Accession Number:

ADA371482

Title:

Forced Convection Condensation of Steam Inside a Horizontal Microtube

Descriptive Note:

Technical rept.

Corporate Author:

UTAH UNIV SALT LAKE CITY

Personal Author(s):

Report Date:

1999-11-10

Pagination or Media Count:

68.0

Abstract:

Preliminary experimental results of forced convection condensation of steam inside a horizontal microtube are reported. The stainless steel microtube has a diameter of 250 micrometers and a length of 48 mm. The inlet saturated vapor Reynolds number ranges from 390 to 4,700 and the average inlet saturated vapor velocities range from 33 to 276 ms. The mean subcooled temperature varies from 12 to 25 deg C. The two-phase pressure drop ranges from near zero to 65 kPa. The vapor quality at the inlet and outlet are 100 and 24 to 94, respectively. The experimental average Nusselt numbers are compared to those from stratified condensation flow and annular condensation flow in macrotubes found in the literature. The experimental average Nusselt numbers are 1 3 to 50 times smaller than the macrotube values, 2 do not depend on the inlet saturated vapor Reynolds number or velocity, and 3 increase nearly linearly with the increase in the change of vapor quality from the inlet to the outlet. The significant deviation from macroscale theory observed may be due to different condensation mechanisms caused by the relatively large droplet sizes relative to the inside diameter of the microtube. The two-phase pressure drop should include the contribution of surface tension.

Subject Categories:

  • Thermodynamics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE