Iran Nezam Mechanical Supervision Exam flashcards
Iran Nezam Mechanical Supervision Exam · Build recall with a focused review session.
37 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Sensible heat equation for air
- Qs = 1.21 × airflow in L/s × temperature difference in °C, yielding watts. Used to size coils, ducts, and terminal units when moisture change is negligible.
- Total coil load
- Sum of sensible and latent loads. Latent heat equals 3.0 × airflow in L/s × humidity ratio difference in g/kg, giving watts.
- Fan affinity laws
- Flow varies linearly with speed, pressure with speed squared, and power with speed cubed. A ten percent speed reduction cuts power about twenty-seven percent.
- Equal friction duct method
- Select duct sizes so friction loss per unit length is constant across the system. Fan pressure is set by the index run and branches are balanced with dampers.
- VAV minimum airflow
- Typically thirty percent of design airflow, set to satisfy ventilation requirements. Verify outdoor air at the breathing zone per ASHRAE 62.1 at minimum flow.
- Composite wall U-value
- Reciprocal of the sum of inside surface resistance, layer resistances (thickness divided by conductivity), and outside surface resistance. Mabhas 19 limits maximum values.
- Degree-day method
- Annual heating energy approximately equals U×A times heating degree-days times twenty-four, divided by one thousand, in kilowatt-hours. Base temperature commonly eighteen degrees Celsius.
- Cooling load versus solar gain
- Peak solar gain through glass does not equal peak cooling load because of thermal storage and time lag. Use CLTD or transfer function methods for hourly loads.
- Air-side economizer
- Free cooling using outdoor air when its enthalpy is below return air enthalpy. Controlled by dry-bulb or enthalpy changeover; common in mild Iranian seasons.
- Fixture unit method
- Hunter method assigning water supply fixture units per fixture, summing them, and applying a probability curve to estimate probable peak flow.
- Trap seal depth
- Minimum fifty millimeters and maximum one hundred millimeters of water seal. Each fixture requires a trap except where the code explicitly lists an exception.
- Drainage slope rule
- Horizontal drainage branches up to one hundred millimeters diameter slope one to two percent; larger pipes at least one percent, per Mabhas 16 tables.
- Residual pressure at fixture
- Minimum one hundred to one hundred fifty kilopascals at the furthest fixture. If street pressure is insufficient, use a booster pump or gravity tank.
- Hazen-Williams formula
- Head loss equals 10.67 × length × flow^1.852 divided by C^1.852 × diameter^4.87 in SI units. C is about 140 for new plastic pipe.
- Rational method
- Storm flow equals runoff coefficient times rainfall intensity times catchment area. Use Iranian intensity-duration curves and minimum roof drain sizes per Mabhas 16.
- Water hammer control
- Use surge arrestors, slow-closing valves, and adequate pipe support. Limit supply main velocity to about one and a half to two and a half meters per second.
- Roof tank head
- Available pressure equals static height above the fixture minus friction losses. Check at peak flow using Hazen-Williams or Darcy-Weisbach calculations.
- Sprinkler design density
- Discharge rate per unit area over a specified remote area, set by occupancy hazard. Light hazard is typically 2.05 mm per minute over 140 square meters.
- Fire pump churn pressure
- Shutoff pressure must not exceed one hundred forty percent of rated pressure. At one hundred fifty percent flow, pressure must remain at least sixty-five percent of rated.
- Stairwell pressurization
- Maintain twenty-five to fifty pascals differential in the stairwell and about twelve and a half pascals in the lobby. Door opening force must not exceed 133 newtons.
- Hydrant flow test
- Measure static, residual, and pitot pressures, then extrapolate available flow at twenty pounds per square inch residual using the standard one-point conversion formula.
- Natural gas heating value
- Iranian natural gas typically has a lower heating value of thirty-five to thirty-eight megajoules per cubic meter. LPG vapor is about ninety-three megajoules per cubic meter.
- Stoichiometric air demand
- One cubic meter of natural gas needs about ten cubic meters of air for complete combustion. Boilers typically operate with twenty-five to fifty percent excess air.
- Gas pipe pressure drop
- Mabhas 17 sizing tables allow about one millibar loss in low-pressure residential systems. Use black steel indoors and buried, polyethylene only for buried exterior lines.
- LPG vapor density
- LPG vapor is heavier than air and accumulates at low points. Install leak detectors near the floor, unlike natural gas detectors which go near the ceiling.
- Refrigeration COP
- Cooling effect divided by compressor work. Carnot COP equals cold temperature divided by the difference between hot and cold temperatures, both in kelvin.
- Chiller efficiency ranges
- Water-cooled chillers typically draw 0.6 to 0.7 kilowatts per ton; air-cooled units about 0.9 to 1.1. Part-load IPLV values matter more than full-load ratings.
- Cooling tower approach
- Leaving condenser water temperature minus entering wet-bulb temperature, usually three to five kelvin at design. Condenser water is commonly supplied at twenty-nine to thirty-five degrees Celsius.
- Evaporator superheat
- Typically five to eight kelvin at the evaporator outlet, set by the thermostatic expansion valve. Excessive superheat signals undercharge or a restricted valve.
- Mabhas 14 scope
- Iranian national code chapter covering HVAC design: outdoor design conditions, ventilation rates, load calculation methods, and duct and pipe sizing criteria.
- Mabhas 22 scope
- Iranian national code chapter on energy efficiency in buildings: envelope thermal limits, HVAC equipment efficiency, lighting power density, and commissioning requirements.
- Code hierarchy rule
- Where the national building code and project specification differ, the stricter requirement governs. Always confirm the current edition and official amendments before approval.
- Supervising engineer duties
- Review shop drawings, approve materials, inspect installation, witness tests, and issue non-conformance reports. Only the registered engineer may seal drawings within their competence.
- Conflict of interest disclosure
- An engineer holding a financial interest in a contractor or supplier must disclose it and recuse from approval decisions involving that party.
- Retention in payment certificates
- Typically five to ten percent withheld from each payment until taking-over. Deduct advance payments according to the contract amortization schedule.
- Mechanical quantity takeoff
- Pipe measured along centerline excluding fittings; duct measured by surface area; equipment counted by unit. Apply the contract's standard method of measurement.
- Variation order requirements
- Must be issued in writing, priced at contract rates or agreed rates, and granted a time extension only if the critical path is affected.