Experimental investigation of the unusual behavior of local heat transfer coefficient in the transition region of a circular tube with a bell-mouth entrance

Book · Tue Dec 31 04:00:00 EST 1996

OSTI ID:419633

Tam, L M; Ghajar, A J ^[1]

---

1. Oklahoma State Univ., Stillwater, OK (United States). School of Mechanical and Aerospace Engineering

The local heat transfer characteristics for ethylene glycol water mixtures flowing in a horizontal circular straight tube with a bell-mouth inlet have been determined experimentally over a flow Reynolds number range of 1,500 to 27,000. A wall-boundary heating condition of uniform heat flux was imposed. The variation of local heat transfer coefficient with length in the transition and turbulent flow regimes is very unusual. For the bell-mouth inlet, the boundary layer along the tube wall is at first laminar and then changes through a transition region to the turbulent condition causing a dip in the Nu-x/D curve. The length of the dip in the transition region is much longer than that in the turbulent region. For the experiments the length of the dip in the transition region varied from x/D = 100 to 175 in comparison to an x/D < 25 for the turbulent region. The presence of the dip in the transition region causes a significant influence on both the local and the average heat transfer coefficients. This is particularly important for heat transfer calculations in short tubes with a bell-mouth inlet.

• OSTI ID: 419633
• Report Number(s): CONF-960815--; ISBN 0-7918-1512-9
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
EXPERIMENTAL DATA
HEAT EXCHANGERS
HEAT FLUX
HEAT TRANSFER
LAMINAR FLOW
OPENINGS
TRANSITION FLOW
TURBULENT FLOW