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Two-dimensional first-principles model for uneven frost accretion in ‘No-Frost’ evaporators.

Number: 2115

Author(s) : SILVA D. Z. C., EBERTH H. T., RICHTER C., DA SILVA D. L., HERMES C. J. L.

Summary

This paper advances a two-dimensional model for predicting local pressure drop, and sensible and latent heat transfer rates in the so-called ‘no-frost’ evaporators used in frost-free refrigerators. The model was devised based upon the first principles of mass, momentum and energy conservation for both the air stream and frosted medium, being able to predict the evaporator blocking over time. The coupling between the heat exchanger air-side pressure drop and the fan characteristic curve has also been considered by means of a fluid-dynamic model able of predicting the two-dimensional airflow redistribution. Frost growth experiments were carried out using a purpose-built test facility comprised of a bottom-mount refrigerated cabinet placed with controlled humidity and temperature in both fresh-food and freezer compartments. A camera was also employed to capture the time evolution of the frost thickness on the evaporator. The model validation exercise showed that the predicted results follow the experimental trends inside the experimental band of errors. The model allowed the identification of the critical region of the evaporator in terms of airflow blockage, which leads to an uneven airflow pattern and underutilization of the air-side heat transfer surface area. Finally, the model was used to propose a new fin distribution aimed at a better utilization of the evaporator. The new geometry reduced the local air-side pressure drop by 65% and homogenized the airflow, resulting in a more uniform utilization of the evaporator area for heat transfer.

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  • Original title: Two-dimensional first-principles model for uneven frost accretion in ‘No-Frost’ evaporators.
  • Record ID : 30032980
  • Languages: English
  • Source: 2024 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2024/07/17

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