Refrigeration and Air Conditioning MCQs 2026

Sensible heat equation for air is approximately

1. Ama × hfg always without cp✓
2. Bonly latent always✓
3. Cpressure × volume only for ideal gas always without cp✓
4. DQ = ma × cp × ΔT✓

Adiabatic mixing of two air streams on chart follows

1. Aconstant pressure line only always✓
2. Bhorizontal line only always✓
3. Cvertical line only always✓
4. Dstraight line between inlet states weighted by mass flow✓

Enthalpy of moist air on psychrometric chart is

1. Aper kg total moist air only always in all charts✓
2. Bonly sensible of water liquid✓
3. Ch per kg dry air including vapor✓
4. Dcompressor work only✓

Unit of refrigeration in SI commonly expressed as

1. Abar only✓
2. BPascal only✓
3. CNewton meter only✓
4. DkW or kJ/s of heat removal✓

Actual COP of domestic refrigerator is typically

1. A1.5 to 3✓
2. B10 to 15✓
3. C0.1 to 0.2✓
4. D50 to 100✓

COP of ideal Carnot refrigerator between TH and TL is

1. ATH / TL✓
2. BTL / (TH − TL)✓
3. C(TH − TL) / TL✓
4. D1 always✓

Heat pump reverses cycle using

1. Areversing valve switching condenser and evaporator functions✓
2. Bfixed valve no switching always✓
3. Cboiler feed pump✓
4. Dsteam ejector✓

Multi-evaporator system with one compressor may use

1. Asingle evaporator only always✓
2. Bsteam trap per room✓
3. Cexpansion valves and solenoids for each evaporator at different temperatures✓
4. Dboiler per zone✓

Cascade refrigeration uses

1. Asingle R-134a stage only for −80 °C easily always✓
2. Babsorption only always✓
3. Cno condenser✓
4. Dtwo cycles with different refrigerants for very low temperatures✓

Brine or secondary coolant used when

1. ACOP exceeds 10 always✓
2. Bno heat transfer needed✓
3. Conly psychrometry study✓
4. Ddirect expansion impractical for long or multiple coils✓

Cold storage design maintains

1. Asteam pressure in boiler✓
2. Bturbine RPM only✓
3. Cdiesel injection pressure only✓
4. Dproduct temperature by matching refrigeration load to infiltration and product heat✓

Defrost cycle in refrigeration evaporators prevents

1. Acondenser scaling only✓
2. Bexcessive frost reducing heat transfer✓
3. Ccompressor oil breakdown only always✓
4. Dsuperheat rise always beneficial✓

Accumulator on suction line protects compressor from

1. Aliquid refrigerant slugging✓
2. Bhigh discharge pressure only always✓
3. Coil shortage only always✓
4. Dexcess superheat always✓

Receiver stores

1. Aonly hot vapor always✓
2. Bcompressor motor windings✓
3. Ccooling tower water✓
4. Dliquid refrigerant after condenser✓

Oil in refrigeration compressor provides

1. Aprimary refrigerant always✓
2. Blubrication and sealing of clearance spaces✓
3. Ccondenser heat rejection medium✓
4. Devaporator frosting agent✓

Charging refrigerant should be done with

1. Aengine running at max always without gauges✓
2. Bwater into condenser always✓
3. Cfuel oil mix always✓
4. Dliquid or vapor per manufacturer spec on suction or liquid line✓

Refrigerant leak detection is important because

1. Aincreases COP always✓
2. Bimproves superheat always✓
3. Closs reduces capacity and harms environment✓
4. Deliminates need for oil✓

Duct design in HVAC considers

1. Aonly refrigerant subcooling✓
2. Bdiesel cetane number✓
3. Cturbine blade pitch only✓
4. Dfriction loss, velocity and noise✓

Fan coil unit uses

1. Asteam turbine expansion only✓
2. Bboiler furnace only✓
3. CRankine pump only✓
4. Dcoil with fan to condition room air locally✓

