Oil and refrigerant pump for centrifugal chiller

A single motor drives both oil and refrigerant pumps in a refrigeration chiller, the motor and oil pump being disposed in the chiller's oil supply tank and the refrigerant pump being disposed exterior thereof. The refrigerant pump pumps liquid refrigerant to the chiller's compressor section so as to cool the motor by which the compressor is driven while the oil pump pumps oil to chiller locations that require lubrication when the chiller is in operation.

BACKGROUND OF THE INVENTION 
The present invention relates to the lubrication of surfaces that require 
lubrication in a refrigeration chiller when the chiller is in operation 
and to the cooling, by system refrigerant, of the motor by which the 
compressor of such a chiller is driven. More particularly, the present 
invention relates to combined oil and refrigerant pump apparatus that 
ensures the delivery, under all operating conditions, of both lubricant 
and liquid refrigerant to the locations at which they are needed in a 
refrigeration chiller that employs a low pressure refrigerant. 
Refrigeration chiller components include a compressor, a condenser, a 
metering device and an evaporator, the compressor compressing a 
refrigerant gas and delivering it, at relatively high pressure and 
temperature, to the chiller's condenser. The relatively high pressure, 
gaseous refrigerant delivered to the condenser rejects much of its heat 
content and condenses to liquid form in a heat exchange relationship with 
a heat exchange medium flowing therethrough. 
Condensed, cooled liquid refrigerant next passes from the condenser to and 
through the metering device which reduces the pressure of the refrigerant 
and further cools it by a process of expansion. Such relatively cool 
refrigerant is then delivered to the system evaporator where it is heated 
and vaporizes in a heat exchange relationship with a liquid, such as 
water, flowing therethrough. The vaporized refrigerant then returns to the 
compressor and the liquid which has been cooled or "chilled" in the 
evaporator flows to a heat load in a building or in an industrial process 
application that requires cooling. 
The compressor portion of a chiller typically includes both a compressor 
and a motor by which the compressor is driven. Such motors, in most if not 
all chiller applications, require cooling in operation and have often, in 
the past, been cooled by system refrigerant. In many chiller designs, 
gaseous refrigerant has been sourced upstream or downstream of the 
compressor for such purposes. In other designs, compressor drive motors 
have been cooled by liquid refrigerant sourced from a location within the 
chiller. 
Chiller compressor drive motor cooling arrangements and chiller lubrication 
systems have, historically, been discrete from each other. In many cases, 
however, operation of the systems by which lubricant and motor cooling 
fluid were delivered to the locations of their use was predicated on the 
existence of a sufficiently high differential pressure within the chiller 
by which to drive oil or refrigerant from a relatively higher pressure 
source location to the relatively lower pressure location of their use in 
the chiller for such purposes. 
The chemical constituencies and operating characteristics of refrigerants 
used in chillers have changed over the years, primarily as a result of 
environmental considerations, and the use of so-called "low pressure" 
refrigerants, such as HCFC 123, has become common in the past decade. 
These refrigerants are such that under certain chiller operating 
conditions the temperature and pressure existing in the system condenser 
approach those existing in the evaporator. As such, a sufficiently high 
pressure differential between the system evaporator and system condenser 
cannot be counted upon to exist under all chiller operating conditions to 
ensure the continuous availability of a pressure that can reliably be used 
to drive oil from the chiller's oil supply tank to chiller surfaces that 
require lubrication. Nor can such a reliably high pressure differential be 
counted upon to exist to ensure the delivery of refrigerant from a first 
chiller location to the motor which drives the system's compressor for 
purposes of cooling that motor. Both, once again, were common past 
practices that were permitted by the use of "higher pressure" refrigerants 
than are used today. 
In view of the above-described circumstances, the present invention seeks 
to advantageously incorporate aspects of both the lubrication system and 
motor cooling system in a refrigeration chiller in which a low pressure 
refrigerant is used to ensure, under all chiller operating conditions, the 
delivery of lubricant and refrigerant to the locations of their use for 
lubrication and motor cooling purposes. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide for lubrication and 
compressor drive motor cooling in a refrigeration chiller. 
It is another object of the present invention to provide for the delivery 
of oil and liquid refrigerant to the locations of their use within a 
refrigeration system by the use of apparatus common to both purposes. 
It is still another object of the present invention to provide apparatus 
for pumping both lubricant and liquid refrigerant in a refrigeration 
chiller which is unaffected by chiller operating conditions. 
It is a further object of the present invention to provide the means by 
which to deliver both oil for lubrication purposes and liquid refrigerant 
for compressor drive motor cooling purposes by the use of liquid 
refrigerant and lubricant pumping apparatus which is driven by a single 
motor and drive shaft in a refrigeration chiller that employs a low 
pressure refrigerant. 
