Best Book, Previous Year Questions, Important Topics for Refrigeration and Air Conditioning for GATE, IES

Hi, Today in this article I will share with you best books for Refrigeration and Air Conditioning(RAC) for GATE or IES/ESE, so here is the list

✅ Textbook of Refrigeration and Air-conditioning (M.E.) by S Chand
✅ Refrigeration and Air Conditioning by Prentice Hall India

Must Have Books for GATE Mechanical:

✅GATE Mechanical Previous Year Questions with Answers Book[Latest Edition]

✅A Handbook on Mechanical Engineering by Made Easy Publications

Table of Contents

Important Topics of Refrigeration and Air Conditioning for GATE

Heat Pump, Heat Engine & Refrigerator
VCRS (Vapour Compression Refrigeration System) Cycle
Refrigerants
VARS (Vapour Absorption Refrigeration System), RBC (Reversed Brayton Cycle)
Psychrometry (Relative and Absolute Humidity Most Important)

5 Tips for Preparation of Refrigeration and Air Conditioning for GATE

Tip- 1 You need to clear basic concept, first read books then watch videos for better understanding, while studying write on note book for much better grip on concept.

Tip- 2 Create your own note topic wise, and leave few pages in between chapters, I will recommend you to watch the below video for preparing better notes.

Tip- 3 First solve simple problems from books, only formula based preferably solved examples or you can even solve MCQ of ESE because questions are comparatively easier than GATE, to build concept of solving numerical as well as build confidence.

Tip- 4 Its time for solving GATE Previous year questions, here you need to separate two types of questions, questions those you can solved easily, questions those you can not solve and later put focus on questions those you can not solve easily(You can put red circle for identifying those questions).

Tip- 5 Don’t do this mistake, write test series if possible buy test series from two providers and after buying write all tests.

✅Recommended Readings 1- Best Books for GATE Mechanical 2020

✅Recommended Readings 2- Best Book of Mechanical Vibration for GATE

Important Formulas of Refrigeration and Air Conditioning

Refrigeration and Air Conditioning GATE Previous Year Questions

Q. (1) 134 a as the refrigerant. The refrigerant enters the compressor as saturated vapor and leaves the condenser as saturated liquid. The mass flow rate of the refrigerant is 0.2 kg/s. properties for R – 134 a are as follows.

The rate at which heat is extracted, in kJ/s from the refrigerated space is-

(a) 34.4 (b) 42.9

Q. (2) The power required for the compressor in kW is

(A) 5.94 (B) 1.83

Q. (3) A standard vapor compression refrigeration cycle operating with a condensing temperature of 35 degree C and an evaporating temperature of – 10 degree C develops 15 kW of cooling.The p-h diagram shows the enthalpies at various states. If the isentropic efficiency of the compressor is 0.75, the magnitude of compressor power (in kW) is _________ (correct to two decimal places).

Q. (4) Which one of the following is a CFC refrigerator?

(a) R- 502

(b) R- 290

(d) R- 744

Q. (5) A refrigerator uses R-134a as its refrigerant and operates on an ideal vapour-compression refrigeration cycle between 0.14 MPa and 0.8 MPa. If the mass flow rate of the refrigerant is 0.05 kg/s, the rate of heat rejection to the environment is _________ kW.

Given data: At P = 0.14 MPa, h = 236.04 kJ/kg, s = 0.9322 kJ/kg-K

At P = 0.8 MPa, h = 272.05 kJ/kg (superheated vapour)

At P = 0.8 MPa, h = 93.42 kJ/kg (saturated liquid)

Q. (6) In an ideal vapour compression refrigeration cycle, the specific enthalpy of refrigerant (in kJ/kg) at the following states is given as:

Inlet of condenser :283, Exit of condenser :116 Exit of evaporator :232 The COP of this cycle is

(a) 2.27 (b) 2.75 (c) 3.27 (d) 3.75

Q. (7) Refrigerant vapor enters into the compressor of a standard vapor compression cycle at − 10°C (h = 402 kJ/kg) and leaves the compressor at 50°C (h = 432 kJ/kg). It leaves the condenser at 30°C (h = 237 kJ/kg). The COP of the cycle is ________

Q. (8) Round the clock cooling of an apartment having a load of 300 MJ/day requires and air conditioning plant of capacity about

(a) 100 tons (b) 10 tons

Q. (9) Environment friendly refrigerant R-134 is used in the new generation domestic refrigerators. Its chemical formula is

(a) CHClF2 (b) C2Cl3F3

Q. (10) In the vapour compression cycle shown in the figure, the evaporating and condensing temperatures are 260 K and 310 K, respectively. The compressor takes in liquid-vapour mixture (state 1) and isentropically compresses it to a dry saturated vapour condition (state 2). The specific heat of the liquid refrigerant is 4.8 kJ/kg-K and may be treated as constant. The enthalpy of evaporation for the refrigerant at 310 K is 1054 kJ/kg

The difference between the enthalpies at state points 1 and 0 (in kJ/kg) is ____________

Q. (11) Ambient air is at a pressure of 100 kPa, dry bulb temperature of 30 degree C and 60% relative humidity. The saturation pressure of water at 30 degree C is 4.24 kPa. The specific humidity of air (in g/kg of dry air) is ________ (correct to two decimal places).

