Freezer Racks Question and Answer

Q: Will the evaporation rate decrease if 6 more freezer racks are added?

A: No. Adding more freezer racks increases the heat transfer paths to LN2 as well as the evaporation rate. This is apparent when aluminum vertical freezer racks are being used since aluminum has a greater thermal conductivity than stainless steel. The result of evaporation rate is minimal when stainless freezer racks are being used. There is an added benefit to using aluminum freezer racks though; because of a slightly higher evaporation rate, the cryogenic freezer is filling slightly more frequently, essentially ‘charging’ the liquid nitrogen vapor with a fresh, cooler supply, meaning that the vapor temperatures inside your vapor phase freezer will be slightly cooler when using aluminum freezer racks.