Frost measurement methods for demand defrost control systems

• Autor(a) principal: Aguiar, Martim
• Data de Publicação: 2018
• Outros Autores: Gaspar, Pedro Dinis, Silva, Pedro Dinho da
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/7405
• topic: Demand defrosting; Frost measurement; Controlling strategy; Frost detection

It is widely known that defrosting operation on commercial refrigerators is one of the main causes of inefficiency on these systems. Several defrosting methods are used nowadays, but the most commonly used are still time-controlled defrosting, usually by either electric resistive heating or reverse cycle, as most demand defrost methods are usually complex, expensive or unreliable. Demand defrost can work by either predicting frost formation by processing measured conditions (fin surface temperature, air humidity and air velocity) and/or frost accumulation symptoms such as pressure drop and refrigerant properties. Other way of knowing when to defrost is to directly measure the frost formation using sensors such as photoelectric, capacitive or resistive. This review gathers some of the methods that can be used for directly measuring frost accumulation on the evaporator fin surface.