Attempt any three 0f the fallowing parts (Answer to each p art should not exceed 200 words)
20x3=60
A solar-powered refrigeration system is run by heal transfer QH 110m solar collector at temperature 400 K and rejects QA heal at 300 K. It receives heat qc space at 110m cold space a l200 K Assuming the cycle to be reversible, and using 1" law of thermodynamics and ClausiUs in quality, find the ratio

Calculate the decrease is available energy when 25 kg of water at 97°C is miXed with 35 kg of water at 47°C, the pressure being constant and temperature of surrounding is 25°C Specific heat of water! SC 4 2 kJikg-K
Describe various stages 0f combustion in C.I. engine by illustrating on pressure-crank angle diagram. Discuss the effect of following operating variables on the first stage of combustion ignition advance compressiOn ratio speed
The brake thermal efficiency of a diesel engine iS 30% if the air to fuel ratio by WeightlS 20 and the calorific value of fuellS 41800 kJikg, find brake mean effective pressure at S.TP (15°C and 760 nun of Hg)

air at 17°C and I I bar occupies 0 05m3 The air lS first heated at constant volume until the pressure lS 4.4 bar and then cooled at constant pressure back to original temperature Calculate the net heat transfer to or 110m the air and the net entropy change Given that for air C 1.005 and C 0.718 kj/kg-k
Two reversible heat engines A and B are arranged in series. Heat engine A rejects heat directly to B. Engine A receives 300 kJ of heat at a temperature of 427°C 110m a high temperature source while engine B rejects heat to a cold in m k at 7°C. If the work oUllut 0f A lS two times that of find intermediate temperature between A and efficiency of each engine, heat rejected by engine A and received by engine B and heat rejected to the sink
A SiX cylinder, four stroke petrol engine with a bore of 120 nun and stroke of 180 mm under tests, iS supplied petrol of composition: C 82% and 18% by mass. The orsat gas analySiS indicated that CO, and 84% by volume. Determine that air­fuel ratio and the percentage of excess air also calculate the volumetric efficiency of engine based on mistake conditions when the mass flow rate of petrol 32 kg/mm at 1600 RPM. Intake conditions are I bar and 17°C ConSider the denSity of petrol vapour to be 3.5 times that of air at same temperature and pressure. air contains 23% oxygen by mass

The venture of a sample carburettor has a throat diameter of 20mm and the fuel orifice has a diameter of 1 12 mm The level of petrol surface 1n the float chamber is 6 0 mm below the throat venturi. Coefficients of discharge for venturi nd fuel orifice are 0.85 and 0.78 respectively. Specific gravity ofpelrollS 0.75. Calculate (i)the air-fuel ratio for a pressure drop of 008 bar, petrol consumption 1n kg/hr and the critical of velocity The mistake conditions are lOb at" and 17°e For air Cp 1 005 and Cv 0.718 kJikg-k

4.(a)an e1ght cylinder auto mobile engine of 80 mm diameter and 90 mm stroke With a compreSSiOn rarion of7, is tested 814000 RPM on a dynamometer of 600 mm arm length During a ten minutes test peroid at a dynamometer scale reading 0f 450 N,48 kg0f gasoline having a calorific value of 45000 kJikg was burnt and air at 27c and 1.0 bar was supplied to the carburettor at the rate of 6.6 kg/mm Find the brake power delivered, the brake mean effective pressure, the brake specific fuel consumption, brake thermal efficiency, the volumetric efficiency and the air-fuel ratio
A salesman reports that he has a steam turbine that delivers 3 MW. The steam enters the " turbine at 6.0 bas, 260°C and leaves the turbine at 0 15 bar and the reqUired rate of steam flowlS 12000 kg/hr Find the m3111mum power output of turbine to Justify his claim Also, verify his claim if the steam flow rate lS 20,000 kg/hr

SECTION B
Answer any three of the folloWlng parts (Answer to each part should not exceed 200 words) 20x3=60
Show that the effectiveness of a parallel flow heat exchangerlS given by
<img src='./qimages/1117-5a.jpg'>
Define Reynolds number, Prandtl number, Stanton number and Nusselt number, and give their phYSical Significance. WhatlS meant by fully developed flow in a pipe? illustrate it with the help of a figure State the parameters upon which the entrance length depends

