Lab Questions in Preparation for the Heat Exchanger Lab:
First, read “Heat Exchangers” in the Resources section of the web page.
1. Do the following heat exchanger analysis using the effectiveness-Ntu method.
A concentric tube heat exchanger for cooling lubricating oil is comprised of a thinwalled, copper inner tube of 25 mm diameter carrying water and an outer tube of 45 mm
diameter carrying the oil in the annular space between the two tubes. The exchanger
operates in counter-flow. The oil enters at 100  C and departs at 60  C; the water enters at
30  C. The oil and water mass flow rates are both 0.1 kg/sec.
Determine:
The total heat transfer rate (W)
The outlet water temperature (  C)
The effectiveness
The Ntu
The heat exchanger length (m)
Properties are:
Property
Water
Oil
3
Density  kg / m
1000
800
Specific heat c p J / kg  K 
4200
1900




Kinematic viscosity  m2 / sec
7x10-7
1x10-5
Thermal conductivity k W / m  K
0.64
0.134
Prandtl number Pr
4.7
140
(taken from Fundamentals of Heat and Mass Transfer, by Incropera and DeWitt)
Look at the ppt. slides on flow measurement in the Resources section of the web page.
Check out the Coriolis meter.
2. For flow moving outward in a pipe that is rotating about one end, there is an
acceleration called the Coriolis acceleration, given by:  2  x u , where  is the
rotation speed in radians per second, u is the velocity at which the fluid is moving
through the pipe and x is the cross product between the two. A force associated with
that acceleration would be the mass of the fluid blob times this acceleration. Now,
suppose the flow velocity is 10 m/sec, the pipe of 1 cm diameter is rotating at 300 rpm
counterclockwise and the fluid is 30  C water. What will be the Coriolis force per mm of
pipe length? In what direction will it be acting? Draw a sketch.