Note: Descriptions are shown in the official language in which they were submitted.
FLAMELESS NITROGEN SKID UNIT
The present invention relates generally to apparatus
for heating fluids, and more particularly, but not by way of
limitation, to a flameless heater adapted for superheating liquid
nitrogen for use in gel fracturing operations on offshore oil
and gas wells.
Numerous operations are performed on oil and gas wells
which require large volumes of nitrogen gas. These operations
may be performed on both onshore and offshore wells. Such
operations include foam fracturing operations, acidizing ser-
vices, jetting down the tubing or down the tubing-casing
annulus, nitrogen cushions for drill stem testing, pressure
testing, insulation of the tubing-casing annulus to prevent
such problems as paraffin precipitation, jetting with proppant
for perforating and cutting operations, reduction of density of
well workover fluids, displacement of well fluid from tubing
during gun perforation operations to prevent excess hydro-
static pressure in the hole from pushing perforation debris into
the formation, placing corrosion inhibitors by misting the in-
hibitor with nitrogen, extinguishing well fires, and otheroperations. The present invention may be utilized with any of
these operations.
One particular such operation with relation to which
the following disclosure is made is the fracturing of a sub-
surface formation of the well by pumping a fluid under veryhigh pressure into the formation. The fracturing fluid which
is pumped into the well often comprises a foamed gel which is
produced by the use
~ b
of nitro~en gas.
The nitrogen for the foam fracturing operation is generally
stored in a liquid form at temperatures of approximately -320F.
Por pressures encountered in these foam fracturing opera-
tions, the nitrogen changes state from a liquid to a gas atapproximately -200F. It is, therefore, desirable to heat up
the nitroqen gas to a superheated state so that the foam frac-
turing fluid being pumped down the well will be at an essentially
ambient temperature. This is because of the numerous adverse
affects upon mechanical equipment of very low temperature ~hich
would otherwise be presented by the nitrogen foam.
For land based wells, the nitrogen-heating equipment generally
includes open f]ame heaters. A further problem is however, pre-
sented when performing foam fracturing operations on offshore
LS wells. For safety and environmental reasons, open flames are
not generally allowed on an offshore drilling platfor~. Therefore,
it is necessary to provide a he~ter for the nitrogen which does
not have an open flame.
~uch flameless nitrogen heaters have previously been ~rovided
by utilizing the heat generated by an internal combustion engine
and mechanical componen's driven thereby to heat a coolant fluid
which transferred that heat to the nitrogen through a coolant
fluid-to-nitrogen heat e~changer.
One such prior art device is manufactured by the zwicl~
Energy Research Organization, Inc. of Santa Ana, California.
_. . . .. _ . . . .
1~4 `i~
The Zwick ap~aratus includes a single i~ternal cor~ustion
engine which drives a hydraulic pump to produce h-~rlraulic
fluid under pressure which in turn drives a hydraulically
powered nitrogen pump.
The Zwick apparatus uses a single coolant-to-nitrogen
heat exchanger means for vaporizing the liquid nitrogen. Zwick
does not include a second heat exchanger for transferring heat
directly from engine exhaust gases to the nitrogen.
The coolant system of the Zwick device circulates the coolant
0 fluid first through a hydraulic oil-to-coolant heat exchanger
where heat from the hydraulic system of the engine and the components
driven thereby are transferred to the coolant. ~hen, the coolant
fluid stream splits into two parallel portions, one of which
flows through the engine block to absorb heat fro~, the engine
and the other of which flows throuah a manifold surroundinq the engine
exhaust for absorbing heat from the engine exhaust into the coolant
_ . . , . ~ _ _
b
fluid. After the tTo str~ams pass through the engine block and
he exhaust cooling manifolds they once again merge into a
single stream which is directed to the coolant fluid-to-nitrogen
vaporizer. From the vaporizer the fluid returns to the hyraulic
oil cooler therehy completing the loop.
With regard to the nitrogen flow system of zwick the nitrogen
flows from the nitrogen pump through the coolant-to-nitrogen heat
exchanger and then to the well head. A bypass i9 provided around
the coolant-to-nitrogen heat exchanger by means of which liquid
nitrogen can be bypassed around the coolant-to-nitrogen heat
exchanger to aid in controlling the ,emperature of the nitrogen
gas being injected into the ~ell.
The load on the single internal combustion engine of Zwick
may be varied by varying the back pressure on the hydraulic pump
driven by the engine.
Another prior art flameless nitrogen heating unit is manu-
factured by Airco Cryo~enics a division of ~irco Inc. of Irvine
California.
The ~irco device also uses a single internal combusion engine
driving a hydraulic pump which produces hydraulic fluid under pres-
sure for driving a liquid nitrogen pump.
The ~irco device utilizes air as the heat exchange medium
for transferrinq hea~ to the liquid nitrogen to varporize the same.
This is accomplished in the following manner. A large plenum
chamber is provided into ~hich ambient air is drawn. Disposed in
ib
the plenum chamber in heat exchange ccntact with the air ,lowing
therethrough is a hydraulic oil-to-air heat exchanger ~herein
hydraulic fluid heated by the engine and its various ~perating
co~ponents is circulated 'hrough the hydraulic oil-to-air heat
exchanger tc heat the air.
An enqine coolant fluid-to-air heat exchanger, i.e., the
engine radiator, is also disposed in the plenum chamber for 'rans-
ferring heat energy from the engine coolant system to the air
flo~ing through the plenum chamber.
