Flow regimes of refrigerant mixtures condensing inside tubes
Abstract
In order to take full advantage of the energy-conservation potential of refrigerant mixtures, the heat-transfer coefficients should be maintained high. More insight was sought into the condensation process by observing and photographing the flow regimes of the nonazeotropic mixed refrigerants condensing in a single-tube glass condenser. Measurements of pressure and temperature profiles through the condenser as well as chromatographic analysis of samples at several points along the condenser were taken. The four principal flow regimes from the entrance to the exit of the condenser are: annular flow, stratified flow, slug flow, and bubble flow. The most significant reduction in heat-transfer coefficient occurred in the midrange of the condenser on the operating system, and the regime was shown in the glass condenser to be stratified flow. Several explanations for the reduction in heat-transfer coefficient are selective diffusivity, temperature and concentration gradients, and vapor-liquid slip. Slip was prominent in the region where the major reduction in heat-transfer coefficient occurred, so inhibiting this slip may prevent at least some of the heat-transfer degradation.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- June 1985
- Bibcode:
- 1985STIN...8723917K
- Keywords:
-
- Condensers;
- Energy Conservation;
- Heat Transfer Coefficients;
- Refrigerants;
- Chromatography;
- Diffusivity;
- Photography;
- Pressure Measurement;
- Temperature Profiles;
- Fluid Mechanics and Heat Transfer