What is the significance of the t.d. (temperature difference) across an evaporator (cooler)?
The t.d. affects the amount of moisture extracted during the refrigeration process and consequently can affect the product being stored. For example, when cooling plants or vegetables a td of 4 C is typical to keep the room humidity up and to stop the product being dried out. A low air velocity cooler should be also used to stop product dehydration. If a product has to be cooled down from a higher temperature a td of 7 C can be used to help draw the heat from the product. Normally the product would be packed to prevent moisture loss. Also a high air velocity cooler should be used to help draw the heat.
