Refrigeration
Exam Duration: 45 Mins Total Questions : 20
TR machine means that
- (a)
one ton of the refrigerant is used
- (b)
one ton of water at DOC is converted into ice at DOC
- (c)
one ton of water at DOC is converted into ice at DOC in 24 h
- (d)
All of the above
COP of a refrigerator working between two fixed temperature limits T1 and T2 (T1 > T2) will have
- (a)
COP increased when the working substance has high specific heat
- (b)
COP increases with the increase in latent heat of vaporization during heat absorption process at T2.
- (c)
Cannot be predicted
- (d)
Fixed COP
A Carnot refrigerator requires 1.5 kW of work for 6 kW of refrigerating effect. If it absorbs heat at 240 K then the temperature of heat reservoir at which the heat is rejected equal to
- (a)
320 K
- (b)
300 K
- (c)
400 K
- (d)
280 K
A Carnot refrigerator has COP = 5. The ratio of higher temperature T1 to lower temperature T2 is
- (a)
6/5
- (b)
5/4
- (c)
5/6
- (d)
3/2
Bell Coleman air refrigeration cycle consists of
- (a)
two adiabatics, one constant volume and one constant pressure process
- (b)
two adiabatics and two constant volume processes
- (c)
two adiabatics and two constant pressure processes
- (d)
None of the above
Heat is absorbed from cold chamber to produce refrigerating effect from
- (a)
evaporator
- (b)
compressor
- (c)
expansion valve
- (d)
condenser
The power required to run the vapour compression cycle is 5 kW and heat rejected to condenser is 15 kW. It's COP is
- (a)
2
- (b)
3
- (c)
1/2
- (d)
1/3
A simple saturated cycle is one in which the refrigerant vapour is
- (a)
wet at entry to compressor
- (b)
dry-saturated at exit of compressor
- (c)
dry-saturated at entry to compressor
- (d)
All of the above
20 TR means
- (a)
20 kW
- (b)
70 kW
- (c)
35 kW
- (d)
None of these
In a simple vapour compression cycle the enthalpy of refrigerant are at entry to compressor = 350 kJ/kg at exit to compressor = 450 kJ/kg, at exit of condenser = 150 kJ/kg. The COP is
- (a)
2
- (b)
\(\frac{7}{3}\)
- (c)
3
- (d)
\(\frac{9}{7}\)
The mass flow rate of refrigerant to compressor is 2kg/s/TR having the volumetric efficiency 0.8 and specific volume of refrigerant as 0.1 m3/kg, the volume of refrigerant to be handled by compressor per TR is
- (a)
16 m3/s
- (b)
0.25 m3/s
- (c)
0.16 m3/s
- (d)
Cannot be determined
Actual COP of vapour absorption system compared to vapour compression cycle while working between same temperature limits is
- (a)
less
- (b)
more
- (c)
equal
- (d)
Cannot be determined
Consider a vapour absorption system as shown:
Ideal COP of this system is
- (a)
\({ COP }=\left( \frac { { T }_{ e } }{ { T }_{ c }-{ T }_{ e } } \right) .\left( \frac { { T }_{ g }-{ T }_{ c } }{ { T }_{ g } } \right) \)
- (b)
\({ COP }=\left( \frac { { T }_{ g } }{ { T }_{ c }-{ T }_{ e } } \right) \times\left( \frac { { T }_{ g }-{ T }_{ c } }{ { T }_{ e } } \right) \)
- (c)
\({ COP }=\left( \frac { { T }_{ c } }{ { T }_{ c }-{ T }_{ e } } \right) .\left( \frac { { T }_{ g }-{ T }_{ c } }{ { T }_{ e } } \right) \)
- (d)
None of the above
Desirable properties of a good refrigerant are
- (a)
low boiling temperature
- (b)
low condensing and high evaporating pressures
- (c)
high latent heat of vaporisation
- (d)
All of the above
At 100% RH the DBT, WBT and DPT are related as
- (a)
DBT > WBT > DPT
- (b)
DBT < WBT < DPT
- (c)
DBT = WBT > DPT
- (d)
DBT = WBT = DPT
Degree of saturation, \(\mu\) is defined as
- (a)
mass of water vapour in wet air
- (b)
mass of water vapour in dry air
- (c)
mass of water vapour in sample of air to mass of water vapour in saturated air at the same temperature
- (d)
None of the above
By-pass factor of a cooling coil increases with
- (a)
increase in fins spacing and decrease in number of rows
- (b)
decrease in fins spacing and decrease in number of rows
- (c)
decrease in fins spacing and increase in number of rows
- (d)
increase in fins spacing and increase in number of rows
On the basis of the given chart answer these questions
Process ab is
- (a)
heating and humidification
- (b)
cooling and dehumidification
- (c)
heating
- (d)
cooling
On the basis of the given chart answer these questions
Process cd is
- (a)
sensible heating
- (b)
adiabatic cooling
- (c)
sensible cooling
- (d)
None of the above
If room sensible heat", 10 kW and latent heat = 70 kW, then room sensible heat factor is
- (a)
0.125
- (b)
0.20
- (c)
0.15
- (d)
0.75
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