TFS · Heat Transfer · Problem 10 PDF Solution in PDF ↓
TFS · Heat Transfer · Problem 10
Problem & Solution
PDF: Heat transfer-10.pdf
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  • Topic: Heat exchanger / heat transfer — 80GPM of 70 degree water, flowing in a 200-foot-long 3-inch diameter standard weight steel pipe is cooled by 10 degrees over the entire length.
  • Method: The flow is turbulent and fully developed.
  • Formula reference: formula for the parental number is given in the reference handbook.
  • Key values: 476.2 BTU per hour, 765,000 BTU per hour, 2, pound mass
  • Reference: table to look up to kinematic viscosity
  • ✅ Answer: C
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Student questions asked in live office hours about this problem
OH 85
Q: Should fluid properties like viscosity be determined at film temperature rather than bulk water temperature for this cooling pipe problem?
A: Generally yes, but not critical here since the temperature delta is only 10°F (70-80°F bulk temps, 75°F average)—properties at 70, 75, or 80°F won't differ meaningfully. On the exam, just pick the nearest available table value; only worry about precise film temperature when ΔT is large enough to actually matter.
MPEP OH Prep Dashboard Problem 10 · Heat Transfer PDF-Embedded Format