Method of measuring changes in the energy transfer efficiency of a thermal transfer system

A method of quantitatively measuring energy transfer efficiency changes resulting from modifications in a boiler system, comprising: measuring the amount of fuel used by the boiler to produce a certain quantity of energy in its output; making modifications to the boiler system; measuring the amount of fuel used by the boiler, after the modifications, to produce the same certain quantity of energy; and determining the difference in the measured fuel usages as a measure of the effectiveness of the boiler system modifications.

FIELD OF INVENTION 
This invention relates to a method of measuring the energy transfer 
efficiency change resulting from the introduction of a device, system, or 
method of operation to a thermal transfer system. 
BACKGROUND OF INVENTION 
It has always been a goal to increase the energy transfer efficiency, 
within practical financial limits and operating specifications, of systems 
which involve heat transfer. Examples of such systems include: steam 
boilers which typically burn fossil fuel to convert water to steam for use 
in heating, cooling, process manufacturing, or the driving of turbines to 
produce electricity; oil refinery furnaces which burn fossil fuel to heat 
crude oil to produce various petroleum products; and food processing 
systems which use fossil fuel to heat vegetable oil to produce a variety 
of products. It is a goal of such systems, within practical financial 
limits and operating specifications, to transfer as much of the heat value 
of the fuel as possible to the substance or material being heated. Many of 
these systems burn millions of dollars of fuel per year, and thus small 
changes in efficiency can translate into large monetary savings. 
The standard basis for measuring efficiency of boilers is the ASME power 
test code 4.1. This test code employs two measurement methods: 
input-output, and heat-loss. These methods are theoretically equivalent, 
and are considered to be measures of the effectiveness of the boiler in 
extracting the available heat energy of the fuel. In the input-output 
method, the efficiency is measured as the amount of heat absorbed by the 
water and steam, compared to the energy input of the fuel. 
This method requires the accurate measurement of fuel input. Also, accurate 
data must be available on steam pressure, steam temperature, steam flow, 
feed water temperature, stack temperature, and air temperature. The 
heat-loss method subtracts individual energy losses from 100% to obtain 
percent efficiency. The losses measured include heat loss due to dry gas, 
heat loss due to moisture in the fuel, heat loss due to water from the 
combustion of hydrogen, heat loss due to combustibles in coal refuse, heat 
loss due to radiation, and other unmeasured losses. The major contributor 
to the heat loss is the flue gas. 
Although these calculations can be accurate, they require the testing party 
to gather a large amount of data, and thus are cumbersome to perform. In 
addition, these tests are performed under a range of operating variables 
that may comprise only a small percent of the actual range of operating 
variables the equipment operates under. The input-output method demands 
precision instruments to measure such items as steam pressure, steam 
temperature, steam flow, fuel input, feed water temperature, stack 
temperature, and air temperature. Furthermore, a steam plant may not be 
able to support testing for long periods of time because of practical 
considerations such as the demand of steam required to produce required 
electricity. 
In the above described methods, accurately measuring the change in 
efficiency resulting from the introduction of a device, system, or 
operational method to the thermal transfer system would be difficult to 
quantify, as only a small range of operating variables may be observed 
before and after such introduction. Additionally, significant changes in 
operating variables such as a high wind velocity may be present before the 
introduction, but not present after the introduction, thereby affecting 
the objective of a controlled comparison. Additionally, operating 
variables have within themselves attributes that affect other operating 
variables, thereby creating an interrelationship that cannot be expressed 
under the above methods. An example of this is barometric pressure. At 
very low barometric pressures, less air is available to mix with the fuel. 
However, this may be offset by high winds that can occur at low pressures: 
the high winds at the stack can pull more volume of this low density air 
into the system's burner. 
SUMMARY OF INVENTION 
It is therefore an object of this invention to provide a method of 
measuring the energy transfer efficiency changes resulting from the 
introduction to the thermal transfer system of one or more modifications 
to the system, for example one or more devices, systems or methods of 
operation, The modification, or modifications, are hereinafter referred to 
as "modifications". This is accomplished by making measurements under 
defined ranges of variables before the modifications and then again after 
the modification under the same defined ranges of variables, in order to 
determine the net effect of the modifications in terms of energy transfer 
efficiency. 
It is a further object of this invention to provide such a method which can 
be performed automatically using a microcomputer. 
It is a further object of this invention to provide such a method which can 
be performed over any desired time interval. 
It is a further object of this invention to provide such a method which can 
be performed continuously if desired. 