~dditionally, the exhaust gases produced by the internal
combustion engine are dumped dlrectl-y into the plenum chamber to
mi,~ with the air flowing therethrough.
The air flo~ing throuah the plenum chamber, after it has ~een
heated by the hydraulic oil-to-air cooler and the engine radiator
and after it has mixed with engine e~haust gases, then passes over
an air-to-nitrogen heat exchanger wherein heat energy is transferred
fxom the hot air to the liquid nitrogen to vaporize the same.
The load imposed upon the internal combustion engine of the
~irco device may be varied by var~ing the pressure in the va~porized
nitrogen discharge line to raise the pressure against which the
nitrogen pump is wor~ing and in turn raise the load on the ~Iydraulic
pump driven by the internal combustion engine which in turn increases
the load on the internal combustion engine.
Numerous problems are encountered with the Airco type device
mainly because of the use of air as a heat transfer medium. Air
`tb
is a notoriously poor ileat transfer medium as compared to a
liquid and the use of ambient air causes the system Lo be very
much depenent ~pon ambient air conditions for proper operation.
Additiotlally, due to the large bul~y nature of the plenum chamber
required for the use of air as a heat transfer medium, the Airco
system is very much larger than a system like that of the present
invention of equal ca~acity.
Thus, it is seen that the prior art has recognized the need
for a flameless nitrogen vaporizer. The devices of this type
included in the pr'ior art, however, have numerous shortcomings
particularly with regard to their capability of providing suffi-
cient heat for vapori7ing large volumes of nitrogen and with
regard to -their capability of accurately controlling the amount
of hea~ transferred to the nitrogen and its corresponding temper-
ature as it enters the well head.
The flameless nitrogen vaporizing unit of the present invention
yreatly improves upon the prior art devices by providing a
second internal combustion engine for the sole purpose of providin~
additional leat for the vaporization of the nitrogen. This second
~O internal combustion engine and its associated heat transfer system
are so interconnected with a first internal con~ustion engine and
its associated heat tr3nsfer system so that the first internal
combustion engine ~a~r be used alone for nitrogen production at
rates for which sufficient heat may be generated by a single engine
for the vaporization thereof, and then for higher rates the second
internal combustion engine can be activated and its heat transfer
system wor~ing in conjunction t~ith that of the first internal
combustion engine provides a total heat transfer sufficient ror
~aporizing nitrogen at these higher rates and superheating it
to essentially ambient conditions. ~umerous refinements in the
load control systems and temperature control systems as connected
to each of the two internal combustion engines are 2rovided also.
The flameless nitrogen vaporizing unit of the present invention
includes a first lnternal combustion engine driving a nitrogen
pump through a transmission. Connected to the transmission is
a transmission retarder for varying the load on the first internal
combustipn engine by varying a level of hydraulic fluid oresent
in the transmission retarder. A second internal combustion engine
drives three hydraulic oil pumps against a variable back pressure
so that a variable load may be imposed upon the second engine.
Liquid nitrogen i5 pumped from the nitroqen pump driven by
the first engine into a first heat exchanger where heat is trans-
ferred fror.l exhaust gases from the f~rst and second internal com-
bustion engines to the liqui~1 nitrogen to cause the nitrogen to
~e transformed into a g~seous s~ate. The gaseous nitrogen then
flows into a second heat exchanger where it is superheated by an
engine coolant fluid to heat the gaseous nitrogen to essentially
an amkient temperature. The superheated nitrogen is then injected
into the well.
The engine coolant fluid flows in a coolant cir-
culation system wherein it receives heat from several sources.
Heat is transferred to the coolant fluid directly from the
internal combustion engine. Heat is transferred to the coolant
fluid from transmission fluid which flows through the trans-
mission of the first internal combustion engine and the trans-
mission retarder thereof. Heat is also provided to the coolant
fluid from lubrication oil pumped by the three pumps attac~ed
to the second internal combustion engine. In an alternative
embodiment these three pumps and their related oil to coolant
heat exchanger are replaced by a water brake dynamometer
which pumps the coolant fluid. The coolant fluid circulating
system includes a comingling chamber for comingling warmer
coolant fluid flowing from the internal combustion engines
to the coolant fluid-to-nitrogen heat exchanger with cooler
coolant fluid flowing from the coolant fluid-to-nitrogen
heat exchanger to the internal combustion engines. This aids
in controlling the temperatures of the internal combustion
engines to prevent overcooling of the same.
Numerous features and advantages of the present
invention will be readily apparent to those skilled in the art
upon a reading of the following disclosure when taken in
conjunction with the accompanying drawings.
In one aspect of the 2resent invention there is
provided an apparatus for heating a first fluid,
comprising, a first internal combustion engine; a second
internal combustion engine; a coolant system means for cir-
culating a coolant fluid and transferring heat energy from
the first and second internal combustion engines to the
coolant fluid, a coolant fluid-to-first fluid heat exchanger
means for transferring heat energy from the coolant fluid
to the first fluid, a main pump means, drivingly connected
-8-
4 ~3
to the first internal com~ustion engine, for pumping the
first fluid, and a variable load means, connected to the
second internal combustion engine, for exerting a varying
load on the second internal combustion engine so that an
amount of heat energy transferred from the second internal
combustion engine to the coolant fluid and from the coolant
fluid to the first fluid increases as the load exerted on the
second internal combustion engine by the variable load means
is increased.
