Share

Modelling of short tube orifices for CO2.

Author(s) : MARTIN K., RIEBERER R., HAGER J.

Summary

The expansion device is an important component in refrigerating systems. For automotive and residential air conditioners, short tube orifices are widely used, because of their low cost, high reliability and easy handling. In the open literature, there are a lot of models for orifices available, but most of them focus on water or commonly used refrigerants like R-22, R-134a, R-410A, but they do not consider R-744 (CO2), i.e. only a few validated models for orifices for CO2 systems exist. This paper presents experimental data and a model for predicting the refrigerant flow rate of CO2 through short tube orifices to be used as expansion device in refrigerant cycles. For this, different tube geometries have been studied, i.e. different tube lengths, bore diameters and the effect of inlet chamfering. The data were analyzed for operating conditions which typically occur in automotive air-conditioning systems. For the inlet conditions the pressure was varied in a range of 75 to 130 bars and the temperature in a range of 15 to 40°C, i.e. all inlet conditions were single phase. The investigations show that for all operating conditions choked flow occurs, if the outlet condition from the orifice is in the two phase region. That means that the refrigerant mass flow rate is independent of the outlet pressure, but strongly depending on the inlet pressure. Of course, the mass flow rate increases with increasing upstream pressure. The inlet temperature plays an important role for the mass flow which increases with decreasing temperature (at constant inlet pressure). The effect of inlet chamfering turned out to be in a range of about 5 to 10%.

Available documents

Format PDF

Available

  • Public price

    20 €

  • Member price*

    15 €

* Best rate depending on membership category (see the detailed benefits of individual and corporate memberships).

Details

  • Original title: Modelling of short tube orifices for CO2.
  • Record ID : 2007-2074
  • Languages: English
  • Source: 2006 Purdue Conferences. 18th International Compressor Engineering Conference at Purdue & 11th International Refrigeration and Air-Conditioning Conference at Purdue [CD-ROM].
  • Publication date: 2006/07/17

Links


See other articles from the proceedings (157)
See the conference proceedings

Indexing