Set No. 1 IV B.Tech I Seester Suppleentary Exainations, Feb/Mar - 2015 REFRIGERATION & AIR CONDITIONING (Mechanical Eineeri) Tie: 3 hours Max. Marks: 75 Anser any FIVE Questions All Questions carry equal arks ***** 1 a) Explain the folloi ters i) Refrigeration effect ii) Ton of refrigeration iii) C.O.P b) With a neat sketch explain the or of Bell Coleann cycle and derive the expression for COP Enthalpy (kj/kg) Liquid vapour Liquid vapour 295 261 151.96 56.32 293.29 322.58 0.554 0.226 1.0332 1.2464 60 25 Entropy (kj/kg K) Saration Tep. (K) Pressure (Bar) 2 a) Distiuish beteen Dry and Wet copression in vapour copression refrigeration syste. b) A vapour copression refrigerator orks beteenthe pressure liits of 60 bar and 25 bar. The or fluid is just dry at the end of the copression and there is no under cooli of the liquid before the expansion valve. Deterine: i) C O P of the cycle and ii) Capacity of the refrigerator if the fluid flo is at the rate of 5 kg/in. Data: 3 a) Explain the role of refrigerants in the depletion if ozone layer b) With a neat sketch explain the or of therostatic expansion valve 4 a) With a neat sketch explain the or of a siple absorption refrigeration syste b) In absorption refrigeration syste, heati, cooli, and refrigeration take place at the teperares of 1500C, 300C, and -200C. Find the theoretical COP of the syste. If the heati teperare is increased to 2000C and refrigeration teperare is decreased to -400C, find the percentage chae in the theoretical COP. 1 of 2
Set No. 1 5 a) What are the advantages and disadvantages of stea jet refrigeration syste over other types of refrigeration syste b) A stea jet refrigeration syste is to supply 1200 kg per inute of chilled ater at 6.50C. The ake up ater fro the ains is at 270C. If the stea supply is available at 9.5 bar and 2000C and nozzle, entrainent and diffuser efficiency can be assued as 89%, 63% and 72% respectively, the quality of vapour enteri the ejector ay be assued 0.98, and condensate leaves the condenser at 330C. Deterine: i) Stea consuption in kg/hour and kg/hr per ton of refrigeration ii) Heat rejected in the condenser in kj/hr and kj/hr per ton of refrigeration 6 a) Explain the folloi ters i) Wet bulb teperare ii) Dry bulb teperare iii) Degree of saration iv) Relative huidity 3 0 b) 400 /in of air at 20 C DBT and 100C DPT coi out fro air conditioned hall is ixed ith 150 3/in of fresh air at 350C DBT and 45% relative huidity. Find a) enthalpy b) specific huidity c) specific volue d) DPT of the ixre 7 a) Explain the requireents of cofort air conditioni b) Air floi at the rate of 100 3/in at 400C DBT and 50% RH is ixed ith another strea floi at the rate 20 3/in at 260C DBT and 50%RH. The ixre flos over a cooli coil hose ADP teperare is 100C and by-pass factor is 0.2. Find DBT and RH of air leavi the coil. If this air supplied to an air-conditioned here DBT of 260C and RH of 50% are aintained, estiate (i) Roo sensible heat factor and (ii) Cooli load capacity of the coil in tones of refrigeration. 8 a) With a neat sketch explain the or of a bag type filter b) With a neat sketch explain the or of a ipact type huidifier 2 of 2
Set No. 2 Code No:R41031 IV B.Tech I Seester Suppleentary Exainations, Feb/Mar - 2015 REFRIGERATION & AIR CONDITIONING (Mechanical Eineeri) Max. Marks: 75 Tie: 3 hours Anser any FIVE Questions All Questions carry equal arks ***** 1 a) Explain the folloi ters i) Heat Pup ii) C.O.P b) In siple air refrigeration syste the regenerative cooli reduces the teperare of air fro the heat exchaer by 200 C before it expands through the cooli rbine. The air leaves the cabin at 270 C and the ra air teperare is 150 C. Obtain the aount of air bled fro the refrigeration and COP. If 0.5 Kg/s of air fro the ain copressor is used for the air conditioni. Calculate the poer requireent and tonnage of the syste. Take Pab= 0.8 bar, Pra= 1 bar, efficiency of copressor = 0.8, efficiency of rbine = 0.8, heat exchaer effectiveness is 0.75. The cool air leaves the regenerative heat exchaer at 270 C 2 a) Explain the effects of sub cooli and super heati on the perforance of a vapour copression refrigeration syste b) An aonia ice plant operates beteen a condenser teperare of 300C and an evaporator teperare of -200C. It produces 10 tons of ice per day fro ater at 250C to ice at -100C. Assui siple saration cycle, deterine i) the capacity of refrigerati plant ii) ass flo rate of refrigerant and iii) COP of the cycle. 