Frost detection method on evaporator in vapour compression systems

• Published in: International journal of refrigeration 2020-02, Vol.110, p.75-82
• Main Authors: Maldonado, José Miguel, de Gracia, Alvaro, Zsembinszki, Gabriel, Moreno, Pere, Albets, Xavier, González, Miguel Ángel, Cabeza, Luisa F.
• Format: Article
• Language: English
• Subjects: Compression refrigeration system; Compressors; Cooling; Cycle de dégivrage; Defrost cycle; Détection de givre; Evaporation; Evaporators; Food; Freezers; Freezing; Frost; Frost detection; Nutrients; Parameter estimation; Refrigeration; Refrigerators; Refroidissement; Supermarkets; Système frigorifique à compression
• ISSN: 0140-7007; 1879-2081
• DOI: 10.1016/j.ijrefrig.2019.10.023

•A novel method for frost detection on evaporator coils was developed.•The new method can be applied to multiple compressor rack systems.•It accurately quantifies the frost level in comparison to the initial dry state.•Frost level detection is a key aspect for controlling the defrost process.•The method can contribute to provide direct energy savings. To preserve food nutrients, texture, and taste, as well as to prevent its putrefaction, food is frozen and kept at around −20 °C. Refrigerators and freezers are highly energy demand systems which can suffer a considerable decrease in operational efficiency due to frost growth on the evaporator. Defrost processes are launched periodically to avoid the frost built-up, consuming a relevant part of the total energy demand. To control the defrost launching and to improve the energy performance of the refrigeration system an accurate measurement of the frost level is required. Many frost detecting methods are expensive, not feasible due to their size, or simply they cannot measure the frost stacking precisely enough to swerve mal-defrost phenomena. This study provides an accurate parameter to indirectly estimate the frost layer built-up on the evaporator. The new parameter called thermal variation easiness (TVE) was experimentally tested and validated by comparison with another frost leveling method, ΔT method, on a walk-in freezer unit. Then the TVE was successfully tested on a multi-cold room refrigeration system, proving its applicability on both walk-in freezers run by remote condensing units and multiple cold rooms fed by a rack of compressors. The novelty of this parameter lays on its capacity to work on refrigeration facilities which are used to feed several walk-in fridges and refrigerated displays in big installations, such as supermarkets.