UNIT-1

1) An engine working on Otto cycle has a volume of 0.45m3,pressure 1bar and temperature 300c at the beginning of compression stroke. At the end of compression stroke, the pressure is 11bar and 210kJ of heat is added at constant volume . Determine

i) Pressure, temperatures and volumes at salient points in the cycle

ii) Efficiency. 16M MAY/JUNE-20072) i) Derive an expression for the air-standard efficiency of a Brayton cycle in terms of pressure ratio. 8M MAY/JUNE-2007 ii) Prove that the pressure ratio for maximum work is a function of the limiting temperature ratio. 8M MAY/JUNE-2007 3) An engine 20cm bore and 30cm stroke works on Otto cycle. The clearance volume is 1600cu cm. The initial pressure and temperature are 1bar and 600C. If the maximum pressure is limited to 24bar,find the following: I) The air standard efficiency of the cycle II) The mean effective pressure of the cycle. 16M NOV/DEC-2007

5) A gas turbine works on an air standard Brayton cycle. The initial condition of the air is 250c and 1bar.The maximum pressure and temperature are limited to 3bar and 6500c.Determine the following:

(i) Cycle efficiency

(ii) Heat supplied and heat rejected/kg of air (iii) Work output/kg of air

(iv) Exhaust temperature. 16M NOV/DEC-2007

4) Air at 1.01bar ,200c is admitted into an oil engine, which is working on the dual combustion cycle. The maximum cycle pressure is 69bar. The compression ratio is 18. Assuming that the heat added at constant volume is equal to the heat added at constant pressure; Calculate the following:(i) Temperature at all salient points

(ii) Total heat supplied

(iii) Heat rejected

(iv) Air standard efficiency. 16M APRIL/MAY-20085) i) Draw the theoretical and actual pV diagram of a four stroke Otto cycle engine and explain the reasons for the deviations. 12M

ii) Calculate the ideal air standard cycle efficiency based on the Otto cycle for a petrol engine with a cylinder bore of 50mm, a stroke of 75mm,and a clearance volume of 21.3mm3. 4M APRIL/MAY-2008

6) Sketch the diesel cycle on P-V and T-S diagrams and derive the expression for its mean effective pressure. 16M NOV/DEC-2008

7) A dual combustion air standard cycle has a compression ratio of 10.The constant pressure part of combustion takes place at 40bar. The highest and lowest temperatures of the cycle are 17270c and 270c respectively. The pressure at the beginning at the compression is 1bar . Calculate :i) The pressure and temperature at the key points of the cycle.ii) The heat supplied at constant pressure,

iii) The heat supplied at constant volume,

iv) The heat rejected,

v) The work output,

vi) The efficiency , and

vii) Mep. 16M NOV/DEC-20088) (i) Fuel supplied to an SI engine has a calorific value 42,000KJ/kg. The pressure in the cylinder at 30% and 70% of the compression stroke are 1.3bar and 2.6bar respectively. Assuming that the compression follows the law pV 1.3 = constant. Find the compression ratio, if the relative efficiency of the engine compared with the air-standard efficiency is 50%. Calculate the fuel consumption in kg/KW-hr. 12M (ii) A gas engine working on the Otto cycle has a cylinder of diameter 0.2m and stroke 0.25m. The clearance volume is 1580cc. Find the air standard efficiency. Assume Cp=1.004KJ/kgK and Cv=0.717KJ/kgK for air. 4M MAY/JUNE-2009 9) i) A diesel engine has a compression ratio of 20 and cut-off takes place at 5% of the stroke. Find the air standard efficiency. Assume = 1.4 6Mii) In an engine working on the diesel cycle, the ratio of the weight of air and fuel supplied is 50:1 . The temperature of air at the beginning of the compression is 333K and the compression ratio used is 14:1 . What is the ideal efficiency of the engine for caloric value of fuel used is 4200KJ/kg. Assume Cp=1.004KJ/kgK and Cv=0.717KJ/kgK for air. 10M MAY/JUNE-200910) Derive an expression for the air standard efficiency of Diesel cycle and then deduce it for mean effective pressure. 16M NOV/DEC-201011) A six cylinder four stroke petrol engine has a swept volume of 300cubic cm per cylinder, a compression ratio of 10 and operates at a speed of 35000rpm. If the engine is required to develop an output of 73.5kW at this speed, calculate the cycle efficiency, the necessary rate of heat addition , the mean effective pressure , maximum temperature of the cycle and efficiency ratio. The pressure and temperature before isentropic compression are 1.0bar and 150c respectively, take Cv=0.72 and =1.4 16M NOV/DEC-201012) A four stroke, four cylinder petrol engine of 250 mm bore and 375 mm stroke works on Otto cycle. The initial pressure and temperature are 1 bar and 470c. If the maximum pressure is limited to 25 bar, find the

