DE HVAC flashcards
DE HVAC · Build recall with a focused review session.
30 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Refrigeration COP
- The useful cooling rate divided by the energy-input rate for a clearly stated system boundary and set of operating conditions.
- Superheat
- The difference between actual vapour temperature and the appropriate local saturation temperature at the same pressure, using the correct refrigerant reference.
- Subcooling
- The difference by which a liquid temperature is below the appropriate saturation reference at its pressure, interpreted with the correct product data.
- Absolute pressure
- Pressure referenced to an ideal vacuum, obtained from a positive gauge reading by adding the relevant local atmospheric pressure.
- Volumetric efficiency
- A comparison of admitted or delivered suction-volume flow with geometric displacement, using compatible reference conditions for the specified compressor calculation.
- Liquid slugging
- An abnormal entry of liquid into a vapour compressor that can create damaging forces because liquid is much less compressible than vapour.
- Net oil pressure
- The useful oil-delivery pressure differential evaluated against the relevant opposing compressor pressure rather than using the gallery indication alone.
- Surge
- An unstable operating phenomenon in a dynamic compressor associated with flow and pressure conditions outside the appropriate stable operating range.
- Approach temperature
- A specifically defined temperature difference between process streams or a stream and refrigerant reference, used with flow and load information to assess performance.
- Dew point
- The temperature at which a given moist-air state begins to condense water when cooled at the relevant pressure without changing its moisture content beforehand.
- Cascade system
- A refrigeration arrangement with separate circuits coupled thermally through an intermediate heat exchanger, rather than one common mixed refrigerant inventory.
- Secondary coolant
- A fluid that carries heat between the load and a primary refrigeration heat exchanger, selected for its thermal, hydraulic, and protection requirements.
- Deadband
- A range between control switching thresholds in which the output state may depend on the preceding operation, preventing an assumption from one temperature alone.
- Interlock
- A control condition that must be satisfied for an operation to be allowed or continued, according to the designed sequence and protection requirements.
- External equalizer
- A pressure-reference connection used by an appropriate expansion valve to account for the relevant evaporator-outlet pressure in its control force balance.
- Calibration
- An established relationship between an instrument indication and a reference quantity, documented so measurement accuracy and any required correction can be assessed.
- Emergency response plan
- The facility-specific arrangement of responsibilities, communication, protective actions, evacuation, and competent response for identified abnormal or hazardous situations.
- Verified isolation
- A controlled process addressing the relevant energy and material sources and checking the required safe condition before maintenance or other exposed work.
- Atmospheric clearance
- The required competent verification and authorization that an affected space is suitable for the intended entry, not merely an absence of odor.
- Pressure relief
- A protective function that limits specified overpressure conditions through an approved device and discharge arrangement, rather than serving as routine temperature regulation.
- Temperature glide
- The range of saturation temperatures across phase change for a zeotropic blend at a specified pressure, requiring appropriate dew or bubble references.
- Fractionation
- A change in blend proportions that can occur because components partition differently between phases during leakage or handling under particular conditions.
- Operating log
- A time-linked record of actual plant readings, states, alarms, observations, and actions that supports trend analysis, handover, and accountable follow-up.
- Performance boundary
- The defined set of plant components and energy transfers included in a performance calculation, necessary for consistent interpretation and comparison of results.
- Sensible load
- The heat-transfer requirement associated with temperature change under the stated model, distinct from latent moisture-removal effects.
- Latent load
- The energy associated with moisture or phase change under the actual air-conditioning model, distinct from dry-bulb temperature change alone.
- Airflow balance
- The allocation and verification of appropriate air quantities through the actual distribution system, not merely opening every damper fully.
- Condensate management
- The planned drainage, trapping, pumping and discharge arrangements for moisture removed by the equipment under its actual operating conditions.
- Commissioning evidence
- The recorded actual settings, conditions, observations and required tests used to evaluate installation performance and restored protection.
- Line-set compatibility
- The suitability of refrigerant piping, joints, material, sizing and service conditions for the actual system rather than a similar-looking installation.