Define relative humidity, degree of saturation, specific humidity and dew point temperature.
Define ASHRAE comfort zone. What factors are caused for comfort air conditioning? Discuss in brief.
Define by-pass factor and contact factor. Describe the heating and humidification process.
Differentiate between sensible heating and sensible cooling process.
Write the importance of food preservation. What are the causes of food spoilage?
Enlist the methods of food freezing.
What are the basic elements of controlling of air conditioning?
2.0 m³/s of moist air at a state of 30°C DBT, 21°C WBT and 101.325 kPa flows across a cooler coil and leaves the coil at 12°C DBT and 8.2 g/kg of dry air. Determine i) the apparatus dew point ii) the contact factor and by-pass factor iii) cooling load.
What are the purpose of duct design? Nowadays, which materials are chosen for duct? Why?
In the air duct system shown in Figure 3(b), air enters at A with a static pressure of 7.5 mm of water. The branch at B is 15m long delivering 120 m³/min and the branch at C is 22.5m long delivering 140 m³/min. At the end D of the main duct, the air delivered is 200m³/min. Using friction chart and equal pressure drop method, determine the correct diameter and velocity pressures in lengths, AB, BC, CD, branch BE and CF. Consider friction losses only.
Define cooling load. What are the purposes of estimating cooling load?
A conference room for seating 100 persons is to be maintained at 22°C DBT and 60% RH. The outdoor conditions are 40° DBT and 27°C WBT. The various loads are- Sensible and latent heat loads per person 80W and 50W respectively; lights and fans 15000W; sensible heat gain through glass, walls, ceiling 15000W, the air filtration is 20 m³/min and fresh air supply is 100 m³/min. 2/3 of circulated room air and 1/3 of fresh air are mixed before entering the cooling coil. The by-pass factor of the coil is 0.1. Determine apparatus dew point, the grand total heat load and ERSHF.
Why is multistage system essential for vapor compression system? Explain the two stage compression system with water inter cooler and a liquid flash chamber. Draw also P-h and T-s diagram.
Calculate the power required to compress 15 kg/min of ammonia from saturated vapor at 1.3 bar to a condensing pressure of 10 bar by two stage compression with inter cooler by liquid refrigerant at 4.5 bar. Assume saturated liquid to leave the condenser and dry saturated vapors to leave the compressor. Use P-h chart. Determine also the power required when inter cooling is not employed.
Why is the vapor absorption refrigeration cycle called a heat operated cycle? Discuss the working principle of vapor absorption refrigeration.
How does heat exchanger help to improve performance of vapor absorption cycle.
A refrigeration system working on Bell-Coleman cycle receives air from cold chamber at 5°C and compresses it from 1 bar to 4.5 bar. The compressed air is cooled to a temperature of 37°C before it is expanded in the expander. Calculate the COP of the system when compression and expansion are i) isentropic and ii) PV1.25=ConstantPV^{1.25} = \text{Constant}PV1.25=Constant.
Define Dry ice. Explain the working principle of production of dry ice. Show the schematic diagram and P-h diagram.
Design the process of liquification of natural gas with neat sketch.
Calculate the sound power level of i) a whisper that emits a power 1MW ii) a rock engine that emits 0.10 MW.
A cascade refrigeration system is required to supply 20 tonnes of refrigeration at an evaporator temperature of -50°C and a condenser temperature of 40°C. The load at -50°C is absorbed by a unit using R-22 refrigerant and is rejected to a cascade condenser at -10°C. This cascade condenser is cooled by a unit using R-12, as the refrigerant and operating between -25°C evaporating temperature and 40°C condensing temperature. The refrigerant leaving the R12 condenser is subcooled by 5°C and there is no subcooling of R22 refrigerant. The gas leaving both the evaporator is dry and saturated and the compressions are isentropic. Neglecting losses, find a) compression ratio of each unit b) quantity of refrigerant circulated per minute for each unit c) COP of the whole system & theoretical power required to drive the system.
Define psychometry and psychometric chart. Why is psychometric chart necessary? Define relative humidity, specific humidity and humidity ratio.
Define psychometric processes. Enlist the psychometric processes. Discuss any two of psychometric processes.
Moist air of DBT 30° C and WBT 22° C mixes adiabatically with another stream of moist air of DBT 12° C and WBT 5° C at atmospheric pressure. The mass flow rates of the streams are 3 kg/s and 2 kg/s respectively. What will be the DBT, WBT and relative humidity of the mixture?
What are the causes of spoilage of food? Why it need to preserve? Explain.
What are the basic elements of controlling of air conditioning? Discuss their functions.
