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In-tube heat transfer and pressure drop characteristics of pure NH3 and CO2 in refrigeration systems.

Author(s) : HRNJAK P. S., PARK C. Y.

Summary

This paper analyzes the differences and similarities between heat transfer in ammonia and carbon dioxide from the perspective of NH3 two-stage, CO2/NH3 cascade, NH3 direct expansion, and CO2 direct expansion systems heat exchanger designer. The focus is on differences in thermophysical properties and thus different performances. Besides a literature review of available correlations, some new experimental data are presented. Because of large deviation of calculated values with exiting correlations from measured results, two new correlations to predict flow condensation heat transfer coefficients are developed based on experimental results for NH3 at 35°C and CO2 at -15°C. With comparison of measured and predicted values, it is shown that some correlations, previously published in open literature, can be used to calculate flow boiling heat transfer coefficients for NH3 at -20°C, CO2 at -30°C and heat transfer coefficient for CO2 gas cooling process. It is shown that some correlations proposed by previous studies can predict the pressure drop with NH3 and CO2 two-phase flow, and with CO2 gas cooling process, relatively well. The NH3 and CO2 flow evaporation heat transfer and pressure drop characteristics at -40°C are compared with predicted values.

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Pages: 2007-2

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Details

  • Original title: In-tube heat transfer and pressure drop characteristics of pure NH3 and CO2 in refrigeration systems.
  • Record ID : 2007-1993
  • Languages: English
  • Source: Ammonia Refrigeration Technology for Today and Tomorrow.
  • Publication date: 2007/04/19

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