Refrigeration – Automatic control – Of closed system sorbent type
Reexamination Certificate
2002-12-04
2004-09-21
Jones, Melvin (Department: 3744)
Refrigeration
Automatic control
Of closed system sorbent type
C062S148000, C062S476000
Reexamination Certificate
active
06792765
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to chillers, and more particularly, but not exclusively, provides a system and method for increasing the efficiency of chillers.
BACKGROUND
Absorption chillers provide chilled water for use in a range of industries including the plastics industry; the printing industry; the magnetic resonance imaging (MRI) industry; the heating, ventilating, and air conditioning (HVAC) industry; and the laser cutting industry. In HVAC applications, absorption chillers pump chilled water to air handling units (AHUs) in buildings, such as warehouses and high-rise buildings. The AHUs for each section of the building open and close to let the chilled water flow through so as to keep the section at a desired temperature.
FIG. 1
is a block diagram illustrating a conventional single stage absorption chiller
100
. The chiller
100
includes a generator
105
; a separator
110
; a condenser
120
; an expansion valve
130
; an evaporator
140
; an absorber
150
; and a heat exchanger
160
, each coupled in series, respectively. The chiller
100
enables the chilling of water via absorbing and then releasing water vapor into and out of a lithium bromide (LiBr) solution. A heat source, such as a natural gas burner, applies heat to the generator
105
, which contains LiBr and a refrigerant, such as water, in liquid form. The LiBr and refrigerant phase change to a vapor state and are then separated in the separator
110
. The LiBr is transferred to the absorber
150
via the heat exchanger
160
, in which the LiBr is phase changed back to liquid form.
The refrigerant, in vapor form, is transferred to the condenser
120
, within which cooling water circulates in pipes. The cooling water can be supplied from a utility company, water tower, or other water source. The condenser
120
, using the cooling water, cools the refrigerant vapor and transfers it to the evaporator
140
via the expansion valve
130
. The expansion valve
130
reduces the pressure of the refrigerant vapor.
The evaporator
140
then transfers ambient heat from the chilled water received from an application (e.g., AHUs) to the water vapor. Accordingly, the chilled water is then cooled and returned to the application. For example, the chilled water may enter the evaporator
140
at 54° Fahrenheit and may leave the evaporator
140
at 44° Fahrenheit.
The refrigerant then leaves the evaporator
140
and recombines with the LiBr in the absorber
150
, within which cooling water circulates, which causes the refrigerant to change state back to a liquid form. The LiBr and refrigerant are then transferred to the generator
105
(via the heat exchanger
160
) to repeat the above-mentioned process.
Conventional chillers, such as chiller
100
, are very efficient compared to other mechanisms used to cool buildings. In addition, conventional chillers use water as a refrigerant, instead of environmentally damaging chloro-fluoro-carbons (CFCs). However, conventional chillers do exhibit some inefficiencies. For example, chilled water and cooling water are generally pumped into and out of conventional chillers at fixed rates, regardless of the load. The same amount of electricity might be used to pump chilled water and cooling water on a cool day as on a hot day. Further, valves located between the pumps and the chiller limit the inflow of water, thereby wasting energy on pumping.
As shown in
FIG. 2.
, one technique of overcoming the above-mentioned deficiency is to install a transducer feedback mechanism that controls the pumps.
FIG. 2
is a block diagram illustrating a chiller system
200
that includes a transducer feedback mechanism. The chiller system
200
includes a chiller, e.g., chiller
100
; a pump
210
; a variable frequency drive (VFD)
220
; a valve
205
; a transducer
260
; AHUs
230
,
240
, and
250
; and corresponding valves
270
,
280
and
290
. The pump
210
is controlled by the VFD
220
, which receives load feedback from transducer
260
. The pump
210
is in fluid communication with chiller
100
via the valve
205
and the AHUs
230
,
240
and
250
. The valve
205
limits water flow into the chiller
100
so as to prevent pipe erosion.
During operation of the chiller system
200
, pump
210
pumps chilled water into chiller
100
to the valves
270
,
280
and
290
. If valve
270
is open, then chilled water will flow to AHU
230
. Similarly, if valve
280
is open, then chilled water will flow to AHU
240
. If valve
290
is open, chilled water will flow to AHU
250
. After the chilled water flows through the AHUs
230
-
250
(if their respective valves are open), the chilled water returns to the chiller
100
. If all the valves
270
,
280
and
290
are closed, then no chilled water will flow to the AHUs
230
,
240
and
250
and the chilled water will return to the chiller
100
via a bypass
255
.
The transducer
260
measures the differential pressure at points A and B. The transducer
260
then transmits a signal proportional to the differential pressure to the VFD
220
via a relay
225
to either increase or decrease the rate that pump
210
pumps chilled water. However, the differential pressure measured by the transducer
260
is not necessarily related to the load. For example, if all the valves
270
,
280
and
290
are closed, the transducer
260
may measure a differential pressure not indicative of the actual load. Accordingly, the transducer
260
may cause the VFD
220
to drive the pump
210
at greater speeds than required, thereby wasting electricity. In addition, the transducer
260
is susceptible to dirt (causing erratic control of the chiller
100
) and often fails.
Accordingly, a new absorption chiller system and method is required that solves the above-mentioned deficiency.
SUMMARY
The present invention provides a system for increasing the efficiency of a chiller. The system comprises a chiller, a burner, a first variable frequency driver and pump, a second frequency drive and pump, and a feedback system measuring burner characteristics. The chiller has a chilled water input and a cooling water input and the burner is coupled to the chiller. The first variable frequency drive and pump is coupled to the chilled water input. The second variable frequency drive and pump is coupled to the cooling water input. The feedback system is coupled to the burner, the first variable frequency drive, and the second variable frequency drive. The feedback system is capable of measuring a characteristic of the burner that is proportional to the cooling load of the chiller system and then transmitting a signal corresponding determined characteristic to the first and second variable frequency drives.
In an embodiment of the invention, the feedback system includes a potentiometer that is capable of determining a position of a modulating motor of the burner.
In another embodiment of the invention, the feedback system includes a potentiometer that is capable of determining a position of an energy input valve of the burner.
The present invention further provides a method for improving the efficiency of a chiller system. The method comprises: determining a characteristic corresponding to a cooling load of a chiller; and transmitting, to a variable frequency drive, a signal corresponding to the characteristic, wherein the variable frequency drive is coupled to a chilled water pump. In another embodiment of the invention, the method further comprises transmitting, to a second variable frequency drive, a signal corresponding to the characteristic, the second variable frequency drive coupled to a cooling water pump.
Therefore, the system and method may advantageously increase the efficiency of a chiller system.
REFERENCES:
patent: 5083438 (1992-01-01), McMullin
patent: 5946926 (1999-09-01), Hartman
patent: 6446941 (2002-09-01), Maheshwari et al.
patent: 6532754 (2003-03-01), Haley et al.
“Using Variable Speed Drives Technology to Reap Rewards of Efficient HVAC Design”, Printed on Nov. 24, 2002; 2 pages.
Kirsner, Wayne; “The Demise of the Primary-Secondary Pumping Paradig
Domnick Frank L.
Elliott Bruce A
Jones Melvin
Squire Sanders & Dempsey L.L.P.
Wininger Aaron
LandOfFree
Chilling system and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chilling system and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chilling system and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3268127