Study of the defrost process in a secondary refrigeration system

Abstract

Consulta en la Biblioteca ETSI Industriales (6110)

[EN] The goal of this project was the study of the defrost process in a secondary refrigeration system. For that, with the aim of identifying the main variables and processes involved in a defrost cycle, firstly an extensive experimental work was carried out in the laboratories of the School of Mechanical Engineering at the UCD. Through this work, it was also compared the performance of an electric and a hot gas defrost in a secondary refrigeration system.

After analyzing the results obtained experimentally, the project was focused in the development of a defrost model for the secondary refrigeration system studied, considering all the elements involved in the process: power supply, pipes, chiller and frost. That model was formulated using the software EES with a finite difference approach, and it predicts the time required to complete the defrost, evaluating the energy distribution and the evolution of the temperatures during the process for both defrost methods, electric and hot gas.

Finally, once validated the model by comparing the simulation results with the experimental ones, it is used to study the influence in the process of variables such as design of the defrost circuit or amount of frost initially present on the chiller. The conclusions obtained in this way provide a good estimation about the unavoidable energy cost that supposes each defrost cycle in a real industrial or transport refrigeration system, permitting in some cases, with the proper defrost settings, an energy save of up to 50%.