Central HVAC chiller plant produces

1. Asteam for turbines only always✓
2. Bchilled water distributed to air handling units✓
3. Chot exhaust to chimney only✓
4. Dcompressed natural gas to burners only✓

Packaged AC unit typically serves

1. Aonly single room window only always✓
2. Bsteam power plant condenser✓
3. Cmedium commercial spaces with ducted air✓
4. Ddiesel engine cylinder✓

Inverter AC varies

1. Aonly fan speed without compressor change always✓
2. Brefrigerant type during operation✓
3. Ccompressor speed to modulate capacity✓
4. Droom humidity to zero always✓

Split AC has

1. Aall parts in one window box always✓
2. Bindoor evaporator unit and outdoor condensing unit✓
3. Conly boiler and turbine✓
4. Dno refrigerant piping between units✓

Window air conditioner is

1. Asplit with remote outdoor only always✓
2. Bcentral plant chiller only✓
3. Cself-contained unit mounting in wall or window✓
4. Dabsorption LiBr only always✓

Water cooled condenser typically connects to

1. Acooling tower for heat rejection✓
2. Bboiler feed line✓
3. Csteam turbine exhaust always✓
4. Dfuel tank✓

Air cooled condenser uses

1. Aambient air blown over coils✓
2. Bcooling tower water always required✓
3. Cunderground brine only always✓
4. Dsteam from boiler✓

Condenser rejects heat from

1. Ahigh pressure refrigerant vapor to cooling medium✓
2. Bevaporator load directly✓
3. Celectrical motor only✓
4. Droom air as cold source always✓

Screw compressor in refrigeration uses

1. Asingle piston stroke only✓
2. Bno oil injection ever always✓
3. Cwater jet only✓
4. Dintermeshing rotors for continuous compression✓

Scroll compressor achieves compression by

1. Areciprocating piston only always✓
2. Borbiting scroll meshing with fixed scroll✓
3. Cscrew roots blower only in exhaust✓
4. Dsteam ejector✓

Centrifugal compressor in refrigeration suits

1. Alarge capacity low compression ratio applications✓
2. Bvery small domestic fridge only always✓
3. Conly absorption cycle always✓
4. Dzero flow chiller✓

Reciprocating compressor uses

1. Aonly centrifugal impeller always✓
2. Bpiston in cylinder to compress refrigerant vapor✓
3. Cabsorption liquid pump only✓
4. Dsteam turbine blades✓

Compressor in VC cycle raises

1. Aonly flow rate without pressure rise✓
2. Brefrigerant pressure and temperature above condensing temperature✓
3. Cevaporator pressure only✓
4. Datmospheric pressure only always✓

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

1. Ahigh latent heat and excellent thermodynamic properties✓
2. Bit is non-toxic and harmless always✓
3. Cit has highest GWP✓
4. Dit cannot be used with compressors✓

R-22 has been largely phased out because

1. Ait is non-toxic always✓
2. Bit has zero GWP✓
3. Cit is HCFC with ozone depletion potential✓
4. Dit cannot compress✓

R-134a is commonly used in

1. Asteam boilers✓
2. BRankine cycle turbines✓
3. Cdiesel fuel injection✓
4. Dautomotive and commercial refrigeration (HFC)✓

Refrigeration ton equals

1. A1000 kJ/s✓
2. B211 kJ/min of heat removal (12,000 Btu/h)✓
3. C1 kW cooling always exactly✓
4. D3.5 kW heating only✓

Coefficient of performance (COP) of refrigerator is

1. Awork input / refrigeration effect✓
2. Brefrigeration effect / work input✓
3. Cheat rejected / work only always labeled COP✓
4. Dcooling ton / power factor✓

Vapour compression refrigeration cycle consists of

1. Aboiler, turbine, condenser, pump only✓
2. Babsorber and generator only always✓
3. Ccompressor, condenser, expansion valve and evaporator✓
4. Donly evaporator and fan✓

Evaporative cooler (desert cooler) cools air by

1. Avapor compression refrigeration always✓
2. Bwater evaporation adding latent heat✓
3. Csteam expansion✓
4. DRankine cycle✓

