To browse Academia. Skip to main content. Log In Sign Up. Download Free PDF. Top refrigeration and air conditioning question and answers. Sanket Gandhi. Pick up the wrong statement.
A refrigerant should have a Tow specific heat of liquid b high boiling point c high latent heat of vaporisation d higher critical temperature e low specific volume of vapour. Ans: b 2. Ans: e 3. Vapour compression refrigeration is some what like a Carnot cycle b Rankine cycle c reversed Camot cycle d reversed Rankine cycle e none of the above.
Ans: e 4. Which of the following cycles uses air as the refrigerant a Ericsson b Stirling c Carnot d Bell-coleman e none of the above. Ans: d 5. Ammonia-absorption refrigeration cycle requires a very little work input Labels b maximum work input 10 Multiple Choice c nearly same work input as for vapour compression cycle and Combustion d zero work input 10 TOP Fuels and C e none of the above.
Clapeyron equation is a relation between and Answers a temperature, pressure and enthalpy Airport Engineering b specific volume and enthalpy Questions c temperature and enthalpy Applied Mechanics d temperature, pressure, and specil volume Objective Questions e temperature, pressure, specific volur and'enthalpy.
Clapeyron equation is applicable for registration at Economics Multiple and Answers pdf a saturation point of vapour b saturation point of liquid Basic chemical eng and answers c sublimation temperature Basic Chemical Eng d triple point Thermodynamics M e critical point.
In vapour compression cycle, the conditii of refrigerant is saturated liquid Basic Environmenta a after passing through the condenser Objective Type Que b before passing through the condensei Basic Fertilizer Tech c after passing through the expansion throttle valve Choice Questions A d before entering the expansion valve Basic Mass Transfer e before entering the compressor.
In vapour compression cycle, the condition of refrigerant is very wet vapour Basic Petroleum Re Multiple choice Que a after passing through the condenser pdf b before passing through the condenser Bio Engineering Ob c after passing through the expansion or throttle valve Questions And Anse d before entering the expansion valve Building Materials a e before entering the compressor.
In vapour compression cycle, the condition of refrigerant is high pressure saturated liquid Answers a after passing through the condenser Chemical Engineeri b before passing through the condenser Type Questions And c after passing through the expansion or thiottle valve Chemical Engineeri d before entering the expansion valve Questions and Answ e before entering the compressor. In vapour compression cycle the condition of refrigerant is superheated vapour a after passing through the condenser Chemical Engineeri Interview Question b before passing through the condenser Chemical Engineeri c after passing through the expansion or throttle valve Lab Viva Questions d before [entering the expansion valve Chemical Engineeri e before entering the compressor.
Allowable pressure on high-pressure side or ammonia absorption system is of the order of pdf a atmospheric pressure competitive and en b slightly above atmospheric pressure Comprehensive MC c bars Combustion d bars Compressors e bars.
The condensing pressure due to the presence of non-condensable gases, as compared to that actually required for Current Electricity O condensing temperatures without non-condensable gases, Questions a will be higher D. Generators Qu b will be lower Answers c will remain unaffected D. Motors Quiz Q d may be higher or lower depending upon the nature of non-condensable gases Answers e unpredictable. Critical pressure of a liquid is the pressure Questions and Answ a above which liquid will remain liquid Design of Steel Stru b above which liquid becomes gas Questions c above which liquid becomes vapour Design of Steel Stru d above which liquid becomes solid Questions e at which all the three phases exist together.Water at C and a pressure of kPa passes through a pressure-reducing valve and then flows to a separating tank at standard atmospheric pressure of From Fig.
Air flowing at a rate of 2. What is the rate of heat transfer? One instrument for measuring the rate of airflow is a venturi, as shown in Fig. The flow rate of air having a density of 1. The flow between A and B can be considered to be frictionless so that Bernoullis equation applies.
K to compute the specific volume of saturated vapor at 20 C. Compare with data of Table A Using the relationship shown on Fig. What is the order of magnitude of heat release by convection from a human body when the air velocity is 0. What is the order of magnitude of radiant heat transfer from a human body in a comfort air-conditioning situation? What is the approximate rate of heat loss due to insensible evaporation if the skin temperature is 32 C, the vapor -9 pressure is Pa, and the vapor pressure of air is Pa?
The latent heat of water is 2. Solution: Equation A sample of air has a dry-bulb temperature of 30 C and a wet-bulb temperature of 25 C. The barometric pressure is kPa.
Using steam tables and Eqs. Using humidity ratios from the psychrometric chart, calculate the error in considering the wet-bulb line to be the line of constant enthalpy at the point of 35 C dry-bulb temperature and 50 percent relative humidity.
An air-vapor mixture has a dry-bulb temperature pf 30 C and a humidity ratio of 0. Calculate at two different barometric pressures, 85 and kPa, a the enthalpy and b the dew-point temperature.
