Film condensation of steam on externally enhanced horizontal tubes. Master's thesis

Technical Report · Sat Mar 01 04:00:00 EST 1986

OSTI ID:5401620

Mitrou, E S

Heat-transfer measurements were made for filmwise condensation of steam on externally enhanced horizontal tubes under vacuum and at atmospheric pressure. Data were obtained for copper tubes with circular fins of rectangular, triangular, trapezoidal, and parabolic cross sections for spiral fins of triangular cross section, for commercially available finned tubes and for wire-wrapped tubes. Four spirally finned tubes from each of Cu, Cu-ni, Al, and stainless steel and two tubes with fins of rectangular cross section from each of Cu-Ni and Al were manufactured and tested to investigate the effect of thermal conductivity. Among sprially finned tubes, the optimum fin pitch was found to be 1.6 mm. The tubes with a parabolic fin shape showed the best performance with steam-side enhancements of 4.1 and 6.2 under vacuum and at the atmospheric pressure respectively. Enhancement ratios as high as 3.5 and 2.1 were obtained under vacuum and at atmospheric pressure, respectively, for the commercially available finned tubes. The heat-transfer performance decreased with decreasing tube-metal thermal conductivity. For the wire-wrapped tubes, an optimum pitch-to-wire diameter ratio of about 5.1 was found, with steam-side enhancements of about 1.9 and 2.2 under vacuum and at atmospheric pressure, respectively. A recent theoretical analysis of laminar film of low-surface-tension fluids on wire-wrapped tubes was modified to include the condensate retention of the tube due to the high surface tension of water. Agreement between this modified analysis Keywords: Heat transfer coefficient.

• Research Organization: Naval Postgraduate School, Monterey, CA (USA)
• OSTI ID: 5401620
• Report Number(s): AD-A-168391/1/XAB; NPS-69-86-001
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400* -- Engineering-- Heat Transfer & Fluid Flow
ALLOYS
ALUMINIUM
CONDENSERS
COPPER
COPPER ALLOYS
CROSS SECTIONS
ELEMENTS
ENERGY TRANSFER
FILMS
FINS
FLUID FLOW
HEAT TRANSFER
LAMINAR FLOW
METALS
NICKEL ALLOYS
OPTIMIZATION
PARABOLAS
PHYSICAL PROPERTIES
SHAPE
STEAM
STEAM CONDENSERS
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
TUBES
VAPOR CONDENSERS