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Several possible flow regimes are known to exist for the flow of a liquid and vapor in a duct. These flow regimes are classified according to the spatial distribution of the two phases. One of these patterns, termed "annular-mist flow," may be described as the confined concurrent flow of a vapor and a liquid in a circular duct where a portion of the liquid flows in a low velocity annular film in contact with the duct wall, while the remainder of the liquid flows as entrained particles in a relatively high velocity gaseous core. The particular flow studied in this investigation is the condensing two-phase annular-mist flow of a single component flowing in a circular duct. Due to the cooling at the duct wall the vapor begins to condense and, for high vapor velocities and suitable wall/liquid wetting characteristics, the two-phase annular-mist pattern forms. The condensation process continues until that point where liquid flows alone in the duct. If the vapor velocity is sufficiently high enough (of the order of 500 ft/s) , then the annular-mist flow regime will exist to a high degree of approximation throughout the entire condensing length. The authors have visually observed, through a short glass tube section, the annular-mist pattern up to the point of complete condensation. After the annular liquid layer fills the tube there are some entrained bubbles which exist for several tube diameters.The design of high performance, high vapor velocity, internal flow tube condensers depends upon how accurately the two-phase pressure drop and heat transfer characteristics can be calculated. At the present time, most of the experimental data for annular-mist, two-phase flow is for two-component systems (usually air-water), while relatively little data exists for single-component systems with heat removal. Attempts at predicting pressure drop and heat transfer coefficients for condensing annular-mist flows usually rely on correlations based on data taken for adiabatic two-component flows. As long as the vapor velocity is not too high these correlations are many times suffiCorrespondence concerning this paper should be addressed to W. P. cient. However, they do not give sufficiently accurate results for the high vapor velocity single-component condensing situations considered in this paper. It was the purpose of this investigation to present an integral analysis that accurately models the high vapor velocity, two-phase annular-mist condensing flow system previously described. Possible applications of the resulting model are the design of compact light-weight tube condensers for space Rankine cycles and external combustion Rankine engines which require very high heat transfer coefficients at the expense of pressure drops which are large compared with those which occur in other tube condenser systems, such as vapor refrigeration cycles. ANALYSISThe pressure drop in annular two-phase flow systems is affected by three factors-friction, momentum, and gravity. Soliman et al. ( I ) , Andeen and Griffith ( 2 ) , and Carpenter and Colbu...

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A survey questionnaire dealing with instrumentation, calibration and error estimation of guarded and calibrated hot boxes was mailed to United States and Canada hot box laboratories capable of measuring the R-value of building assemblies. Questions pertaining to types of instrumentation, estimated accuracy of the specific instruments and error analysis calculations were asked. Responses from those laboratories responding to the survey are summarized in the paper. This information will be beneficial to future revisions of the ASTM guarded and calibrated hot box test methods.