Study of circulation ratio for natural circulation in water-tube boiler at different operating conditions.

Abstract

The basic objective of the paper is to identify the desired circulation ratio for the natural circulation of water tube boilers in different operating conditions. This requires the basic study of heat flux and the mode of the boiling heat transfer, and the phenomenon like departure from nucleate boiling and tube overheating. The parameters, which need to be studied are heat flux, pressure, dryness fraction, void fraction, liquid velocity and their impact on the required circulation ratio. For a natural circulation boiler, the circulation ratio is one of the most important design parameters as the other design parameter like critical heat flux and skin temperature are mainly derived from the circulation ratio. The required circulation ratio can vary with the boiler pressure, liquid velocity and maximum heat flux. This study is intended to provide input for the safe and optimum design of a natural circulation boiler.

Steady State Two-Phase Flow Analysis of Natural Circulation in Hybrid Boiler

“…The performance of a circulation circuit is measured by circulation ratio. Circulation ratio is defined as the ratio of the mass flow rate of the steam-water mixture in the circulation loop to the steam generation rate in evaporator tubes [3]. The circulation does not provide sufficient information about the flow circulation in individual tubes, which is very important for the thermal and hydraulic performance of the boiler.…”