In a further aspect of the present invention, there
is provided an apparatus for heating a first fluid, com-
prising a first internal combustion engine, a main pump for
pumping said first fluid; transmission means connecting said
engine and said main pump so that said main pump is driven
by said engine, a coolant system means for circulating a
coolant fluid and transferring heat energy from said internal
combustion engine to said coolant fluid, a coolant fluid-to-
first fluid heat exchanger means for transferring heat
energy from said coolant fluid to said first fluid, and
a transmission retarder means, connected to said
transmission means, for exerting a varying load on said
engine so that an amount of heat energy transferred from said
internal combustion engine to said coolant fluid, and from
said coolant fluid to said first fluid, is increased as said
load exerted on said engine by said transmission retarder
means is increased.
The invention is illustrated by way of example
with accompanying drawings wherein:
FIG. 1 is a plan view of the flameless nitrogen
unit of the present invention.
-8a-
~b
FIG. 2 is a left side elevation view of the apparatus
of FIG. l;
FIG . 3 is a schematic representation of the nitrogen flow
system;
FIG . 4 is a schematic representation of the coolant flo~
circulatina system;
FIG. 5 is a schematic representation of the flow of lube
oil from the nitrogen pump to the lube oil-to-coolant fluid
exchangers, the flow of the transmission fluid from the trans-
mission to the transmission-to-coolant fluid exchanger, and the
flow of hydraulic oil from the three pumps attached to the sec-
ond internal combustion ensine to the hydraulic oil-to-coolant
fluid exchangers;
FIG. 5 is a sectional view of the nitrogen vaporizer discharge
1~ manifold showing the connection of a bypass line thereto for
bypassing liquid nitrogen around both the exhaust gas-to-nitrogen
heat exchanger and the coolant fluid-to-nitrogen heat exchanger;
FIG. 7 is an elevation view of one of the coolant fluid co-
minglin~ chambers;
FIG. 8 is a sectional elevation view along line 8-8 of
FIG. 7; and
FIG. 9 is a horizontal section view akout line 9-9 of
FIG. 8.
FIG. 10 is a schematic representation, similar -to FIG. q,
illustrating an alternative embodiment of the present invention
wherein ~he second engine drives a water ~rake dynamometer.
_g_
Referrinq now to the drawings and particularly to FI~S. 1
and 2, the flameless nitrogen vaporizing unit of the present
invention is shown and generally designated by the numeral 1~.
The vaporizing unit 10 may generally be referred to as an appa-
ratus for heating a first fluid, said fluid being the liquidnitrogen.
The apparatus 10 includes a rectangular transporta~le skid
frame 12 havin~ first and second opposed sides 14 and 16, and
haviny third and fourth opposed sides 1~ and 20. The first and
second sides 14 and 16 define a width of frame 12, which width
is approximately 95 inches in a preferred em~odiment. The
third and'fourth sides 18 and 20 define a length of frame 12
which lerlath is approximately 168 inches in a preferred e~bodimen'_.
The vaporizing apparatus 10 is surrounded by a protective
cage 21 t~hich, in a preferred embodiment, has a 'neight of 9Ç inches.
The protective cage 21 is not shot~n in FI5. 1 so that the other
components mav be more clearly illustrated.
~lounted upon the frame 12 are first and second internal
comb~stion engines 22 and 24, respectively, which may also be
referred to as first and second power sources. In a preferred
embodiment, engines 22 and 24 are General Motors ÇV-92T diesel
engines. Engines 2, and 24 are oriented upon frame 12 so that
the respective axes of rotation, 2h and 23, of the crank shafts
of engines 22 and 24 are oriented substantially parallel to third
and fourth sides 1~ and 20 of frame 12.
--10--
, ~
A compressed air system is provided on the apparatus 10
with an air compressor driven by first engine 22 connected to
a compressed air stora~e tank for use with compressed air driven
starters on the englnes 22 and 24.
S A nitrogen pump 30, which may also be referred to as a
main pump, is located on fra~e 12 between the first engine.22 and
second side 16 of frame 12. In a preferred embodiment pump 30 is
preferably a Hallil~urton ~T-150 positive displacerllent pump ha~-in~
Linde HP-60 fluid ends.
0 Nitrogen pum~ 30 is drivlngly connected to first en~ine 22
by transmission means 32 and by a gear reduction box 31. In a
preferred embodiment transmission 32 is an Allison HT-7;0 transmission,
and gear reduction box 31 provides a ~-to-l gear reduction between
transmission 32 and pu~p 30.
The transmission 32 is equipped with a hydraulic transmission
retarder 33 of a design well known to those skilled in the art
which operates in a manner similar to that of a torque convertor
with a load exerted on the transmission by the transmission retarder
being dependent upon a controllable level of a transmission ~luid
0 present in the transmission retarder. The higher the fluid level in
the retarder is, the higher the load exerted will be.
The second engine 24 has a triple pump drive unit 3~ attached
to the rear end thereof to which are drivingly connected first, sec-
ond and third hydraulic pumps 36, 33 and 40, two of which can ~e
seen in FIG. 1.
The exhaust systems from engine 22 and 24 ar~ connected to
an exhaust gas-to-nitrogen heat exchanger 4~ which is located
b
between and abo~7e the engines ~2 and 2~ as shown in FIGS. 1
ar.d 2. The exhaust heat exchanger 42 is a means for transferrin~
h~at energy from the exhaust gases produced by engines 22 and
24 directly to the nitrogen flo~Jing through the tube side of
exchanger 44. ~he term "directly" is used to indicate that the
heat energy is not passed through any intermediate heat transfer
fluid medium bet~een the exhaust gas and the nitrogen.
