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Numerical assessment of frosting and defrosting of ‘no-frost’ evaporators.

Number: pap. n. R14, 2111

Author(s) : KNABBEN F. T., HERMES C. J. L., MELO C.

Summary

This paper presents a numerical study on the frosting and defrosting processes in ‘no-frost’ evaporators, a type of heat exchanger typically found in household refrigerators. A two-dimensional numerical model, based on mass and energy balances within the frost layer, was developed to predict the time variation in the frost thickness, and also the heat and mass transfer rates. The model takes into account the hydrodynamic coupling between the fan and the frosted coil, in such a way as to predict the airflow changes due to progressive evaporator blockage. The model predictions for pressure drop and frost mass were compared with experimental data taken under different operating conditions (cabinet air temperature and relative humidity, and coil surface temperature), and a reasonable level of agreement was achieved, with all predictions falling within a ±10% error band. The model was then used to assess the impact of several design parameters (including fin pitch and distribution, and defrost heater power and distribution) on both the evaporator blockage and defrosting efficiency. It was found that an almost ideal defrosting efficiency is achieved when the process is carried out by two simultaneous heaters, one for the first 6 rows and another for the last 4 rows.

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Pages: 7 p.

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Details

  • Original title: Numerical assessment of frosting and defrosting of ‘no-frost’ evaporators.
  • Record ID : 30000765
  • Languages: English
  • Source: 2010 Purdue Conferences. 13th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2010/07/12

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