Registered Public Utility Engineer - HVAC (China) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Sol-air temperature

An equivalent outdoor air temperature combining real air temperature and absorbed solar radiation, used to compute wall and roof heat gain with a single conduction equation.

Sensible heat ratio

The ratio of sensible cooling load to total cooling load. It determines whether the coil can hold room humidity and sets the required apparatus dew point.

Apparatus dew point

The coil surface temperature at which the air process line intersects saturation. It sets the coil leaving-air condition and the bypass factor.

Design outdoor heating temperature

The winter dry-bulb value with 50 percent cumulative frequency, not the extreme minimum. It balances installed capacity against hours of unmet load.

Reverse-return piping

A two-pipe layout where supply and return paths are equal length for every terminal, so flows stay near design without balancing valves on near terminals.

Condensing boiler efficiency

Efficiency above 95 percent on higher heating value is possible only when return water is below the flue-gas dew point, recovering latent heat from water vapor.

Stairwell pressurization

A smoke control method maintaining 25 to 30 pascals in the stairwell with doors closed, keeping smoke out of the egress path during evacuation.

Capture velocity

The air velocity at the contaminant source needed to draw emissions into an exhaust hood. Values depend on hood type and contaminant toxicity.

Make-up air ratio

The fraction of smoke exhaust volume supplied as replacement air, typically 50 percent for natural and 80 percent for mechanical supply.

Equivalent duct diameter

For a rectangular duct of sides a and b, the equal-friction equivalent diameter is 2ab divided by a plus b, used with friction charts.

Chiller COP

The ratio of refrigerating effect to compressor work. Real chillers reach 40 to 60 percent of the Carnot COP for the same evaporating and condensing temperatures.

Bypass factor

The fraction of air passing a coil without contacting the surface, computed from inlet, outlet and apparatus dew point temperatures. Fewer rows reduce it.

Fan laws

For a fixed fan, flow varies with speed, pressure with speed squared, and power with speed cubed. They justify variable-speed drives for part-load savings.

Low delta-T syndrome

A chilled-water temperature difference well below design, often under 3 kelvin, caused by coil or valve faults, forcing higher pump flow and energy.

IPLV

Integrated part-load value, a weighted efficiency metric combining chiller performance at 100, 75, 50 and 25 percent load. It reflects seasonal operation.

Window-to-wall ratio

The glazed area divided by gross facade area. Codes cap it by climate zone and orientation to limit solar gain and envelope heat loss.

Economizer free cooling

A control strategy using outdoor air for cooling when its temperature or enthalpy is below return air, reducing chiller operation in transitional seasons.

Heat recovery effectiveness

The ratio of actual heat transferred to the maximum possible between exhaust and supply air. Sensible cores reach 50 to 70 percent, enthalpy wheels 60 to 80.

Specific fan power

Fan electrical input power divided by airflow, expressed in watts per cubic meter per hour. Codes set maximum values to limit fan energy.

Control valve authority

The valve pressure drop divided by the total circuit pressure drop. Values of at least 0.3 to 0.5 give stable modulating control.

Static pressure reset

A control strategy lowering duct static pressure setpoint as terminal dampers open, keeping the critical zone damper mostly open and saving fan energy.

Testing, adjusting, balancing

The process of measuring and setting air and water flows to design values before functional performance testing. Supply airflow tolerance is typically plus or minus 10 percent.

Condenser approach temperature

The difference between condensing refrigerant temperature and leaving condenser water. A rising value signals fouling or poor heat transfer and reduced efficiency.

Fire damper

A closure installed where a duct penetrates a fire-rated wall or floor, closing on fire signal or fusible link to stop fire spread through the duct.

Smoke exhaust rate

The design volumetric exhaust for smoke control, commonly 60 cubic meters per hour per square meter of floor area for corridors and 120 for atria.

Door-opening force limit

In pressurized stairwells the force needed to open a door against the pressure differential must not exceed 110 newtons for safe evacuation.

Design fire size

The assumed heat release rate used to size smoke exhaust, typically 2.5 to 5 megawatts for atria and large spaces with steady burning.

280 degree fan rating

Smoke exhaust fans and ducts must operate at 280 degrees Celsius for 30 minutes to remain functional during a fire and remove hot smoke.

Professional seal

The registered engineer's stamp on design documents certifying personal preparation or supervision. Sealing work not prepared by the engineer violates registration rules.

Conflict of interest

A financial or personal interest in a supplier or contractor that could bias design decisions. It must be disclosed and avoided in specifications.

Continuing education requirement

The minimum hours of approved professional training a registered engineer must complete each registration cycle to renew and maintain the license.

Record retention

The obligation to keep design calculations, load calculations, commissioning reports and as-built drawings for the regulated period to support audits and liability defense.