JNTU B.Tech III REFRIGERATION AND AIR CONDITIONING Previous Question Paper (August/September - 2024 - R16)

Define refrigeration, State the Name of different types of system used for cooling of aircraft cabin, Also Explain with schematic diagram Bootstrap air Refrigeration system.

Refrigerating machine working between the temperature limits of – 130C and 370C and has 90% relative COP. It consumes 4.8 kW power. Determine TR capacity. For same TR capacity, how much power will be consumed by carnot refrigerator? Also for the same power consumption, determine TR capacity of carnot refrigerator operating between same temperature limits.

An air refrigerator working on Bell coleman cycle takes in air at 1 bar and at a temperature of 100C. The air is compressed to 5 bar abs. The same is cooled to 250C in the cooler before expanding in the expansion cylinder to cold chamber pressure of 1 bar. The compression and expansion laws followed are PV^1.35 = C and PV^1.3 = C respectively. Determine C.O.P of the plant and net refrigeration effect per kg of air. Take C_p = 1.009 kJ/kg K and R = 0.287 kJ/kg K for air.

For a sample of air having 220C DBT, Relative humidity 30% at barometric pressure of 760mm of Hg. Calculate i) Vapour pressure ii) Vapour density iii) Humidity ratio iv) Enthalpy.

Explain the working of Vapour compression refrigeration system with the help of a neat sketch. Mention the advantages of vapour compression refrigeration system over air refrigeration system.

A R-12 vapour compression system has saturated suction temperature of -50C and saturated discharge temperature of 400C. The refrigerant vapour is dry-saturated at the suction of compressor and becomes superheated after compression. For one ton of refrigeration capacity, Calculate (i) Refrigerating effect (ii) mass flow rate (iii) Power and (iv) COP of the system.

Explain standard vapour compression refrigeration cycle with T-S and P-H diagram.

A vapour compression machine is used to maintain a temp of 250K is refrigerated space. The ambient temp is 310K. The compressor takes is dry saturated vapour of R-12. A minimum 100C temp difference is required at the evaporator as well as at condenser. There is no sub cooling of liquid. If refrigerant flow rate is 2 kg/min, find i) Tonne of refrigeration ii) Power requirement iii) Ratio of COP of this cycle to COP of Carnot cycle.

What are desirable characteristics of ideal refrigerant? Explain how refrigerants are designated.

What are the advantages of multistage compressor?

Explain multiple evaporator at different temperature with individual expansion valve with neat sketch and P-H diagram.

State the classification of condenser used in refrigeration system?

Briefly explain construction and working of Practical vapour absorption refrigeration system. Also mention the advantages of this system.

Distinguish between vapour absorption refrigeration system with vapour compression refrigeration system.

State the principle of Steam jet refrigeration system. Explain the working of Steam jet refrigeration system.

Derive an expression for the COP of an ideal vapour absorption system in terms of temperature T_G at which heat is supplied to the generator, the temperature T_E at Which heat is absorbed in the evaporator and the temperature T_C at which heat is discharged from the condenser and absorber.

Classify air conditioning systems. Explain Central air conditioning system with a neat sketch.

A small office hall of 25 persons capacity is provided with summer air conditioning system with the following data: Outside conditions = 340C DBT and 280C WBT, Inside conditions = 240C DBT and 50 % RH, Volume of air supplied = 0.4 m³/min/person, Sensible heat load in room = 125600 kJ/h, Latent heat load in the room = 42000 kJ/h. Find the sensible heat factor of the plant.

What is effective temperature? What factors affect effective temperature and explain its significance in design of air-conditioning systems.

A summer air –conditioning system for a small office building is to be designed. The design is to be based on the following information: Outside design condition 350C Tdb, 280C Twb, Inside design condition 260C Tdb, 50% RH, Room sensible heat gain 45 kW, Room latent heat gain 9 kW, Ventilation air 0.95 m³/s, A four row direct expansion refrigerant 134a coil with bypass factor of 0.2 is to be used. Analyze the problem on a psychrometric chart and determine the following: i) The room apparatus dew point (ADP) ii) The temperature of the air leaving the coil iii) The total quality of air required (m³/s) iv) The temperature of mixed air entering the coil v) The coil apparatus dew point temperature.