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In a refrigerator refrigerant134a enters the compressor as superheated vapor at a rate of 0.12 kg/s with h = 246.36 kJ/kg and it leaves with h = 288.53 kJ/kg. The isentropic enthalpy of refrigerant leaving compressor is h_{s} = 281.16 kJ/kg. The refrigerant is cooled in the condenser and it leaves the condenser in subcooled region with h = 84.98 kJ/kg. It is then throttled to 0.15 MPa. The isentropic efficiency of compressor and COP of refrigerator respectively are
In a certain cooling dehumidification operation 360 kg/h of air (DBT 35^{0}C & RH 50%) is blown over a cooling coil having apparatus dew point of 5^{0}C, assuming a bypass factor of 15%, the outlet temperature of air is
An air refrigerator of 10 ton capacity operates in Bell coleman cycle between pressure limits of 1bar and 4 bar. Air at inlet of compressor is at 1 bar and 253K. Air at exit of cooler is at 313 K. After air is cooled to 290K at
constant pressure in cooler, it is allowed to expand isentropically to 1 bar in expansion cylinder. Cold air is then sent to cold chamber to extract heat (Refrigeration effect). Determine COP of refrigerator.
Under saturated ambient air conditions:
[DBT = Dry bulb temperature,
WBT = Web bulb temperature]
For Saturated air
WBD = DBT  WBT = 0
DBT = WBT
Common data question 5 & 6
A refrigerator operates on an ideal vapor  compression refrigration cycle between 0.14 MPa and 0.8 MPa. The mass flow rate of the refrigerant is 0.05 kg/s. Take h_{g} (at 0.14 MPa) = 239.16 kJ/kg, S_{g} (at 0.14 MPa) = 0.94456 kJ/kgK, h_{f} (at 0.8 MPa) = 95.47 kJ/kg and h (at compressor exit) = 275.39 kJ/kg
Q. The rate of heat removal from refrigerated space and the heat rejected to the atmosphere respectively are
Common data question 5 & 6
A refrigerator operates on an ideal vapor  compression refrigration cycle between 0.14 MPa and 0.8 MPa. The mass flow rate of the refrigerant is 0.05 kg/s. Take h_{g} (at 0.14 MPa) = 239.16 kJ/kg, S_{g} (at 0.14 MPa) = 0.94456 kJ/kgK, h_{f} (at 0.8 MPa) = 95.47 kJ/kg and h (at compressor exit) = 275.39 kJ/kg
Q. The COP of the refrigerator is
Horizontal lines moving towards the saturation curve on the psychrometric chart represents
Common Data Question 8 & 9
In a Carnot vapor refrigeration cycle refrigerant R  134a is used as the working fluid. The refrigerant enters the condenser as saturated vapor at 28^{0}C and leaves as saturated liquid. The evaporator operates at a temperature of 100C. The thermodynamic properties for the refrigerant are given below.
Q. The net work for the cycle is given by
Common Data Question 8 & 9
In a Carnot vapor refrigeration cycle refrigerant R  134a is used as the working fluid. The refrigerant enters the condenser as saturated vapor at 28^{0}C and leaves as saturated liquid. The evaporator operates at a temperature of 100C. The thermodynamic properties for the refrigerant are given below.
Q. The coefficient of performance of the cycle is
The drybulb, wet bulb and dew point temperatures are identical at
For the saturation air (100% ralative humidity), the dry bulb, wet bulb and dew point temperature identical.
A room is filled with saturated moist air at 25^{0}C and a total pressure of 100 kPa. The saturated pressure at 25^{0}C is 3.1698 kPa. If the mass of dry air in the room is 100 kg, what is the mass of water vapour?
Common data for 12 & 13
A commercial refrigerator is used to keep the refrigerated space at 30^{0}C by rejecting its waste heat to cooling water. This cooling water enters the condenser at 18^{0}C (h_{w} = 75.47 kJ/kg) with a rate of 0.25 kg/s and leaves at 26^{0}C (h_{w} = 108.94 kJ/kg). The refrigerant enters the condenser at 1.2 MPa, 65^{0}C (h = 295.16 kJ/kg) and leaves at 42^{0}C (h = 111.23 kJ/kg). The inlet state of the compressor is 60 kPa, 34^{0}C (h = 230.03 kJ/kg) and the compressor is estimated to gain a net heat of 450W from the surroundings:
Q. The refrigeration load will be
Common data for 12 & 13
A commercial refrigerator is used to keep the refrigerated space at 30^{0}C by rejecting its waste heat to cooling water. This cooling water enters the condenser at 18^{0}C (h_{w} = 75.47 kJ/kg) with a rate of 0.25 kg/s and leaves at 26^{0}C (h_{w} = 108.94 kJ/kg). The refrigerant enters the condenser at 1.2 MPa, 65^{0}C (h = 295.16 kJ/kg) and leaves at 42^{0}C (h = 111.23 kJ/kg). The inlet state of the compressor is 60 kPa, 34^{0}C (h = 230.03 kJ/kg) and the compressor is estimated to gain a net heat of 450W from the surroundings:
Q. The theoretical maximum refrigeration load for the same power input to the compressor is
A heat pump operates between the temperature of 32^{0}C and 10^{0}C. The rates of heat addition and heat rejection are 650W and 1000 W respectively. The COP for the heat pump is ____
(Important  Enter only the numerical value in the answer)
In a VARs heating in generator is done at 200^{0}C, refrigeration in evaporator at 5^{0}C and cooling in condenser at 27^{0}C. The maximum COP of the system is
In an ideal VCRS, the enthalpy of the refrigerant before and after the evaporator are 90 kJ/kg and 200 kJ/kg. The circulation rate of refrigerant for each tonn of refrigerant is_____kg/min.
(Important  Enter only the numerical value in the answer)
The chemical formula for the refrigerant R22 is given by
The efficiency of Carnot engine is given as 0.80. If the cycle direction is reversed, the COP of the Carnot
refrigerator is_____
(Important  Enter only the numerical value in the answer)
Organic material of 1800 kg is to be stored in refrigerator storage. The material is supplied at 27^{0}C and is to be cooled to 30^{0}C for preserving it. The cooling takes place in 12 hours. The specific heat of material is 2 kJ/kgK above freezing point and 0.6 kJ/kgK below freezing point, which is 3^{0}C. The latent heat of freezing is 230 kJ/kg. If the actual COP is half of the ideal COP, the power required to drive the plant is ____ kW.
(Important  Enter only the numerical value in the answer)
Moist air exists at a pressure of 1.01 bar. The partial pressure and saturation pressure of water vapour are 0.01 bar and 0.02 bar respectively. The relative humidity and humidity ratio of the moist air, respectively are
27 docs243 tests

27 docs243 tests