It is a further object of this invention to provide such a method which 
takes into account weather conditions affecting efficiency. 
It is a further object of this invention to provide such a method which 
takes into account any measurable variable condition that affects 
efficiency. 
This invention results from the realization that the energy transfer 
efficiency of systems which transfer heat energy, such as boiler systems, 
can be determined by measuring the amount of fuel required to create a 
predefined quantity of energy at the system output. The effect on 
efficiency resulting from modifications made to the system may then be 
determined by determining the difference in the amount of fuel required to 
create the same amount of energy after the modifications. 
This invention features a method of quantitatively measuring energy 
transfer efficiency changes resulting from modifications in a boiler 
system, comprising: measuring the amount of fuel burned by the boiler to 
produce a predefined quantity of energy in its output; making the 
modifications to the boiler system; measuring the amount of fuel burned by 
the boiler after the modifications to produce the same predefined quantity 
of energy; and determining the difference in the measured fuel usages as a 
measure of the effectiveness of the boiler modifications. The method may 
further include measuring a number of operating variables while fuel usage 
is being measured, and correlating the measured values of these variables 
with the fuel burned by the boiler to produce a predefined quantity of 
energy, to establish baseline conditions before the boiler system 
modifications. Determining the difference in fuel usage may include 
finding the baseline conditions which match the variable values during 
fuel usage measurement after the boiler modifications. Determining the 
difference in fuel usage may further include resolving the measured amount 
of fuel used by the boiler to produce the predefined quantity of energy 
for the found baseline conditions, and comparing the measured amount of 
fuel used by the boiler after the modifications, to the resolved measured 
amount of fuel. 
Also featured is a method of determining changes in energy usage resulting 
from modifications in a thermal transfer system in which a number of 
system variables are measured, comprising: (a) selecting a quantity of 
transferred energy as a thermal transfer trigger point; (b) establishing a 
database with a number of entries, each including a value for each 
operating variable, and a fuel quantity value; (c) periodically measuring 
and storing the values of the operating variables, until the thermal 
transfer trigger point is reached; (d) determining the quantity of fuel 
used to transfer the selected quantity of energy; (e) determining a single 
representative value for all of the stored values for each variable; (f) 
creating a database entry including the representative value for each 
variable, and the determined quantity of fuel; (g) before the system 
modifications, repeating steps (c) through (f) for a period of time to 
establish a meaningful baseline database; (h) after the modifications, 
repeating steps (c) through (e); (i) finding the database entry with the 
operating variable values most closely matching the respective single 
representative values for the operating variables determined after the 
modifications; (j) retrieving the fuel quantity value which is part of the 
found database entry; and (k) comparing the quantity of fuel used to 
transfer the selected quantity of energy after the modifications, to the 
retrieved fuel quantity value to determine the effect of the modifications 
on the amount of fuel required to result in the transfer of the selected 
quantity of energy under the matching operating variables. 
Also featured is a method of measuring the energy transfer efficiency 
change resulting from a modifications in a thermal transfer system, 
comprising: measuring the transfer of a predetermined quantity of energy, 
and the amount of fuel used by the system to accomplish the energy 
transfer; making the modifications to the thermal transfer system; after 
the modifications, measuring the amount of fuel used by the system to 
accomplish the transfer of the same predetermined quantity of energy; and 
determining the difference in the measured fuel usage as a measure of the 
effectiveness of the thermal transfer system modifications. 
In another embodiment, featured is a method of measuring the energy 
transfer efficiency change resulting from a modifications in a thermal 
transfer system, comprising: measuring the usage of a same predetermined 
quantity of fuel, and the resulting quantity of energy transferred; making 
the modifications to the thermal transfer system; after the modifications, 
measuring the quantity of energy transferred during the usage of the 
predetermined quantity of fuel; and determining the difference in the 
measured quantities of energy as a measure of the effectiveness of the 
thermal transfer system modifications. 
Another embodiment features a method of determining changes in energy usage 
resulting from modifications in a thermal transfer system in which a 
number of system variables are measured, comprising: establishing a 
quantity of one variable as a thermal transfer trigger point; operating 
the system and periodically measuring and storing the system variable 
values, until the trigger point is reached; making the modifications to 
the thermal transfer system; after the modifications, operating the system 
and periodically measuring the system variable values, until the trigger 
point is reached; and determining, from the values of at least one system 
variable both before and after the modifications, the effectiveness of the 
thermal transfer system modifications. The variables may include the 
quantity of fuel used and the quantity of energy transferred, and the step 
of establishing a quantity of one variable as a thermal trigger point may 
then include establishing a quantity of energy transferred as the trigger 
point. The step of determining the effectiveness of the thermal transfer 
system operating change may then include comparing the quantities of fuel 
used both before and after the modifications to determine the change in 
fuel usage caused by the modifications, as a measure of the effectiveness 
of the thermal transfer system modifications. 