Briefly discuss the acoustic design in building air conditioning.
What types of common materials are used in duct air conditioning system? What are their advantages?
What methods are available for duct designing? Discuss one of them.
An air duct system is provided as shown in Fig.3(c). Determine the dimensions of AB, BC and CD using equal-friction method choosing a friction rate of 0.08 mm of water per meter length of the duct. Use the following formula for friction rate: PfL=2.268×10−3×Q1.852D4.973mm of water / m\frac{P_f}{L} = \frac{2.268 \times 10^{-3} \times Q^{1.852}}{D^{4.973}} \quad \text{mm of water / m}LPf=D4.9732.268×10−3×Q1.852mm of water / m Where Q is in m³/s and D and L are in meters.
Define cooling load. What are the parameters for estimating cooling load? Describe the indoor and outdoor loads.
Describe the space heat gain for air-conditioning. What are the general guidelines for space cooling load calculations?
Briefly describe the essential components of air-conditioning system with net sketch.
What are the basic differences between refrigeration and air con-conditioning?
Draw and label the P-V and T-S diagrams of Bell-Coleman air refrigeration cycle and hence prove the COP of the cycle for isentropic compression and expansion is COP=1(rp)γ−1γ−1COP = \frac{1}{(r_p)^{\frac{\gamma-1}{\gamma}} - 1}COP=(rp)γγ−1−11 Where rpr_prp is the compression or expansion ratio.
In a refrigeration plant working on Bell-Coleman cycle, air is compressed to 5 bar from 1 bar. Its initial temperature is 10° C. After compression, the air is cooled upto 20° C in a cooler before expanding back to a pressure of 1 bar. Determine the theoretical COP of the plant and net refrigerating effect. Take Cp=1.005C_p = 1.005Cp=1.005 kJ/kgK.
Mention advantages of multistage compression with intercooler. Explain three stage compression with intercooler providing proper figure, p-h diagram and mathematical expression.
The refrigeration system using R-12 as refrigerant consists of three evaporators of capacities 20 TR, 30TR and 10TR with individual compression valves and individual compressors. The temperature in the evaporators is to be maintained at -10° C, 5°C and 10°C respectively. The vapors leaving the evaporators are dry and saturated. The condenser temperature is 40°C and the liquid leaving the condenser is subcooled to 30°C. Assuming isentropic compression in each compressor, find (i) the mass of refrigerant flowing through each evaporator; (ii) the power required to drive the system and (iii) COP of the system.
What is dry ice? Explain the working principle of production of dry ice using schematic process diagram and p-h diagram.
Design the process of liquefaction of natural gas with neat sketch.
What are the advantages of Claude system over Linde system for liquefaction of air?
What is refrigerant? Write the factors considered for the selection of refrigerant for a system.
How does thermo-static expansion valve work? Discuss with neat sketch.
Discuss the pressure control defrosting method.
What are the key factors for comfort air conditioning?
Define Psychrometry and Psychrometric processes. Enlist the Psychrometric processes. Briefly describe two of the Psychrometric processes.
Moist air of DBT 32°C and WBT 25°C mixes adiabatically with another stream of moist air of DBT 12°C and WBT 5°C at atmospheric pressure. The mass flow rates of the steams are 4 kg/s and 3 kg/s respectively. What will be the DBT, WBT and specific humidity of the mixture?
What are the purposes of ducting? What prime factors are considered for duct designing?
What are the methods available for duct designing? What materials are used for ducting?
An air duct system is provided as shown in Figure 2(c). Choosing friction rate of 0.75 mm H₂O/m length of the duct, find the diameter of section AB, BC and CD for total flow of air 10 m³/s.
Define metabolic rate and define also mechanism of body heat loss.
Define comfort air conditioning. Describe the indoor design condition of air conditioning for different application.
Define solar constant and its correction factor. Which types of solar radiation comes into the building?
What are the essential components of air conditioning system? Write their functions.
Describe the space heat gain for air conditioning. What are the general guidelines for space cooling calculations?
What is cooling load? Why is it needed? Describe the design day, outdoor loads and indoor loads.
Define heat engine, heat pump and refrigerating machine. Make a comparison among them by schematic diagram and relevant mathematical expressions.
Draw the schematic, P−vP-vP−v and T−sT-sT−s diagram and label all the components and process of air refrigerator working on Bell-Colemon cycle.
A simple air cooled system used for an aeroplane having a load of 10 tonnes. The atmospheric pressure and temperature are 0.9 bar and 10°C respectively. The pressure increases to 1.013 bar due to ramming. The temperature of the air is reduced by 50°C in the heat exchanger. The pressure in the cabin is 1.01 bar and the temperature of air leaving the cabin is 25°C. Determine (i) Power required to take the load of cooling in the cabin; and (ii) COP of the system. Assume that all the expansions and compressions are isentropic. The pressure of the compressed air is 3.5 bar.
