Question: What is the difference between direct and indirect heating systems.
Short answer:
A direct gas heating system is the most efficient, with nearly 100% efficiency. Which means that nearly all of the combustion energy goes into heating the air in the kiln. Normally the gas flame is located in a seperate duct (should be stainless steel) with air circulation from the general chamber, which is heated with the gas flame and returned to the kiln chamber at a higher temperature. A direct heat system uses a heat transfer surface to seperate the combustion air from the kiln air. On a indirect heat system the combustion air is vented to the outside normally at a stack temperature or 200-350 degrees F. Since some of the energy from the combustion escapes out the stack these system will often have an efficiency between 70-90%, this will result in 15-40% higher energy consumption.
Detailed answer:
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