Staying Cool – Basic Heat Loads
by Jayson Noetzelman
When it comes to refrigeration, Carlson & Stewart is in the business of helping you stay running and stay cool, but even a system running perfectly might not always be as cold as you’d like. What can be done to improve your situation? A business owner or refrigeration operator is faced with a plethora of different refrigerants, several different compressor styles, a multitude of brands, not to mention refrigerant feed types, and that’s only the start of it. Don’t let the technical side leave you with a hot head, stay cool by starting with the basics. By basics we mean the basic heat sources imposing on your refrigerated workrooms, coolers, and freezers. A quick check of the basic heat loads you’ll likely find at your facility should insure you are maximizing your cooling potential.
The most basic, and probably most obvious, of the four primary heat loads is product load. Whether it’s milk, meat, cheese, or anything else, the product is the reason we build refrigeration systems. While the product load is the only necessary load of the four, there are still practices that can be used to improve cooling. Consider carefully before introducing excessive packaging on product that needs cooling, as packaging can stifle proper heat transfer. Make sure cooled spaces have proper airflow to keep things cool, otherwise, small centralized warm zones can pop up and lead to product damage. Finally, remember that produce products generate heat through respiration and products that are being frozen must overcome the latent heat of fusion. Both respiration and latent heat cause additional cooling loads you may not be anticipating.
Transmission loads are those loads that are transmitted through hard surfaces and into your cooler. Consider opting for insulated floors for new construction whenever possible. Make sure you properly insulate the ceiling of refrigerated rooms as rooftops can often get very warm, especially in the summer. Finally, opt for high insulation value walls to prevent the transmission of heat into the room from nearby rooms or the outdoors.
Infiltration loads are those loads that sneak in through cracks in the walls and open doorways. By allowing warm air to enter the room, it creates additional load on the refrigeration system. This additional load is often quite substantial, and the severity of the loss is proportional to the difference between the cooled room and the adjacent room. To help prevent these types of losses, consider sealing wall penetrations to reduce draft. Keeping doors closed and installing rapid roll up doors between rooms is especially helpful. Strip curtains and air curtains are less efficient but nonetheless helpful substitutes when other solutions aren’t easily instituted.
As the name implies, the final category is a bit of a catch all. Consider anything in your refrigerated space that would generate heat, often by the use of electricity. Fan motors, equipment motors, forklifts, and lights are basic heat sources that need to be considered. Not to be forgotten, but often overlooked, is the load imposed by personnel working in the room.
Most refrigeration system owners or operators will likely not ever need to design a cooler or freezer. However, knowing the criteria that goes into cooler design can help you identify potential losses and maximize efficiency. If you’d like help designing a cooler or workroom to your specific needs, Carlson & Stewart would be happy to help.