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Effect of gas-cooler geometry on heat transfer and pressure drop characteristics.

Number: pap. n. TP-039

Author(s) : MATSUO Y., ICHIHARA M., KOYAMA M., et al.

Summary

To understand the effects of tube geometry on the heat transfer and pressure drop characteristics of the CO2and water sides in the gas coolers of CO2 water heaters, two tubes of different geometry were tested in this study. The tested tubes consisted of a pair of twisted smooth tubes or a pair of twisted dimple tubes and an outer tube. CO2 flows in the pair of twisted inner tubes, while water flows in the annulus between the inner tubes and the outer tubes with a counter flow configuration. The CO2 and the water side heat transfer coefficients and the pressure drops were measured at CO2 pressures ranging from 8 to 10 MPa, mass flow rates ranging from 19.2 to 34.6 kg.h-1 and temperatures ranging from 20 to 70°C. The heat transfer rate and volumetric flow rate of the water were set to 300 W and 1.50 L min-1. The thermal resistance was broken down into CO2 and water side components to quantify the role of each thermal resistance in the total resistance. The experimental results indicate that the CO2 side heat transfer coefficient strongly depends on the CO2 temperature and is maximized at the pseudo-critical temperature. However, the heat transfer enhancement achieved by the dimples is very slight for the CO2 side. On the other hand, due to the dimples, the water side heat transfer coefficient is increased by a factor of approximately two over all of the test conditions. Thus, the total thermal resistance is minimized near the CO2 pseudo-critical temperature and reduced by approximately 0.5 x 10-4 m2K W-1 for the entire range of test conditions. The results suggest that applying dimpled tubes is a promising technique for enhancing the water side heat transfer coefficient.

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Pages: 8 p.

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Details

  • Original title: Effect of gas-cooler geometry on heat transfer and pressure drop characteristics.
  • Record ID : 30008112
  • Languages: English
  • Source: 4th IIR Conference on Thermophysical Properties and Transfer Processes of Refrigerants
  • Publication date: 2013/06/17

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