A coolan-t fluid-to-nitrogen heat exchanger 44 is located
behind second engine 24 near the fourth side 20 of frame 12, for
transferring lleat from the coolant fluid directly to the nitrogen.
First and second coolant fluid comingling chambers 46 and
48 are located near third and fourth sides 1~ and 20, respectively,
of frame 12 just to the rear of first and second engines 22 and
24, respectively.
Located above transmission 3~ are a plurality of heat
exchanaers for transferrinc heat energy from various sources on
the apparatus 10 to the engine coolant fluid which circulates
through the cooling systems of the engines 22 and 24. These heat
exchangers include the following.
First and second hydraulic system coolers 50 and 52, respecti~ely,
are provided for transferring heat energy from a hydraulic fluid
pumped by pumps 36, 38 and 40 to the coolant fluid. Hydraulic
coolers 5Q and 52 may also be referred to as hydraulic fluid-to-
coolant fluid heat exchangers.
A transmission cooler 54 is provided for transferring heat
-12-
.. ... . . _ _
energy from the trallsmission fluid circulating through transmission
32, and its associated transmission retarder 33, to the coolant
flui~.
First and second nitrogen pump coolers 56 and 58, respectiv-ly,
are provided for trans erring heat energy from a lubrica~ing
fluid circulating through nltrogen pump 30 to the coolant fluid.
Nitrogen pump coolers 56 and 58 may also be referred to as nitrogen
pump lubricating fluid-to-coolant fluid heat exchangers.
Referring now to FIG. 3, a schematic flow diagram is shown
for the nitrogen system of the nitrogen heating apparatus 10.
The nitrogen pump 30 takes liquid nitrogen from a liquid nitrogen
source 60 which, in a preferred embodim.ent, has a c~pacity of
approximately 2,00~ gallons. T.he liquid nitrogen source 60 is
1;, not located on frame 12. A discharge line 62 connects the dis-
charge of nitrogen pump 30 to the tube side of exhaust heat exchanger
42.
Ilot exhaust qases from engines 22 and 24 are passed through
the shell side of exchanger 42 as indicated by arrows 64 and 66.
2a The liquid nitrogen from pump 30 enters exhaust heat exchanger
42 at a temperature of aporoximately -320F. ~he heat supplied by
exhaust exchanger 42 is approximately sufficient to vaporize the
nitrogen and the vaporized nitrogen exits exhaust exchanger 42 by
means of conduit 68 at a temperature of approximately -200F.
Con~uit 68 directs the vaporize~ nitrogen into the tube side
~ ib
of coolant fluid-to-nitrogen heat exchanger 4~. ~Jarm coolant
fluicl from the svstem ge!lerallv sho~n in FI~. 4 is passed tnrough
the shell side of exchanger '4 as indicated by arrows 70 and 72.
The heat transferred frorn the coolant fluid to the vapori~ed
nitrogen in coolant fluid heat exchanger 44 superheats the
~tapori~ed nitroqen to approximately ambient temperatures of 7~F
+ 20F at conduit 73 e~iting exchanger 44.
As is shown in FIG. 3, the exhaust heat exchanger 42 and
the coolant heat exchanger 44 are so arranged relative to the
direction of flow of the nitrogen that the exhaust heat exchanger
42 is located upstream of the coolant heat exchanger 44.
A first bypass conduit means 74 is provided for bypassing
liquid nitro~en past e~haust heat exchanger means 42. Disposed
in first bypass conduit 74 is a manually operable control valve
76 which provides a means for controlling the amount of liquid
nitrogen which is byPassed around exhaust heat exchanger 42 so
that a controlled portion oE nitrogen is so bypassed.
~ second bypass conduit means 78 provides a means for
bypassing liquid nitrogen past both the exhaust heat exchanger
means 42 and the coolant heat e~changer means 44. Disposed in
second bypassing conduit 78 is a manually operable control valve 80,
which is a needle valve, by means of whic.l t'ne amount of liquid
nitrogen passed through second bypass conduit 78 may be controlled.
The first and second bypass conduit means 74 and 78 are
2~ connecte~ in parallel so that the second bypass means 7~ is operable
b
independent of firs. by?ass means 74 allowing liquid nitroaen
to by bv~assed throu~h either one or both of the by~ass means.
Discharge conduit 73 from coolant heat e~changer means 44
and second bypass conduit 73 are bo~h connected to a discharge
manifold 82.
Discharge ~anifold 82 is shown in section in FIG. 6. Dis-
charge ~anifold ~2 includes a first inlet ~4 to which is con-
nected conduit 73, and a second inlet ~6 to which is connected
bypass conduit 7~.
A thermowell 33 is disposed in manifold ~2 so that a temp-
erature indicating means (not shown) may be connected there.o
to measure the temperature of the sul?erheated nitrogen which is
discharged from manifold 82 through outlet 90 thereof. The
outlet 90 is connected to a nitrogen discharge line 9, which
1~ directs the superheated nitrogen vapors to a foaming unit 96
where the nitrogen gas is used to prcduce the fracturing gel solu-
tion which is in turn directed through a conduit 9~ to the well
head 100 of the well which is being treated.
