ISSN Online: 2377-424X
ISBN Print: 978-1-56700-474-8
ISBN Online: 978-1-56700-473-1
International Heat Transfer Conference 16
TIME-RESPONSE OF TURBULENT HEAT TRANSFER IN A PIPE FLOW AT SUDDEN ACCELERATION AND DECELERATION
Abstract
To predict the enhancement or suppression of heat transfer as a result of application of a pulsating flow in a pipe, the time response of the heat transfer to the sudden acceleration or deceleration of the flow was investigated experimentally. Quasi-rectangular flow pulsation was generated by opening and closing of a solenoid valve installed downstream of the test section. The Reynolds number with the valve open was varied
from 5,000 to 18,000, and that with the valve close was varied from 500 to 12,000. The spatiotemporal variation of the heat transfer in a pipe was measured using infrared thermography and the temporal variation of the flow properties in the pipe was simultaneously measured. Based on the experimental results, it was found that the variation of the heat transfer coefficient in response to the acceleration or deceleration of the flow can
be characterized using the corresponding time lag Δt and first-order time constant τ. From the data measured in this study, the time constants and time lags for the acceleration and deceleration cases were modeled as
functions of the wall friction velocity.