Desiccant dehumidification removes moisture by

1. Aadsorption on desiccant material not only cooling✓
2. Bcompressor suction only✓
3. Cboiler steam only✓
4. Dincreasing humidity ratio✓

Hydrocarbon refrigerants like propane (R-290) require

1. Ano safety concern ever✓
2. Buse in unlimited charge always✓
3. Ccharge limits and explosion-safe design✓
4. Doperation without ventilation always✓

CO2 (R-744) transcritical cycle used because

1. Anatural refrigerant with low GWP suitable for heat pumps✓
2. Brequires no pressure always✓
3. Coperates below 1 bar always✓
4. Dcannot transfer heat✓

Greenhouse warming potential (GWP) drives shift toward

1. Amore R-11 use✓
2. Blow GWP refrigerants like R-32, CO2 and hydrocarbons✓
3. Csteam in compressors✓
4. Ddiesel in evaporators✓

R-12 was replaced primarily due to

1. Aozone depletion potential✓
2. Blow cooling capacity only✓
3. Cnon-flammability✓
4. Dhigh efficiency problem✓

R-410A is

1. ACFC ozone depleter✓
2. Bnear-azeotropic HFC blend for many modern AC systems✓
3. Cammonia solution✓
4. Dwater only refrigerant✓

EER and COP relation approximately

1. ACOP = EER × 0.293 for IP units conversion context✓
2. BEER equals COP always numerically✓
3. Cno relation exists✓
4. DCOP equals EER squared✓

Electrical energy input to 1 ton AC roughly

1. A10 kW always✓
2. B0.01 kW always✓
3. C100 kW always✓
4. D1 to 1.5 kW at rated conditions depending on EER✓

Hot gas bypass valve prevents

1. Acondenser flooding always beneficial✓
2. Bevaporator superheat always✓
3. Coil return always failure✓
4. Dcompressor short cycling at low load✓

Frost on evaporator indicates

1. Acondenser too hot always beneficial✓
2. Bexcess superheat always✓
3. Cevaporating temperature below 0 °C with moisture in air✓
4. Dperfect dehumidification always✓

Cooling load tonnage for building estimated using

1. Aonly compressor displacement✓
2. BCLTD/CLF methods or software with solar, internal and ventilation gains✓
3. Conly boiler efficiency✓
4. Donly pipe friction✓

Chilled water temperature from central plant often

1. A100 °C supply always✓
2. Bbelow 0 °C always without brine✓
3. C6–7 °C supply for dehumidification and cooling✓
4. D200 °C steam always✓

VAV system varies

1. Arefrigerant type hourly✓
2. Bcompressor displacement fixed only always without variation✓
3. Cair volume to zones while maintaining temperature✓
4. Dboiler steam pressure only✓

Fresh air load in AC includes

1. Aonly compressor oil heat✓
2. Bsensible and latent heat to treat outdoor ventilation air✓
3. Conly lighting latent always zero✓
4. Dsteam turbine loss✓

Comfort air conditioning typically maintains

1. A24–26 °C and 40–60% RH approximately✓
2. B50 °C and 90% RH always✓
3. C0 °C and 100% RH always✓
4. Donly pressure control✓

Humidification adds moisture by

1. Acooling coil condensate removal only✓
2. Bcompressor suction only✓
3. Csteam injection, pan evaporators or spray✓
4. Dcondenser rejection only✓

Dehumidification process on psychrometric chart moves air

1. Atoward lower humidity ratio usually with cooling✓
2. Balong constant dry bulb upward always✓
3. Cto higher moisture always at constant RH 100%✓
4. Dwithout energy transfer✓

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

1. Asupply air condition design✓
2. Bboiler efficiency only✓
3. Cturbine expansion only✓
4. Ddiesel injection timing✓

Bypass factor of cooling coil indicates

1. Afraction of air not contacting coil surface perfectly✓
2. Bcompressor volumetric efficiency✓
3. Ccondenser approach✓
4. Dfuel octane✓

