Scientific Refrigeration Learning Center
Selecting a refrigerator or freezer for your lab or scientific application is not difficult. Just watch these videos and you'll understand everything you need to know to make an informed decision.
How Refrigerators Work
When a liquid evaporates it absorbs heat and when a gas condenses to a liquid it releases heat. Refrigeration is based on this concept of heat exchange. A liquid refrigerant such as R-134a in your refrigerator or freezer is passed through an expansion valve where some of it changes to a gas causing the remaining refrigerant to cool. Next it passes through an evaporator coil and absorbs heat from inside of the unit as it changes completely to a gas. Heat is released outside the unit when the gas passes through the compressor and condenser. During this process the refrigerant changes back to a liquid and the cycle is repeated.
Auto and Manual Defrost Refrigerators
Auto-defrost lab refrigerators use fans to blow air over the evaporator coils to remove frost that accumulates from normal operation. The compressor is shut down during the defrost cycle. Most auto-defrost refrigerators have internal fans to provide uniform internal temperature. Manual defrost refrigerators have no fans, which makes them ideal for storing products that should not dry out. Water condenses on the inside walls of the manual defrost refrigerator and should be wiped down on a regular basis.
Auto and Manual Defrost Freezers
Auto-defrost freezers have heaters that, depending on the model, cycle on a regular or controlled basis to remove ice on evaporator coils. Temperature cycling inside the unit is minimized by keeping it full of product or ice packs. Manual defrost freezers, while providing very stable temperature, must be shut off on a regular basis to remove ice accumulation. Because of this a back-up unit is required when defrosting the primary freezer.