Mention advantages of multistage compression system with intercooler. Explain 3 stage compression with water intercooler providing proper figure P−hP-hP−h diagram and mathematical expressions.
A vapor compression system with Ammonia as refrigerant works between the pressure limits of 2 bar and 12 bar with 3 stage compression, The vapour leaving the water intercoolers at pressures 4 bar and 8 bar are in a saturated state. If the load is 10 TR, find the power required to drive the three compressors and compare the COP of this system with that of a simple saturation cycle working between the same overall pressure limits.
Briefly describe the aqua-ammonia absorption refrigeration cycle.
Dry air at 17°C and 1 bar is to be liquefied by the simple Linde method. The air is compressed isothermally at 17°C to 200 bar. The make-up air is supplied to the system also at 17°C and 1 bar. Find the yield of liquid air in kg per kg of air compressed and the temperature of air before throttling.
Give an illustration on Primary and Secondary refrigerant. What are the desirable proportions of an ideal refrigerant?
Define "Cryogenics". Mention its application. Why dry ice, despite its high manufacturing cost. is used as a refrigerant?
Write short notes on the following:
Define air-conditioning and refrigeration. Write the history of refrigeration.
Discuss briefly the frozen food chain in the global with sketches.
We have to design a cold storage with a temperature -5°C while the surrounding temperature is maintained at 34°C. Heat will be transferred from the hot surrounding into the cold storage room amount is to be 25 kW. The COP of the refrigerating plant is 1/3 of an ideal plant. Calculate the power required to drive the plant.
What are the main disadvantages of refrigeration cycle with air as working substance?
Why aircraft cooling is needed? If an airplane is moving at 1500 km/hr, how much temperature will rise?
In a Bell-Coleman refrigeration plant, the air is drawn from cold chamber at 1.0 bar and 12°C and compressed to 6 bar. The same is then cold to 15°C and the cooler depending in the expander to cold chamber pressure of 1.0 bar. Determine the theoretical COP of the plant and the net refrigeration effect per kg of air if the compression and expansion is followed by PV1.4=constantPV^{1.4} = \text{constant}PV1.4=constant.
What are the advantages and disadvantages of vapor compression refrigeration system over air refrigeration system?
Why is multi pressure system needed in vapor compression system? Explain the working principle of a two-stage compression system with water intercooler, liquid intercooler and a liquid flash chamber. Draw P-v and T-s diagram.
Calculate the power needed to compress 20 kg/min of ammonia from saturated vapor at 1.4 bar to a condensing pressure of 10 bar by two-stage compression with intercooling by liquid refrigerant at 4.0 bar. Assume saturated liquid to leave the condenser and dry saturated vapors to leave the evaporator. Use the P-h chart.
Mention five cryogenic fluids with their boiling temperature in °C.
What are the application and limitation of low temperature refrigeration system?
Determine the power required per 1000 kg of dry ice produced using single compression and also the COP of the plant. The pressures are in snow chamber 1.03 kg/cm² and in condenser 69.35 kg/cm². Dry saturated carbon dioxide enters the throttle valve and dry saturated gas leaves the snow chamber. Dry saturated solid ice is collected from snow chamber. Make-up carbon dioxide gas is supplied at 28°C.
Why do foods become spoilage? Explain
Write down the working principle of thermostatic expansion valve with neat sketch.
Differentiate among frosting evaporator, non-frosting evaporator and de-frosting evaporator. Also write the advantages of food preservation.
Prove that the equivalent diameter for circular duct to replace rectangular duct for the same velocity of air is de=1.265[a3b3a+b]1/5d_e = 1.265 \left[ \frac{a^3 b^3}{a+b} \right]^{1/5}de=1.265[a+ba3b3]1/5 where, ded_ede = equivalent diameter for circular duct, aaa = width of the rectangular duct, bbb= breadth of the rectangular duct.
Twenty three hundred liters of partially frozen ice cream at -4°C are entering a hardening room 3m×5m×3m high each day. Hardening is completed and the temperature of the ice cream is lowered to -28°C in 10h. The walls, including floor and ceiling are insulated with 150mm of polyurethane and overall thickness of the wall is 250mm. The ambient temperature is 32°C and the RH is 50%. Assume the average density of ice cream is 0.6 kg/L. The average specific heat below freezing is 2.1 kJ/kg-K and the average latent heat per kg is 233 kJ. Determine the average hourly load based on 18h operation.
