Numerical simulation and prevention of water freezing in outdoor penstocks

Pipes laid in open air and conveying water can freeze in winter times. A blockage due to freezing can be effectively prevented by providing a minimum discharge. This precaution ensures the free flow of water through the pipe, but does not stop the forming of an ice layer on the inner pipe wall. In this paper a mathematical model is developed to determine minimal protection discharge and simulation of variation in time along the pipe of ice layer formed inside outdoor pipes during non-stationary atmospheric regime. The model allows the study of the pipe capacity to transport the normal discharge in operation and minimal protection discharge without affecting the hydraulic characteristics of the flow. Also, it gives the possibility to adopt economical solutions for the problem of protecting these pipes from frost. The performance of the developed model is illustrated using a numerical example.