If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be
0.2
1.2
5
6
Correct Answer :
D. 6
Related Questions
The curved lines on a psychrometric chart indicates
Dry bulb temperature
Wet bulb temperature
Dew point temperature
Relative humidity
Which of the following refrigerant is highly toxic and flammable?
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
A one tonne refrigerating machine means that
One tonne is the total mass of machine
One tonne refrigerant is used
One tonne of water can be converted into ice
One tonne of ice when melts from and at 0° C in 24 hours, the refrigeration effect is equivalent to 210 kJ/min
Absorption system normally uses the following refrigerant
Freon-11
Freon-22
CO2
Ammonia
Choose the correct statement
A refrigerant should have low latent heat
If operating temperature of system is low, then refrigerant with low boiling point should be used
Pre-cooling and sub-cooling bf refrigerant are same
Superheat and sensible heat of a refrigerant are same
In a psychrometric process, the sensible heat added is 30 kJ/s and the latent heat added is 20 kJ/s. The sensible heat factor for the process will be
0.3
0.6
0.67
1.5
In a vapour compression system, the condition of refrigerant before entering the expansion or throttle valve is
High pressure saturated liquid
Wet vapour
Very wet vapour
Dry vapour
The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called
Sub-cooling or under-cooling
Super-cooling
Normal cooling
None of these
The air cooling system mostly used in transport type aircrafts is
Simple air cooling system
Simple evaporative air cooling system
Bootstrap air cooling system
All of these
The vertical and uniformly spaced lines on a psychrometric chart indicates
Dry bulb temperature
Wet bulb temperature
Dew point temperature
Specific humidity
The wet bulb depression is zero when relative humidity is
Zero
0.5
0.75
1.0
The desirable property of a refrigerant is
Low boiling point
High critical temperature
High latent heat of vaporisation
All of these
The fluids used in Electrolux refrigerator are
Water and hydrogen
Ammonia and hydrogen
Ammonia, water and hydrogen
None of these
For better C.O.P of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be
Small
High
Equal
Anything
The sub-cooling in a refrigeration cycle
Does not alter C.O.P.
Increases C.O.P.
Decreases C.O.P.
None of these
The coefficient of performance is the ratio of the refrigerant effect to the
Heat of compression
Work done by compressor
Enthalpy increase in compressor
All of the above
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 heat rejection factor (HRF) is given by
1 + C.O.P
1 - C.O.P.
1 + (1/C.O.P)
1 - (1/C.O.P)
The process, generally used in winter air-conditioning to warm and humidity the air, is called
Humidification
Dehumidification
Heating and humidification
Cooling and dehumidification
The wet bulb temperature during sensible cooling of air
Remains constant
Increases
Decreases
None of these
Oil separator in a refrigeration cycle is installed
Before compressor
Between compressor and condenser
Between condenser and evaporator
Between condenser and expansion valve
In a lithium bromide absorption refrigeration system
Lithium bromide is used as a refrigerant and water as an absorbent
Water is used as a refrigerant and lithium bromide as an absorbent
Ammonia is used as a refrigerant and lithium bromide as an absorbent
None of the above
For obtaining high COP, the pressure range of compressor should be
High
Low
Optimum
Any value
Reducing suction pressure in refrigeration cycle
Lowers evaporation temperature
Increases power required per ton of refrigeration
Lowers compressor capacity because vapour is lighter
All of the above
Which of the following refrigerants has lowest freezing point?
Freon-12
NH3
CO2
Freon-22
The reciprocating refrigerant compressors are very suitable for
Small displacements and low condensing pressures
Large displacements and high condensing pressures
Small displacements and high condensing pressures
Large displacements and low condensing pressures
Which of the following statement is correct?
The constant enthalpy lines are also constant wet bulb temperature lines.
The wet bulb and dry bulb temperature are equal at saturation condition.
The wet bulb temperature is a measure of enthalpy of moist air.
All of the above
The refrigerant used in small tonnage commercial machines (hermetically sealed units) is
Ammonia
Carbon dioxide
Sulphur dioxide
R-12
Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since
These react with water vapour and cause acid rain
These react with plants and cause greenhouse effect
These react with oxygen and cause its depletion
These react with ozone layer
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