The influence of temperature stratification in the lower atmospheric boundary layer on the operating point of a natural draft dry-cooling tower

[摘要] ENGLISH ABSTRACT:Natural draft dry-cooling towers for power stations are designed to reject heat at aprescribed rate under specified atmospheric conditions. In the past, cooling towerdesigns were based on the annual average ambient air temperature, measured at 1. 5 mabove the ground (the reference temperature). Furthermore, the air flow through thetower was calculated according to an adiabatic temperature lapse rate in the atmosphere.However, the air inlet temperature at the heat exchanger may deviate significantly fromthe reference temperature due to temperature stratification in the atmosphere and the factthat the tower draws in air from considerable heights above the ground. Furthermore,the buoyancy force that drives the air through a natural draft cooling tower is alsoaffected by ambient air temperature stratifications. In this thesis, a logical build-up to afinal numerical model is followed. The physics of the formation of atmospherictemperature profiles and their relation to large scale weather patterns are discussed first,followed by a section on the heat and momentum transfer processes encountered in anatural draft dry-cooling tower. This is followed by a discussion of field data, and it allculminates in the application of this theory and data in a numerical example, illustratingthe usefulness of the proposed model.

[发布机构] Stellenbosch University