BACKGROUND ART
[0001] This invention relates to a heat exchanging apparatus designed to allow control of
the perfusate temperature easily, promptly and economically.
[0002] The use of heat exchangers is widespread in multiple fields, either to cool a warm
fluid or to warm a cold fluid. In the medical field these devices must be sterile,
and preferably disposable, which implies limitations as to the design and materials
that can be used to construct them. Changing the temperature of the heat dissipating
bath fluid allows cooling or warming the perfusate fluid using the same heat convecting
unit. Conventional heat exchangers require changing the temperature of the entire
bathing fluid volume to induce a change of the perfusate temperature. Since the temperature
exchange efficiency is a function of the heat convecting surface area, for a given
configuration of that convecting surface (coils, convoluted spirals, straight tubes,
parallel corrugated sheets, etc), the exchanging capabilities will be maximized by
forcing the bathing fluid to move around, to maintain the maximum temperature gradient
which facilitates the transport of the heat to or from the heat convecting unit to
the heat dissipating bath fluid. To effectively pump and circulate the bathing fluid
at a high flow rate around the heat convecting unit, this has been encased within
a small closed chamber, and the bulk of the bathing fluid compartmentalized, together
with the refrigerating or warming device within another large main tank.
[0003] Although conventional heat exchangers are very efficient, controlling the effective
heat convecting surface area is precluded by design. Changing the bathing fluid circulating
flow rate and/or the temperature of the bath fluid itself are the only means to change
the perfusate or effluent temperature. The ready temperature control range achievable
by changing the bath fluid circulating flow rate is rather limited; and changing the
temperature of the entire bath fluid volume is time and energy consuming which precludes
effecting prompt perfusate temperature changes. It also requires sophisticated but
costly means to change and to maintain the temperature of the bathing fluid to and
at the newly chosen one.
SUMMARY OF THE INVENTION
[0004] This invention is aimed at solving these shortcomings providing a simple and economic
means to control the effluent temperature easily, promptly and very effectively over
a wide range, without the need of changing the temperature of the bathing fluid with
highly sophisticated but expensive temperature controlled refrigerating or warming
devices.
[0005] According to the present invention, there is provided a heat exchanging apparatus
comprising:
(a) a heat exchanging reservoir for containing a heat dissipating bath fluid therein;
(b) a heat convecting unit including a fluid pathway for flowing a perfusate therethrough,
the heat convecting unit being accommodated in the heat exchanging reservoir so as
to be immersed in the bath fluid at a prescribed extent of immersion; and
(c) an immersion adjusting means attached to at least one or both of the components,
the heat convecting unit and the heat exchanging reservoir, for controlling the extent
of immersion of the heat convecting unit in the bath fluid. In the foregoing, the
immersion adjusting means may include a mast attached to the heat exchanging reservoir,
a support vertically slidably attached to the mast for holding the heat convecting
unit, and a holding means for holding the support in a prescribed position on the
mast.
[0006] Moreover, the apparatus may be constructed so as to include a driving unit for driving
the immersion adjusting means, a sensing means attached to the heat convecting unit
for sensing the effluent temperature of the perfusate to produce an effluent temperature
signal, and a control unit connected to the sensing means and the driving unit for
operating the driving unit based on the signal from the sensing means. With this construction,
the driving unit operates the immersion adjusting means (for example, slides up or
down the support along the mast), to adjust the extent of immersion of the heat convecting
unit within the bath fluid in response to the effluent temperature signal obtained
by the sensing means to thereby maintain the effluent temperature within a narrow
predetermined range. Accordingly, the effluent temperature can be servo-controlled
automatically based on the sensed temperature of the effluent exiting the heat convecting
unit. The mechanisms of the servo-control are relatively simple and reliable to maintain
a given effluent temperature.
[0007] The immersion adjusting means may be modified to include a plurality of chambers
defined in the heat convecting unit-heat exchanging reservoir complex and a plurality
of valves each attached to an inlet port of a respective chamber of the heat convecting
unit-heat exchanging reservoir complex. A further modified adjusting means may be
provided by forming a plurality of drainage ports in the heat exchanging reservoir
in vertically distributed relation to one another, and providing a plurality of valves
each attached to a respective drainage port of the heat exchanging reservoir containing
the heat convecting unit. In either modification, the extent of immersion of the heat
convecting unit in the bath fluid can be controlled by manual or servocontrolled operation
of the valves.
