A pressure gauge on the discharge side of a refrigerant compressor reads too high. The reasons will be
Lack of cooling water
Water temperature being high
Dirty condenser surface
All of these
Correct Answer :
D. All of these
Related Questions
Nusselt number (NN) is given by
NN = hl/k
NN = μ cp/k
NN = ρ V l /μ
NN = V²/t.cp
The Freon group of refrigerants are
Halocarbon refrigerants
Zoetrope refrigerants
Inorganic refrigerants
Hydrocarbon refrigerants
During sensible cooling of air ________ decreases.
Wet bulb temperature
Relative humidity
Dry bulb temperature
Specific humidity
One tonne of refrigeration (1TR) means that the heat removing capacity is
21 kJ/min
210 kJ/min
420 kJ/min
620 kJ/min
In actual air-conditioning applications for R-12 and R-22, and operating at a condenser temperature of 40° C and an evaporator temperature of 5° C, the heat rejection factor is about
1
1.25
2.15
5.12
In a vapour compression system, the condition of refrigerant is dry saturated vapour
Before entering the compressor
After leaving the compressor
Before entering the condenser
After leaving the condenser
The operating pressure for refrigerating units using R-12 as a refrigerant is
2 bar
8 bar
15 bar
30 bar
For evaporators and condensers, for the given conditions, the logarithmic mean temperature difference (tm) for parallel flow is ________ that for counter flow.
Equal to
Less than
Greater than
None of these
The C.O.P. of an absorption type refrigerator is given by (where T₁ = Temperature at which the working substance receives heat, T₂ = Temperature of cooling water, and T₃ = Evaporator temperature)
[T₁ (T₂ - T₃)] / [T₃ (T₁ - T₂)]
[T₃ (T₁ - T₂)]/ [T₁ (T₂ - T₃)]
[T₁ (T₁ - T₂)] / [T₃ (T₂ - T₃)]
[T₃ (T₂ - T₃)] / [T₁ (T₁ - T₂)]
The temperature of ammonia after compression in a vapour compression system is
20 to 50°C
50 to 70°C
70 to 110°C
None of these
R-12 is generally preferred over R-22 in deep freezers since
It has low operating pressures
It gives higher coefficient of performance
It is miscible with oil over large range of temperatures
All of the above
The lowest temperature during the cycle in a vapour compression system occurs after
Compression
Expansion
Condensation
Evaporation
For proper refrigeration in a cabinet, if the temperature and vapour pressure difference between cabinet and atmosphere is high, then
Bigger cabinet should be used
Smaller cabinet should be used
Perfectly tight vapour seal should be used
Refrigerant with lower evaporation temperature should be used
The wet bulb temperature during sensible cooling of air
Remains constant
Increases
Decreases
None of these
The process, generally used in summer air conditioning to cool and dehumidify the air, is called
Humidification
Dehumidification
Heating and humidification
Cooling and dehumidification
The difference between dry bulb temperature and wet bulb temperature, is called
Dry bulb depression
Wet bulb depression
Dew point depression
Degree of saturation
Wet bulb temperature is the temperature of air recorded by a thermometer, when
It is not affected by the moisture present in the air
Its bulb is surrounded by a wet cloth exposed to the air
The moisture present in it begins to condense
None of the above
Which of the following refrigerant has the highest freezing point.
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be
1.33
2.33
3.33
4.33
For obtaining high COP, the pressure range of compressor should be
High
Low
Optimum
Any value
In order to cool and dehumidify a stream of moist air, it must be passed over the coil at a temperature
Which lies between the dry bulb and wet bulb temperatures of the incoming stream
Which lies between the wet bulb and dew point temperatures of the incoming stream
Which is lower than the dew point temperature of the incoming stream
Of adiabatic saturation of incoming stream
In Electrolux refrigerator
Ammonia is absorbed in hydrogen
Ammonia is absorbed in water
Ammonia evaporates in hydrogen
Hydrogen evaporates in ammonia
The difference between dry bulb temperature and dew point temperature, is called
Dry bulb depression
Wet bulb depression
Dew point depression
Degree of saturation
The C.O.P. of a Carnot refrigerator in winter will be _________ as compared to C.O.P. in summer.
Same
Lower
Higher
None of these
The bypass factor, in case of sensible cooling of air, is given by (where td₁ = Dry bulb temperature of air entering the cooling coil, td₂ = Dry bulb temperature of air leaving the cooling coil, and td₃ = Dry bulb temperature of the cooling coil)
(td₁ -td₃)/( td₂ -td₃)
(td₂ -td₃)/( td₁ -td₃)
(td₃ -td₁)/( td₂ -td₃)
(td₃ -td₂)/( td₁ -td₃)
A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg)
25 kJ/kg
50 kJ/kg
100 kJ/kg
125 kJ/kg
It is desired to condition the outside air from 70% relative humidity and 45° C dry bulb temperature to 50% relative humidity and 25° C dry bulb temperature (room condition). The practical arrangement will be
Dehumidification
Cooling and humidification
Cooling and dehumidification
Dehumidification and pure sensible cooling
As relative humidity decreases, the dew point temperature will be ________ wet bulb temperature.
Same as
Lower than
Higher than
None of these
The evolution of heat of solution takes place in ammonia absorption plant when
Ammonia vapour goes into solution
Ammonia vapour is driven out of solution
Lithium bromide mixes with ammonia
Weak solution mixes with strong solution
Which of the following statement is correct for ammonia as a refrigerant?
It is toxic to mucous membranes.
It requires large displacement per TR compared to fluoro carbons.
It reacts with copper and its alloys.
All of these