Biomedical Engineering Reference
In-Depth Information
QQQ
hp
==
=+
2
1
(4.34)
hp
hp
total
1
2
However, when two identical pumps are placed in parallel with their suction
and discharges connected, they will produce the same head and equal flow rates.
Q
=
==
2*
Q
total
one
(4.35)
hp
hp
hp
2
1
EXAMPLE 4.10
An LVAD is an implantable pump that can be used to treat a patient whose heart muscle
is too weak to provide adequate blood flow to the circulatory system on its own. An LVAD
is connected as a shunt from the pulmonary vein to the aorta. The total blood flow rate is
5.0 L/min and blood has a density of 1.056 g/mL. At rest, the mean velocity and pressure
of the blood in the pulmonary vein are 30 cm/s and 6 mmHg, respectively; the average
velocity and pressure of the blood in the aorta are 30 cm/s and 90 mmHg, respectively. If
the LVAD provides work at the rate of 0.500 mhp at rest, what is the rate of work, in hp,
provided by the patient's left atrium and left ventricle at rest?
Solution: System = blood in L. atrium, L. ventricle, LVAD for expanding the work term
into the heart, LVAD and flow work components
WW W PV PV
WWV P
0
=
+
−
+
=
heart
LVAD
in in
out
out
(
P
)
=−
+
−
heart
LVAD
in
out
W
( 0.00050 hp)
(5.0 L/min)(6
90 mmHg)
0.00050 hp
420 L.mmHg/min
=− −
+
−
=
−
heart
0.0007515 hp
0.00075 hp
=−
≈ −
The magnitude of the heart's work is comparable to that of the LVAD.