These and other objects of the present invention, which will be appreciated 
by reference to the attached drawing figures and the following Description 
of the Preferred Embodiment, are accomplished by combined 
refrigerant/lubricant pump apparatus in a refrigeration chiller, the pumps 
being driven by a common drive shaft which is driven by a single electric 
motor disposed, along with the lubricant pump, in the chiller's oil supply 
tank. The use of electric motor driven pumps by which to deliver oil and 
liquid refrigerant for lubrication and compressor drive motor cooling 
purposes assures the continuous availability of both lubricant and liquid 
refrigerant for those purposes irrespective of the conditions under which 
the chiller operates. The refrigerant pumping mechanism is driven by the 
same drive shaft as the lubricant pump but is disposed exterior of the oil 
supply tank in which the motor and lubricant pump are disposed. By the 
integral mounting of both the refrigerant pump and lubricant pump to a 
single drive shaft driven by a single electric motor, the lubrication and 
compressor drive motor cooling functions are reliably carried out in a low 
pressure refrigerant environment by apparatus which employs a minimum 
number of parts and is of relatively low cost.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring initially to FIGS. 1A and 1B, the major components of 
refrigeration chiller 10 are a compressor portion 12, a condenser 14, a 
metering device 16 and an evaporator 18. Compressor portion 12 of chiller 
10 is comprised of a centrifugal compressor 20 which is driven, through a 
drive shaft 21, by an electric motor 22 which is encased in a motor 
housing 23. 
In operation, the driving of centrifugal compressor 20 by compressor drive 
motor 22 causes a relatively low pressure refrigerant gas, such as the 
refrigerant commonly know as HCFC 123, to be drawn from evaporator 18 into 
the compressor. By a process of centrifugal compression, the gas drawn 
from evaporator 18 is compressed and discharged from centrifugal 
compressor 20, in a heated, relatively high pressure state, to condenser 
14. 
The relatively high pressure, high temperature refrigerant gas delivered to 
condenser 14 transfers heat to a cooling medium, such as water, flowing 
therethrough. The heat exchange medium, if water, is typically sourced 
from a municipal water supply or a cooling tower. The refrigerant 
condenses in the course of rejecting its heat content to the cooling 
medium and next flows to metering device 16. Device 16 further reduces the 
pressure and temperature of the condensed refrigerant by a process of 
expansion. 
The now relatively cool, relatively low pressure refrigerant, which is in 
two-phase but primarily liquid form after passage through the expansion 
device, next flows to evaporator 18 where it undergoes heat exchange with 
a fluid flowing therethrough, most typically, once again, water. In this 
heat exchange process, the relatively more warm fluid flowing through the 
evaporator rejects its heat content to the relatively cooler liquid 
refrigerant causing the refrigerant to vaporize. The now cooled or 
"chilled" fluid then flows from the evaporator to a location, such as a 
space in a building or a location in an industrial process, where chilled 
water is used for cooling purposes. The heated, now vaporized, relatively 
low pressure refrigerant is drawn back into compressor 20 to start the 
process anew. 
In refrigeration chillers that employ certain so-called low pressure 
refrigerants, the pressure differential between the chiller evaporator and 
the chiller condenser is not as high, under all chiller operating 
conditions, as was the case in earlier chillers in which relatively higher 
pressure refrigerants were used. It is to be noted that some of these 
relatively higher pressure refrigerants, such as CFC 11, were themselves 
considered to be low pressure refrigerants during the period of their use. 
Where such relatively higher pressure refrigerants were previously used, a 
relatively large pressure differential between the evaporator and 
condenser of a chiller could be counted upon to develop and continue to 
exist under all chiller operating conditions. In some chiller designs, 
particularly those employing a screw rather than centrifugal compressor, 
that made it convenient to use that differential pressure for purposes 
such as driving lubricant from the chiller's oil supply tank to lower 
pressure chiller locations requiring lubrication and/or to drive liquid 
refrigerant from a first location in the chiller to the lower pressure 
location of the chiller's compressor drive motor for drive motor cooling 
purposes. 
Referring additionally now to FIGS. 2 and 3, lubricant pump 24, in the 
chiller of the present invention, and electric motor 26 which drives it 
are disposed in the chiller's oil supply tank 28. Motor 26, to which power 
is delivered through electrical leads 27, drives a shaft 30 which, in 
turn, drives lubricant pumping element 32. Shaft 30 is likewise coupled to 
impeller 34 which is the pumping element of centrifugal refrigerant pump 
36 and is mounted exterior of oil supply tank 28. 