3 a) Explain the desirable properties of ideal refrigerants. Write the properties of carbon dioxide refrigerant b) Write the advantages and disadvantages of centrifugal copressor over reciprocati copressor 4 a) With a neat sketch explain the or of Li-Br absorption refrigeration syste b) In a vapour absorption refrigeration syste, the refrigeration teperare is 150C. The generator is operated by solar heat here the teperare reached is 1000C. The teperare of the heat sink is 550C. What is the axiu possible COP of the syste? 1 of 2
Set No. 2 Code No:R41031 5 a) With a neat sketch explain the or of stea jet refrigeration syste b) With the help of graphs explain ho the perforance of stea jet refrigeration syste is affected varyi the evaporati and condensi teperares. 6 a) Explain the folloi i) cofort chart. ii) Zone of cofort for year round air conditioni. iii) Bypass factor 0 b) Air at 37 C, 44 percent relative huidity, is cooled to 230C by sprayi ater at 130C into it. The ixre pressure reains constant at 101.3 kpa. Assui that all of the ater evaporates and that the ixi occurs in an insulated duct, calculate the ass of ater added per logra of air. 7 a) Explain the factors governi optiu effective teperare b) An air-conditioned buildi has a space volue of 1000 3 and a roo sensible heat gain of 20 kw. The roo is aintained at 250C DBT and 50% RH. The outside design conditions are 430C DBT and 26.50C WBT. The ventilation air is 20% of the supply air.the apparas de point of the coil is 110C and its bypass factor is 0.1. Deterine: i) The state and ass flo rate of the supply air ii) The latent heat gain of the roo iii) The cooli load of the refrigeration plant 8 a) Differentiate beteen central, district and Unitary air-conditioni systes b) With a neat sketch explain the or of a forced evaporation huidifier 2 of 2
Set No. 3 IV B.Tech I Seester Suppleentary Exainations, Feb/Mar - 2015 REFRIGERATION & AIR CONDITIONING (Mechanical Eineeri) Max. Marks: 75 Tie: 3 hours Anser any FIVE Questions All Questions carry equal arks ***** 1 a) What are the advantages of dense air refrigeration syste over an open air refrigerati syste b) A siple air cooled syste is used for an aero plane to take a load of 10 tons. Atospheric teperare and pressure is 25 C and 0.9 at respectively. Due to rai the pressure of air is increased fro 0.9 at, to 1 at. The pressure of air leavi the ain copressor is 3.5 at and its 50% heat is reoved in the air-cooled heat exchaer and then it is passed through a evaporator for fure cooli. The teperare of air is reduced by 10 C in the evaporator. Lastly the air is passed through cooli rbine and is supplied to the cooli cabin here the pressure is 1.03 at. Assui isentropic efficiency of the copressor and rbine are 75% and 70%, find i) Poer required to take the load in the cooli cabin ii) COP of the syste. The teperare of air leavi the cabin should not exceed 25 C 2 a) Explain in detail all the four ethods to iprove the COP of a vapour copression refrigeration syste b) Under hat circustances the superheati of vapour before coi to copressor is ore objectionable? Mention the ays to prevent it. 3 a) Explain the role of refrigerants in global ari b) Explain the role of a condenser in a refrigeration syste. With a neat sketch explain the or of evaporative condenser 1 of 2
Set No. 3 Code No:R41031 4 a) With a neat sketch explain the or of triple fluid absorption refrigeration syste. Write its salient feares b) In an absorption type refrigeration syste, the heat supplied to NH3 generator by condensi stea at 2 bar and 0.9 dry. The teperare to be aintained in the refrigerator is -50C. The teperare of the atosphere is 300C. Find the axiu COP possible for the syste. If the refrigeration load is 20 tons and acal COP is 70% of ax COP, Find the ass of stea required per hour. 5 a) Derive the expression for findi the quantity of stea required per ton of refrigeration in a stea refrigeration syste b) With a neat sketch explain the or of Vortex be refrigerator. 