MP 6011
Elements of Heat Transfer and Principles of Refrigeration
Assignment-2
Submission Date: 17.07.2023
Vapour Absorption Refrigeration
Part I
An absorption refrigeration system that receives heat from a source at 95°C and
maintains the refrigerated space at 0°C is claimed to have a COP of 3.1. If the
environmental temperature is 19°C, can this claim be valid? Justify your answer.
Part II
An ammonia-water absorption refrigeration cycle is used to keep a space at -4°C when
the ambient temperature is 21°C. Pure ammonia enters the condenser at 2.62 MPa and
60°C at a rate of 0.02 kg/s. Ammonia leaves the condenser as a saturated liquid and is
expanded to 207.6 kPa in an isenthalpic process. Ammonia leaves the evaporator as a
saturated vapour. Heat is supplied to the generator by geothermal liquid water that
enters at 116°C at a rate of 0.25 kg/s and leaves at 93°C. The enthalpy of ammonia at
the condenser inlet is 1600 kJ/kg. Take the specific heat of the geothermal water to be
4.2 kJ/kg.K.
a) Sketch the state of the ammonia on a T-S diagram with respect to the saturation
lines.
Determine,
b) The rate of cooling provided by the system in kW.
c) The COP
d) The second-law efficiency of the system.
Part III
What benefit does the use of LiBr-H2O vapour absorption refrigeration system offer over
the H2O-NH3 system? What are its limitations; and where do LiBr-H2O systems find use
in the industry?