Connected to the conduit 73 between coolant heat exchanger
means 44 and discharge manifold ~ is a safety~ relief valve 102
and an access flange 104 adjacent an access valve 106.
Referring now to FIG. 4, 'here is thereshown a schema~ic
flow diagram for the coolant fluid which flows ~hrough the shell
side of coolant .luid heat exchanger 44 as indicated by arrows
70 and 72 on FI5. 3.
In FIG. 4, coolant fluid-to-nitrogen heat e~changer means
44 is sho-~n schematically in a 'manner similar to that in which it
is shown in FIG. 3. Conduits leading into and out of the shell
side of exchanger 44 are desianated by numerals 70 and 72, res-
pectively, corresponding to the arrows 70 and 72 of FIG. 3. The
warm coolant fluid enters heat exchanger 44 through conduit 7~
and in the exchanger 44 transfers heat to the nitrogen flowing
through the tube side of exchanger 44, as indicated by arrows 6~
I and 73 shown in phantom lines, and a cooler coolant fluid exits
~10 exchanger 44 ~y means of conduit 72.
¦ The other end of conduit 72 is attached to a tube side inlet
lOS of hydraulic cooler 50. A tube side outlet 110 of hydraulic
cooler 50 is connected to a tube side inlet 112 of second hydraulic
cooler 52 by a conduit 114.
A tube side outlet 116 of second hydraulic cooler 52 is con-
nected to a tube side inlet 113 of transmission cooler 54 by
conduit 120. A tube side outlet 122 of transmission cooler 54 is
connected to a conduit 124 which in turn is connected to~draulically
parallel conduitsl26 and 12~ leading to tube side inlets 13~ and
132 of first and second nitrogen pu.~p coolers 56 and 58, respec~tively.
A tube side outlet 134 of first nitrogen pump cooler 56 is
I connected to a firs~ inlet 137 of first comingling chamber 46 by
t a conduit 136. ~ tube side outlet 138 of second nitrogen pump
cooler 58 is connected to a first inlet 141 of second comingling
chamber 48 by a conduit 140.
.
'~ -16- ,
~,
l .
The details of construction of comingling chambers 46 and
48 are shown in detail in FIGS. 7-9.
Coolant fluid exits a first outlet 142 of comingling chamber
46 through a conduit 144. The other end of conduit~144 is con-
nected to an inlet lq6 to the water jacket of first engine 22. Thecoolant fluid then flows through the water jac~et of engine 22
and exits the water jac~et at outlets 148 and 150. A conduit 15
is connected at one end to outlets 148 and 150 and at the other end
to a three-way thermostatically controlled valve 154.
A first outlet 156 of valve 154 is connected to a conduit 1~8
for directing coolant fluid to a radiator 160. A second outlet
162 of valve 154 is connected to a conduit 164 for directing cool-
ant fluid to a second inlet 166 of first comingling chamber 146.
Depending upon the temperature of the coolant fluid entering
thermostatically controlled val~te 154, the coolant flui~ is directed
to one of first and second outle-ts 156 or 162. If the coolant
fluid is too hot it is directed to first outlet 1,6 and to conven-
tional radiator 150 where the coolant fluid is cooled by heat
exchange with air flowing past the outside of radiator 160. ~ther-
wise, the coolant fluid is directed to second outlet 162 and dir-
ectly to second inlet 166 of first comingling chamber 146.
The coolant fluid directed through conduit 158 to radiator
160 enters the tube side of radiator 160 through inlets 170 and 172.
-17-
That coolant fluid then e~its a tube side outlet 174 of
radiator 160 and is directed to inlet 146 of the water jacket
of first engine 22 by a conduit 176.
An overflow conduit means 17~ is connected to an overflow
outlet 180 of radiator 160 and an overflow outlet 182 of first
comingling chamber 46. Overflow conduit 178 is connected to
a first surge tank 134 from which a coolant fluid make-up conduit
186 directs coolant fluid to a ma~e-up inlet 1~8 of first radiator
160. Surge tank 184 serves to de-aerate the coolant fluid and
.o provide make-up fluid.
All of the coolant fluid which flows from first comingling
chamher 46 throuyh conduit 144 to the engine 22, or which is recycled
through the radiator 160 and then bac~ to the engine 22, eventually
returns through the conduit 164 to the second inlet 166 of co-
.5 mingling chamber 46 as previously described. The coolant fluid
entering second inlet 166 which has just been heated by the first
engine 22 is physically mixed with or co~ingled with the cooler
coolant fluid entering first inlet 137 within the comingling chamber 96.
A portion of this comingled coolant fluid is tha. which was
0 previously described as exiting first outlet 142 of comingling ~
chamber 46. A second portion of the comingled coolant fluid within
the chamber 46 exits second outlet 19~ of comingling chamber
46 by means of conduit 192.
The temperature of the coolant fluid entering first inlet
~5 137, in a pre~ferred embodiment, is approximately 160 to 170F.
,~ . . .
~L~
The teml~erature of the _0012llt rluid entering second inlet lfi6 is
approximately 190~. The temperature of the coolant fluid exiting
first and second outlets 142 and l~0 is approximatel~f~ 180~ for
each outlet.
The comingling chamber 46 serves to raise tlle temperature
of the coolant fluicl directed to the coolant system of first
engine 22 higher than it would be if the comingling chamber a~
were eliminated and the conduit 136 were connected directly to
the conduit 144. This hel~s prevent over-cooling of the first
L0 engine 22 and Prevents the mechanical problems which can arise
as a natural consequence of over-cooling an internal cor,lbustion
engine.