What iS the role of a cooling tower in a power plant? What iS meant by range and approach and what purpose does the fill serve m a cooling tower?
Discuss the trends m the deSign of modem power plant boilers. Explain the zones of heat transfer and 10 cation 0f evaporators, super heaters and reheater
Calculate the number of tubes reqU1red for a single pass steam condenser of 25m length to handle 20000 hg/hr of dry saturated steam at 60°C The cooling water enters the tubes at 20°C and leaves at 30°C. The tubes are of 25 mm outSide diameter and 22 5 mm lnSide diameter The thermal conductivity of tube matenallS 100 The water velocity lS 1 5 m/s Assume that the steam Side film coefficlentlS 4500 For water use, Nu= 0023 ReO8 pr0.4 The properties 0f water at25°C are p=996 95kg/m3, C=4178J/kg-K, k 60.78 10-2 v 0 9055 x 10-6 Pr 6 22, hfg (at 60 2358.5 kj/kg
A small hemilspherical oven lS built of two insulating materials. The inner layer lS of fire brick, 125 mm thick and outer 1ayer of 85% magneSia, 40 mm thick The lMer surface 0f the oven lS at 800°C and the heat transfer coefficient for the outer surface is 10 The room temperature lSI 20° C. Calculate the heat loss through hemlSphere IS the mSide radius lS 0.6 m The thermal conductivities of fire brick and 85% magneSia are 0.31 and 0 05 respectively. Also, calculate the temperature at contact between insulating materials and at the outer surface
In a refrigeration system of 10 TR cooling capacity using CHC1F" the evaporator and condenser temperatures are _10°C and 45°C respectively. Properties 0f CHC1F, at saturation are
<img src='./qimages/1117-7a.jpg'>
ConSider standard vapour compreSSiOn cycle With inlet to compressor as saturated vapour and inlet to expanSiOn valve as saturated liqUid. Assume that vapour may be treated as perfect gas is desuperheating process with average specific heat of 0 9335 kJikg-K show the cycle on T­sand p diagrams. Find compressor outlet temperature and enthalpy, mass flow rate of refrigerant, work reqUirement, condenser heat rejection COP and swept volume of compressor m m31s assuming 100% volumetric efficiency 30
In an air-conditioning system 30 m3/mm of fresh outdoor air introduced at 43°C dry-bulb temperature and 30% relative hUffildity The remaining air iS re-circulated from the room maintained at 25°C dry-bulb temperature and 50% RH. The by-p ass factor 0f the cooling coil lS 0.15 and apparatus dewpomtlS 118°C RSH 100 kW and RLH 15kW Determine humidity ratios for outdoor and room condition, DASH and DALH, ERSH and ERLH, supply air temperature, supply air volume flow rate using ERSH and temperature at Inlet to cooling coil by assuming the density of outdoor air and recalculated air to be the same. Given that saturation pressures of water at 25°C and 43°C are 3 1693 kPa and 8.6495 kPa respectively Show that process on psychrometric chart schematically Standard atmospheric pressure=101325bar. 30

Discuss the effect of pre-whirl on the performance of centrifugal compressors A single Sided centrifugal air compressor delivers 1800 kg of air per minute The air enters the eye 0f the Imp ell er axially at total pressure 0flO 0 kPa and total temperature 0f 29 0 K. The overall diameter of the Impeller lS 70 0 mm and it rotates at 1600 RPM The slip factor lS 0 9 and work input factor lS 1 1 isentropic efficiency lS 85%. Calculate power reqUired by the compressor, pressure coeffiCient and total pressure at delivery 30
Derive an expressiOn for the blade efficiency of a single row Impulse steam turbine assuming eqUiangular blades in terms of nozzle angle a" blade velocity coeffiCient K and blade speed ratio 1fa, 20° and K 0.9, what lS the ma111mum blade efficiency and corresponding blade angles? If the blade efficiency lS 85% of the maXimum value, what are the possible blade speed ratios for the same nozzle angle aI, blade velocity coeffiCient, K and eqUiangular blades? Also, find the corresponding blade angles 30