Cooperation of a Steam Condenser with a Low-pressure Part of a Steam Turbine in Off-design Conditions

Abstract

A steam condenser is an important component of a power plant, in which the heat of condensation is discharged to the environment. Changes of inlet temperature and mass flow rate of cooling water affect the steam pressure, which has a significant impact on the efficiency and power generated in the low-pressure (LP) part of the steam turbine. On the basis of data obtained from a simulator of the steam condenser and the actual measurement data from a 200-MW power plant, an analysis was performed of how the inlet cooling water temperature, the cooling water mass flow rate, and the steam mass flow rate affect the steam condenser effectiveness, the heat flow, the steam pressure in the condenser, and the efficiency and power of the LP part of the steam turbine. In the case of heat exchangers with a condensation zone, e.g. in a regenerative heat exchanger, the maximum value of the effectiveness e means obtaining the maximum value of the heated fluid temperature at the outlet. Since the role of the steam condenser (providing the lowest possible vacuum) is slightly different from the role of a classical heat exchanger, increasing the value of e does not mean better performance of the steam condenser. An even greater disparity exists in the evaluation of the performance of a system comprising the steam condenser and the LP part of the steam turbine. It was therefore suggested to evaluate the performance of the steam condenser and the LP part of the steam turbine using the parameter of efficacy, defined as: δ=(1-e)=δtmin /ΔTmax. Moreover, for practical purposes, the relation (6) was given for the power of the LP part of the steam turbine as a function of the cooling water mass flow rate and its temperature at the inlet to the steam condenser. Knowing the characteristics of the LP part of the steam turbine and of the steam condenser, one can optimize operating conditions of the system.