Product entry temperature (Product temperature at the time it is introduced into the Coldroom) may be entered from -40ºC to a maximum of 90ºC.
Entering a Product entry temperature below the Coldroom design temperature (in error [or legitimately in Thaw Rooms] ) will result in a message asking you to reconfirm your entry. Computed 'Negative' heat gains will be returned as zero to avoid accidental Refrigeration plant undersizing.
By default, Product Exit Temperature is set the same as room design temperature. The facility to enter a higher temperature than the coldroom design operating temperature as a product EXIT temperature is provided with the 'Higher Product Exit Temperature' button. The exit temperature may be entered from room temperature up to a maximum of 1 degree below the Product Entry Temperature, thus enabling accurate Blast Freezer or Blast Chiller refrigeration loads to be computed.
Users are urged to exercise caution when using this facility as although the refrigeration load will be accurate, there can be no guarantee that the product will be capable of giving up its energy in the time that has been entered for product temperature reduction time. This is because the program does not take the heat transfer coefficient of the product (only the specific heat, latent heat and where applicable, the respiration heat values) into account. No reliable data is generally available on this subject.
Choice of Blast Freezer/Blast Chiller operating temperatures, product exit temperatures and product temperature reduction times must therefore be entered with consideration to cooler air velocities, the product surface roughness, and hence laminar and turbulent air flow characteristics over the product, and the ratio of product surface area to its mass.
Some computer programs and text books dealing with the complex subject of Blast Freezers and Blast Chillers refer to 'Product Chill Factors'. The so called 'Chill Factor' has no scientific basis and is purely an empirically based 'fudge' factor. This attempts to combine the complex considerations in the above paragraph into a single value for application as a correction factor. Mistral's extensive research into the subject has proven that 'Chill Factors' have no valuable or reliable contribution to make in a scientifically provable and reliable program such as 'COLDWIND'. Application of the skills of experienced refrigeration engineers are essential for successful Blast Freezer and Blast Chiller designs.
See also:-
Product selection
Product turnover
Product temperature reduction cycle (time)