Using a Michelson interferometer and a light source of 400nm, a change from bright to dark indicates a change in distance of
a. 
b. 
c. 
d. 
d.
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Determine the appropriate size of a shell-and-tube heat exchanger with two tube passes and one shell pass to heat 8.82 kg/s of pure ethanol from 15.6 to 60°C. The heating medium is saturated steam at 152 kPa condensing on the outside of the tubes with a condensing coefficient of 15,000 W/(m2K). Each pass of the exchanger has 50 copper tubes with an OD of 1.91 cm and a wall thickness of 0.211 cm. For the sizing, assume the header cross-sectional area per pass is twice the total inside tube cross-sectional area. The ethanol is expected to foul the inside of the tubes with a fouling coefficient of 5678W/(m 2 K). After the size of the heat exchanger, i.e., the length of the tubes, is known, estimate the frictional pressure drop using the inlet loss coefficient of unity. Then estimate the
pumping power required with a pump efficiency of 60% and the pumping cost per year with $0.10 per kw-hr.
GIVEN
• Shell-and-tube heat exchanger, ethanol in copper tubes, steam in shell
• One shell pass and two tube passes
• Ethanol flow rate m e= 8.82 kg/s
• Ethanol temperatures
? Te,in = 15.6°C
? Te,out = 60°C
• Steam pressure = 152 kPa
• Number of tubes (N) = 50
• Tube outside diameter (Do) = 1.91 cm = 0.0191 m
• Tube wall thickness (t) = 0.211 cm = 0.00211 m
• Header area per pass = 2 (total inside cross-sectional area)
• Tube side fouling coefficient (1/Ri) = 5678 W/(m2 K)
• Shell-side transfer coefficient h o= 15,000 W/(m2 K)
FIND
(a) Size: length of one pass (Lp)
(b) The frictional pressure drop (?p)
(c) The pumping power required (Pp) with a pump efficiency (?p) = 60%
(d) Pumping cost per year for energy cost of $0.10/kw-hr
ASSUMPTIONS
• The variation of thermal properties with temperature is negligible
• Shell side fouling is negligible
• The tubes are smooth
• Entrance pressure drop effects are negligible
SKETCH
PROPERTIES AND CONSTANTS
the temperature of saturated steam at 152 kPa (Ts) = 110°C
for ethanol (ethy1 alcohol) at 20°C
Density (?) = 790 kg/m3
Thermal conductivity (k) = 0.182 W/(m K)
Absolute viscosity (?) = 12.0 × 10–4 (Ns)/m2
Prandtl number (Pr) = 16.29 Specific heat (cp) = 2470 J/(kg K)
the thermal conductivity of copper (kc) = 392 W/(m K) at 127°C
Exhibit 12-1
The figure below shows a graph of angular velocity versus time for a woman bicycling around a circular track.
?
?
Use this exhibit to answer the following question(s).
Refer to Exhibit 12-1. What is her angular displacement (in rad) in the first 8 minutes?
A. 0 B. ? C. 4? D. 8? E. 16?
A depth change of 10 metres/33 feet causes a pressure change of.
a. 1 bar/ata b. 2 bar/ata c. 3 bar/ata d. 4 bar/ata
What field of science are the experiments on the two Mars Rovers Sojourner, Spirit, Opportunity and Curiosity most closely related to?
A) physics B) biology C) geology D) astronomy