The entire system shown in FIG. 4 may generally be referred
to as a coolant system means.
The various conduits which return the coolant fluid from
engines 22 and 24 to the heat e,cchanaer 44 may generally be
described as a first coolant fluid conducting means, and the
various conduits conducting coolant fluid from coolant fluid
heat e~changer 44 to the first and second engines 22 and 24 may
gerlexally be described as a second coolant fluid conducting means.
All of the various heat exchangers, comingling chambers,
radiators, surge tanks, pumps and tlle like shown in FIG. 4 mav
generally be described as being disposed in one of these first
or second coolant fluid conducting means.
The second coolant fluid conducting means supPlying fluid
-19-
_ _ _ _
b
from exchanger 44 to the engines 22 and 24 s~lits in~o two
parallel streams at the tee 125. The two parallel st`reams are
again combined at the tee 204 in the first coolant fluid con-
ducting means. The first and second engines 22 and 2a may
therefore, be said to be connected in parallel between the first
and second coolant fluid conducting means, so that the coolant
fluid flowing from the second coolant fluid conducting means to
the first coolant fluid conducting means is split in~o first
and second coolant fluid streams flowing past said first and
second internal combustion engines 22 and 24, respectively.
The cominglins chambers 46 and 4~ may each ~e ~enerally
referred to as a transfer means, connected to the first and
second coolant fluid conducting ;neans between the engines 22
ancl 24 and the heat exchanger means 44, for transferring heat
~15 energy from coolant fluid in the first coolant fluid conducting
means to coolant fluid in the second coo~ant fluid conducting
means.
The ccmingling chamber 46 could be replaced by a more
conventional heat exchanger which does not mix the fluid flowing
to and from engine 22, but due to the fact that the fluids
are identical and the temperature differential is small the
comingling chamber is preferred because it provides a much
larger heat e~change than ould a conventional shell and tube
exchanger of similar physical size.
-20-
I
~=~
b
The conduits connectina second comingling chamber 43
with second engine 24 ~re similar to that just described between
first comingling chamber 46 and first ensine 22.
The second cominglins cnamber 4~ includes the first in-
S let 141 and a second inlet 194. It also includes first and secondoutlets 196 and 198. Second outlet 198 is connected to a conduit
200.
Conduits lg2 and 200 returning coolant fluid from cominglinu
chambers 46 and 48 both connect to a comnlcn return line 202 at
a tee connection 204.
Return conduit 20 is connected to a suction side of a
coolant fluid pump 206. The discharge 5ide of coolant fluid
pump 206 is connected to the conduit 70 which has previouslv
been described as connected to the inlet of the shell side of
L~ coolant fluid heat exchanger 44. Pump 206 is a hydraulically
powered pump which is driven by a hydraulic motor.
Although not illustrated in FIG. 4, it is desirable to
conduct a smaller portion of the flow of warm coolant fluid
~: from the discharge of pump 206 throush a heating jac~et around
the fluid end o nitrogen pump 30 to heat the same.
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_ . . . _. . . _
. =~ '=Y
~15~ ib
The details of construction of comingling chamber 46 are
shown in FIGS. 7-9. Second comingling chamber 48 is similarly
constructed. FIG. 7 is an outer elevation view of comingling
chamber 45.
Cominglinq chamber 46 includes a vertically oriented cylin-
drical housing 208 to which tlle inlets 137 and 166 and the outlets
142 and 190 are connected.
A cap 210 is connected to the upper end of housing 208
by a locking collar 212. The overflow outlet 182 is attached to
L0 cap 210.
Referring now to FIG. 3 a sectional elevation view about
line 8-8 of PIG. 7 is thereshown. A base plate 214 seals the
lower end of cylindrical housing 20~. First and second mounting
brackets 216 and 218 are attached to the outer surface of housing
208 for attaching the same to the frame 12 of the flameless nitro-
gen vaporizing unit 10.
Inside the housing 20S are first, second and third baffles
220, 222 and 224.
As is best shown in FIG. 9 which is a horizontal section
) view along line 9-9 of FIG. 8, the baf~les are attached to two
central vertica].ly oriented parallel support legs 226 and 228
which set in rectangular cut-out spaces in the baffles. The baffles
are attached to the support legs 226 and 228 by welding or other
suitable means.
j The operation of the cor~lingling chamber 46 is as follows.
, _ _ . . _, . . .
`}b
The cooler coolant fluid enters first inlet 137 and the warmer
coolant fluid en~_ers second inlet 166 and the two streams of
fluid begin comingling with each other above firs~ baffle 220.
As the comingled fluid flows downward through comingling chamber
~6 to the outlets 142 and 130, the direction of the fluid is
deflected twice by the second and third baffles 222 and 224 to
insure thorough mixing or comingling or the two liquid streams
so that the liquid exiting the two outlets 142 and 190 is essen-
tially of the same te~perature at each of those outlets.
Referring now to FIG. 5, a schematic flow diagram is
shown for the shell side fluids of the hydraulic coolers 50 and
52, the transmission cooler 54 and the nitrogen pump coolers
56 and 58. ~he flow of coolant fluid through 'the tube sides of
t~ose exchangers is represented b'y phantom lines in a manner
lS similar to that shown in FIG. ~ for aid in correlation of the
two drawings.
In the lower portion of FIG. 5, the three hydraulic pumps
36, 38 and 40 which are driven by second engine 22 are thereshown.
