31 июля, 2013 
admin PTC 4.1 issued in 1964 and reaffirmed in 1991 was superseded and withdrawn in 1998 to be replaced by a new code PTC 4 that corrects many deficiencies of PTC 4.1 and makes the testing more accurate. However, PTC 4.1 in many parts of the world continues to be followed. Table 1.7 shows the essential differences between the two codes.
Even if the test uncertainty is eliminated and the tests are performed with the same type of instruments to the same levels of accuracy, the results of the tests conducted by the two methods would marginally vary. This is, first of all, because of slight differences in fuel efficiency as per PTC 4 and gross efficiency as per PTC 4.1 in the way the heat credits are treated. PTC 4 defines the reference temperature, makes heat credit accounting compulsory, and adopts certain minor improvements in the calculation methods. PTC 4 is, on the whole, a more comprehensive test code based on modern measurement, data reduction, and calculation with uncertainty analysis included and is therefore superior to PTC 4.1. There are certain differences in the estimation of loss and credits between the two codes as shown in Table 1.8.
|
Performance Test |
Performance Test |
||
|
Parameter |
Codes (PTC) 4.1 |
Codes (PTC) 4 |
Remarks |
|
Gross versus |
100 — (heat loss/fuel |
100 — (heat loss — heat |
Fuel efficiency replaces gross |
|
Fuel efficiency |
Input + heat credits) % |
Credits/fuel input) % |
Efficiency of PTC 4.1; fuel flow is directly calculable |
|
Test |
Not considered |
Uncertainty values |
Mainly driven by economical |
|
Uncertainty |
Listed in 1.3-1 and level to be agreed |
Instrumentation and data sampling procedures chosen; Section 4 of PTC 4 provides background and guidance |
|
|
Radiation and |
ABMA radiation loss |
Losses are accurately |
|
|
Unaccountable |
Curve to be used |
Evaluated; ABMA |
|
|
Loss |
Curve not used |
||
|
Reference |
Usually ambient; heat |
25°C to be adopted and |
With a fixed reference |
|
Temperature |
Credits can be |
Heat credits and loss |
Temperature, all results are on |
|
Neglected |
Are calculated |
The same basis and are directly comparable |
|
|
Output |
Energy absorbed by working fluid |
Energy absorbed by working fluid that is not recovered within steam generator envelope; for example, steam to SCAPH |
|
|
Objectives |
Better covered |
Test objectives or performance parameters |
|
|
Corrections |
Better defined |
Corrections to design conditions |
|
|
Flue gas |
Based on measured O2 and CO2 |
Based on measured O2, both wet and dry |
For efficiency calculations |
|
Calculation of |
Specific heat |
Enthalpy |
In PTC 4, the enthalpies of dry |
|
Losses and |
Air, dry flue gas, moisture |
||
|
Credits |
Vapor, and fuels are defined by equations (curve fits) |
||
|
Fuel analysis |
Mass basis |
Conversion from volumetric to mass is also provided |
|
TABLE 1.7 |
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