What is Unfavourable Frost

Proper control and performance of evaporators in food refrigeration facilities are vital to provide a suitable temperature regime, safety, quality and wholesomeness of refrigerated products at minimum electricity costs. When humid air passes along the surfaces of a low-temperature evaporator, frost is usually formed, which decreases the heat transfer efficiency. Frosting and defrosting phenomena have been extensively investigated for different industrial scenarios and extensive literature exists in the matter. However, no studies have been published so far to address in a comprehensive way the methods and patterns of evaporator defrosting as affected by hygienic design implications and criteria. This book chapter is intended to fill in this gap by enforcing hygienic imperatives in the evaporator design. Various design solutions and conditions of operation are considered as decisive in determining the amount, thickness and structure of the frost build-up. Advantages and drawbacks of diverse defrost methods are outlined with regards to contamination risks in refrigeration facilities.