Mechanical engineering : Refrigeration Online Test

Which of the following method (s) is/are adopted in the design of air duct system? 1.Velocity reduction 2. Equal friction 3. Static regain Select the correct answer using the codes given below
1 alone
1 and 2
2 and 3
1, 2 and 3
A valve which maintains a constant degree of superheat at the end of the evaporator coil is called
Automatic expansion valve
Thermostatic expansion valve
High side float valve
Low side float valve
Which of the followings is a false statement?
A flooded evaporator is bulky and requires a relatively large quantity of refrigerant
In the dry expansion evaporator, whole of the refrigerant gets gradually vaporized when it reaches the end of the coils
A bare tube evaporator consists of tues added between two plates which are welded together at the edges
Finned evaporators have more surface area per unit length and width than a bare tube or plate surface evaporator of some capacity
Suggest the condenser mostly used in the self-contained units like domestic refrigerators, water coolers and room air-conditioners
Air cooled condenser
Double pipe condenser
Shell and tube condenser
Evaporative condenser
Desert coolers are suitable for hot and dry outside conditions because
Water is recirculated in the spray
Heat is neither added to or removed from water
Large quantitiy of air can be conditioned
Wet bulb depression is very large
The drift loss in a cooling tower is about
2 to 5%
10 to 20%
20 to 30%
40 to 50%
The cooling effect in a cooling tower can be increased by reducing the humidity of air increasing the air velocity over the wall surface lowering the barometric pressure Select the correct answer using the codes given below:
1, 2
1, 3
2, 3
1, 2 and 3
/
1 and 2
1, 2 and 4
2, 3 and 4
1, 2, 3 and 4
The dissipation of heat in a cooling tower is mainly due to
Convection
Radiation
Condensation
Evaporation
A fibrous material such as glass wool having cardboard frames and retaining grills is used in
Throw-away or replaceable filters
Manually cleaned filters
Automatic or self-cleaning filters
Electrostatic filters
The filters used to arrest the impurities from air in an air-conditioning system are placed
At entry to the fan
Ahead of heating/ cooling coils
Behind the heating/cooling coils
Ahead or behind the heating/cooling coils
Which is not true in the context of axial flow fan?
Produces flow of air in a direction parallel to the axis of rotation
Suitable for handling large volumes
Quiet and efficient operation
Used in industrial ventilation and air conditioning system
Which is not the feature of unit air-conditioner?
Small units 1 ton to 3 ton capacity
Temperature control by means of a built in thermostat
Condensers are water cooled
Adjustable louvers provided to control the direction of air flow
Identify the air-conditioning system suitable for air conditioning large space such as theatres, cinemas, restaurants and exhibition halls etc.
Central
Unitary
Zonal
Unitary-central
The coefficient of performance of an air-conditioner as compared to a domestic refrigerator is
Low
High
May be low or high depending on the refrigerant used
Same
As compared to cold storage plant, air-conditioner of an auditorium requires air at
Low relative humidity and high temperature
High relative humidity and low temperature
High relative humidity and high temperature
Low relative humidity and low temperature
Which of the following is considered comfort conditions in air-conditioning
10oC dry bulb temperature and 50% relative humidity
15 oC DBT and 40% RH
20 oC DBT and 60% RH
25 oC DBT and 70% RH
The effective temperature is a measure of the combined effects of
Dry bulb temperature and relative humidity
Dry bulb temperature and air motion
Wet bulb temperature and air motion
Dry bulb temperature, relative humidity and motion
The operation theater in a hospital is to be air conditioned. Suggest the percentage of outside air in the air being circulated in the theatre
Zero
20
50
100
Ina 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
Sensible heat factor is defined as the ratio of
Sensible heat to total heat
Sensible heat to latent heat
Latent heat to total heat
Latent heat to sensible heat
The reason for a person feeling more comfortable on a warm day if seated in front of an electric fan is that the
Metabolic heat production is reduced
Body loses more heat by convection and evaporation
Body loses more heat by radiation
Body loses more heat by evaporation and radiation
A person feels comfortable when the heat produced due to metabolism of his body is equal to
Heat dissipated to surroundings
Heat stored in the body
Difference between heat dissipated to surroundings and heat stored in the body
Sum of heat dissipated to surroundings and heat stored in the body
/
1, 2 and 3
1 and 2
1 and 3
2 and 3
All of the following statements in the context of sensible cooling to dew point are correct, except
Dew point and specific humidity remain constant
Dry bulb temperature equals the wet bulb temperature
Relative humidity becomes 100 per cent
The air gets saturated and condensation of vapour commences
During the process of sensible cooling, air at dry bul temperature db1 passes over a cooling surface with average surface temperature db3 and leaves at a temperature db2. then the by-pass factor is given by
db1-db2/db3
db1-db2/db1-db3
db1-db2/db1-db3
Db2-db3/db1-db3
By pass factor of a cooling will decreases with
Increase in fin spacing and increase in number of rows
Increase in fin spacing and decrease in number of rows
Decrease in fin spacing and decrease in number of rows
Decrease in fin spacing and increase in number of rows
When the dry bulb and wet bulb temperature of air are same, then relative humidity of air will be
Zero percent
50 per cent
66.7 per cent
100 per cent
During sensible cooling of air, the coil efficiency is given by
1-BF
1+BF