The step of establishing a quantity of one variable as a thermal transfer 
trigger point may alternatively include establishing a quantity of fuel 
used as the trigger point, and then the step of determining the 
effectiveness of the thermal transfer system modifications may include 
comparing the quantities of energy transferred both before and after the 
operating change to determine the change in energy transfer efficiency 
caused by the modifications, as a measure of the effectiveness of the 
thermal transfer system modifications.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
This invention may be accomplished in methods of measuring the energy 
transfer efficiency changes resulting from modifications made to a thermal 
transfer system. In the preferred embodiment, the method is accomplished 
by measuring the amount of fuel used by the energy transfer system to 
produce a predefined quantity of energy at the system output, making the 
modifications, and then again measuring the amount of fuel used to produce 
the same quantity of energy at the system output, under the same operating 
conditions as the test performed before the modifications, to determine 
the fuel conservation associated with the modifications. Alternatively, 
the amount of fuel used may be the constant, and the output energy may be 
the measured variable. 
In order to make accurate, meaningful comparisons of data taken before and 
after system modifications, it is important to build a baseline database 
which includes such fuel usage/energy creation data across a wide range of 
possible operating conditions of the thermal transfer system. This 
database may be created by identifying system variables in advance, and 
taking measurements of the operating variables before making the 
modifications. An amount of output energy to be used as the comparison 
point, called the "trigger point" herein, is determined in advance. The 
system is then operated under different conditions, and measurements of 
all the system variables are made over the time it takes to create a 
trigger point amount of energy. The values of each of the operating 
variables over this time are then averaged and stored in the database 
along with the amount of fuel used to create the trigger point amount of 
energy. Preferably, the trigger point is chosen to be small enough such 
that these baseline tests are of short enough duration so that there is 
not a great variation in the values of the variables during any given 
test. The variables which change most rapidly are wind speed near the top 
of the stack and system load. Furthermore, the values of the variables are 
preferably measured or sampled at a rate of at least once per second. 
A measurement range is determined in advance for each of the variables. For 
example, the range of outside temperatures could be selected to be between 
-10.degree. F. and 110.degree. F. This range for each of the variables is 
then divided into a number of equal-sized increments, called "bins" 
herein. For example, there may be 12 bins for temperature, each 
encompassing ten degree increments. To simplify the use of the database, 
each variable has the same number of bins. The total number of possible 
combinations of bins is therefore equal to the number of bins, raised to 
the power equal to the number of independent variables. Thus, if there are 
two bins, and three variables, there are 2.sup.3, or 8, possible 
combinations of bins. Accordingly, a table with eight entries will provide 
a database which has an entry for each possible combination of bins. 
Fuel usage data is provided for each database entry in the baseline 
database established before the modifications. Since it will likely not be 
possible to actually take measurements across the entire measurement range 
for each operating variable, in order to create a complete table it is 
necessary to conduct multivariate multiple regression 
interpolation/extrapolation on the measured data. Preferably, a 
commercially-available software package, such as "Statistica" software, 
sold by StatSoft Company, Tulsa, Okla., is used to perform the 
interpolation/extrapolation, although other commercially available 
software packages may be used. 
Once the table is prepared, one or more modifications are made to the 
thermal transfer system. The system is then operated, and the same 
variables measured until the trigger point is reached. The variable values 
during the measurement time are averaged, and the bin number for each 
variable average value is then determined. The database entry having 
corresponding bin numbers is then found, and the fuel usage measurement 
associated with that database entry is retrieved. The amount of fuel used 
after the modifications is then compared with this retrieved fuel usage 
value to determine the change in fuel usage caused by the modifications. 
There is shown in FIG. 1 boiler system 10 employing the method of this 
invention of determining changes in energy usage resulting from 
modifications in the boiler system. The boiler system consists of boiler 
12 and flue gas stack 14. Boiler 12 is fed with water and fuel. This 
invention contemplates the development of data from the boiler system, 
which in the preferred embodiment is accomplished as follows. 
