FUNDAMENTAL STUDIES IN HEAT TRANSFER AND FLUID MECHANICS. Status Report July 1, 1959-Feb. 29, 1960

Technical Report · Tue Oct 31 04:00:00 EST 1961

DOI:https://doi.org/10.2172/4101768· OSTI ID:4101768

Hoffman, H W; Gambill, W R

Experimental determinations of heat-transfer coefficients, burn-out heat fluxes, and frictlon factors were made for swirl flow of low- and moderate- pressure water through electrically heated aluminum, nickel, and copper tubes containing full-length Inconel twisted tapes. For nonboiling conditions, swirl- flow heat-transfer coefficients were successfully correlated with both the Froude modulus (the ratio of inertial to centrifugal forces) and a grouping of the Grashof and Reynolds moduli (ratio of buoyant to inertial forces). Under local- boiling conditions the effect of tape-twist ratio was clearly noted with the tighter tapes supporting a higher surface heat flux for a given superheat. At low pressures, swirl-flow burn-out heat fluxes were about twofold larger than for straight flow through the same tube at equal pumping power. Recommended correlations are given for the separate flow regimes and for burn-out. Friction factors for swirl flow were observed to be as much as threefold larger than those found for axial flow in smooth pipes. A systematic study has been undertaken of the effects of injection velocity, mass flow rate, pressure, and tube geometry on the vortex strength and the velocity profile in a gaseous jet-driven vortex tube under conditions approximating a two-dimensional flow field. It was found for the same jet input power and pressure that subsonic injection was more effective than supersonic injection in generating vorticity and that reducing the tube diameter resulted in a pronounced increase in the peripheral Mach number. No effect of L/d was observed. The degree of approach to potential vortex flow appears to be influenced primarily by the ratio of the radial to tangential Reynolds modulus (the higher the ratlo, the closer to potential vortex flow). An estimate of the degree of turbulence at the tube wall was obtained by using the velocity-profile data to estimate a virtual viscosity ( - /sup *// - ) for the fluid. The lowest value determined for - /sup *// - was 30 for a wall pressure of 2.5 psia; it is concluded that flow near the wall in jet-driven vortex tubes will in all probabillty be turbulent for pressures in excess of a few tenths psia. (auth)

• Research Organization: Oak Ridge National Lab., Tenn.
• NSA Number: NSA-15-008948
• OSTI ID: 4101768
• Report Number(s): CF-60-10-6
• Country of Publication: United States
• Language: English

Related Subjects

ALUMINUM
BOILING
BURNOUT
CENTRIFUGATION
CHROMIUM ALLOYS
CONFIGURATION
COPPER
EFFICIENCY
ELECTRICITY
ENGINEERING AND EQUIPMENT
FLUID FLOW
FLUIDS
FRICTION
GAS FLOW
GRASHOF NUMBER
HEAT TRANSFER
HEATING
INJECTION
JETS
MACH NUMBER
MASS
MECHANICS
NICKEL
NICKEL ALLOYS
PRESSURE
PUMPS
QUANTITATIVE ANALYSIS
REYNOLDS NUMBER
SUPERHEATING
SURFACES
THERMODYNAMICS
TUBES
TURBULENCE
ULTRASONICS
VELOCITY
VISCOSITY
VORTEX FLOW