Corrosion has wasted away large sections of the fins attached to an air conditioning cooling coil. In assessing the effects on the system you would assume which of the following to be accurate?
• Heat transfer surface area of finned coils and how fins affect coil performance • Meaning of coil efficiency in terms of heat transfer between air and refrigerant • Definition of bypass factor (portion of air that effectively does NOT contact the active coil surface)
• If fins are partially wasted away, what happens to the effective heat transfer area between air and coil? How does that change how well the coil can cool the air? • Think about what happens to the path of air through the coil when there is less fin area: does more air effectively skip good contact with the coil, or less? • If more air passes through without good contact, what does that do to the relationship between actual air temperature leaving the coil and the ideal apparatus dew point temperature?
• Be clear on the definition: higher bypass factor = larger fraction of air effectively bypasses the coil’s active surface. • Relate coil efficiency directly to how closely the leaving air temperature approaches the coil (apparatus dew point) temperature. • Mentally compare two coils: one with full fins and one with many fins corroded away. Which one cools air more effectively, and which one allows more air to pass through with little temperature change?
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