Method for measuring upper terminal difference and lower terminal difference of horizontal-type three-section feed water heater

Abstract

The invention discloses a method for measuring upper terminal difference and lower terminal difference of a horizontal-type three-section feed water heater. Data fitting is conducted on a dewatering cooling section, a condensation section and a superheated steam cooling section to obtain simplified linear function relations between the number of heat-transfer units of all the sections and a certain parameter, and the upper terminal difference and the lower terminal difference are calculated according to the simplified linear function relations. According to the method, analysis can be respectively conducted on the dewatering cooling section, the condensation section and the superheated steam cooling section of the heater on the basis of the dimension analysis principle and operation measurable parameters. By means of the simplified linear function relations between the number of the heat-transfer units of all the sections of the horizontal-type three-section feed water heater and the certain parameter, all thermal parameters of an inlet and an outlet of the water heater in any given operation condition can be finally obtained, and the upper terminal difference and the lower terminal difference can be obtained. The method provides reference for guaranteeing variable operation condition performance of the water heater, and is simple, rapid, wide in application range, and high in accuracy.

Description

technical field [0001] The invention relates to a horizontal three-stage feed water heater, in particular to a method for measuring and calculating the upper end difference and the lower end difference of the horizontal three-stage feed water heater. Background technique [0002] Modern large-scale thermal power plants all use heat recovery systems to reduce cold source losses and improve unit cycle heat efficiency, which can generally increase thermal economy by 10% to 20%. Among them, the feed water heater is the core of the heat recovery system, and its operating performance has a great impact on the entire unit. The site usually uses the size of the end difference to evaluate the operating characteristics of the heater. [0003] At present, most high-pressure heaters of large-scale thermal power units use horizontal three-stage U-shaped tube heaters. The feed water enters the water chamber from the feed water inlet pipe, enters the heat transfer section through the lower...

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Problems solved by technology

[0004] In the actual operation of the unit, although there are water outlet and drain temperature measurement points of the heater, its variable working condition characteristics can be obtained, but due to poor operating conditions, weak maintenance and other reasons, the measurement reliability and economic efficiency are generally poor. Problems: Resistive sensors are often used in thermal measurement systems, and the corresponding data acquisition system has a high measurement cost; when the working conditions change greatly, the water temperature response shows a large thermal inertia, which affects the measurement accuracy; the site installation location is complicated , once the sensor fails, the measurement data will be wrong or missing, so a method suitable for quickly measuring the end difference in the field is needed

[0005] In the traditional calculation method of heater end difference, some of them assume that the heat transfer coefficient of the heater remains unchanged when the conditions such as unit load and heater inlet water temperature change. Although the calculation process is simplified, it is inconsistent with the actual situation and has certain errors; some Using the heat transfer theory and heat balance theory, considering the influence of heater inlet water temperature and steam turbine load on the heat transfer coefficient, a calculation method for the difference between the upper and lower ends of the low pressure should be proposed, but the superheated steam cooling in the drain cooling section is not considered section, which is only applicable to low-pressure heaters; some methods assume the parameters of the steam side at the boundary points of each section of the heater when calculating the end difference, which affects the calculation accuracy; other calculation methods may also be limited to two-stage low pressure Heater, or solution limited to upper end difference

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