[0008] In addition, there may be provided means to create motion of the bathing fluid in
the vicinity of the heat convecting unit by using a tubular mast with multiple side
ejecting holes thus playing the role of a bath fluid disperser as well, the open end
of which is connected to a pumping system that draws the heat dissipating bath fluid
directly from the bath tank. The incorporation of such a means to create bath fluid
motion increases the efficiency of the heat convecting unit.
[0009] The bath fluid containing reservoir may be separated from the fluid disperser/heat
convecting unit support mast that has been fixed onto a portable base that also supports
the inlet tube for the bath fluid pump, and thus the portable base can be moved and
placed within any tank such as an ordinary bucket, thus increasing its versatility.
[0010] Furthermore, the heat convecting unit may be disposed in a small reservoir, and a
major tank separately provided for holding the bulk of the bathing fluid as well as
a heat source for controlling the temperature of the bath fluid. The small reservoir
could be of the open configuration as described above, or of totally enclosed type
having a variety of designs either to allow sliding the heat convecting unit in or
out of the encasing reservoir, or the heat convecting unit being incorporated fixedly
in the encasing reservoir as a single complex but having the bath fluid pathway compartmentalized
in a number of chambers, whose filling or emptying could be controlled individually,
as described previously. In these modifications, the bath fluid is obligated to circulate
between the major tank and the fluid disperser disposed in the small heat exchanging
reservoir, at a fixed rate or at a controllable rate, by a suitable circulating pump
system. With this construction, the heat exchanging reservoir can be easily moved
and located at some distance away from the major bathing fluid tank. Also, when the
circulating pump is designed to have a means for adjusting the circulating flow rate,
it is possible to effect minor adjustments of the effluent temperature of the perfusate
independently from the operation of the immersion adjusting means.
[0011] The heat exchanging apparatus may further be constructed so as to provide bathing
fluid motion at a fixed rate, or at controllable rate, by any stirring means other
than a pump, such as a propeller, disposed at the bottom or the lateral wall of the
bath fluid reservoir, independent from but in the vicinity of the heat convecting
unit.
[0012] According to the heat exchanging apparatus thus constructed, as the effluent flows
through the heat convecting unit immersed in the bathing fluid, its temperature will
tend to approximate that of the bathing fluid. Changing the effective heat convecting
surface area, i.e., the extent of immersion of the heat convecting unit in the bath
fluid by the immersion adjusting means will afford ready and easy control of the effluent
temperature, with minimal time lag, over a wide range of temperatures, without ever
changing the bath fluid temperature to a new one. The apparatus is rather simple in
construction and does not require complex and expensive systems that conventional
heat exchangers would require if they were to achieve the same controllability of
the effluent temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
Fig. 1 is a schematic cross-sectional view of a heat exchanging apparatus in accordance
with a first embodiment of this invention;
Fig. 2 is a plan view of the heat exchanging apparatus of Fig. 1;
Fig. 3 is a schematic side elevational view of a heat convecting unit used in the
heat exchanging apparatus of Fig. 1;
Fig. 4 is a schematic perspective view of a modified heat convecting unit used in
the apparatus of Figs. 9 and 10;
Fig. 5 is a schematic cross-sectional view of a heat exchanging apparatus in accordance
with a second embodiment of this invention, the heat exchanging reservoir having the
open configuration;
Fig. 6 is a schematic cross-sectional view showing an essential part of a heat exchanging
apparatus in accordance with a third embodiment of this invention, the disposable
or reusable heat exchanging reservoir (in solid line) having the closed configuration
in which the bath fluid pathway has been compartmentalized into a number of chambers,
each chamber being connected to the detachable inlet and outlet ports of the bath
fluid circulating valved manifold (one dotted line);
Fig. 7 is a schematic cross-sectional view of a heat exchanging apparatus in accordance
with a fourth embodiment of this invention, the heat exchanging reservoir being the
closed configuration version of that illustrated in Fig 5., while the coils of the
disposable heat convecting unit have been cut off for simplicity and only the origin
(2c) of the coils are illustrated;
Fig. 8 is a schematic cross-sectional view of a heat exchanging apparatus in accordance
with a fifth embodiment of this invention;
Fig. 9 is a view similar to Fig. 1, but showing a heat exchanging apparatus based
on a sixth embodiment of this invention;
Fig. 10 is a plan view of the heat exchanging apparatus of Fig. 9; and
Fig. 11 is a schematic cross-sectional view of a heat exchanging apparatus based on
a seventh embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0014] A heat exchanging apparatus in accordance with a first embodiment of the invention
is illustrated in Fig. 1 and Fig. 2. A heat convecting unit 2 through which the fluid
effluent E is flowed, is disposed within an open reservoir or heat exchanging reservoir
or tank 1 containing a prescribed bathing fluid F at the desired temperature. To maximize
the heat convecting surface area of the heat convecting unit 2, multiple small diameter
coils arranged in parallel spirals 2c between an inlet tubing 2a and an outlet tubing
2b has been illustrated in Fig. 3. When they are to be used as a component of circuits
coming in contact with blood that is to be returned to patients, these units must
be made from medical grade material, polyvinyl chloride being the most economic and
practical one, but not limited to it, to afford the luxury of making them disposable.