6 a) Define the ter effective teperare and explain its iportance in air conditioni syste. Describe the factors hich affect effective teperare. b) 180 3 of air at 400C DBT and 15% relative huidity is passed through an adiabatic cooli pad and it coes out at 250C DB and 200C WBT. Find i) DPT of the air coi out ii) aount of ater vapour added into the air per inute. 7 a) Discuss the requireents of industrial air-conditioni b) A big hall ith 1200 seati capacity is to be air conditioned hen outdoor condition is 390C DBT and 200C WBT. The required inside condition is 200C DBT and 60% Relative huidity. The outdoor air supplied is 0.3 3/in/person. The required condition is achieved first by adiabatic huidification and then by cooli. Deterine i) capacity of cooli ii) capacity of huidifier 8 a) What are the different Heat pup circuits? Explain any one of the ith the help of neat sketch b) With a neat sketch explain the or of a echanical separator huidifier 2 of 2
Set No. 4 IV B.Tech I Seester Suppleentary Exainations, Feb/Mar - 2015 (Mechanical Eineeri) Tie: 3 hours REFRIGERATION & AIR CONDITIONING Max. Marks: 75 Anser any FIVE Questions All Questions carry equal arks ***** 1 a) The COP of air refrigeration syste is very lo, even then hy air refrigeration syste is ost coon in the aircraft. Explain? b) An air refrigerator or on the principle of Bell-Colean cycle. The air enters into the copressor 1 at at -10ºC. It is copressed to 10 at and cooled to 40ºC atthe sae pressure. It is then expanded to 1 at and discharged to take cooli load.the air circulation is 1 kg/s. The isentropic efficiency of the copressor = 80% The isentropic efficiency of the expander = 90% Find the folloi: i) Refrigeration capacity of the syste ii) C.O.P of the syste Take γ = 1.4, Cp = 1.00 kj/kg ºC 2 a) List out the advantages of vapour copression refrigeration syste over air refrigeration syste. b) With a neat sketch explain the or of a siple vapour copression refrigeration syste and derive the expression for COP.Also indicate the processes on a T-S diagra 3 a) Ho are refrigerants classified? Explain the properties of aonia refrigerant. b) Explain the role of an evaporator in a refrigeration syste? With a neat sketch explain the or of a flooded type evaporator 4 a) Write the advantages of absorption refrigeration syste over copression refrigeration syste. b) In absorption refrigeration syste, the heati in generator is carried out by usi stea at 3 bar and 85% dry. The refrigeration teperare is 100C. the condensation of the refrigeration is carried out at 300C usi cooli ater. Deterine i) axiu possible COP of the syste ii) if the stea leaves the generator as sarated ater at sae pressure, deterine the quality of stea required to run a plant of 20 tons. Assue relative COP as 0.4. 1 of 2
Set No. 4 5 a) With a neat sketch explain the or of stea jet refrigeration syste ith baroetric condenser. b) The folloi data is collected for stea jet refrigeration syste Stea condition supplied to nozzle = 7 bar and 0.95 dry Flash chaber (evaporator) ater teperare = 40C Teperare of akeup ater to flash chaber = 170C Pressure in condenser = 0.6 bar Nozzle, entrainent and copressor efficiency can be assued as90%, 60% and 70% respectively Deterine the folloi i) Mass flo of stea / Kg of flash vapour ii) Refrigeration capacity in TOR/Kg of flash vapour iii) ass of stea/tor iv) Volue flo rate of vapour leavi flash chaber/tor 6 a) Explain ho psychoetric chart is prepared b) The air-handli unit of an air-conditioni plant supplies a total of 4000 3/in of dry air hich coprises by eight 25% fresh air at 400C DBT and 250C WBT, and 75% recirculated air at 230C DBT and 50% relative huidity. The air leaves the cooli coil at 120C sarated state. Calculate the total cooli load and roo heat gain 7 a) Define the ter cofort factor as used for cooli coils and explain under hat conditions it reain constant b) What are the different loads to be considered to estiate the total cooli load in the design of air-conditioni systes? Discuss in detail each of these loads and give the design procedure consideri various paraeters 8 a) What are the different ethods of huidifyi the air? Explain the or of any one of the atoizi the ater type huidifier b) With a neat sketch explain the or of a coil type dehuidifier 2 of 2