Previous year question paper for RAC (B-TECH Mechanical Engineering 7-8th)

Unit I Introduction: Definition of refrigeration & air conditioning; Necessity; Methods of

refrigeration; Unit of refrigeration; Coefficient of performance (COP), Fundamentals of airconditioning

system; Refrigerants- Definition, Classification, Nomenclature, Desirable

properties, Comparative study, secondary refrigerants, Introduction to eco-friendly

Refrigerants; Introduction to Cryogenics.

Unit II Air Refrigeration System: Carnot refrigeration cycle. Temperature. Limitations; Brayton

refrigeration or the Bell Coleman air refrigeration cycle; Necessity of cooling the aero

plane; Air craft refrigeration systems, Simple cooling and Simple evaporative types, Boot

strap and Boot strap evaporative types, Regenerative type and Reduced Ambient type

system, Comparison of different systems, problems.

Unit III Vapour Compression (VC) Refrigeration Systems: (A) Simple Vapour Compression

(VC) Refrigeration systems-Limitations of Reversed Carnot cycle with vapour as the

refrigerant; Analysis of VC cycle considering degrees of sub cooling and superheating; VC

cycle on p-v, t-s and p-h diagrams; Effects of operating conditions on COP; Comparison of

VC cycle with Air Refrigeration cycle.

(B) Multistage Ref. Systems- Necessity of compound compression, Compound VC cycle ,

Inter-cooling with liquid sub –cooling and / or water inter cooler: Multistage compression

with flash inter-cooling and / or water inter-cooling; systems with individual or multiple

expansion valves; Individual compression system with individual or multiple expansion

valves; Individual compression systems with individual or multiple expansion valves but

with and without intercoolers.

Unit IV Other Refrigeration Systems: (A) Vapour Absorption Refrigeration Systems – Basic

Systems, Actual COP of the System, Performance, Relative merits and demerits; Properties

of aqua ammonia; Electrolux Refrigeration; Problems.

(B) Steam Jet Refrigerating System- Introduction, Analysis, Relative merits and demerits,

Performance Applications, Problems.

(C) Cascade Refrigerating Systems-Necessity Selection of Pairs of refrigerants for the

system, Concept of cascade temperature, Analysis, Multistaging, Comparison with V.C.

systems, Applications, Problems.

Unit V Psychrometry of Air & Air Conditioning Processes: Properties of moist Air-Gibbs

Dalton law, Specific humidity, Dew point temperature, Degree of saturation, Relative

humidity, Enthalpy, Humid specific heat, Wet bulb temp., Thermodynamics wet bulb

temp., Psychrometric chart; Psychrometry of air-conditioning processes, Mixing Process,

Basic processes in conditioning of air; Psychrometric processes in air washer, Problems.

Unit VI Air- Conditioning Load Calculations: Outside and inside design conditions; Sources of

heating load; Sources of cooling load; Heat transfer through structure, Solar radiation,

Electrical applications, Infiltration and ventilation, Heat generation inside conditioned

space; Apparatus selection; Comfort chart, Problems.

Unit VII Air Conditioning Systems with Controls & Accessories: Classifications, Layout of plants;

Equipment selection; Air distribution system; Duct systems Design; Filters; Refrigerant

piping; Design of summer air-conditioning and Winter air conditioning systems;

Temperature sensors, Pressure sensors, Humidity sensors, Actuators, Safety controls;

Accessories; Problems.

Unit VIII Refrigeration and Air Conditioning Equipments: Type of compressors and their

performance curves; Types of Condensers, Heat transfer in condensers; Types of expansion

devices; types of evaporators, Cooling and Dehumidifying coils, Problems