[0015] The heat convecting unit 2 is mounted on a sliding system 3 constituted from a support
mast 4 solidly fixed in the center of the bottom 1a of tank 1, and a heat convecting
unit supporting frame 5. The support frame 5 is a cylindrical frame with a top 5a
and a bottom 5b joined by vertical beams 5c around which the coils 2c of the disposable
heat convecting unit 2 is placed and secured, coaxially movable and fixed to the mast
4 by the holding means 6. The holding means 6 is fixedly attached to 5a on one hand,
and movably attached to the mast 4 by its C-clamp 6a which is secured at the desired
level by a bolt 6b. Accordingly the sliding system 3 allows to move the support frame
5 up or down along the support mast 4 and fix it at the desired level by tightening
the bolt 6b.
[0016] The central and coaxial location of the support mast 4 in relation to the tank 1
and coils 2c lends itself to using the mast 4 not only as a supporting mast, but also
as an effective bath fluid disperser 7 by using a tubular structure with multiple
fluid ejecting side holes 7a along the immersed portion of the mast that will eject
the bath fluid forcefully towards the coils 2c that come in close apposition. The
tank 1 is large enough to contain sufficient amounts of bath fluid and the cooling
(refrigerating unit or simply prefabricated ice) or warming source(s). To increase
the heat exchanging efficiency, a circulating device 9 for pumping the bath fluid
from the reservoir into the bath fluid disperser 7 has been incorporated. More specifically,
a pump 9a is provided for drawing bath fluid through an inlet tube 9b attached to
an opening made in the bottom 1a of the tank 1 and pumping it into the fluid disperser
7 through an outlet tube 9c. With this construction, the bath fluid rushes through
the ejecting holes 7a creating motion of the bath fluid surrounding the coils 2c,
thus forcing the bath fluid to circulate which will increase dissipation of the temperature,
i.e., efficiency of the heat exchange.
[0017] Fig. 5, Fig. 6 and Fig. 7 illustrate second, third and fourth embodiments of this
invention, respectively, in which the heat exchanging reservoir 1 has been made just
big enough to house the heat convecting unit for portability, and the bulk of the
bath fluid as well as the heat source (refrigerating unit or prefabricated ice, or
warming device) have been disposed in a separate large tank, the bath fluid being
circulated between the two reservoirs.
[0018] In the second embodiment shown in Fig. 5, the heat exchanging reservoir 1 has the
economic open configuration for its easy construction according to the previous description,
but could be one with a totally enclosed configuration in which the heat convecting
unit could be slid in or out of the encasing reservoir as means to control the extent
of immersion but maintaining water tightness to allow circulating the bath fluid (not
illustrated because of the cost and complexity involved in its design).
[0019] In the third embodiment shown in Fig. 6, the heat exchanging reservoir 1 and the
heat convecting unit (that portion with the array of arrows indicating the perfusate
pathway coming from or leading to E) have been incorporated in a single enclosed complex
(represented by the solid line) that could be made either with disposable material
for single use or resterilizable material for multiple use. The means to control the
area of the heat convecting unit that comes in contact with the bath fluid is provided
by subdividing the bath fluid pathway (represented by the wavy arrows) portion of
the complex unit in a number of chambers through which the bath fluid is flowed individually
in a controllable manner using valves 17a disposed upstream each of the branches of
the detachable bath fluid distributing inlet and outlet manifolds 17 (one dotted line
components) equivalent to the disperser 7, and a one way air valve 20 to allow emptying
of each of the excluded bath fluid pathway chambers.
[0020] In the fourth embodiment of Fig. 7 which is the enclosed version of the heat exchanging
reservoir 1 of Fig. 5 by providing a water tight lid 21 with water tight entrance
and exit ports 22 for the effluent tubes 2a and 2b, the level of the bath fluid is
controllable by changing the level of the drainage port using a draining manifold
17 with multiple controllable ports by similar valves 17a and the one way air valve
20, or by a height controllable siphon type port instead of a multiple draining manifold
(not illustrated).