1/BF
Where BF is the by pass factor
Which is not true in the context of sensible heating achieved by passing air over a dry surface which is at a temperature greater than its (air) dry bulb temperature?
Dry bulb and enthalpy increase
Wet bulb and dew point temperatures decrease
Relative humidity and percentage saturation decrease
Vapour pressure and moisture content remain constant
During the process of sensible heating air at dry bulb temperature db1 passes over a heating coil with average surface temperature db3. if the air leaves at temperature db2 then the by pass factor is given by
db2-db1/db3
db2-db1/db3-db1
db3-db2/db2-db1
db3-db2/db3-db1
Air at 20oC dry bulb temperature and 40% relative humidity is heated upto 40oC using an electric heater whose surface temperature is maintained uniformly at 45oC. the bypass factor of the heater is
0.2
0.25
0.88
1.0
The atmospheric air at dry bulb temperature 15oC enters a heating coil maintained at 40oC. if the air leaves the heating coil at 30oC the coil efficiency would be equal to
0.2
0.4
0.6
0.75
Which is not true in the context of sensible heating and sensible cooling?
No moisture is added to or removed from the air
Dew point temperature decreases
Vapour pressure remains constant
These processes plot as straight horizontal line on the psychrometric chart
All of the following statements pertaining to humidification process are correct except
Moisture is added
Dry bulb temperature remains unchanged
Specific humidity and relative humidity increase
Humidification process plots as an inclined line on the psychrometric
Which is false statement in respect of dehumidification process?
Moisture is removed
Dry bulb temperature remains unchanged
Specific humidity and relative humidity decrease
Enthalpy of saturation increases
Which is the false statement in relation to combined heating and humidification of moist air?
Moist air is made to pass over a surface heater with controlled injection of steam
Specific humidity and dry bulb temperature increase
Relative humidity decreases
This process is generally used in winter air conditioning to warm and humidify the air
During combined cooling with humidification process
Air passes through air washer
Specific humidity and relative humidity increase
Dry bulb temperature decreases
Dew point and wet bulb temperatures increase
The process generally used for summer air conditioning is
Cooling with humidification
Cooling with dehumidification
Adiabatic cooling or evaporative process
Chemical dehumidification
The mixin of two or more streams of moist air in air conditioning is
An isothermal process
An adiabatic process
A constant pressure process
A general polytropic process
Quite often atmospheric air is made to pass through a wet khas-khas or bamboo mat to render a surface cool in summer. Thermodynamically this process may be called
Sensible cooling
Cooling and humidification
Cooling and dehumidification
Adiabatic saturation
Line A represents
Sensible cooling
Humidification
Adiabatic cooling
Adiabatic mixing of two streams
Curve B represents________
Adiabatic cooling
Adiabatic mixing of two streams
Cooling and dehumidification
Chemical dehumidification
The combined heating a dumidification of moist air is represented by
Curve A
Curve B
Curve C
Curve D
The constant wet bulb temperature line D represents
Sensible cooling
Adiabatic cooling
Cooling and dehumidification
Chemical humidification
The constant wet bulb temperature line E represents
Cooling and dehumidification
Evaporative process
Mixing of two or more streams of air
Dehumidification by chemical substances
It is desired to condition the outside air from 70% relative and 45oC dry bulb to 50% relative humidity and 25oC dry bulb condition. The practical arrangement would be
Cooling and dehumidification
Cooling and humidification
Cooling alone
Dehumidification alone
In a spray washer system, the temperature of the water is noted to be higher than the dry bulb temperature. This suggests that the air is
Heated and dehumidified
Heated and humidified
Cooled and dehumidified
Cooled and humidified
The minimum temperature to which moist air can be cooled under ideal conditions in a spray washer is
Dew point temperature of inlet air
Wet bulb temperature of inlet air
Water inlet temperature
Water outlet temperature
All of the following statements are correct, except
Dew point is reached by cooling air at constant moisture content
A sensible factor of 0.8 means that 80% of total heat changes is due to sensible heat
The simultaneous addition of sensible heat and latent heat represents a heating and humidifying process
The combined process of cooling and humidifiying is known as spray cooling
Description:

this paper has 50 questions which are required to be finished in an hours time approximately.

Discussion

syed mohsin

its awesome

3504 days 2 hours 25 minutes ago

gagan

its good for preparing any kind of aptitude test for future.......

3651 days 3 hours 58 minutes ago

Kalyan Sarkar
Psychological interventions in Mathematics Study
User
33 Members Recommend
362 Followers

Your Facebook Friends on WizIQ

More Tests By Author

WizIQ Product Knowledge Assessment (WPKA)
90 Questions | 23 Attempts

GRE VOCAB (Antonyms + Analogies)
20 Questions | 1072 Attempts

AIEEE Maths: Algebra
10 Questions | 1275 Attempts