The discharge sides 226, 2 3 and 230 of pumps 36, 38 and 40,
respectively, are connected to a common discharge line 232. Dis-
posed in discharge line 232 is a pilot controlled relief valve
234 which allows the discharge pressure in discharge line 232 to
be controlled and varied. The pilot controlled relief valve 234
includes a relief valve which may be set at the desired operating
backpressure for the discharge line~32, The relief valve remains
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b
closed for a very short period of tir.le after the positive dis-
placement pumps '26, 228 and 230 have begun operating until
the pressure in discharge 232 reaches the preset value at ~hich
the relief valve isdesigned to open. Lhe relief val~e opens
at that point and maintains a constant backpressure against
the pumps 226, 223 and 230 at the ~reset level.
In a control consol~ (not shown) supported from the frame
12 of flameless nitrogen heating unit 10, there is located an
overriding relief valve which is interconnected with pilot
controlled relief valve 23~ so that the setting of pilot con-
trolled relief valve 234 may be overriden and changed by operation
of the relief valve located in the control con.sole.
Heat is generated and transferred to the hydraulic fluid
as it is pumped through the pumps 36, 38 and ~0 and as it drops
across the restriction in pilot controlled relief valve 234.
The pumps 36, 38 and 40 along with pilot controlled relief
valve 234 provide a variable load means, connected to second
internal co~bustion engine 24, for exerting a varying load on
second internal combustion engine 24, so that an amount of heat
energy transferred from engine 24 to the coolant fluid in the
system illustrated in FIG. 4, and then from the coolant fluid to
the liquid nitrogen in the coolant fluid heat exchanger 44, increases
as the load exerted on second internal combustion engine 24 is
increased by raising the backpressure controlled by pilot controlled
relief valve 234.
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_, _ . . . _ _ ,_~" . _ . _ .. ____ :_ ,, T~ I _ - , ' ' -- '
b
~ conauit 236 connec-s pilot controlled relief valve
234 to a shell side inlet 23, or second hy~raulic cooler 52.
conduit 240 connects a shell side outlet 242 of second hydraulic
cooler 25 with a shell side inlet 244 of first hydraulic cooler
~0. A shell side outlet 246 of first hydraulic cooler 50 is
connPcted to a conduit 248.
Conduit ,48 is connected to two parallel conduits 250 and
252 which are connected to first and second filters ?.54 and 255.
The outlets of filters 25~ and 256 are connected to conduits
L0 253 and 260 which are connected to a common return conduit 262.
Suction sides 264, 266 and 268 of pumps 36, 38 and 40,
respectiveiy, are all connected ~o the return line 262 thereby
completing the circuit for the hydraulic fluid through the
shell side of hydraulic coolers 50 and 52.
Return line 262 is connected to a hydraulic oil reservoir
263 by a conduit 265 and a back pressure check valve 267. Another
hydraulic fluid return line 269 from a hydraulic motor (not shown)
which drives coolant pump 206, see FIG. 4, connects to conduit
265 between check valve 267 and conduit 262.
8ack pressure check valve 267 maintains a constant back
pressure of 22 psi on conduits 265 and 269. This provides a
constant pressure supply of hydraulic fluid to the suction sides
of pumps 36, 38 and 40.
Referring now to the middle portion of FIG. 5, the first
internal combustion enyine 22, the transmission 32 and transmission
retarde- 33 are there schematically illustrated.
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~ l outlet 270 from transmission 32 and transmission retarder
33 is connected to a suction side of transmission fluid pump 272
by a conduit 274. The discharge from pump 272 is connected to
a shell side inlet 276 of transmission cooler S4 by a conduit 278.
A shell side outlet 2~0 of transmission cooler 54 is connected to
a conduit 282 the other end of which is connected to a filter 284.
The outlet from filter 2~4 is connected to a return conduit 286
which is connected to an inlet 288 of transmission 32 and trans-
mission retarder 33. The transmission fluid is heated by the
friction incurred in the tra~smission 32 and transmission retarder
33 and that heat is transferred to the coolant fl~id by means of
transmission cooler 54.
Referring now to the upper portion of FIG. 5, the circulation
system for lubricating oil for the nitrogen pump 30 is thereshown.
A lubricating oil manifold which distributes lubrica-ting oil to
the various moving parts of nitrogen pump 32 is represented schema-
tically by nitrogen pump lube manifold 290. The lubrication oil
is heated as it flows through the manifold 290. The lubrication
oil from manifold 290 is carried by a conduit 292 to the gear
reduction bo~ 31 which was previously described with relation to
FIG. 1. The gear reduction box 31 connects transmission 32 to
nitrogen pump 30. The lubrication oil is then carried from
~ear reduction box 31 by a conduit 294 to a lubricating oil
reservoir 296.
. 25
: -
j! -26-
,'
l . ~
~ T
, . . ~
A lube oil pump 298 has a suction t`nereof connected to the
lube oil reservoir 296 by a conduit 300. A discharge side of
pump 298 is cor.nected to a shell side inlot 302 of first nitrogen
pump cooler ~6 by a conduit 304.
A shell side outlet 306 of first nitrogen pump cooler ~6 is
connected to a shell side inlet 308 of second nitrogen pump cooler
58 by a conduit 310. A shell side outlet 312 of second nitroqen
pump cooler 58 is connected to a conduit 314.