[0021] In the above three embodiments, a large main tank 8 has been designed to hold enough
bath fluid and ice, and in addition obligatory means 9 to circulate the bath fluid
between the tank 8 and the tank 1 have been provided. Accordingly the pump 9a draws
bath fluid from the main tank 8 through the inlet tube 9b connected to an opening
in the bottom portion 8a of the main tank 8, and pumps it through the outlet tube
9c into the mast 4/disperser 7 or distributing manifold 17 of the heat exchanging
reservoir 1, so that the fluid is forcefully dispersed via the side holes 7a, or the
active branch(es) controlled by the valves 17a of the distributing manifold 17 creating
motion of the bath fluid surrounding the coils 2c of the heat convecting unit 2 or
straight tubes 12a, and returned to the main tank 8 via a drainage tube 10. The drainage
tube 10 is connected to the overflow opening disposed high enough in the lateral wall
of the tank 1 to allow full immersion of the heat convecting unit 2 in the bath fluid
in the open reservoir configuration as depicted in Fig. 5, or to a multiple ports
draining manifold in the closed reservoir configuration as in Fig. 6 and Fig. 7. The
connection of tube 9b is preferably made to the bottom of the tank 8 to draw the coldest
bath fluid.
[0022] The above embodiments use prefabricated ice as cooling source, but complex and sophisticated
refrigerating or heating devices, such as those used in conventional heat exchangers,
could be incorporated in the main tank 8 to serve as heat sources for providing the
desired temperature of the bath fluid F.
[0023] The temperature of the effluent E exiting the heat convecting unit 2 of the heat
exchanging apparatus with the above embodiments can be controlled easily by loosening
the bolt 6b of the holding means 6, sliding up or down the support frame 5 to the
level where the desired temperature downstream the unit 2 is obtained and fixing it
at that new position by tightening the bolt 6b of the first and second embodiments
illustrated in Fig. 1, 2 or 5. When using the third embodiment illustrated in Fig.
6, the branch(es) of the fluid dispersing or distributing manifold 17 is(are) individually
controlled using their respective valve 17a to shut the bath fluid flow and let the
air in via the one way air valve 20 to empty the chamber(s) to be excluded, thus controlling
the extent of immersion of the heat convecting unit 12. When using the fourth embodiment
of Fig. 7, the draining port valve(s) 17a to the desired bath fluid level as well
as the one way air valve are open, thus emptying part of the reservoir and controlling
the extent of immersion of the heat convecting unit. Although temperature control
could be accomplished by adjusting the temperature of the bath fluid in the main tank
8, it is simpler to keep enough ice in the main tank 8 to maintain the bath fluid
temperature as close to the constant ice-melting temperature, and the effluent temperature
control achieved by changing the extent of immersion of the heat convecting unit 2
or 12, i.e., by adjusting the effective heat convecting surface area in contact with
the heat dissipating fluid. Additional minor or fine effluent E temperature control
can be effected by adjusting the rate of turnover or flow rate of the bath fluid contacting
the heat convecting unit 2 or 12 which determines the heat carrying capacity of the
system by controlling the rate of the pump 9a.
[0024] From the previous descriptions and regardless of the embodiment used, controlling
the effluent temperature is reduced to the rather simple maneuver of adjusting the
height of the holder 6 or the number of active bath fluid dispersing branches or the
draining ports of the manifold 17. The embodiments of the apparatus are rather simple,
not requiring complex, sophisticated and expensive devices to achieve it. The heat
convecting unit 2 made out of multiple small tubes in parallel allows maximizing the
heat convecting surface area, at the minimum cost of priming volume and pressure drop
across the unit. The effluent temperature could almost be predicted if effluent E
flows and the temperature of the effluent at the inlet of the unit 2 are known based
on the extent of heat convecting unit immersed in the bath fluid, and final adjustments
be made very simply by either fine control of the height of the holder 6, or altering
the number of active branches of the manifold 17, and/or the bath fluid pump 9a rate.
The use of the embodiment according to claim 4 allows easy portability of the heat
convecting unit 2 or 12 portion of the apparatus to bring it close to the patient
for example. Concerning bath fluid temperature handling during operation of any of
the described embodiments it can be kept fixed and close to that of the melting ice,
simply by adding prefabricated ice to the main tank, regardless of the desired effluent
temperature, therefore obviating the need of incorporating expensive and sophisticated
temperature controllable refrigerating or warming units.