Microcomputer 26 (a 486-DX-50, with 8 Mb RAM) is enabled to accept inputs 
comprising the fuel flow rate using flow meter transmitter 16, the steam 
output pressure and differential pressure using pressure and differential 
pressure meter 20 and 22, respectively. Steam temperature must also be 
included if the boiler produces superheated steam. The signals from 
transmitters 16, 18, 20 and 22 are typical 4-20 mA signals that are 
converted to 1-10 VDC signals by conditioners 32. These signals are 
digitized by A/D card 34. The windspeed, ambient temperature, and 
barometric pressure near the top of stack 14 are also collected using 
anemometer 24, temperature sensor 26, and pressure sensor 28, which are 
inputs to weather monitor station 30, that may be a Davis Instruments 
"Weather Monitor II", although other commercially-available weather 
monitoring instruments may be used. The data is acquired and processed by 
computer 36 using a commercially-available data acquisition program, for 
example the Labtech Control 4.21 data acquisition software development 
system. Hardware drivers are installed in weather monitor 30 to produce a 
serial output that is compatible with computer 36. Monitor 38 is used to 
display the data as described below in conjunction with FIG. 2. 
The data is used by computer 36 to calculate the wind speed, ambient 
temperature, barometric pressure, gallons of fuel, steam gauge pressure, 
steam load in thousands of pounds per hour, and boiler output energy in 
millions of BTUs. The calculation of load and energy from the collected 
data is accomplished using information known in the field. 
One form of a display displayed on monitor 38 is shown in FIG. 2. Display 
40 in this example consists of subdisplays 42 through 44, one for each of 
three boiler units in a power generating plant. Each sub-display, such as 
sub-display 42, includes a running total of millions of BTUs in the output 
steam stream, 46, and gallons of fuel burned to produce this amount of 
energy, 48. The load and steam pressure are displayed in real time, 50 and 
52, respectively, and numerical values for bar charts 46, 48, 50, and 52, 
are below the bar charts, 47, 49, 51, and 53, respectively. The time of 
day is reported in area 56, and the wind speed, ambient temperature, and 
barometric pressure are also reported, 58, 60 and 62, respectively. 
The basic methodology of this invention is to establish a trigger point 
which is either the production of a predetermined quantity of energy, or 
the burning of a predetermined quantity of fuel. The thermal transfer 
system is then operated until this trigger point is reached. Transmitted 
data, either in analog or digital format, from each of the transmitters is 
collected periodically, for example once per second, during this time 
period. In the example of FIG. 2, the trigger point is 25 million BTUs, 
indicated by the number 25 just above bar chart 46. The amount of fuel 
consumed to produce the selected amount of energy, along with averages of 
the operating variables during the energy production period, are then 
determined and saved. 
The preferred method of building a database of baseline system information, 
taken before the modifications are made to the operation of the system, is 
described in the flow chart of FIGS. 3A and 3B. Flow chart 100 begins with 
step 102, in which the operator establishes a trigger quantity of energy. 
In the example carried through in the description, there would be selected 
an amount in millions of BTUs. Alternatively, the operator could select a 
trigger point of gallons of fuel burned. 
The sensors are connected to the computer, step 104, and data acquisition 
to fill in the constructed database is then begun, step 106. The real-time 
display of FIG. 2 is also enabled. Preferably, the trigger quantity of 
energy is selected to be small enough so that the operating system runs 
required to generate a single database entry are relatively short, no 
greater than one hour is recommended. When the test is begun, the computer 
acquires the value of each variable once per second, step 108. The data is 
converted to the desired engineering quantities, step 110. Some variable 
values are continuously reported, as shown in FIG. 2. 
When the trigger of 25 million BTUs produced is reached, step 112, data 
acquisition ends. All the stored values for each variable are then 
averaged and the data is stored in a database, step 114. This process is 
repeated until enough data is collected to achieve a desired level of data 
in the database, step 116, so that the database can be accurately 
completed using interpolation techniques described below. 
The operator would then set a range of values for each operating variable 
being measured. The range for each variable is then divided into a number 
of smaller segments, called "bins", step 118. The number of bins is 
selected by the operator. The number of database entries equals the number 
of bins raised to the power equal to the number of independent variables, 
assuming there are the same number of bins for each independent variable. 
The database entry with bin numbers matching those of the bin numbers 
determined for each variable average value of a single test is then 
resolved, and the quantity of fuel used in the run is then written into 
that database entry, step 114. 