i) The air standard efficiency of the cycle

ii) Mean effective pressure. Take Cp = 1.005KJ/kg0K and =1.4 (16M) NOV/DEC-201113) In an air standard dual cycle, the pressure and temperature at the beginning of compression are 1 bar and 570c, respectively. The heat supplied in the cycle is 1250KJ.kg, two third of this being added at constant volume and rest at constant pressure. If the compression ratio is 16, determine ratio is 16, determine the maximum pressure , temperature in the cycle, thermal efficiency and mean effective pressure. 16M NOV/DEC-201114) In an engine working on Dual cycle, the temperature and pressure at the beginning of the cycle are 90oC and 1 bar respectively. The compression ratio is 9. The maximum pressure is limited to 68 bar and total heat supplied per kg of air is 1750 kJ. Determine

i) The pressure and temperature at all salient pointsii) air standard efficiency

iii) Mean effective pressure. 16M APRIL/MAY-2012

15) (a)Consider an air standard cycle in which the air enters the compressor at 1bar and 200c. The pressure of air leaving the compressor is 3.5 bar and the temperature at turbine inlet is 6000c. Determine per kg of airi) Efficiency of the cycle (3)ii) Heat supplied to air (2)

iii) Work available at the shaft (2)

iv) Heat rejected in the cooler, and (3)

v) Temperature of air leaving the turbine. (3) (b) The efficiency of an Otto cycle is 60% and =1.5. What is the compression ratio. (3M) APRIL/MAY-201216) A spark ignition engine working on ideal Otto cycle has the compression ratio 6. The initial pressure and temperature of air are 1 bar and 37oc. The maximum pressure in the cycle is 30 bar. For unit mass flow, calculatei) P,V and T at various salient points of the cycle and

ii) The ratio of heat supplied to the heat rejected. Assume =1.4 and R=8.314KJ/Kmol K. 16M NOV/DEC-2012

17) An air standard dual cycle has a compression ratio of 18, and compression begins at 1 bar, 400c. The maximum pressure is 85 bar. The heat transferred to air at constant pressure is equal to that at constant volume. Estimatei) The pressure and temperature at the cardinal points of the cycle

ii) The cycle efficiency and

iii) Mean effective pressure of the cycle 16M NOV/DEC-2012

18) Derive an expression for the air standard efficiency of diesel cycle. Explain why the efficiency of Otto cycle is more than that of the diesel cycle for the same compression ratio. 16M MAY/JUNE-2013 19) In an oil engine working on dual cycle, the heat supplied at the constant pressure is twice that of heat supplied at constant volume. The compression and expansion ratios are 8 and 5.3. The pressure and the temperature at the beginning of cycle are 0.93 bar and 270c. Find the efficiency of the cycle and mean effective pressure. Take Cp=1.005KJ/kgK and Cv =0.718KJ/kgK 16M MAY/JUNE-201320) An air standard Diesel cycle has a compression ratio of 18. The pressure at the beginning of compression stroke is 1 bar and the temperature is 300c .The heat supplied is 1800KJ/kg.Determine

i) The efficiency

ii) The pressure and temperature at all salient points

iii) Heat rejected

iv) Mean effective pressure. Assume Cp , CV ,R and suitably.16M NOV/DEC-201321) An Otto cycle has a compression ratio of 7. The initial pressure and temperature at the beginning of compression stroke is 1 bar and 4000c. The heat supplied is 2510KJ/kg.Findi) The maximum temperature and pressure

ii) Work done per kg of air

iii) The cycle efficiency

iv) Mean effective pressure. Take Cv =0.713KJ/kgK and R=287J/kg K. 16M NOV/DEC-2013

UNIT-2

1) Discuss the construction and working principle of a four stroke engine with sketch.16M NOV/DEC-2013

2) Explain the construction and working principle of battery coil ignition system with neat sketch. 16M NOV/DEC-2013

3) i) Explain the construction and working of fuel injector with a neat sketch.8M

ii)Draw and explain the port timing diagram of two stroke cycle diesel engine. 8M MAY/JUNE-20134) The following observations were taken during a test on a single cylinder four-stroke cycle engine having a bore of 300 mm and stroke of 450 mm.

Ambient air temperature = 220c Fuel consumption = 11kg/hr

Engine speed = 300rpm

CV of fuel = 42,000KJ/kg

Mean effective pressure = 6bar

Net brake load = 1.0kN Brake drum diameter = 2m

Quantity of jacket cooling water = 590kg/hr

Temperature of entering cooling water = 220c

Temperature of leaving cooling water = 700c

Quantity of air as measured = 225kg/hr

Specific heat of exhaust gas = 4050cRope diameter = 2cm

Deter mine indicated power, brake power, mechanical efficiency and draw a heat balance sheet on hour basis. 16M MAY/JUNE- 20135) Compare SI and CI engines with respect to

i) Basic cycle

ii) Fuel used

iii) Introduction of fueliv) Ignition

v) Compression ratio

vi) Speed

vii) Efficiency

viii) Weight 16M NOV/DEC-2012

6) Mention the various important qualities of food ignition system and with a neat sketch explain the battery and magneto ignition system. 16M NOV/DEC-2012

7) i)Explain the main difference between a two stroke cycle and four stroke cycle internal combustion engine.8Mii)Explain valve timing diagram for four stroke cycle spark ignition engine.8M APRIL/MAY-2012

8) In a constant speed compression ignition engine operating on four stroke cycle and fitted with band brake, the following observation were taken; Brake wheel diameter 60cm

Band thickness 5mm Speed 450rpm

Load on band 210N

Sparking balance reading30N

Area of indicator diagram 4.15cm2 Length of indicator diagram6.25cm Spring No.11,ie11bar/cm

Bore10cm

Stroke15cm

Specific fuel consumption 0.3kg/kW-hr

Heating value of fuel41800kJ/kg

Determine the brake power , indicated power, mechanical efficiency, the indicated thermal efficiency and the brake thermal efficiency. 8M

ii)Explain with the help of sketches ignition system for a spark ignition engine.8M APRIL/MAY-2012

9) I)Explain the working principle of a four stroke petrol engine. 12MII)What are the advantages of lubrication? 4M NOV/DEC-201110) I) With neat diagram, explain magneto ignition system. 10M

II) Compare between petrol and diesel engine. 6M NOV/DEC-2011

11) i)Explain the working principle of a four stroke engine.8Mii)With neat diagram explain the working of battery ignition system. 8M NOV/DEC-2010

12) i) Describe the working of Diesel fuel pump. 8M

ii)Explain the pressure feed lubrication system with a neat diagram. 8M NOV/DEC-201013) i) Compare four stroke and two stroke cycle engines. 9M

ii)Explain with a sketch the non-exhaust emission from a vehicle.7M MAY/JUNE-2009

14) An eight-cylinder, 4 is stroke engine of 0.09m bore and 0.08m stroke with a compression ratio of 7 is tested at 4500rpm on a dynamometer which has 0.54m arm. During a 10min test the dynamometer scale beam reading was 42kgf and the engine consumed 4.4kg of gasoline having a calorific value of 44,000KJ/kg. Air 300k and 1 bar was supplied to the carburetor at the rate of 6kg/min find the brake power delivered brake mean effective pressure, brake specific fuel consumption, brake specific air consumption, brake thermal efficiency, volumetric efficiency and the air fuel ratio.16M MAY/JUNE-200915) Explain why cooling is necessary in IC engine? With neat sketches describe the working of water cooling system used for a multi cylinder engine. Why should a pump and the thermostat be provided in the cooling system of an engine?(4+8+4) NOV/DEC-200816) The following details were noted in a rest on a four cylinder , four stroke engine, diameter = 100mm; stroke = 120mm; speed of the engine =1600rpm; fuel consumption = 0.2kg/min; fuel calorific value = 44,00KJ/kg; difference in tension on either side of the brake pulley = 40kgf ; brake circumference is 300cm. If the mechanical efficiency is 80%, calculatei) Brake thermal efficiency

ii) Indicated thermal efficiency

iii) Indicated mean effective pressure and

iv) Brake specific fuel consumption.16M NOV/DEC-2008

17) Describe the working of a simple carburetor and derive the expression for the Air-fuel ratio.16M APRIL/MAY-2008 UNIT-3

1) Steam expands isentropically in a nozzle from 1Mpa, 2500c to 10kpa. The flow rate of the steam is 1kg/s. Find the following when the inlet velocity is neglected.i) Quality of steam 6M

ii) Velocity of steam at exit of the nozzle5M

iii) Exit area of the nozzle.5M NOV/DEC-2013

2) Explain the pressure and velocity compounding diagram of a multi-stage turbines with sketch.16M NOV/DEC-2013

3) I) What are the effects of friction in a nozzle? Explain.8M

II) A convergent divergent nozzle is required to discharge 2 kg of steam per second. The nozzle is supplied with steam at 7 bar and 1800c and discharge takes place against a back pressure of 1 bar. The expansion up to throat is isentropic and the frictional resistance between the throat and exit is equivalent to 63KJ/kg of steam. Taking approach velocity of 75m/s and throat of 4 bar, estimate:a) Suitable areas for the throat and exit, and

b) Overall efficiency of the nozzle based on the enthalpy drop between the actual inlet pressure and temperature and the exit pressure.8M MAY/JUNE- 20134) i) The velocity of steam leaving the nozzle of an impulse turbine is 1000 m/s and the nozzle angle is 200 . The blade velocity is 350 m/s and the blade velocity of coefficient is 0.85 . Assuming no losses due to shock at inlet, calculate for a mass flow of 1.5kg/s and symmetrical blading.

a) Blade inlet angle 3M

b) Driving force on the wheel 3M

c) Axial thrust in the wheel 3M

d) Power developed by the turbine 3M

ii) Differentiate between impulse and reaction turbine? 4M MAY/JUNE- 20135) Derive the condition for maximum discharge and the expression for maximum discharge in steam nozzle. 16M NOV/DEC-2012

6) I) Steam at a pressure of 10.5 bar and 0.95 dry is expanded through a convergent divergent nozzle. The pressure of steam leaving the nozzle is 0.85 bar. Find the velocity of steam at the throat for maximum discharge if the throat area is 1.2 cm2. Assume flow as isentropic and there are no friction losses. 12M

ii)Distinguish between impulse and reaction turbines. 4M NOV/DEC-20127) I) Explain the physical significance of Wilsons line as referred to super saturated flow through steam nozzles. 8M

ii)Steam enters a nozzle in a dry saturated condition and the expands from a pressure of 1 bar. It is observed that super- saturated flow is taking place and the steam flow reverts to a normal flow at 1 bar. What is the degree of under cooling and increase in entropy and the loss in the available heat drop due to irreversibility. 8M APRIL/MAY-20128) I) Describe briefly the various methods of steam turbine governing. 6M

II) 300kg/min of steam (2 bar, 0.08 dry) flows through a given stage of a reaction turbine. The exit angles blades as well as moving blades are 200 and 3.68KW of power is developed. If the rotor speed is 360 rpm and tip leakage is 5 percent, calculate the mean drum diameter and the blade height. The axial flow velocity is 0.8 times the blade velocity.10M APRIL/MAY-20129) Steam enters a convergent divergent nozzle at 2 MPa and 4000c with a negligible velocity and mass flow rate of 2.5 kg/s and it exits at a pressure of 300kPa. The flow is isentropic between the nozzle entrance and throat and overall nozzle efficiency is 93% . Determine i) Throat area and

ii) Exit area. 16M NOV/DEC-2011

10) The nozzle of a deLaval turbine deliver 1.5kg/s of steam of 800 m/s to a ring of moving blades having a speed of 200 m/s. The exit angle of the nozzle is 180. If the blade velocity coefficient is 0.75 and the exit angle of the moving blades is 250, calculatei) Inlet angle of moving and fixed blades

ii) Diagram efficiency

iii) Energy lost in blades per second

iv) Power developed and

v) Axial thrust on the turbine rotor. 16M NOV/DEC-2011

11) In a steam nozzle, the steam expands from 4 bar to 1 bar. The initial velocity is 60 m/s and initial temperature is 2000c . Determine the exit velocity if the nozzle efficiency is 92% and the dryness fraction at exit. 16M NOV/DEC-201012) A single row impulse turbine develops 132.4kW at a blade speed of 175 m/s using 2kg of steam per sec. Steam leaves the nozzle at 400m/s. Velocity coefficient of the blade is 0.9. Steam leaves the turbine blades axially. Assuming no shock determine the nozzle angle, blade angles at entry and exit. 16M NOV/DEC-2010

13) I) Derive an expression for maximum mass flow rate through convergent divergent nozzle for steam.12MII) Dry air at a pressure of 12 bar and 573k is expanded isentropically through a nozzle at a pressure of 2 bar. Determine the maximum mass flow rate through the nozzle of 0.00015m2 area.4M MAY/JUNE- 200914) Dry saturated steam at a pressure of 8 bar enters a convergent - divergent nozzle and leaves it at a pressure of 1.5bar. If the flow is isentropic , and the corresponding expansion index is 1.135; find the ration of cross-sectional area at exit and throat for maximum discharge. 16M MAY/JUNE- 200915) Dry saturated steam at 2.8 bar is expanded through a convergent nozzle to 1.7 bar. The exit area is 3cm2. Estimate the exit velocity and the mass flow rate, assuming isentropic expansion and supersaturated flow exits. 16M NOV/DEC-2007

UNIT-4

1) In a two stage compressor in which inter-cooling is perfect , prove that work done in the compressor is minimum when the pressure in the inter-cooler is geometric mean between the initial and final pressure. Draw the p-V and T-s diagram for TWO stage compression.16M NOV/DEC-20132) Explain the construction and working principle of multi-stage compressor and discuss the perfect and imperfect inter-cooling with neat sketch. 16M NOV/DEC-20133) A single acting reciprocating air compressor has a piston diameter of 200 mm and a stroke f300 mm and runs at 350 rpm . Air is drawn at 1.1 bar pressure and is delivered at 8 bar pressure. The law of compression is pV 1.35 = constant and clearance volume is 6% of the stroke volume. Determine the mean effective pressure and the power required to drive the compressor. 16M MAY/JUNE- 20134) Derive the work done by a two stage reciprocating air compressor with inter-cooler and derive the condition for minimum work input and the expression for minimum work required for two stage reciprocating compressor? 16M MAY/JUNE- 20135) A single acting two stage air compressor deals with 4 m3/min of air at 1.013 bar and 150c with a speed of 250 rpm. The delivery pressure is 80 bar .Assuming complete inter-cooling. Find the minimum power required by the compressor and the bore and stroke of the compressor. Assume a piston speed of 3m/s ,mechanical efficiency of 75% and volumetric efficiency of 80% per stage . Assume the polytropic index of compression in both the stages to be n = 1.25 and neglect clearance. 16M NOV/DEC-20126) Explain with neat sketch the construction and working of Roots blower with two lobe and three lobe rotor and Vane type compressor. 16M NOV/DEC-2012

7) A two cylinder single acting air compressor is to deliver 16 kg of air per minute at 7 bar from suction conditions 1 bar and 150c. Clearance may be taken as 4% of stroke volume and the index for both compression and re-expansion as 1.3. Compressor directly coupled to a four cylinder four stroke petrol engine which runs at 2000 rpm with a brake mean effective pressure of 5.5 bar. Assuming a stroke bore ratio of 1.2 for both engine and compressor and a mechanical efficiency of 82% for compressor , Calculate the required cylinder dimensions.16M APRIL/MAY-20128) I) Prove that the work done/kg of air in a compressor is given by

W = RT(n/n-1)[( rp) n-1/n - 1] where rp = pressure ratio. 8M II) A single stage single acting air compressor delivers 0.6 kg of air per minute at 6 bar. The temperature and pressure and the end of suction stroke are 300c and 1 bar. The bore and stroke of the compressor are 100 mm and 150 mm respectively. The clearance is 3% of the swept volume . Assuming the index of compression and expansion to be 1.3 , find:

a) Volumetric efficiency of the compressor 3M

b) Power required if the mechanical efficiency is 85% ,and 3M

c) Speed of the compressor. 2M APRIL/MAY-2012

9) A single stage, single acting reciprocating air compressor has a bore of 20cm and stroke of 30 cm. The compressor runs at 600 rpm. The clearance volume is 4% of the swept volume and the index if compression and expansion is 1.3. The suction conditions are 0.97 bar and 270c and delivery pressure is 5.6 bar. The atmospheric conditions are at 1.01 bar and 270c . Determine i) The free air delivered in m3/min

ii) The volumetric efficiency referred to the free air conditions

iii) The indicated power 16M NOV/DEC-201110) 2 kg/s of air enters the LP cylinder of a two stage, reciprocating air compressor. The overall pressure ratio is 9. The air at inlet to compressor is at 100 kPa and 350c . The index of compression in compressor is 1.3 . Find the intercooler pressure for perfect intercooling . Also , find the minimum power required for compression, and percentage saving over single stage compression. Take R=0.287KJ/kg0K and Cp=1 KJ/ kg0K. 16M NOV/DEC-201111) A Single acting reciprocating air compressor has clearance volume 5% of stroke volume of 0.05 m3/sec, the intake conditions are 95kN/m2, 300K. The delivery pressure is 720kN/m2. Determine the volumetric efficiency referred to

i) atmospheric conditions of 100 N/m2 and 290kii) Intake conditions

iii) FAD and

iv) Power required to drive the compressor, if the ratio of actual to indicated power is 1.5. Take index of compression expansion as 1.3. 16M NOV/DEC-201012) A single acting 14 cm 10 cm reciprocating compressor is operating at p1 = 1bar, T1 =200C, P2 = 6 bar and T2 = 1800 c. The speed of compressor is 1200 rpm and shaft power is 6.25 kW. If the mass of air delivered is 1.7 kg/min , calculate the actual volumetric efficiency , the indicated power , the isothermal efficiency , the mechanical efficiency and the overall efficiency. 16M NOV/DEC-201013) A single stage, single acting reciprocating air compressor has a bore of 0.2 m and stroke of 0.3 m. It receives air at 1 bar and 293k and delivers it at 5.5 bar. If the compression follows the law pV 1.3 = constant and clearance volume is 5% of the stroke volume . Determine the mean effective pressure and the power required to drive the compressor , if it runs at 500 rpm. 16M MAY/JUNE- 200914) i) Derive the expression for minimum work required for a two stage reciprocating air compressor. 12M

ii)Estimate the minimum work required to compress 1 kg of air from 1 bar and 300k to 16 bar in two stage , if the law of compression is pV 1.25 = constant and the inter cooling is perfect. Take R=287J/kg K. 4M MAY/JUNE- 200915) i) Define Relative Humidity, Dew point temperature and Wet Bulb temperature. 6M

ii)100 m3 of air per minute at 150c DBT and 80% R.H is heated until its temperature is 220c . Calculate heat added to air per minute , R.H of the heated air and wet bulb temperature of the heated air. 10M APRIL/MAY-200822) i)Explain with suitable sketches the of two stage air compressor with actual P-v diagram. MAY/JUNE-2006

ii)A single acting single stage compressor is belt driven from an electric motor at 400rpm.The cylinder diameter is 15cm and the stroke 17.5 cm .The air compressed from 1bar to 7bar and the law of compression pV 1.3 =constant. Find the power of motor, if transmission efficiency is 97% and the mechanical efficiency of the compressor is 90% Neglect clearance effects. MAY/JUNE-2006

UNIT-5

1) Explain the construction and working of vapour compression refrigeration with neat sketch. 16M NOV/DEC-2013

2) The temperature limits of ammonia refrigeration system are 250c and -100c . If the gas is dry at the end of compression. Calculate the COP of the cycle assuming no under cooling of the liquid ammonia. The properties of Ammonia are given below 16M NOV/DEC-2013 Temperature

in oc Liquid heat KJ/kgLatent heat KJ/kg Liquid entropy KJ/kgK

25298.901166.941.2420

-10135.371297.680.5443

3) I) What are the properties of a good refrigerant? 4MII)An Ammonia refrigerator produces 30 tons of ice at 00c is from c in a day of 24 hours. The temperature range in the compressor is from 250c to -150c . The vapour is dry saturated at the end of compressor. Assume a COP of 60% of theoretical value. Assume latent heat of ice as 335 KJ/Kg. For properties of NH3 , refer the table below 12M MAY/JUNE-2013Temperature in oc hf

KJ/kg hg

KJ/kg

sf

KJ/kgK sg

KJ/kgK

25298.91465.81.1245.039

-15112.341462.50.45725.549

4) An office is to be air-conditioned for 50 staff when the outdoor conditions are 300c DBT and 75% RH if the quantity of air supplied is 0.4 m3/min/person, find the following:a) Capacity of the cooling coil in tones of refrigeration. 4Mb) Capacity of the heating coil in KW

4M

c) Amount of water vapour removed per hour.

4M

Assume the required air inlet conditions are 200c DBT and 60% RH. Air is conditioned first by cooling and dehumidification and then by heating.

d)Describe the factors that affect human comfort.

4M MAY/JUNE-20135) I)Explain the construction and working of vapour absorption refrigeration system with neat sketch. 10MII) Write the advantages and disadvantages of vapour absorption and vapour compression refrigeration system. 6M NOV/DEC-20126) Explain the construction and working of summer and winter air conditioning systems. 16M NOV/DEC-20127) I) Discuss the function of absorber in vapour absorption refrigeration system. 4M II)A Freon -12 refrigerator producing a cooling effect of 20 KJ/s operates on a simple cycle with pressure limits of 1.509 bar 9.607 bar. The vapour leaves the evaporator dry saturated and there is no under cooling . Determine the power required by the machine. If the compressor operates at 300 rpm and has a clearance volume of 3% of compressor assume that the expansion following the law pV1.13 = constant . 12M APRIL/MAY-2012Properties of Freon -12:

Temperature in 0cPs barVg m3/kg hf

KJ/Kghg KJ/kgSf KJ/kg/KSg KJ/kg/KSpecific heat , KJ/kg/K

-201.5090.108817.8178.610.0730.7082 _

409.607 _74.53203.050.27160.6820.747

8) a)For a summer air conditioning installation for industrial application the following data is given:

Room Design 50% RH, 260C DBT

Outside Design 10% RH, 400C DBT

Room sensible heat gain 40Kw

Room latent heat loss 10kW

50% of return air from the room is mixed with outdoor air and pre cooled sensibly in a cooling coil to 280c before being passed through adiabatic washer. Determine

i) Supply air condition to the space

ii) Quantity of fresh out side air

iii) Refrigerating capacity of the pre cooler coil

iv) Humidifying efficiency of the adiabatic washer or evaporator cooler and entering and leaving conditions at the washer. 12M

b)Enumerate the main parts of the equipment in the air conditioning cycle. 4M APRIL/MAY-20129) A vapour compression refrigerator works between the pressure limits of 60 bar and 25 bar. The working fluid is just dry at the end of compression and there is no under cooling of the liquid before the expansion value. Determine 16M NOV/DEC-2011i) COP of the cycle and

ii) capacity of the refrigerator if the fluid is at the rate of 5 kg/mmPressure(bar) temperature(K) Saturation Enthalpy(KJ/Kg) Entropy(kj/kg 0K)

60

295

151.96 293.29 0.554 1.0332

25 261

56.32 332.58 0.2261.2464 10)a . In a heating application , moist air enters a steam having coil at 100c ,50% RH and leaves at 300c. Determine the sensible heat transfer , if mass flow rate of air is 100 kg of dry air per second. Also determine the steam mass flow rate if steam enters saturated at 1000c and condensate leaves at 800c. 8M b)The air enters a duct at 100c and 80% RH at the rate of 150 m3/min and is heated to 300c without adding or removing any moisture. The pressure remains constant at 1 atm. Determine the RH of air at exit from the duct and the rate of heat transfer. 8M NOV/DEC-201111) One kg of air at 350c DBT and 60% RH is mixed with 2kg of air at 200c DBT and 130c dew point temperature. Calculate the vapour pressure and dew point temperature of steam one ,enthalpy of both the steams and specific humidity of the mixture. 16M NOV/DEC-2010

12) The temperature range in a Freon 12 plant is -60c to270c. The compression is isentropic and there is no cooling of the liquid. Fins the COP assuming that the refrigerant (i) after compression is dry and saturated (ii) leaving the evaporator is dry and saturated. The properties of F-12 are given in the table 16M NOV/DEC-2010SI.NOt0chfhgSfSgCp

1-64135714.174.760.641

2274455854.284.750.714

13) Explain the working of Lithium Bromide water system with a schematic layout. 16M MAY/JUNE-200914) A vapour compression refrigerator uses R-12 as refrigerant and the liquid evaporates in the evaporator at 258K. The temperature of this refrigerant at the delivery from the compressor is 288K when the vapour is condensed at 283K. Find the coefficient of performance, if i) there is no under cooling

ii) the liquid is cooled by 278K before expansion by throttling. Take specific heat at constant pressure for the superheated vapour as 0.64KJ/kgK and that for liquid as 0.94KJ/kgK . The other properties of R-12 as follows 16M MAY/JUNE-2009 Temperature (k)Enthalpy(KJ/kg)Entropy(Kj/kgK)

LiquidVapourLiquidVapour

25822.3180.880.09040.7051

28345.4191.760.17500.6921

15)Explain with neat sketch practical Ammonia-water vapour absorption refrigeration system. Also bring out any four important difference between vapour compression and vapour absorption refrigeration systems. (12M+4M) NOV/DEC-2008