[0025] Because the cooling temperature range usually required for medical uses can be provided
with water or water based heat dissipating solutions, the use of prefabricated ice
to cool the water of the bath fluid becomes highly practical. For warming, the use
of hot water is also the simplest and cheapest means.
[0026] Using metallic tubes with better heat conducting characteristics than plastic material
to construct the heat convecting unit 2 further increases its efficiency, and allows
designing the heat convecting pathways in any of the known configurations. Fig. 4
illustrates the simplest unit 12 in which multiple segments of straight tubes 12a
are bundled and joined in parallel by means of two hollow collecting or distributing
end plates 12b, one end 12c being connected to the inlet tube, and the other end 12d,
disposed parallel to 12c for easy maneuverability, to the outlet tube. The rigid nature
of the metallic tubes lends to their use for the construction of disposable or reusable
heat exchanging complex units with multiple bath fluid chambers as that illustrated
in Fig. 6. Although not illustrated, the heat convecting pathway(s) could be of the
convoluted spirals, corrugated sheets or any other configuration known to increase
the effective heat convecting surface area.
[0027] The two-dotted line components of Fig. 1 represent a servo-control mechanism to maintain
the effluent at a predetermined temperature, by adjusting the height of the support
frame 5 with a somewhat more complex and automated mechanism. Specifically, there
is a sensor 14 to monitor the effluent temperature downstream to the heat convecting
unit 2 that feeds the information to a microprocessor control unit 16 that in turn
activates a motorized drive device 15 to move up or down the heat convecting unit
supporting frame 5 to control the extent of its immersion in the bath fluid F thus
adjusting the effective heat convecting surface area of the unit 2, and also obviates
the need for manual fixing of holder 6 with the bolt 6b. Although a winding mechanism
15b has been illustrated in Fig. 1 for simplicity purposes, obviously an endless screw
mechanism would be better fitted to impart accurate up or down movement to the frame
holder 6 along the mast 4. It is also obvious, though not illustrated that servo-control
could be achieved using the embodiment illustrated in Fig. 6 or Fig. 7 by providing
means to adjust the opening or closure of valves 17a of inlet or outlet manifold 17.
[0028] A fifth embodiment of this invention is illustrated in Fig. 8, in which components
with the same or similar function to those already described have been identified
with the same numbers and their explanation is omitted. Accordingly the mast/disperser
4/7 has been fixed in the center of a portable base 18 which is constituted by a plate
18b and supporting feet 18a that allows accommodating the tube 9c beneath the plate
18b. The mast/disperser 4/7 pierces the center of the base plate 18b to be connected
to tube 9c, and the tube 9b which is the other arm of the means to circulate the bath
fluid has been fixed at the periphery of the plate 18b with the opening facing the
bottom of the tank. If bath fluid motion is desired, tubes 9b and 9c are connected
to the inlet and outlet of the pump 9a respectively which has been omitted from the
Figure. Because these components are not attached to the tank itself, the heat exchanging
components can be moved with ease and immersed into any big enough reservoir such
as an ordinary bucket with iced water, thus making it a versatile device.
[0029] According to the sixth embodiment of this invention illustrated in Fig. 9 and Fig.
10, a plurality of bath fluid dispersers 7, one of which has been extended upwards
to play the role of the supporting mast 4 as well, have been disposed in such a manner
as to eject the bath fluid centripetally via the multiple ejecting holes 7a to force
the bath fluid to flow between the multiple vertical pathways 12a of the heat convecting
unit 12. This unit 12 is supported by the support bar 5 and held by the holder 6,
in turn attached to the mast/disperser 14/7 to allow sliding up or down the entire
unit 12 along the mast 14 and its fixing at the proper height. Each of the fluid dispersers
7 that pierces the bottom of the bath fluid tank and ultimately connect to tube 9c,
the tube 9b whose inlet opens at the bottom of the tank 1, and the pump 9a constitute
the bath fluid circulating system 9. Sliding the holder 6 up or down alongside the
mast 14, will change the extent of immersion of the unit 12 in the bath fluid F from
none to all. The apparatus could be constructed following the aspects of this invention
outlined in Fig. 5, Fig. 6, Fig. 7 or Fig. 8 as well.
