B.TECH - Semester 7 refrigeration and air conditioning Question Paper 2013 (dec)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Use of psychrometric chart and Refrigeration properties table permitted.
- Answer all questions from Part A and any four full questions from Part B. > PART - A (Answer all questions. Each question carries 2 marks.)
- A heat pump works on reversed Carnot cycle between temperature limits of $-10^{\circ} \mathrm{C}$ and $27^{\circ} \mathrm{C}$. Find its COP.
- Which air refrigeration system will you prefer for cooling exceptionally high speed aircrafts? Why?
- Give the p-V diagram of Reversed Joule cycle showing various processes on it.
- Draw the P-h and T-s diagram of a refrigerant in its superheated state entering the compressor and leaving the condenser as saturated liquid.
- What are mixed refrigerants? Where they are used?
- What is the function of LSHE? Where is it used? Explain.
- Mention any two advantages of vapour absorption refrigeration system over vapour compression refrigeration system.
- Write the equation for enthalpy of moist air in its superheated state.
- Briefly explain the working of thermostat with sketches.
- Show the diagram of year round air-conditioning. ( $10 \times 2=20$ Marks) (Answer any one full question from each module; each carries 20 marks)
- (a) Describe with neat sketches the principle of working of Boot strap air refrigeration system and derive the expression for COP and power required. 10
- (b) Explain with neat sketches the working of :
- (i) Vortex tube refrigerator (ii) Magnetic refrigerator
- (a) A bootstrap cooling system of 9 tonnes refrigeration capacity is employed in an airplane. The ambient air temperature and pressure are $20^{\circ} \mathrm{C}$ and 0.86 bar respectively. The pressure of air increases from 0.86 bar to 1 bar due to ...
- (i) The power required to operate the system, and (ii) COP of the system Draw the schematic and temperature-entropy diagrams of the system Take for air: $\mathrm{C}_{\mathrm{p}}=1 \mathrm{~kJ} / \mathrm{kg} \mathrm{K} ; \gamma=1.4$ 10
- (b) Describe the historical development of Refigeration
- (a) Describe the effect of various operating parameters on the COP of vapour compression refrigeration system.
- (b) A standard vapour compression refrigeration system uses R-12 as refrigerant. The system has a condensing temperature of $50^{\circ} \mathrm{C}$ and evaporating temperature of $0^{\circ} \mathrm{C}$. The refrigeration capacity is 7 TR . The liquid...
- (i) The refrigerant flow rate (ii) The power required to run the compressor (iii) The heat rejected in the plant (iv) COP of the system The properties of R-12 are: | Saturation temperature ${ }^{\circ} \mathrm{C}$ | Pressure bar | Enthalpy $\mathrm...
- (a) Explain a multi-evaporator system with flash intercooling with sketches.
- (b) What are the different desirable properties of refrigerants?
- (c) How mixing of refrigerants are significant in developed improved systems. Module - III
- (a) Describe the working of Lithium bromide water vapour absorption refrigeration system with neat sketches.
- (b) Derive the expression for maximum coefficient of performance of an ideal vapour absorption refrigeration system. OR 3
- (a) Describe with neat sketches the working of ice plant and cold storage 10
- (b) Describe the different refrigerant leakage and detection methods.
- (a) Define and derive expressions for the following terms :
- (i) Specific humidity (ii) Relative humidity
- (b) In an air-conditioning plant, an air handling unit supplies a total of $4000 \mathrm{~m}^{3} / \mathrm{min}$ of dry air which comprises by mass $20 \%$ fresh air at $39^{\circ} \mathrm{C}$ DBT and $26^{\circ} \mathrm{C}$ WBT and $80 \%$ recircula...
- (i) Total cooling load; and (ii) Room heat gain
- (a) A mixture of dry air and water vapour is at a temperature of $22^{\circ} \mathrm{C}$ under a total pressure of 730 mm Hg . The dew point temperature is $15^{\circ} \mathrm{C}$. Find:
- (i) Partial pressure of water vapour (ii) Relative humidity (iii) Specific humidity (iv) Enthalpy of air per kg of dry air
- (v) Specific volume of air per kg of dry air
- (b) Write short notes on the following :
- (i) Dew point temperature (ii) Adiabatic saturation process (iii) Degree of saturation (iv) BPF of cooling coil
- (v) Adiabatic mixing of air streams 10