BBA Iind SEMESTER EXAMINATION 2008-09 s26

B.Tech VI (Sixth) Semester Examination 2014-15

Course Code: EME601 Paper ID: 0966123

Refrigeration and Air Conditioning

Time: 3 Hours Max. Marks: 70

Max Marks: 75

Note: Attempt six questions in all. Q. No. 1 is compulsory.

1. Answer any five of the following (limit your answer to 50 words). (4x5=20) a) What do you understand by term DART. b) Name the refrigerant used for following application. i) Cold storage ii) Ice plant iii) Household refrigerator iv) Water cooler. c) Define the term effective temperature and explain its significance in the design of air Conditioning system. d) Define ‘one Tonne of Refrigeration’. e) Explain the effect of sub cooling of condensate in VCRS. f) How ‘compression’ is achieved in VARS. g) When is dehumidification of air is necessary and how it is achieved? h) What do you understand by static and velocity pressure in a duct?

2. a) Describe boot-strap cycle of refrigeration system, with a schematic diagram and show the cycle on T-S co-ordinates. (5) b) Discuss the advantages of the dense air refrigerating system over an open air refrigeration system. (5) b) Write the factors considered for the selection of 3. a) Discuss the effect of variation of condenser and evaporator refrigerant for a system. pressures and sub-cooling of condensate on COP of a vapour (5) compression refrigeration system. (5) b) Discuss the applications of flash chamber with the help of P- 7. A room 7m X 4m X 4m is occupied by an air-water vapour h chart and schematic diagrams. (5) mixture at 380C. The atmospheric pressure is 1 bar and the relative humidity is 70%. Determine the humidity ratio, dew 4. A two stage refrigerating system is operating between the point, mass of dry air and mass of water vapour. If the pressure limits of 8 bar and 1.4 bar. The working fluid is mixture of air-water vapour is further cooled at constant R134a. The refrigerant leaves the condenser as a saturated pressure until the temperature is 100C, find the amount of liquid and is throttled to a flash chamber operating at 3.2 bar. water vapour condensed. (10) The part of refrigerant evaporates during flashing process and this vapour is mixed with the refrigerant leaving the low 8. a) Classify the air conditioning system on the basis of pressure compressor. The mixture is then compressed to the season, purpose and arrangement of equipment. condenser pressure by the high pressure compressor. The (5) liquid in the flash chamber is throttled to the evaporator b) Explain with neat sketches two losses in duct. pressure and cools the refrigerated space as it vaporises in the (5) evaporator. Assuming the refrigerant leaves the evaporator as saturated vapour and both compressions are isentropic, determine: (i) The fraction of refrigerant that evaporates as it is throttled to the flash chamber (ii) The amount of heat removed from the refrigerated space and compressor work per unit mass of refrigerant flowing through the condenser and (iii) COP. (10)

5. Explain the working of Practical Aqua Ammonia Vapour Absorption Refrigeration System. How do we ensure pure ammonia at the entry to the condenser? Discuss the significance and working of aqua heat exchanger. (10)

6. a) Explain the following terms: (5) i) Specific humidity ii) Degree of saturation iii) Relative humidity iv) Enthalpy of moist air v) DBT, WBT and dew point temperature