Latent cooling load removes moisture by

1. Araising dry bulb only always✓
2. Badding steam to room✓
3. Ccondensing water vapor from air✓
4. Dheating air only✓

Sensible cooling load removes heat

1. Awithout change in moisture content ideally✓
2. Bonly latent heat of vaporization always✓
3. Conly humidity addition✓
4. Donly fuel combustion heat✓

Sensible heat factor (SHF) in AC indicates

1. Aonly latent load fraction always inverted always✓
2. Bcompressor efficiency✓
3. Cfraction of sensible to total cooling load✓
4. Drefrigerant charge mass only✓

Humidity ratio (specific humidity) is

1. Amass of water vapor per mass of dry air✓
2. Bvolume of air only✓
3. CRH percentage directly✓
4. Denthalpy of steam table only✓

Dew point temperature is

1. Aalways equal to dry bulb✓
2. Bwet bulb plus 10 °C always✓
3. Ccompressor discharge temperature✓
4. Dtemperature at which condensation begins at given pressure✓

Wet bulb temperature is measured with

1. Athermometer with moist wick in moving air✓
2. Bdry bulb in still air only always✓
3. Cinfrared gun only✓
4. Dmercury barometer✓

Dry bulb temperature is

1. Awet wick thermometer reading always✓
2. Bdew point always✓
3. Cadiabatic saturation always✓
4. Dtemperature measured by ordinary thermometer✓

Psychrometry deals with

1. Aonly dry nitrogen✓
2. Bliquid water only without vapor✓
3. Cproperties of moist air✓
4. Drefrigerant R-22 only✓

COP of absorption system is generally

1. Aalways higher than VC always✓
2. Blower than vapour compression for same temperature lift✓
3. Cinfinite without heat input✓
4. Dequal to Carnot always in practice✓

Lithium bromide absorption chiller uses

1. Aammonia water only always✓
2. BR-410A always✓
3. Cwater as refrigerant and LiBr solution as absorbent✓
4. DCO2 only always✓

Vapour absorption system uses

1. Aonly electric compressor always✓
2. Bsteam turbine only in evaporator✓
3. Cdiesel engine in condenser✓
4. Dheat energy instead of mechanical work for circulation✓

Bell-Coleman cycle is

1. Avapour compression with R-134a only✓
2. Breverse Brayton cycle using air as refrigerant✓
3. CRankine cycle✓
4. DOtto cycle✓

Subcooling at condenser outlet improves

1. Acompressor discharge temperature rise always✓
2. Brefrigeration capacity and efficiency✓
3. Cevaporator frost always✓
4. DCOP reduction always✓

Superheat at evaporator outlet ensures

1. Aliquid enters compressor for cooling✓
2. Bzero refrigeration effect✓
3. Conly vapor enters compressor avoiding liquid slugging✓
4. Dmaximum condenser pressure✓

Evaporator absorbs heat by

1. Acondensing vapor at high pressure✓
2. Bcompressing air only✓
3. Cburning fuel✓
4. Dboiling low pressure liquid refrigerant✓

Capillary tube metering device is

1. Afixed small bore tube without moving parts✓
2. Bthermostatic valve with bulb always✓
3. Chigh pressure float only always✓
4. Dsteam trap✓

Thermostatic expansion valve (TXV) controls flow using

1. Acondenser pressure only always✓
2. Bbulb sensing evaporator outlet superheat✓
3. Croom humidity only always✓
4. Dcompressor RPM only always✓

Expansion valve throttles refrigerant to

1. Araise condenser pressure✓
2. Bcompress vapor again✓
3. Clow pressure causing partial flash and cooling✓
4. Dsuperheat in evaporator inlet always only✓

Air washer cools and humidifies air by

1. Arefrigerant expansion only✓
2. B combustion heating✓
3. Cdirect contact with water spray✓
4. Dsteam turbine✓

Latent heat equation for air is

1. Ama × cp × ΔT only always✓
2. Bcompressor power only✓
3. Ccondenser UA only✓
4. DQ = ma × hfg × Δω✓