R&AC Important Questions | Unit-wise R23 Exam Guide
Refrigeration & Air Conditioning (R&AC) is one of the most practical and industry-oriented subjects in mechanical engineering. It deals with cooling systems, comfort conditioning, refrigerants, heat pumps, and real-life thermal management. Whether you are preparing for university exams, interviews, or competitive tests, studying the R&AC important questions unit-wise helps you stay confident and score high.
R&AC Important Questions for R23 JNTU Students (Unit-Wise)
Unit 1: Basics of Refrigeration
Key Theory Questions
What is refrigeration and how is it different from air conditioning?
Explain the concept of COP in refrigeration.
Describe the working principle of a heat pump.
What is refrigerating effect?
Why is insulation important in refrigeration systems?
Explain the difference between natural and artificial refrigeration.
What are the common applications of refrigeration?
Describe the standards used in R&AC.
What is the effect of superheating?
What is subcooling and why is it required?
Explain sensible and latent cooling.
What is a closed refrigeration system?
Define ton of refrigeration.
Explain vapor compression and vapor absorption refrigeration.
Why is the reversed Carnot cycle used as a reference?
What is throttling?
Describe the types of refrigeration loads.
What are psychrometric properties?
Explain the term “refrigeration capacity.”
What factors reduce the COP of a system?
Numerical Focus Question
Calculate COP if refrigerating effect = 150 kJ/kg and work = 30 kJ/kg.
Find tonnage when cooling load = 12,600 kJ/hr.
A refrigerator consumes 0.8 kW and provides 3000 kJ/hr cooling. Find COP.
Calculate ideal COP of reversed Carnot cycle between 5°C and 35°C.
Determine refrigeration effect when mass flow rate = 0.1 kg/s and Δh = 120 kJ/kg.
Unit 2: Refrigerants & Components
Key Theory Questions
What is a refrigerant?
Explain primary vs secondary refrigerants.
What are desirable properties of an ideal refrigerant?
Describe ozone-friendly refrigerants.
Explain R-134a and its applications.
Why is ammonia used in industrial refrigeration?
What is the function of a compressor?
Describe different types of compressors.
Explain the working of condensers.
What are evaporators and their types?
What is capillary tube?
Why is expansion valve used?
Explain accumulator in refrigeration.
What is the function of filter-drier?
What is oil separator?
Describe refrigerant charging procedure.
What is retrofitting in refrigeration?
Explain refrigerant line sizing.
Why pressure testing is important?
What is refrigerant recovery?
Numerical Focus Question
Calculate mass flow rate for 5 kW cooling load and 120 kJ/kg refrigerating effect.
A compressor handles 0.2 kg/s at 150 kJ/kg. Find power.
Determine condenser heat rejection = RE + work (given values).
Find pressure ratio for given suction and discharge pressure.
Calculate evaporator capacity for given coil rating.
Unit 3: Psychrometry & Comfort Air Conditioning
Key Theory Questions
What is psychrometry?
Define DBT, WBT, and DPT.
Explain humidity ratio.
Describe sensible heat factor (SHF).
What is comfort cooling?
Explain summer and winter AC systems.
What is bypass factor?
Explain adiabatic cooling.
What is mixing of air streams?
Why ventilation is essential?
What are different air distribution methods?
Explain U-factor in heat gain.
What is infiltration load?
What is the purpose of diffusers?
Define effective temperature.
Describe cooling coil performance.
What is enthalpy of moist air?
What is dew point depression?
Explain fan coil units.
What affects indoor air quality?
Numerical Focus Question
Find humidity ratio from DBT and WBT.
Calculate SHF for given sensible and total loads.
Determine bypass factor of a coil.
Calculate room sensible heat.
Find mixture state from two air streams.
Unit 4: Vapor Compression & Absorption Systems
Key Theory Questions
Explain VCR cycle with P-H diagram.
What are dry and wet compression?
Describe two-stage compression.
What is the function of an economizer?
Explain cascade refrigeration system.
Difference between VCR and VAR systems.
Why lithium bromide is used in absorption systems?
Describe solar refrigeration.
What is flash chamber?
Explain defects in VCR system.
What are the advantages of multi-evaporator systems?
Explain gas refrigeration cycle.
What is aircraft refrigeration?
Explain air cycle refrigeration.
What is bootstrap cycle?
Describe regenerative cooling.
What is refrigerant leakage test?
Explain thermostat working.
What is electronic expansion valve?
Describe oil management in compressors.
Numerical Focus Question
COP of VCR cycle from enthalpy values.
Work input from compressor power and duration.
Mass flow rate based on RE.
Two-stage compression power.
Heat rejected in condenser = m(h2 – h3).
Preparation Tips for R&AC
Understand diagrams—P-H, T-S, and psychrometric charts.
Practice numerical problems daily.
Revise all refrigerant properties and components.
Focus on real-life applications like AC, refrigerators, cold storage.
Watch animations to understand cycles clearly.
Solve previous university question papers.
Observe real AC systems for practical understanding.
Conclusion
R&AC is one of the most scoring and practical subjects. By studying the R&AC important questions unit-wise, you gain clarity, problem-solving ability, and strong basics required in HVAC industries. This blog gives you a clear, structured preparation plan to help you perform well in exams and interviews.