Data acquisition steps 108 through 114 are repeated a number of times to 
generate a fuel quantity for a number of different database entries. It is 
typically impractical to conduct enough tests to fill in the entire 
database, due to conditions outside of the control of the operator. For 
example, if the baseline data acquisition takes place during the summer 
months, the lower ranges of ambient temperatures will not be reached. All 
the ranges of barometric pressure and wind speed also may not be reached, 
especially since there are such a large number of possible of combinations 
of bin numbers in the database. Accordingly, it is necessary to complete 
the table by interpolating/extrapolating from existing data with a 
technique such as the multivariate regression technique of the 
"Statistica" software package from StatSoft Company, Tulsa, Okla. 
Once the baseline database is complete, one or more modifications are made 
to the system. For example, a new burner nozzle may be installed, or the 
furnace draft may be altered in some manner. The effect of these 
modifications on the efficiency of the energy transfer system may then be 
determined as set forth in flow charts 130 and 150, FIGS. 4 and 5, 
respectively. 
The modification is introduced, step 132, and the operator begins data 
acquisition, step 134. The system stores the variable values once per 
second, step 136, and the data is converted, step 138. When the trigger 
point is reached, step 140, data acquisition ends. All stored values of 
each operating variable are then averaged, and the amount of fuel consumed 
is computed and stored, step 142. 
The change in the amount of fuel used to create the trigger point amount of 
energy is then determined and displayed as set forth in flow chart 150, 
FIG. 5. When the operator selects the "reports" icon, he is presented with 
a calendar which allows him to select an operating time period of any one 
or more days or months in which the stored data is displayed, and the fuel 
usage change determined and displayed. 
At step 156, the computer finds a match in the baseline database for each 
trigger period in the time period selected by the operator. This database 
matching is accomplished as follows. The baseline database represents 
pre-modification consumption values for energy production periods under 
various conditions which affect efficiency. The baseline database is 
established in the form of a table, with a number of baseline database 
entries equal to the number of bins raised to the power of the number of 
independent variables. For example, if there are two bins and three 
independent variables, the database has 2.sup.3, or 8, entries, numbered 1 
through 8. Table I sets forth such a database. The "baseline value" in the 
far right column would be the fuel consumption for the database entry 
number. 
TABLE I 
______________________________________ 
Variable Variable Variable 
db# 3-bin no. 2-bin no. 1-bin no. 
Baseline Value 
______________________________________ 
1 0 0 0 baseval.sub.-- 1 
2 0 0 1 baseval.sub.-- 2 
3 0 1 0 baseval.sub.-- 3 
4 0 1 1 baseval.sub.-- 4 
5 1 0 0 baseval.sub.-- 5 
6 1 0 1 baseval.sub.-- 6 
7 1 1 0 baseval.sub.-- 7 
8 1 1 1 baseval.sub.-- 8 
______________________________________ 
The database entry number for the entry matching each trigger period is 
determined as follows. The bin number for the average value for each 
variable is first determined by subtracting the lowest data value of the 
range from the average value, and dividing the result by the width of the 
bins. The bin number is the greatest integer value less than or equal to 
the variable number. For example, if the temperature range is 20.degree. 
to 100.degree., and there are eight bins, the 80.degree. temperature range 
would be divided into ten-degree increment bins. The width of the bins 
would then be ten. If the average temperature for the currently-computed 
trigger period is 50.degree., the bin number for the temperature variable 
would be equal to 50-20.div.10 or 3. If the temperature was 51, the bin 
number would be 4. 
Once the bin numbers are determined for each of the independent variables, 
the database entry number is determined by the following equation: 
EQU Database entry no.=1+Variable 1 bin no.+variable 2 bin no..times.no. 
bins.sup.(2-1) + . . . Variable n bin no..times.no. bins.sup.(n-1) 
Once the baseline database entry number is found, the baseline value (the 
amount of fuel used to establish the baseline database entry) is retrieved 
from the database. The post-modification fuel quantity is then subtracted 
from this quantity to determine the fuel savings associated with the 
modifications, step 158. The results are displayed in a desired form, such 
as graphically and in a tabular form, both in summary for the entire 
selected report period, and in detail for each trigger period of the 
entire report period. One or more corrections are then applied to the fuel 
savings to account for the BTU content of the fuel, and other post-data 
acquisition correction factors, for example a correction to account for 
soot or scale buildup on the heat exchanger tubes, in an attempt to 
attribute the fuel savings as closely as possible to only the 
modifications, step 162. These correction techniques are known in the art. 
Operation then returns to real time display, in which the operator may 
select another time period for calculation and display, step 164. 
Although specific features of this invention are shown in some drawings and 
not others, this is for convenience only as each feature may be combined 
with any or all of the other features in accordance with the invention. 
Other embodiments will occur to those skilled in the art and are within the 
following claims: