Refrigeration and Air Conditioning MCQs 2026

Evaporative cooler (desert cooler) cools air by

1. A vapor compression refrigeration always ✓
2. B water evaporation adding latent heat ✓
3. C steam expansion ✓
4. D Rankine cycle ✓

Desiccant dehumidification removes moisture by

1. A adsorption on desiccant material not only cooling ✓
2. B compressor suction only ✓
3. C boiler steam only ✓
4. D increasing humidity ratio ✓

Hydrocarbon refrigerants like propane (R-290) require

1. A no safety concern ever ✓
2. B use in unlimited charge always ✓
3. C charge limits and explosion-safe design ✓
4. D operation without ventilation always ✓

CO2 (R-744) transcritical cycle used because

1. A natural refrigerant with low GWP suitable for heat pumps ✓
2. B requires no pressure always ✓
3. C operates below 1 bar always ✓
4. D cannot transfer heat ✓

Greenhouse warming potential (GWP) drives shift toward

1. A more R-11 use ✓
2. B low GWP refrigerants like R-32, CO2 and hydrocarbons ✓
3. C steam in compressors ✓
4. D diesel in evaporators ✓

R-12 was replaced primarily due to

1. A ozone depletion potential ✓
2. B low cooling capacity only ✓
3. C non-flammability ✓
4. D high efficiency problem ✓

R-410A is

1. A CFC ozone depleter ✓
2. B near-azeotropic HFC blend for many modern AC systems ✓
3. C ammonia solution ✓
4. D water only refrigerant ✓

EER and COP relation approximately

1. A COP = EER × 0.293 for IP units conversion context ✓
2. B EER equals COP always numerically ✓
3. C no relation exists ✓
4. D COP equals EER squared ✓

Electrical energy input to 1 ton AC roughly

1. A 10 kW always ✓
2. B 0.01 kW always ✓
3. C 100 kW always ✓
4. D 1 to 1.5 kW at rated conditions depending on EER ✓

Hot gas bypass valve prevents

1. A condenser flooding always beneficial ✓
2. B evaporator superheat always ✓
3. C oil return always failure ✓
4. D compressor short cycling at low load ✓

Frost on evaporator indicates

1. A condenser too hot always beneficial ✓
2. B excess superheat always ✓
3. C evaporating temperature below 0 °C with moisture in air ✓
4. D perfect dehumidification always ✓

Cooling load tonnage for building estimated using

1. A only compressor displacement ✓
2. B CLTD/CLF methods or software with solar, internal and ventilation gains ✓
3. C only boiler efficiency ✓
4. D only pipe friction ✓

Chilled water temperature from central plant often

1. A 100 °C supply always ✓
2. B below 0 °C always without brine ✓
3. C 6–7 °C supply for dehumidification and cooling ✓
4. D 200 °C steam always ✓

VAV system varies

1. A refrigerant type hourly ✓
2. B compressor displacement fixed only always without variation ✓
3. C air volume to zones while maintaining temperature ✓
4. D boiler steam pressure only ✓

Fresh air load in AC includes

1. A only compressor oil heat ✓
2. B sensible and latent heat to treat outdoor ventilation air ✓
3. C only lighting latent always zero ✓
4. D steam turbine loss ✓

Comfort air conditioning typically maintains

1. A 24–26 °C and 40–60% RH approximately ✓
2. B 50 °C and 90% RH always ✓
3. C 0 °C and 100% RH always ✓
4. D only pressure control ✓

Humidification adds moisture by

1. A cooling coil condensate removal only ✓
2. B compressor suction only ✓
3. C steam injection, pan evaporators or spray ✓
4. D condenser rejection only ✓

Dehumidification process on psychrometric chart moves air

1. A toward lower humidity ratio usually with cooling ✓
2. B along constant dry bulb upward always ✓
3. C to higher moisture always at constant RH 100% ✓
4. D without energy transfer ✓

Room sensible heat ratio (RSHR) line on psychrometric chart used for

1. A supply air condition design ✓
2. B boiler efficiency only ✓
3. C turbine expansion only ✓
4. D diesel injection timing ✓

Bypass factor of cooling coil indicates

1. A fraction of air not contacting coil surface perfectly ✓
2. B compressor volumetric efficiency ✓
3. C condenser approach ✓
4. D fuel octane ✓

Latent cooling load removes moisture by

1. A raising dry bulb only always ✓
2. B adding steam to room ✓
3. C condensing water vapor from air ✓
4. D heating air only ✓

Sensible cooling load removes heat

1. A without change in moisture content ideally ✓
2. B only latent heat of vaporization always ✓
3. C only humidity addition ✓
4. D only fuel combustion heat ✓

Sensible heat factor (SHF) in AC indicates

1. A only latent load fraction always inverted always ✓
2. B compressor efficiency ✓
3. C fraction of sensible to total cooling load ✓
4. D refrigerant charge mass only ✓

Humidity ratio (specific humidity) is

1. A mass of water vapor per mass of dry air ✓
2. B volume of air only ✓
3. C RH percentage directly ✓
4. D enthalpy of steam table only ✓

Dew point temperature is

1. A always equal to dry bulb ✓
2. B wet bulb plus 10 °C always ✓
3. C compressor discharge temperature ✓
4. D temperature at which condensation begins at given pressure ✓

Wet bulb temperature is measured with

1. A thermometer with moist wick in moving air ✓
2. B dry bulb in still air only always ✓
3. C infrared gun only ✓
4. D mercury barometer ✓

Dry bulb temperature is

1. A wet wick thermometer reading always ✓
2. B dew point always ✓
3. C adiabatic saturation always ✓
4. D temperature measured by ordinary thermometer ✓

Psychrometry deals with

1. A only dry nitrogen ✓
2. B liquid water only without vapor ✓
3. C properties of moist air ✓
4. D refrigerant R-22 only ✓

COP of absorption system is generally

1. A always higher than VC always ✓
2. B lower than vapour compression for same temperature lift ✓
3. C infinite without heat input ✓
4. D equal to Carnot always in practice ✓

Lithium bromide absorption chiller uses

1. A ammonia water only always ✓
2. B R-410A always ✓
3. C water as refrigerant and LiBr solution as absorbent ✓
4. D CO2 only always ✓

Vapour absorption system uses

1. A only electric compressor always ✓
2. B steam turbine only in evaporator ✓
3. C diesel engine in condenser ✓
4. D heat energy instead of mechanical work for circulation ✓

Bell-Coleman cycle is

1. A vapour compression with R-134a only ✓
2. B reverse Brayton cycle using air as refrigerant ✓
3. C Rankine cycle ✓
4. D Otto cycle ✓

Subcooling at condenser outlet improves

1. A compressor discharge temperature rise always ✓
2. B refrigeration capacity and efficiency ✓
3. C evaporator frost always ✓
4. D COP reduction always ✓

Superheat at evaporator outlet ensures

1. A liquid enters compressor for cooling ✓
2. B zero refrigeration effect ✓
3. C only vapor enters compressor avoiding liquid slugging ✓
4. D maximum condenser pressure ✓

Evaporator absorbs heat by

1. A condensing vapor at high pressure ✓
2. B compressing air only ✓
3. C burning fuel ✓
4. D boiling low pressure liquid refrigerant ✓

Capillary tube metering device is

1. A fixed small bore tube without moving parts ✓
2. B thermostatic valve with bulb always ✓
3. C high pressure float only always ✓
4. D steam trap ✓

Thermostatic expansion valve (TXV) controls flow using

1. A condenser pressure only always ✓
2. B bulb sensing evaporator outlet superheat ✓
3. C room humidity only always ✓
4. D compressor RPM only always ✓

Expansion valve throttles refrigerant to

1. A raise condenser pressure ✓
2. B compress vapor again ✓
3. C low pressure causing partial flash and cooling ✓
4. D superheat in evaporator inlet always only ✓

Air washer cools and humidifies air by

1. A refrigerant expansion only ✓
2. B combustion heating ✓
3. C direct contact with water spray ✓
4. D steam turbine ✓

Coefficient of performance (COP) of refrigerator is

1. A work input / refrigeration effect ✓
2. B refrigeration effect / work input ✓
3. C heat rejected / work only always labeled COP ✓
4. D cooling ton / power factor ✓

Latent heat equation for air is

1. A ma × cp × ΔT only always ✓
2. B compressor power only ✓
3. C condenser UA only ✓
4. D Q = ma × hfg × Δω ✓

Vapour compression refrigeration cycle consists of

1. A boiler, turbine, condenser, pump only ✓
2. B absorber and generator only always ✓
3. C compressor, condenser, expansion valve and evaporator ✓
4. D only evaporator and fan ✓

Refrigeration ton equals

1. A 1000 kJ/s ✓
2. B 211 kJ/min of heat removal (12,000 Btu/h) ✓
3. C 1 kW cooling always exactly ✓
4. D 3.5 kW heating only ✓

R-134a is commonly used in

1. A steam boilers ✓
2. B Rankine cycle turbines ✓
3. C diesel fuel injection ✓
4. D automotive and commercial refrigeration (HFC) ✓

R-22 has been largely phased out because

1. A it is non-toxic always ✓
2. B it has zero GWP ✓
3. C it is HCFC with ozone depletion potential ✓
4. D it cannot compress ✓

Ammonia (R-717) is preferred in industrial refrigeration because

1. A high latent heat and excellent thermodynamic properties ✓
2. B it is non-toxic and harmless always ✓
3. C it has highest GWP ✓
4. D it cannot be used with compressors ✓

Compressor in VC cycle raises

1. A only flow rate without pressure rise ✓
2. B refrigerant pressure and temperature above condensing temperature ✓
3. C evaporator pressure only ✓
4. D atmospheric pressure only always ✓

Reciprocating compressor uses

1. A only centrifugal impeller always ✓
2. B piston in cylinder to compress refrigerant vapor ✓
3. C absorption liquid pump only ✓
4. D steam turbine blades ✓

Centrifugal compressor in refrigeration suits

1. A large capacity low compression ratio applications ✓
2. B very small domestic fridge only always ✓
3. C only absorption cycle always ✓
4. D zero flow chiller ✓

Scroll compressor achieves compression by

1. A reciprocating piston only always ✓
2. B orbiting scroll meshing with fixed scroll ✓
3. C screw roots blower only in exhaust ✓
4. D steam ejector ✓

Screw compressor in refrigeration uses

1. A single piston stroke only ✓
2. B no oil injection ever always ✓
3. C water jet only ✓
4. D intermeshing rotors for continuous compression ✓

Condenser rejects heat from

1. A high pressure refrigerant vapor to cooling medium ✓
2. B evaporator load directly ✓
3. C electrical motor only ✓
4. D room air as cold source always ✓

Air cooled condenser uses

1. A ambient air blown over coils ✓
2. B cooling tower water always required ✓
3. C underground brine only always ✓
4. D steam from boiler ✓

Water cooled condenser typically connects to

1. A cooling tower for heat rejection ✓
2. B boiler feed line ✓
3. C steam turbine exhaust always ✓
4. D fuel tank ✓

Window air conditioner is

1. A split with remote outdoor only always ✓
2. B central plant chiller only ✓
3. C self-contained unit mounting in wall or window ✓
4. D absorption LiBr only always ✓

Split AC has

1. A all parts in one window box always ✓
2. B indoor evaporator unit and outdoor condensing unit ✓
3. C only boiler and turbine ✓
4. D no refrigerant piping between units ✓

Inverter AC varies

1. A only fan speed without compressor change always ✓
2. B refrigerant type during operation ✓
3. C compressor speed to modulate capacity ✓
4. D room humidity to zero always ✓

Packaged AC unit typically serves

1. A only single room window only always ✓
2. B steam power plant condenser ✓
3. C medium commercial spaces with ducted air ✓
4. D diesel engine cylinder ✓

Central HVAC chiller plant produces

1. A steam for turbines only always ✓
2. B chilled water distributed to air handling units ✓
3. C hot exhaust to chimney only ✓
4. D compressed natural gas to burners only ✓

Fan coil unit uses

1. A steam turbine expansion only ✓
2. B boiler furnace only ✓
3. C Rankine pump only ✓
4. D coil with fan to condition room air locally ✓

Duct design in HVAC considers

1. A only refrigerant subcooling ✓
2. B diesel cetane number ✓
3. C turbine blade pitch only ✓
4. D friction loss, velocity and noise ✓

Refrigerant leak detection is important because

1. A increases COP always ✓
2. B improves superheat always ✓
3. C loss reduces capacity and harms environment ✓
4. D eliminates need for oil ✓

Charging refrigerant should be done with

1. A engine running at max always without gauges ✓
2. B water into condenser always ✓
3. C fuel oil mix always ✓
4. D liquid or vapor per manufacturer spec on suction or liquid line ✓

Oil in refrigeration compressor provides

1. A primary refrigerant always ✓
2. B lubrication and sealing of clearance spaces ✓
3. C condenser heat rejection medium ✓
4. D evaporator frosting agent ✓

Receiver stores

1. A only hot vapor always ✓
2. B compressor motor windings ✓
3. C cooling tower water ✓
4. D liquid refrigerant after condenser ✓

Accumulator on suction line protects compressor from

1. A liquid refrigerant slugging ✓
2. B high discharge pressure only always ✓
3. C oil shortage only always ✓
4. D excess superheat always ✓

Defrost cycle in refrigeration evaporators prevents

1. A condenser scaling only ✓
2. B excessive frost reducing heat transfer ✓
3. C compressor oil breakdown only always ✓
4. D superheat rise always beneficial ✓

Cold storage design maintains

1. A steam pressure in boiler ✓
2. B turbine RPM only ✓
3. C diesel injection pressure only ✓
4. D product temperature by matching refrigeration load to infiltration and product heat ✓

Brine or secondary coolant used when

1. A COP exceeds 10 always ✓
2. B no heat transfer needed ✓
3. C only psychrometry study ✓
4. D direct expansion impractical for long or multiple coils ✓

Cascade refrigeration uses

1. A single R-134a stage only for −80 °C easily always ✓
2. B absorption only always ✓
3. C no condenser ✓
4. D two cycles with different refrigerants for very low temperatures ✓

Multi-evaporator system with one compressor may use

1. A single evaporator only always ✓
2. B steam trap per room ✓
3. C expansion valves and solenoids for each evaporator at different temperatures ✓
4. D boiler per zone ✓

Heat pump reverses cycle using

1. A reversing valve switching condenser and evaporator functions ✓
2. B fixed valve no switching always ✓
3. C boiler feed pump ✓
4. D steam ejector ✓

COP of ideal Carnot refrigerator between TH and TL is

1. A TH / TL ✓
2. B TL / (TH − TL) ✓
3. C (TH − TL) / TL ✓
4. D 1 always ✓

Actual COP of domestic refrigerator is typically

1. A 1.5 to 3 ✓
2. B 10 to 15 ✓
3. C 0.1 to 0.2 ✓
4. D 50 to 100 ✓

Unit of refrigeration in SI commonly expressed as

1. A bar only ✓
2. B Pascal only ✓
3. C Newton meter only ✓
4. D kW or kJ/s of heat removal ✓

Enthalpy of moist air on psychrometric chart is

1. A per kg total moist air only always in all charts ✓
2. B only sensible of water liquid ✓
3. C h per kg dry air including vapor ✓
4. D compressor work only ✓

Adiabatic mixing of two air streams on chart follows

1. A constant pressure line only always ✓
2. B horizontal line only always ✓
3. C vertical line only always ✓
4. D straight line between inlet states weighted by mass flow ✓

Sensible heat equation for air is approximately

1. A ma × hfg always without cp ✓
2. B only latent always ✓
3. C pressure × volume only for ideal gas always without cp ✓
4. D Q = ma × cp × ΔT ✓