Q. (12) Air (at atmospheric pressure) at a dry bulb temperature of 40 degree C and wet bulb temperature of 20 degree C is humidified in an air washer operating with continuous water recirculation. The wet bulb depression (i.e. the difference between the dry and wet bulb temperature) at the exit is 25% of that at the inlet. The dry bulb temperature at the exit of the air washer is closest to

(a) 10 C (b) 20 C (c) 30 C (d) 25 C

Q. (13) The partial pressure of water vapour in a moist air sample of relative humidity 70% is 1.6 kPa, the total pressure being 101.325 kPa. Moist air may be treated as an ideal gas mixture of water vapour and dry air. The relation between saturation temperature (Ts in K) and saturation pressure (Ps in kPa) for water is given by ln(Ps /Po ) = 14.317 − 5304/Ts , where Po = 101.325 kPa. The dry bulb temperature of the moist air sample (in C) is __________

Q. (14) Dew point temperature is the temperature at which condensation begins when the air is cooled at constant

(a) volume (b) entropy (c) pressure (d) enthalpy

Q. (15) A sample of moist air at a total pressure of 85 kPa has a dry bulb temperature of 30°C (saturation vapour pressure of water = 4.24 kPa). If the air sample has a relative humidity of 65%, the absolute humidity (in gram) of water vapour per kg of dry air is _______

Q. (16) Atmospheric air at a flow rate of 3 kg/s (on dry basis) enters a cooling and dehumidifying coil with an enthalpy of 85 kJ/ kg of dry air and a humidity ratio of 19 grams/kg of dry air. The air leaves the coil with an enthalpy of 43 kJ/kg of dry air and a humidity ratio of 8 grams/kg of dry air. If the condensate water leaves the coil with an enthalpy of 67 kJ/kg, the required cooling capacity of the coil in kW is

(a) 75.0 (b) 123.8 (c) 128.2 (d) 159.0

Q. (17) Moist air at 35 C and 100% relative humidity is entering a psychrometric device and leaving at 25 C and 100% relative humidity. The name of the device is

(a) Humidifier (b) Dehumidifier

Q. (18) In a mixture of dry air and water vapor at a total pressure of 750 mm of Hg, the partial pressure of water vapor is 20 mm of Hg. The humidity ratio of the air in grams of water vapor per kg of dry air (gw/kgda) is __________

Q. (19) Air in a room is at 35 C and 60% relative humidity (RH). The pressure in the room is 0.1 MPa. The saturation pressure of water at 35 C is 5.63 kPa. The humidity ratio of the air (in gram/kg of dry air) is ________

Q. (20) During the chemical dehumidification process of air (a) dry bulb temperature and specific humidity decreases

(b) dry bulb temperature increases and specific humidity decreases

(d) dry bulb temperature and specific humidity increases

Q. (21) The thermodynamic cycle shown in figure (T-s diagram) indicates

(A) reversed Carnot cycle (B) reversed Brayton cycle

Q. (22) The COP of a Carnot heat pump operating between 6 C and 37 C is ___________

Q. (23) A reversed Carnot cycle refrigerator maintains a temperature of −5 C. The ambient air temperature is 35 C. The heat gained by the refrigerator at a continuous rate is 2.5 kJ/s. The power (in watt) required to pump this heat out continuously is _______

Q. (24) A vapor absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the figure. A refrigeration effect of 100W is required at 250 K when the heat source available is at 400 K. Heat rejection occurs at 300 K. the minimum value of heat required (in W) is

(A) 167 (B) 100

Q. (25) An industrial heat pump operates between the temperatures of 27 C and 13 C. The rates of heat addition and heat rejection are 750 W and 1000 W, respectively. The COP for the heat pump is

(A) 7.5 (B) 6.5 (C) 4.0 (D) 3.0

Q. (26) A heat engine having an efficiency of 70% is used to drive a refrigerator having a coefficient of performance of 5. The energy absorbed from low temperature reservoir by the refrigerator for each kJ of energy absorbed from high temperature source by the engine is

(A) 0.14 kJ (B) 0.71 kJ (C) 3.5 kJ (D) 7.1 kJ

Q. (27) Clearance volume of a reciprocating compressor is 100 ml and volume of the cylinder at bottom dead centre (BDC) is 1 litre. Clearance ratio of the compressor is-

(A) 1/9 (B) 1/11 (C) 1/10 (D) 1/1.1

Q. (28) A thin layer of water in field is formed after a farmer has watered it. The ambient air conditions are: temperature 20 C and relative humidity 5%. An extract of steam tables is given below.

Neglecting the heat transfer between the water and the ground, the water temperature in the field after phase equilibrium is reached equals

(A) 10.3 C (B) -14.5 C (C) -10.3 C (D) 14.5 C

Q. (29) A heat pump with refrigerant R22 is used for space heating between temperature limits of −20 C and 25 C. The heat required is 200 MJ/h. Assume specific heat of vapour at the time of discharge as 0.98 kJ/kg.K. Other relevant properties are given below. The enthalpy (in kJ/kg) of the refrigerant at isentropic compressor discharge is _______

Q. (30) Match the list

List- 1

A. Liquid to suction heat exchanger

B. Constant volume heat addition

C. Normal shock

D. Ammonia water

List- 2

1. Vapour absorption refrigeration

2. Otto cycle

3. Vapour compression refrigeration

4. Diesel cycle

5. Converging Nozzle

6. Converging and diverging nozzle

Q. (31) Moist air is treated as an ideal gas mixture of water vapor and dry air (molecular weight of air = 28.84 and molecular weight of water = 18). At a location, the total pressure is 100 kPa, the temperature is 30 C and the relative humidity is 55%. Given that the saturation pressure of water at 30 C is 4246 Pa, the mass of water vapor per kg of dry air is _____________ grams

Q. (32) The pressure, dry bulb temperature and relative humidity of air in a room are 1 bar, 30 C and 70%, respectively. If the saturated steam pressure at 30 C is 4.25 kPa, the specific humidity of the room air in kg water vapour/kg dry air is

(A) 0.0083 (B) 0.0101 (C) 0.0191 (D) 0.0232

Q. (33) For a typical sample of ambient air (at 35 C (Ps = 0.05628 ), 75% relative humidity and standard atmospheric pressure), the amount of moisture in kg per kg of dry air will be approximately

(A) 0.002 (B) 0.027 (C) 0.25 (D) 0.75

Q. (34) Dew point temperature of air at one atmospheric pressure (1.013 bar) is 18 C. The air dry bulb temperature is 30 C. The saturation pressure of water at 18 C and 30 C are 0.02062 bar and 0.04241 bar respectively. The specific heat of air and water vapour respectively are 1.005 and 1.88 kJ/kg K and the latent heat of vaporization of water at 0 C is 2500 kJ/kg. The specific humidity (kg/kg of dry air) and enthalpy (kJ/kg of dry air) of this moist air respectively, are

(A) 0.01051, 52.64 (B) 0.01291, 63.15

Q. (35) Moist air at a pressure of 100 kPa is compressed to 500 kPa and then cooled to 35 C in an after cooler. The air at the entry to the aftercooler is unsaturated and becomes just saturated at the exit of the aftercooler. The saturation pressure of water at 35 C is 5.628 kPa. The partial pressure of water vapour (in kPa) in the moist air entering the compressor is closest to

(A) 2.26 (B) 0.57 (C) 1.13 (D) 4.52

Q. (36) A room contains 35 kg of dry air and 0.5 kg of water vapor. The total pressure and temperature of air in the room are 100 kPa and 25 C respectively. Given that the saturation pressure for water at 25 C is 3.17 kPa, the relative humidity of the air in the room is

(A) 67% (B) 55% (C) 83% (D) 71%

Q. (37) A moist air sample has dry bulb temperature of 30 C and specific humidity of 11.5g water vapour per kg dry air. Assume molecular weight of air as 28.93. If the saturation vapour pressure of water at 30 C is 4.24 KPa and the total pressure is 90 KPa, then the relative humidity (in %) of air sample is

(A) 56.5 (B) 50.5 (C) 38.5 (D) 68.5

Q. (38) A stream of moist air (mass flow rate = 10.1 kg/s) with humidity ratio of 0.01 kg / kg dry air mixes with a second stream of superheated water vapour flowing at 0.1 kg/s. Assuming proper and uniform mixing with no condensation, the humidity ratio of the final stream (in kg /kg dry air ) is _____________

Q. (39) If a mass of moist air in an airtight vessel is heated to a higher temperature, then

(A) Specific humidity of the air increases

(B) Specific humidity of the air decreases

(D) Relative humidity of the air decreases

Q. (40) Atmospheric air from 40 C and 60% percent relative humidity can be bought to 20 C and 60% relative humidity by-

(A) Cooling and dehumidification process

(B) Sensible cooling process

(D) Adiabatic saturation process

Refrigeration and Air Conditioning Solution of GATE Previous Year Questions with Basic Concepts-

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