Mechanical: HVAC and Refrigeration PE

Range is a key cooling tower performance parameter. Typical ranges are 10-15°F for HVAC applications. Remember: Range = hot water in - cold water out. Don't confuse with approach temperature (outlet - wet bulb).

COP is dimensionless and represents cooling output per unit of work input. For air conditioning, COP typically ranges 2.5-4.5. Don't confuse with EER (Energy Efficiency Ratio) which has units. Higher COP means better efficiency. Carnot COP provides theoretical maximum.

The Darcy-Weisbach equation is fundamental for pipe flow calculations on the PE exam. The friction factor f must be determined from the Moody diagram using Reynolds number and relative roughness. For fully turbulent flow in rough pipes, f becomes independent of Reynolds number. Always check units carefully - diameter must be in same units as length.

Fan affinity laws are fundamental for HVAC system modifications. Remember the complete set: Flow ∝ N, Pressure ∝ N², Power ∝ N³. Often tested with variable speed drives or belt/pulley changes. Always check if other fan parameters change proportionally.

Always remember that Q_max = C_min(T_h,in - T_c,in) where C_min is the smaller of the two heat capacity rates. Effectiveness is always between 0 and 1. Given NTU and heat capacity ratio, you can find effectiveness from standard charts.