Lubricant is pumped by pump 24 through a pipe 40 disposed internal of oil 
supply tank 28 that communicates between lubricant pump 24 and an aperture 
42 in the head wall 44 of the oil supply tank. A lubricant manifold 46, 
such as the one which is the subject of U.S. Pat. No. 5,675,978, assigned 
to the assignee of the present invention, is mounted to oil supply tank 
head wall 44 and has an intake chamber 48 into which lubricant is pumped 
by the operation of lubricant pump 24. 
Lubricant manifold 46 is positionable to accomplish various lubrication 
related functions within the chiller, such as providing a set-up for the 
normal flow of lubricant to chiller bearings and surfaces, a set-up 
allowing for the change of the chiller oil supply while isolating the 
chiller's refrigerant charge, a set-up to allow the sampling of the 
chiller's oil supply for chemical analysis purposes and a set-up allowing 
for the change of oil filter 50 while isolating the chiller's oil supply. 
Among the bearings and surfaces to which lubricant must be provided in 
chiller 10 are the bearings which rotatably support the drive shaft 21 
which connects compressor drive motor 22 and centrifugal compressor 20. 
Referring primarily now to FIG. 3, it will be seen that in the preferred 
embodiment of the present invention lubricant pump element 32 is secured 
by key 52 to shaft 30 for rotation therewith and is disposed in lubricant 
pump element housing 54. Lubricant pump element housing 54 is attached to 
and supported by motor housing 56 which is, in turn, connected to and 
supported by head wall 44 of oil supply tank 28. It is to be noted that 
disposal of pump motor 26 in oil supply tank 28 brings with it the 
advantage of its being able to reject the heat it develops in operation to 
the oil which surrounds it. Motor 26 is, in fact, flooded with oil which 
is admitted into motor housing 56 through an aperture 57 therein. 
Lubricant pump element housing 54 also houses bearing 58 in a bearing 
housing 59 integrally defined by it. Bearing 58 rotatably supports shaft 
30 and rotor 60 of motor 26 at a first end. Lubricant pump port plate 62 
is attached to and supported by lubricant pump element housing 54 and 
defines the flow path 64 by which oil is delivered from the interior of 
supply tank 28 to oil pump element 32 and the flow path 66 by which oil is 
delivered from oil pump element 32 to pipe 40. 
Motor housing 56, as noted above, is mounted at its opposite end to oil 
supply tank head wall 44. Head wall 44, in the preferred embodiment, 
integrally defines a bearing housing 68 in which bearing 70 is disposed. 
Bearing 70 rotatably supports drive shaft 30 and motor rotor 60 at the 
ends thereof which are opposite the ends on which they are supported by 
bearing 58. Shaft 30 extends through and past bearing 70 and penetrates 
oil supply tank head wall 44. A portion of shaft 30 is surrounded by a 
seal 72 ensconced in oil supply tank head wall 44. 
Refrigerant pumping impeller 34 is connected to shaft 30 for rotation 
therewith by a screw 74 which threads into an end face of shaft 30. 
Impeller 34 is disposed in impeller cavity 76 which is defined in volute 
housing 78. Volute housing 78 is mounted to the exterior surface of oil 
supply tank head wall 44. Seal 72 acts as a seal between impeller cavity 
76 through which liquid refrigerant flows and the interior of oil supply 
tank 28. Because refrigerant pump 36 is of a centrifugal type it does not 
employ contacting parts, such as gear or other types of positive 
displacement pumps might and, as such, needs no lubrication. 
Referring once again to all of the drawing figures, refrigerant pump 
impeller cavity 76 is in flow communication on an intake side with 
condenser 14 of chiller 10 via intake piping 80 and is likewise in flow 
communication with the interior of compressor drive motor housing 23 via 
discharge piping 84. By the operation of pump motor 26, both lubricant 
pumping element 32 and refrigerant pumping impeller 34 are driven. As a 
result, lubricant is pumped out of oil supply tank 28, through piping 40, 
lubricant manifold 46 and lubricant piping 86 to various locations within 
chiller 10 that require lubrication, such lubricant being returned to 
supply tank 28 via return piping 88. Simultaneously and by operation of 
the same apparatus, liquid refrigerant is pumped from chiller condenser 14 
into the interior of compressor drive motor is housing 23 where it is 
delivered into heat exchange contact with compressor drive motor 22 so as 
to cool that motor. By the combined driving of both a liquid refrigerant 
pump and a oil pump by a single motor on a single drive shaft, the 
delivery of liquid refrigerant for compressor drive motor cooling purposes 
and the delivery of oil for lubrication purposes is reliably accomplished 
under all operating conditions within centrifugal chiller 10, which 
employs a low pressure refrigerant, all in a manner which reduces the 
number of parts associated with those functions as well as the costs 
involved in doing so. 
While the present invention has been described in terms of a preferred 
embodiment, it will be appreciated that many modifications thereto are 
contemplated and within the scope of the present invention which is more 
broadly claimed as follows.