[0030] According to the seventh embodiment of this invention depicted in Fig. 11, the bath
fluid disperser 7 has been eliminated, and instead a fluid stirrer 25 has been provided
at the bottom of the tank 1, the propellers 25b being actuated via a shaft by a motor
25a located outside of the tank 1, or coupled by electromagnetic means which is not
illustrated in the Figure. The mast 24 to provide support of the said heat convecting
unit 2 or 12 is disposed on the lateral wall of the tank 1. When the stirring propellers
25b are set in motion, the bath fluid will move in the same direction as the stirring
propellers thus creating a flow of the bath fluid surrounding the heat convecting
unit, increasing the heat exchanging efficiency. In addition, controlling the speed
of rotation of the stirring propellers affords some degree of perfusate temperature
control, similarly to controlling the pump rate of the bath fluid in previously described
embodiments.
1. A heat exchanging apparatus comprising:
a heat exchanging reservoir (1) for containing a heat dissipating bath fluid (F)
therein; and
a heat convecting unit (2) including a fluid pathway for flowing a perfusate (E)
therethrough, said heat convecting unit being accommodated in said heat exchanging
reservoir so as to be immersed in said bath fluid at a prescribed extent of immersion;
characterized by an immersion adjusting means attached to at least one or both
of said heat convecting unit and said heat exchanging reservoir for controlling the
extent of immersion of said heat convecting unit in said bath fluid.
2. A heat exchanging apparatus as defined in claim 1, further comprising a driving unit
(15) for driving said adjusting means, a sensing means (14) attached to said heat
convecting unit for sensing the temperature of said perfusate to produce an effluent
temperature signal, and a control unit (16) connected to said sensing means and said
driving unit for operating said driving unit based on the signal from said sensing
means.
3. A heat exchanging apparatus as defined in claim 1, wherein said immersion adjusting
means includes:
a mast (4) attached to said heat exchanging reservoir,
a support (5) vertically slidably attached to said mast for holding said heat convecting
unit, and
a holding means (6) for holding said support in a prescribed position on said mast.
4. A heat exchanging apparatus as defined in claim 3, further comprising means for producing
bath fluid motion around said heat convecting unit; wherein said mast includes a tubular
portion accommodated in said heat exchanging reservoir and having a plurality of apertures
(7a) formed therethrough; and wherein said bath fluid motion-producing means includes
a bath fluid disperser (7) defined by said tubular member, a circulating device (9)
arranged between said heat exchanging reservoir and said disperser for circulating
the bath fluid in said heat exchanging reservoir through said disperser to thereby
forcefully eject the bath fluid against said heat convecting unit.
5. A heat exchanging apparatus as defined in claim 4, further comprising a portable base
(18), said circulating device including an inlet tube (9b) for permitting the bath
fluid to return thereto and an outlet tube (9c) connected to said disperser for permitting
the bath fluid to flow into said disperser, said inlet and outlet tubes being secured
to said portable base, whereby said portable base as well as said inlet and outlet
tubes are capable of being carried independently from the reservoir.
6. A heat exchanging apparatus as defined in claim 1, further comprising a major tank
(8) for containing the bath fluid and a heat source for controlling temperature of
the bath fluid, and a circulating device (9) arranged between said heat exchanging
reservoir and said major tank for circulating the bath fluid between said major tank
and said reservoir.
7. A heat exchanging apparatus as defined in claim 6, wherein said circulating device
includes a means for adjusting a circulating flow rate to further control the effluent
temperature of said perfusate.
8. A heat exchanging apparatus as defined in claim 1, further comprising a stirring means
(25) attached to said heat exchanging reservoir for stirring the bath fluid contained
in said heat exchanging reservoir.
9. A heat exchanging apparatus as defined in claim 8, wherein said stirring means further
includes means for controlling bath fluid motion rate.
10. A heat exchanging apparatus as defined in claim 1, wherein said heat convecting unit
is incorporated within the heat exchanging reservoir which is partitioned in a plurality
of separated chambers each having an inlet port; said immersion adjusting means including
said chambers and a plurality of valves each attached to a respective inlet port of
a heat dissipating fluid distributing manifold, whereby the valves are operated to
select the chambers into which the bath fluid is flowed to control the extent of immersion
of the heat convecting unit in the bath fluid.
11. A heat exchanging apparatus as defined in claim 1, wherein said heat exchanging reservoir
includes a plurality of drainage ports arranged in vertically distributed relation
to one another, said immersion adjusting means including a plurality of valves (17a)
each attached to a respective drainage port of said heat exchanging reservoir, whereby
the valves are operated to determine a level of the bath fluid in the reservoir to
control the extent of immersion of the heat convecting unit in the bath fluid.