Q1:

In milk chilling plants, the usual secondary refrigerant is

Q2:

Air cooling is used for Freon compressors whereas water jacketing is adopted for cooling ammonia compressors. This is because

Q3:

Vapour absorption refrigeration system works using the

Q4:

Hydrogen is essential in an Electrolux refrigeration system beasuse

Q5:

Which one of the following statement regarding ammonia absorption system is correct?

Q6:

Consider the following statements:

In ammonia refrigeration system, oil separator is provided because

1. Oil separation in evaporator would lead to reduction in heat transfer coefficient.

2. Oil accumulation in the evaporator causes choking of evaporator.

3. Oil is partially miscible in the refrigerant.

4. Oil cause choking of expansion device.

Q7:

Consider the following statements:

1. Practically all common refrigerants have approximately the same COP and power requirement.

2. Ammonia mixes freely with lubricating oil and this helps lubrication of compressors.

3. Dielectric strength of refrigerant is an important property in hermetically sealed compressor units.

4. Leakage of ammonia can be detected by halide torch method.

Which of these statements are correct?

Q8:

Match List-I (Basic components of aqua-ammonia refrigeration system) with List-II (Functions of the components in the system) and select the correct answer using codes given below the lists:

List-I	List-II
A. Generator	1. Dehydration
B. Analyzers	2. Removal of vapour from strong aqua ammonia solution
C. Rectifier	3. Producing dry ammonia vapour by removing traces of water particles completely
D. Receiver	4. Storage of high pressure liquid ammonia
	5. Formation of liquid ammonia from high pressure vapours.

 

Q9:

Waste heat can be effectively used in which one of the following refrigeration system?

Q10:

The sensible heat factor of a room is given by (S.H.L = Sensible heat load and L.H.L. = Latent heat load)

Q11:

A single-acting two-stage compressor with complete inter cooling delivers air at 16 bar. Assuming an intake state of 1 bar at 15°C, the pressure ratio per stage is:

Q12:

In a centrifugal compressor assuming the same overall dimensions, blade inlet angle and rotational speeds, which of the following blading  will given the maximum pressure rise?

Q13:

Consider the following characteristics:

1. The fluid enters the pump axially and is discharged radially.

2. Maximum efficiency may be of the order of 90%.

3. Development of a low head

4. A limited suction capacity

Which of the above characteristics are possessed by axial flow pumps?

Q14:

In a vapour compression refrigeration system, the high pressure liquid from the condenser / receiver is cooled down below its saturation temperature to

Q15:

An ideal vapour compression refrigerator operates between a condenser pressure P₁ and an evaporator pressure P₂. Which of the following changes would increase its COP?

Q16:

A vapour compression refrigeration has a COP of 4 and extracts 10 KJ of heat from the cold reservoir. If this machine is worked as a heat pump , how much heat will it deliver to the environment ?

Q17:

State of wet vapour can not be specified only by

Q18:

In vapour compression refrigeration system, at entrance to which component the working fluid is superheated vapour?

Q19:

When a refrigerator system is started  from ambient conditions, the evaporator temperature decreases from ambient temperature to design value. This period is known as a pull-down period. The power require by compressor during pull-down period is

Q20:

Subcooling heat exchanger is used in  a refrigeration cycle. The enthalpies at condenser outlet and evaporator outlet are 78 and 182 kJ/kg respectively. The enthalpy at outlet of isentropic Compressor is 230 kJ/kg and enthalpy of sub cooled liquid is 68 kJ/kg. The COP of the cycle is

Q21:

A standard vapour compression refrigeration cycle consists of the following four thermodynamic processes in sequence

Q22:

Which one of the following is correct?

During sensible cooling of moist air, its relative humidity

Q23:

During sensible cooling of air,

Q24:

Consider the following statements regarding Psychrometric processes:

1. Sensible heating is a process in which moisture content remains unchanged.

2. In the dehumidification process the dew point temperature remains same.

3. The process of adding moisture at constant dry bulb temperature is known as pure humidification process.

Which of the statements given above is/are correct?

Q25:

Which one of the following is correct?

On Psychrometric chart, the constant wet bulb temperature lines coincide with.

Q26:

Consider the following statements in a Psychrometric  chart

1 Vertical lines indicate wet bulb temperature

2 Horizontal lines indicate specific humidity

3 Sensible heating or cooling is represented by an inclined line which of the statements given above is/are correct 

Q27:

When the wet bulb and dry bulb temperature are equal which of the following statements is/are correct?   

1. Air is fully saturated

2. Dew point temperature is reached

3. Partial pressure of vapour equal to the total pressure.

4. Wet bulb temperature and dry bulb temperature

Q28:

Air at state 1 (dpt 10°C, W = 0.0040 kg/kg_air) mixes with air at state 2 (dpt 18°C, W = 0.0051 kg/kg_air) in the ratio 1 to 3 by weight. The degree of saturation (%) of the mixture is (the specific humidity of saturated air at13.6°C, W = 0.01 kg/kg_air)

Q29:

If the volume of moist air with 50⁰ /₀ relative humidity is isothermally reduced to half its original volume then relative humidity of moist air become

Q30:

When the lower temperature is fixed. COP of a refrigerating machine can be improve by:

Q31:

The values of enthalpy at the beginning of compression, at the end of compression and at the end of condition are 185 kJ/kg, 210kJ/kg and 85 kJ/kg respectively. What is the value of the COP of the vapour compression refrigeration system?

Q32:

Assertion (A): In vapour compression refrigeration system throttle valve is used and not expansion cylinder.

Reason (A): Throttling is a constant enthalpy process. 

Q33:

The operating temperature of a cold storage is – 2⁰ C. Heat leakage from the surrounding is 30 kW for the ambient temperature of 40⁰ C .The actual COP of the refrigeration plant used is one fourth that of an ideal plant working between the same temperatures. The power required to drive the plant is:

Q34:

A capillary tube is employed in a refrigeration cycle to

Q35:

In a certain ideal refrigeration cycle. The COP of heat pump is 5. The cycle under identical condition as heat engine will have efficiency as

Q36:

The COP of a Carnet heat pump used for heating a room at 20⁰ C by exchanging heat with river water at 10⁰C is:

Q37:

In a reversible cycle the source temperature is 227⁰ C and the sink temperature is 27⁰ C .the maximum available work for a heat input  of 100 kJ will  be:

Q38:

A Carnot refrigerator works between the temperatures of 200 K and 300 K. if the refrigerator receives 1kW of heat the work requirement will be

Q39:

A refrigerating machine working on reversed carnot cycle takes out 2kW of heat from system at 200 K while working between temperature limits of 300 K and 200 then COP and power consumed by the cycle will be…….

Q40:

A refrigerating machine working on reversed cycle consumes 6kW to produce a refrigerating effect of 1000kJ min for maintaining a region are - 40⁰C the higher temperature (in degree centigrade) of the cycle will be :