Mechanical Engineering Flashcards
7 cards from real Building Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Mechanical Engineering flashcards as text
In a two-pipe hydronic heating/cooling system, what is the main operational limitation compared to a four-pipe system?
Answer: Cannot simultaneously heat some zones while cooling others
A two-pipe system uses the same piping for both heating and cooling, so it can only be in heating mode or cooling mode at any given time, not both simultaneously.
What is the function of a pressure-reducing valve (PRV) in a domestic water system?
Answer: Reduces incoming street pressure to a safe working pressure for building fixtures
A PRV reduces the typically high municipal supply pressure (often 80–150 psi) to a safe building pressure, usually 50–80 psi, protecting fixtures and piping.
Which refrigerant property is expressed by the term 'superheat' at a compressor suction port?
Answer: Temperature of vapor above its saturation temperature at that pressure
Superheat is the number of degrees by which a vapor's temperature exceeds its saturation (dew point) temperature at the same pressure.
According to IMC/IBC, what is the minimum clearance required between the bottom of a gas-fired furnace and a combustible floor?
Answer: 0 inches if listed for floor installation
Gas furnaces listed and labeled for installation on combustible floors may be installed with zero clearance when installed per manufacturer instructions.
A chilled water system uses 'delta-T' as a key performance metric. What does a degraded (low) delta-T across a chiller evaporator indicate?
Answer: Fouled heat transfer surfaces reducing capacity
Low delta-T syndrome means the difference between return and supply chilled water temperatures is smaller than design, often caused by fouling, coil bypass, or low coil loads that reduce heat transfer.
What is the primary code requirement that determines the minimum size of a plumbing vent stack in a multi-story building?
Answer: Drainage fixture unit (DFU) load of the connected drains
IPC sizing tables use drainage fixture units (DFUs) to determine minimum vent pipe diameters, ensuring adequate air circulation to prevent siphoning of traps.
In seismic design of mechanical systems, what is the purpose of a flexible pipe connector at equipment connections?
Answer: To allow relative movement between equipment and piping without imposing stress
Flexible connectors absorb differential movement between anchored equipment and building-restrained piping during seismic events, preventing pipe joint failures.