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In addition, current operational data available from the plant might help with verification of the thermo-hydraulic model The reliability and accuracy of the operational plant data should be known and understood before it is used with assisting in verification of the thermo-hydraulic model.
Primary review - Expected thermal performance for power uprate conditions
The next step of the process is to consider the thermal effects of the power uprate on the existing condenser. This is accomplished by reviewing the power uprate data and running the thermo-hydraulic model with this new data in order to predict the expected performance. This process might need to be repeated several times if a series of power uprate conditions are specified in order to determine the primary (highest duty) design point.
All of the changes associated with a power uprate should be known so that the effects on the condenser can be properly understood. Changes to equipment associated with the steam surface condenser need to be reviewed in parallel with those of the condenser.
Steam/shellside: An increase in the steam flow (and/or enthalpy) from the boilers, reactors, etc. to the condenser will create an increase in the resultant condenser duty.
Effects on drains routed to the condenser also should be reviewed (e.g. BFPTE, heater drains, etc.) since these too may increase the anticipated overall duty on the condenser during power uprate.
Water/tubeside: Improvements in the supply of the cooling water to the condenser can occur during power uprates. For example, cooling tower refurbishment and upgrades (packing internals, fans, etc.) can often result in a cooling water supply to the condenser being at a lower temperature than the original design. Modifications to the circulating water pumps can also affect the cooling water flow rates to the condenser.
All of the proposed changes presented during any power uprate should be reviewed in order to understand the overall effects on the condenser.
Options available for increasing thermal performance to meet power uprate conditions
Once the prior steps are all completed, and the operational capabilities and limitations of the existing condenser are known, an accurate assessment of the options available to the plant, including the condenser designer, can be properly evaluated. This is accomplished by reviewing the expected performance from the thermo-hydraulic model.
Given the specified criteria for the power uprate, it might be the case that the existing steam surface condenser, as is, will be able to attain the required performance parameters as defined without any necessary modifications. Since most condensers are typically custom designed, this is unusual, but not unknown. In some cases, condensers might have been designed with additional surface area capacity over and above that required to meet the original design capacity. For example, it is not uncommon that an additional quantity of tubes, e.g. 2 percent, 5 percent or 10 percent extra tubes, might have been included in the original design. In these situations, the additional surface area capacity might be sufficient to accommodate a proposed power uprate. However, it is a far more common occurrence that the existing steam surface condenser, as is, will not meet the required performance parameters. Typically, this will manifest such that a desired back-pressure cannot be attained by the existing steam surface condenser at the power uprate conditions, and therefore the output of the steam turbine cannot be achieved and/or guaranteed.