Research Initiation: Heat Transfer and Pressure Drop in Tubes in the Transition Region for Various Entry Configurations

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The objective of the proposed research project is to study the effects of various entry configurations on local heat transfer and pressure drop in tubes in the transition region. This includes Reynolds numbers from about 200 up to 10,000, depending on the type of inlet configuration. Local heat transfer, pressure drop, and intermittency factor measurements will be made near the entrance of a tube, with those measurements continuing far enough downstream that fully- developed laminar or turbulent flow is achieved and the usually cited correlations presumably become valid. Various entrance configurations will be tested. Flow near the entrance of the tube will be modeled using existing numerical techniques, and the results will be compared to the experimental study. Independent measurements of pressure drop and velocity profiles in unheated transparent tubes and flow visualization studies will be used to assist in modeling the flow phenomena. An enormous amount of data and analytical modeling is available for fluid flow processes in tubes in the laminar and fully-turbulent flow regimes. However, very little has been done to examine the problems in the transition flow regime encompassing Reynolds numbers from perhaps 200 to 10,000. In practical engineering design, the usual recommendation is to avoid design and operation in this regime; however, this is not always feasible under design constraints. Much of the information available furthermore deals with the fully- developed flows far from the entrance, or involves entrance effects downstream from highly idealized entrances. The proposed research, therefore, will provide a basic understanding and data in the spectrum of tube flows, and also could have important practical design applications leading to improved design methods.