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37. Effect of Inundation Upon the Condensation Heat Transfer Performance of R-134a: Part II -- Results (RP-984).

Author

Randall, Duane L. and Eckels, Steven J.

Subjects
*STRUCTURAL shells, *HEAT exchangers, *HEAT transfer, *CONDENSATION, *THERMAL expansion, *HEAT flux transducers
Abstract

Shell-side heat transfer coefficients were experimentally determined for three different types of tubes in a 25-tube bundle designed to simulate a single-pass heat exchanger. Smooth tubes, two-dimensional integral fin tubes, and three-dimensional enhanced-surface tubes were arranged in a three-column-by-ten-row staggered pattern with a horizontal and vertical pitch of 22.9 mm. Bundle average heat transfer coefficients and row-by-row heat transfer coefficients were measured as part of this study. Results showed the three-dimensional enhanced tube had the highest condensation heat transfer coefficient of any tube tested during the course of the study. Bundle average heat transfer coefficients for the three-dimensional tube showed a steady decline with increased heat flux and Ihe row-by-row heat transfer coefficients showed an almost linear decrease with increased row number. The performance of the two-dimensional tube showed variations with heat flux but showed less sensitivity to inundation level. The experimental results for all tubes were compared with published correlations. Experimental results for the two-dimensional tube were predicted well by the correlations, but no suitable correlation was found for the three-dimensional tube so one was developed. [ABSTRACT FROM AUTHOR]

Published
2005
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38. Effect of Inundation Upon the Condensation Heat Transfer Performance of R-134a: Part I -- Facility Overview and Data Analysis (RP-984).

Author

Randall, Duane L. and Eckels, Steven J.

Subjects
*HEAT transfer, *CONDENSATION, *HEAT flux transducers, *TUBES, *STRUCTURAL shells, *DATA analysis
Abstract

An experimental facility was designed and constructed to measure shell-side condensation heat transfer data for R-134a condensing on three different tube types: a smooth tube, a two-dimensional tube, and a three-dimensional tube. The 1575 fin-per-meter tubes had an equivalent or nominal outside diameter of 19.1 mm. Twenty-five tubes were arranged in a three-column by ten-row staggered pattern with a horizontal and vertical pitch of 22.9 mm. The facility was designed to operate at saturation temperatures of 35°C and 40°C over a heat flux range of 7500 to 63000 W/m²2. This paper presents a detailed facility description, the facility operating procedure, data analysis, and uncertainty analysis. Experimental results from this study are presented in a companion paper (Part II). [ABSTRACT FROM AUTHOR]

Published
2005
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40. Correlations for Heat Transfer and Pressure Drop of Glycol-Water and Air Flows in Minichannel Heat Exchangers.

Author

Jokar, Amir, Hosni, Mohammad H., and Eckels, Steven J.

Subjects
*HEAT transfer, *AIR conditioning, *THERMODYNAMICS of heat exchangers, *WALK-in coolers & freezers, *REFRIGERATION & refrigerating machinery, *REFRIGERANTS, *PRESSURE, *ETHYLENE glycol, *FLUID dynamics
Abstract

The thermo-hydrodynamic performance of three different minichannel heat exchangers (MCHEs) of an automotive air-conditioning system is studied and discussed in this paper. The minichannel heat exchanger, a kind of cross-flow compact heat exchanger; is used as a component of an automotive air-conditioning system. The automotive air-conditioning system in this study is a standard refrigeration cycle that uses refrigerant R-134a as the working fluid. The MCHE is installed within a secondary fluid loop, which uses a 50% glycol-water mixture as the cooling fluid and exchanges energy with the main refrigeration loop. In other words, the energy absorbed by the MCHE from the passenger cabin is transferred to the evaporator using the glycol-water mixture circulating through the secondary fluid loop. A modified version of the Wilson plot technique is applied to find the single-phase heat transfer coefficients for both the glycol-water and air sides. This paper proposes semi-empirical correlations for the heat transfer and pressure drop for the glycol-water flow within the minichannels and airflow through the louvered fin surfaces. The uncertainty estimates for the measured and calculated parameters are also presented. The results for the glycol-water heat transfer and pressure drop are plotted, discussed, and compared with the relevant studies. The results show that the Nusselt number of the glycol-water flow within the minichannels continue to increase with Reynolds number, even at low Reynolds numbers (less than 1000), due to application of unique surface enhancements within the minichannels. [ABSTRACT FROM AUTHOR]

Published
2005

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