| Popis: |
The results of a comparison between traditional one-dimensional (1-D) models and a 1-D/2-D model for closed-loop thermosyphons with vertical heat transfer sections are reported in this paper. Attention is limited to problems in which the flow is laminar. For cases where heat losses from the insulated portions of the loop are negligible,St m=o, it is shown that traditional 1-D models can significantly overpredict the average fluid velocity in the loop for high power inputs (highGr m). Local results of two-dimensional numerical simulations in the heated and cooled sections reveal that this discrepancy arises because the 1-D models do not account for mixed-convection effects which distort the velocity and temperature profiles from their fully developed forced convection shapes. Furthermore, for cases whereSt m ≠ o, predictions of heat losses (or gains) produced by the 1-D models are handicapped by inaccuracies in the corresponding temperature predictions inside the loop. |