Define Psychometry and Psychometric chart. Describe the sensible heating and cooling method.
Define the following term: (Any Four) (i) Relative humidity (ii) Degree of saturation (iii) Dry bulb temperature (iv) Dew point temperature (v) Comfort Air-conditioning
Discuss briefly with neat sketch the four types of air-conditioning system.
The atmospheric air at 25°C DBT and 10°C WBT is flowing at the rate of 100m³/min through the duct. The dry saturated steam at 100°C is injected into the air stream at the rate of 70 kg/hr. Calculate the specific humidity and enthalpy of the leaving air.
What are the basic elements of air-conditioning control system? Discuss the self-actuated air-conditioning control system with figure.
Calculate the sound power level of (i) a whisper that emits of 1 MW and (ii) a rocket engine that emits 12 MW.
Define 1st law and 2nd law of thermodynamics. What are their applications in the field of Refrigeration system?
State Joule's law. Write the equation of Joule's law.
A cold storage is to be maintained at -5°C while the surroundings are at 35°C. The heat transfer from the surrounding into the cold storage is estimated to be 29 kW. The COP of the refrigeration plant is one-third of an ideal plant. Find the power required to drive the plant.
Draw and level the P-V and T-S diagram of Bell Coleman air refrigeration cycle and hence prove the COP of the cycle for isentropic compression and expansion.
COP=1(rp)γ−1γ−1COP = \frac{1}{(r_p)^{\frac{\gamma-1}{\gamma}} - 1}COP=(rp)γγ−1−11
The atmospheric air at pressure 1 bar and temperature -5°C is drawn in the cylinder of the compressor of Bell-Coleman refrigerating machine. It is compressed isentropically to a pressure of 5 bar. In the cooler, the compressed air is cooled to 15°C, pressure remaining the same. It is then expended to a pressure of 1 bar in an expansion cylinder, from where it is passed to the cold chamber. Find (i) the work done per kg of air and (ii) COP of the plant. (Assume for air expansion law, pv1.2=constantpv^{1.2} = \text{constant}pv1.2=constant; compression law pv1.4=constantpv^{1.4} = \text{constant}pv1.4=constant and specific heat of air at constant pressure = 1 KJ/kg°K.
Why is multi pressure system important in vapor compression system? Explain the working of a two stage compression system with water inter cooler, liquid inter cooler and a liquid flash chamber. Draw P-h and T-S diagram.
Calculate the power needed to compress 20 kg/min of ammonia from saturated vapor at 1.4 bar to a condensing pressure of 10 bar by two-stage compression with inter cooling by liquid refrigerant at 4 bar. Assume saturated liquid to leave the condenser and dry saturated vapors to leave the compressor. Use the P-h chart. Determine also the power required when inter cooling is not employed.
Explain the working principle of production of dry Ice with net sketch the process. Also draw and level the P-h diagram.
Dry air at 20°C and 1 bar is to be liquefied by the simple Linde method. The air is isothermally compressed at 20°C to 170 bar. The make-up air is supplied to the system at 20°C and 1 bar. Find the yield of liquid air in kg per kg of dry air compressed and the temperature of air before throttling.
Describe the production of low temperature by adiabatic demagnetization of a paramagnetic salt with net sketch the schematic diagram.
What do you mean by refrigerant? Write the factors considered for the selection of refrigerant for a system.
How does thermo static expansion valve work? Discuss with net sketch.
What are the factors to be kept in mind while storing the foods in cold storages? Explain in brief.
A cooler 4 m×3 m×3 m high equipped with 6 m×0.7 m×1 m triple-glass doors is used for general purposes storage in a grocery store. The cooler is maintained at 2°C and the service load is heavy. The walls are insulated with the equivalent of 100 mm of corkboard and the ambient temperature is 25°C. Determine the cooling load in kW based on a 16 hr operating time.
Define Psychometry and Psychometry chart. What is the necessity of Psychometric chart? Define relative humidity, specific humidity, dry bulb temperature and wet bulb temperature.
Describe the heating and Humidification by steam injecting showing the Psychometric process and Psychometric chart.
Velocity of air chosen through a circular duct which carries standard air is 360 m/min. The size of the duct is 0.3 m diameter. If this duct is replaced by a rectangular duct of aspect ratio 1.5. Determine the size of the rectangular duct for equal friction method. When (i) the velocity of air in two ducts is same, (ii) the discharge rate through the line duct is same.
Define the basic element of controlling of air conditioning. Discuss their function.
Calculate the sound power level of (i) a whisper that emits a power of 1MW and (ii) a rocket engine that emits 10 MW.