Biomedical Transport Processes - Introduction to Biomedical Engineering - page 992

slow a process to remove all heat from the body core. Without the greenhouse effect, the
earth's temperature would fall, since most of the thermal radiation from the sun would
be reflected back into space. Even heat exchangers for blood cooling and reheating make
extended surgeries possible.

14.4 EXERCISES
1. What would be the new values in Table 14.2 if the outside water partial pressure were
25 mm Hg?
2. During cell depolarization, the relative diffusivity of sodium increases 1,000-fold. What
would be the new electrical potential across the cell membrane in mv?
3. How long would it take for changes in the arteriolar diameter that affect transcapillary fluid
exchange to affect the venous return? The cardiac output is 5,000 ml/min. Assume an average
diameter of a blood vessel and the average time course of blood through the cardiovascular
system.
4. If the glomerular filtration rate (GFR) is 125 ml/min (125 cc/min), then how many pores are
there in all glomeruli?
5. Based on the relative densities, compute the ratio of pressure differences in the manometer
(shown in Figure 14.25) as a function of the same height difference for the following fluids
(use water as a reference):
Mercury/water ratio:
Glycerin/water ratio:
Oil to water ratio:
6. Research and describe the nonlinear behavior (stress vs. strain rate) for several non-
Newtonian fluids such as a dilatant fluid, a pseudoplastic fluid, and a Bingham plastic fluid.
Use the form of the stress versus strain rate equation for a Newtonian fluid as a reference
point.
7. In Figure 14.33, there is a notch in the aortic pressure waveform where the aortic valve closes.
Explain why that might happen in terms of valve movement.
8. Using the Reynolds number values listed in Section 14.2.6 for various blood vessels, compute
the ratios of V

D for these vessels, assuming that the blood density and viscosity do not
change. Then, researching the average vessel diameters, compute their average velocities.
9. Using the combination equation relating Q to (T1-T4) in the three-layer model for heat
conduction, compute the overall term consisting of the thermal conductivities for a thermal
window with glass on the outer sides and air in the middle. Use the K values in the list of
thermal conductivities and assume that all thicknesses ( X) are the same.

10. Over a ten-day period, note the nighttime low temperature on each day, as well as whether
the sky was clear at night, partly cloudy, or cloudy. How does that relate to the greenhouse
effect?
11. Using a breathing rate of 18 breaths per minute instead of 12 and an external temperature of
30 C (303 K) instead of the 20 used in the example in the text, compute the new latent and
sensible heat losses from the body. Assume all other parameters are unchanged.
12. Research Nomex and PBI and determine their thermal conductivities. Is one a better insulator
than the other for use in firefighter protective clothing? Gortex is also used as a material.
Compare that as well

D

.