ME-801 Refrigeration and Air Conditioning - May 2026 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aExplain thermodynamic and chemical properties of refrigerants.
   How to answer

   • Define thermodynamic properties: boiling point, freezing point, latent heat, specific heat, COP, pressure ratio
   • Explain desired ranges for efficient operation
   • Define chemical properties: stability, inertness, non-corrosiveness, non-toxicity, non-flammability
   • Relate properties to material compatibility and safety
2. 7 Marks
   bDiscuss favourable properties of a ideal refrigerant.
   How to answer

   • Define ideal refrigerant concept
   • List thermodynamic favourable properties: low boiling point, high latent heat, low specific volume
   • List chemical/safety properties: non-toxic, non-flammable, stable, non-corrosive
   • List practical properties: low cost, easy leak detection, miscibility with oil
3. 7 Marks
   aState the limitations due to which it has not been possible to build a Carnot refrigeration system.
   How to answer

   • State Carnot refrigeration cycle processes
   • Explain isothermal compression with liquid entry / wet compression difficulty
   • Explain isentropic expansion with two-phase mixture and expander vs throttle
   • Conclude impracticality due to compressor damage and low COP control
4. 7 Marks
   bDiscuss the working of steam jet refrigeration system with neat sketch.
   How to answer

   • Draw schematic of boiler, ejector/nozzle, flash chamber/evaporator, condenser
   • Explain motive steam expansion and entrainment of flash vapour
   • Explain vacuum cooling and make-up water cycle
   • State applications, advantages and COP limitations
5. 7 Marks
   aExplain dry ice? Write a short note on production of dry ice.
   How to answer

   • Define dry ice as solid carbon dioxide subliming at -78.5°C
   • Describe production: compression, cooling, expansion to snow, pressing into blocks
   • Mention storage and handling precautions
   • Mention applications in refrigeration
6. 7 Marks
   bWrite down the short note on Li-Br Refrigerant Cycle with Neat Sketch.
   How to answer

   • Draw schematic of generator, condenser, absorber, evaporator, heat exchanger, pump
   • Explain LiBr-water as absorbent-refrigerant pair with water as refrigerant
   • Explain cycle flow and crystallization control
   • State applications in air-conditioning
7. 7 Marks
   aWrite down the short note on comfort air conditioning? What are the factors affecting comfort air conditioning?
   How to answer

   • Define comfort air conditioning and comfort zone
   • List factors: DBT, humidity, air motion, purity, noise
   • Explain human comfort: metabolic rate, clothing
   • Mention ASHRAE comfort chart
8. 7 Marks
   bDiscuss the effect of change in suction and discharge pressure on the performance of refrigeration cycle.
   How to answer

   • Explain effect of lowering suction pressure on refrigerating effect and work
   • Explain effect of raising discharge/condenser pressure on power and COP
   • Show trends on p-h diagram
   • Conclude optimum pressure range for performance
9. 7 Marks
   aDiscuss property of Ammonia and R-22 as refrigerant.
   How to answer

   • List key properties of Ammonia: boiling point, latent heat, toxicity, material compatibility
   • List key properties of R-22: boiling point, stability, ODP, applications
   • Compare safety and environmental aspects
   • Mention typical applications of each
10. 7 Marks
    bDiscuss seven desirable property of an ideal refrigerant.
    How to answer

    • List seven desirable properties: thermodynamic, chemical, safety, economic
    • Briefly explain each requirement
    • Relate to COP and practical use
    • Conclude no single ideal refrigerant exists
11. 7 Marks
    aIn a cooling application, moist air enters a refrigeration coil at the rate of 100 kg of dry air per minute at $35^{\circ}C$ and $50\%$ RH. The apparatus dew point of coil is $5^{\circ}C$ and by-pass factor is $0.15$. Determine the outlet state of moist air and cooling capacity of coil in TR.
    How to answer

    • Determine inlet enthalpy and humidity from psychrometric chart at 35°C, 50% RH
    • Apply by-pass factor formula to find outlet DBT and enthalpy with ADP 5°C
    • Calculate mass flow 100 kg/min dry air basis
    • Calculate cooling capacity = m*(h1-h2) and convert to TR
12. 7 Marks
    bThe amount of air supplied to an air-conditioned hall is $300\ m^3/min$. The atmosphere conditions are $35^{\circ}C$ DRT and $55\%$ RH. The required conditions are $20^{\circ}C$ DBT and $60\%$ RH. Find out the sensible heat and latent heat removed from the air per minute. Also find the sensible heat factor for the system.
    How to answer

    • Find enthalpies and specific volumes at 35°C 55% RH and 20°C 60% RH
    • Calculate mass flow from 300 m³/min supply volume
    • Calculate total, sensible and latent heat removed per minute
    • Calculate sensible heat factor = SH/(SH+LH)
13. 14 Marks
    Moist air enters a chamber at $5^{\circ}C$ DBT and $2.5^{\circ}C$ thermodynamic WBT at a rate of $90$ cmm. The barometric pressure is $1.01325$ bar. While passing through the chamber, the air absorbs sensible heat at the rate of $40.7$ kW and picks up $40$ kg/h of saturated steam at $110^{\circ}C$. Determine the dry and wet bulb temperatures of the leaving Air.
    How to answer

    • Determine inlet humidity ratio and enthalpy at 5°C DBT, 2.5°C WBT and mass flow from 90 cmm
    • Apply steady flow energy and mass balance with 40.7 kW sensible heat and 40 kg/h steam at 110°C
    • Solve for outlet humidity ratio and enthalpy
    • Read outlet DBT and WBT from psychrometric relations/chart
14. 14 Marks
    Write short note on any **four** :

    1. a)Grand sensible heat factor
    2. b)Advantages of Air refrigeration
    3. c)Leak detection methods
    4. d)Cascade system
    5. e)Electrolux
    How to answer

    • Define grand sensible heat factor with formula
    • List advantages of air refrigeration: safety, low cost, light weight
    • Describe leak detection methods: soap, halide torch, electronic
    • Explain cascade system and Electrolux system briefly