1. **What is the purpose of the fins on finned tube coils?**
The fins on finned tube coils significantly increase the external surface area of the tubes. This enhances heat transfer between the fluid inside the tubes and the air (or gas) flowing outside the tubes, compensating for the relatively poor heat transfer characteristics of gases compared to liquids.
2. **What is the purpose of coil tubing?**
The coil tubing provides the primary pathway for a fluid (liquid or refrigerant) to flow through the heat exchanger. Its purpose is to efficiently transport this fluid while allowing heat to be transferred either *into* the fluid (heating) or *out of* the fluid (cooling) through the tube walls.
3. **How does a fin and tube heat exchanger work?**
A hot fluid flows inside the tubes, transferring heat through the tube wall. Fins attached to the outside of the tubes greatly increase the surface area exposed to cooler air (or gas) blown or drawn across them. The heat conducts through the tube wall into the fins, and the air flowing over the large finned surface efficiently carries the heat away. Conversely, if heating air, a hot fluid inside the tubes heats the fins, and air flowing over the fins picks up the heat.
4. **Why do coils have fins?**
Coils have fins primarily to overcome the limitation of poor heat transfer between a tube surface and a gas (like air). Fins dramatically increase the surface area in contact with the gas. This allows much more heat to be transferred between the fluid inside the tubes and the gas flowing outside than would be possible with bare tubes alone, making the coil far more efficient and compact.
5. **What is the purpose of the fins in some heat exchangers the tubes are fitted with fins?**
The purpose of attaching fins to the tubes in certain heat exchangers is to boost the heat transfer rate on the side where the heat transfer coefficient is weak, typically the gas/air side. The fins extend the surface area exposed to the gas/air stream, conduct heat from (or to) the tube wall, and allow the gas/air to absorb (or release) heat much more effectively than it could from the smooth tube surface alone. They compensate for the gas's inherent inefficiency as a heat transfer medium.