Conduit 314 is connected to an inlet of filter 316. The
outlet of filter 316 is connected to the inlet of nitrogen pump
lube manifold 290 by a conduit 318, thereby completing the circu-
lating loop for the lube oil.
A safety relief valve 320 is connected to conduit 314 by a
conduit 322 and the outlet of relief valve 320 is connected to
lube oil reservoir 296 by a conduit 324.
The operation of the flameless nitrogen vaporizing unit 10
¦ is generally as follows.
¦ For relatively low pumping rates of nitrogen, only the first
~ internal combustion engine 22 need be utilized. The engine 22 is
i ~ started and it drives the nitrogen pump 30 which pumps the nitrogen
through the flow system illustrated in FIG. 3. The flow rate of
nitrogen pumped by pump 30 is controlled by controlling the speed
of engine 22 and by the transmission gearing in transmission 32.
Simultaneously, exhaust gases from the engine 22 flow throug~
the shell s-ide of eY.haust heat exchanger 42 and heat the liquid
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; ~
nitrogen. If too much heat is being provided by the exhaust
exchanger 42 it may be partially or entirely bypassed by means
of bypass conduit 74 and con~rol valve 76.
The nitrogen then flows into coolant fluid heat exchanger
44 ~here it is further heated by heat transferred from the cool-
ant fluid. Both the exchanger 42 and the coolant fluid exchanger
44 may be bypassed by means of second bypass conduit 78 and
control valve 80. By watching the temperature indicated by a
temperature indicator (not shown) disposed in thermowell 88,
an operator may utilize the valves 76 and 80, primarily the
valve 80, for fine adjustment of the temperature of the nitrogen
flowing out the outlet 90 of the discharge manifold 8
A larger but less accurate adjustment of the temperature of
the nitrogen can be made by varying the load on transmission
retarder 33 so as to vary the load on engine 22 and correspondingly
vary the heat generated thereby in the various heat exchange
systems. Simultaneously with all of this, of course, heat is
transferred from the transmission 32 and transmission retarder 33
to transmission fluid and then to the coolant fluid ~y means of
transmission cooler 54. Also, heat flows in the nitrogen pump
lube oil system shown in the upper part of FIG. 5 to the nitrogen
pump coolers 56 and 58.
If all the systems connected to the first internal combustion
engine 22 are not capable of providing sufficient heat for the
vaporization of the desired flow rates of liquid nitrogen, then
-2~-
_ _ _ _ _ _ _ _ _ _ ~
the second internal combustion engine 24 is activated. The
second internal combustion engine 24 is operable independently
of first internal combustion engine 22, so that the second
internal combustion en~ine 24 may be selectively used as an
auxiliary heat source in addition to first internal combustion
engine 22 when the amount of heat energy transferred from the
first engine 22 to the coolant fluid is insufficient to provide
sufficient heat energy for heating the nitrogen to a desired
temperature in the coolant heat exchanser means 44.
o Once the second internal combustion engine 24 is activated,
the amount of heat provided thereby may be grossly adjusted by
varying theback pressure on the pumps 36, 38 and 40 by means
of the pilot controlled relief valve 234. The fine temperature
adjustment is still provided by the bypass means 73 and control
valve 80.
The apparatus 10 provides pumping rates in the overall
ran~e of from 15,000 to 230,000 standard cubic feet per hour
at a pump pressure of 10,000 psi.
~0 In FIG. 10 an alternative embodiment of .he present invention
is illustrated, in which the pumps 226, 22~ and 230 and the
~ attached system shown in the lower portion of FIG. S are replace,d
1~ b~ a water brake dynamometer 400 which is driven by a second engine
24. ~7ater brake dynamometer 400 is an alternative means for
exerting a varying load on engine 24 so that the amo~nt of heat
--2g--
I
b
transferred from engine 24 to the coolant fluid, and then from
the coolant fluicl to the liquid nitrosen in the coolant fluid
heat exchanger 44, increases as the load exerted on engine 24
is increased.
In the embodiment of FIG. 10, coolant fluid exiting the
shell side of heat exchanger 44 is carried by a conduit 402 to
an inlet 404 of water brake dynamometer 400. Water brake dyna-
mometer 400 acts as an inefficient centrifugal pump to convert
mechanical energy from engine 24 into heat energ~l~ in the coolant
L0 fluid. The load exerted on engine 2a is varied by varying the
bac~c pressure against which dynamometer 400 is pumping. This
is done by means of a bac~c pressure valve 406.
Coolant fluid e~iting back pressure valve 406 is at approxi-
mately ~1 psig and is carried h-~ conduit 403 to a sump 410.
L5 The coolant fluid is tal;en from sump 410 bv a suction
line 412 leading to a coolant fluid booster pump 414 which boosts
the pressure of the coolant fluid up to approximately 8 psig as
is required for proper operation of the remainder of the system.
A conduit 416 carries the coolant fluid from pump 414 to
tube side inlet 113 of transmission cooler 54. Tl e remainder
of the system shown in FIG. 10 is similar to that of FIG. 4.
Thus it is seen that the flameless nitrogen vaporizing skid
unit of the present invention is readily adapted to attain the
ends and advantages m~entioned as well as those inherent therein.
2~ ~hile presently preferred embodiments of the invention have been
--3û--
'}b
illustrated for the purposes of the present disclosure, nu~erous
changes in the construction and arrangement of parts may be
made by those skilled in the art which changes are encom~assed
within the spirit and scope of this invention as defined by the
appended claims.
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