A cooling tower is a device that cools a spray of water by passing it through a stream of air. Solution: At 35 C dry-bulb, 24 C wet-bulb. In an air-conditioning unit 3. The leaving condition of the air is 13 C dry-bulb temperature and 90 percent relative humdity. Using properties from the psychrometric chart, a calculate the refrigerating capacity inkilowatts and b determine the rate of water removal from the air. A stream of outdoor air is mixed with a stream of return air in an air-conditioning system that operates at kPa pressure.
Determine a the enthalpy of the mixture, b the humidity ratio of the mixture, c the dry-bulb temperature of the mixture from the properties determined in parts a and b and d the dry-bulb temperature by weighted average of the dry-bulb temperatures of the entering streams. Solutions: Use Fig.
At From Psychrometric Chart, Fig.Refrigerator Numerical Example 1
The air conditions at the intake of an air compressor are 28 C, 50 percent relative humidity, and kPa. The air is compressed to kPa, then sent to an intercooler. If condensation of water vapor from the compressed air is to be prevented, what is the minimum temperature to which the air can be cooled in the intercooler?
A winter air-conditioning system adds for humidification 0. The air is initially at a temperature of 15 C with a relative humidity of 20 percent. What are the dry- and wet-bulb temperatures of the air leaving the humidifier?To browse Academia.
Skip to main content. Log In Sign Up. Download Free PDF. The coefficient of performance, the amount of heat absorbed from the refrigerated space, and the net work input are to be determined. Assumptions 1 Steady operating conditions exist.
Limited distribution permitted only to teachers and educators for course preparation. If you are a student using this Manual, you are using it without permission. The coefficient of performance, the quality at the beginning of the heat-absorption process, and the net work input are to be determined. It is not practical to design refrigeration or air-conditioning devices that involve such extremely low pressures.
Therefore, the recommended pressure would be 0. This is because the latter cycle involves an irreversible process for which the process path is not known.
The quality of the refrigerant at the evaporator inlet, the refrigeration load, the COP of the refrigerator, and the theoretical maximum refrigeration load for the same power input to the compressor are to be determined. The COP and the power requirement are to be determined.
Analysis In an ideal vapor-compression refrigeration cycle, the compression process is isentropic, the refrigerant enters the compressor as a saturated vapor at the evaporator pressure, and leaves the condenser as saturated liquid at the condenser pressure.
The mass flow rate of the refrigerant and the power requirement are to be determined. Analysis The problem is solved using EES, and the solution is given below. The rate of heat removal from the refrigerated space, the power input to the compressor, the rate of heat rejection to the environment, and the COP are to be determined.
Analysis a In an ideal vapor-compression refrigeration cycle, the compression process is isentropic, the refrigerant enters the compressor as a saturated vapor at the evaporator pressure, and leaves the condenser as saturated liquid at the condenser pressure. The throttling valve in the cycle is replaced by an isentropic turbine. The percentage increase in the COP and in the rate of heat removal from the refrigerated space due to this replacement are to be determined.
QH 2 Analysis If the throttling valve in the previous 3 0. The rate of heat removal from the refrigerated space, the power input to the compressor, the isentropic efficiency of the compressor, and the COP of the refrigerator are to be determined. The COP of the system is to be determined. The increase in the COP if the throttling process were replaced by an isentropic expansion is to be determined.
The COP of the system and the cooling load are to be determined. The power input to the compressor, the rate of heat removal from the refrigerated space, and the pressure drop and the rate of heat gain in the line between the evaporator and the compressor are to be determined. The effects of the compressor isentropic efficiency and the compressor inlet volume flow rate on the power input and the rate of refrigeration are to be investigated.
The mass flow rate of the refrigerant, the condenser pressure, and the COP of the refrigerator are to be determined. Other desirable characteristics of a refrigerant include being nontoxic, noncorrosive, nonflammable, chemically stable, having a high enthalpy of vaporization minimizes the mass flow rate and, of course, being available at low cost.
At lower pressures, the refrigerant will have to condense at temperatures lower than the temperature of the surroundings, which cannot happen. Reasonable pressures for the evaporator and the condenser are to be selected. The saturation pressures corresponding to these temperatures are 0. Therefore, the recommended evaporator and condenser pressures are 0.The compression follows the law PV 1.
Determine the size of the cylinder. Given data. Hence it is a polytropic pr ocess. To find. Size of the cylinder d? It is given that. The indicated mean eff ective pressure. The power required to drive the compressor. Indicted Mean Effectiv e Pressure. We know that isothermal work done. A two stages, single acting air compressor compresses air to 20bar.
The air enters the L. P cylinder at 1bar and 27 o c and leaves it at 4. The air enters the H. P cylind er is mm diameter and mm stroke.
The compressor runs at rpm, taking index of compression and ex pansion in the two cylinders as 1. The indicated power required to run the comp ressor; and 2. The heat rejected in the intercooler per minute. Indicated power required to run the compressor. We know the sw ept volume of the L.
P cylinder. Total indicated work done by the compressor. BS Developed by Therithal info, Chennai. Toggle navigation BrainKart.
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Refrigeration and Air Conditioning. Classification of Refrigeration System. Types of Air Conditioning.
Solved Problems: Refrigeration and Air Conditioning. Technical Terms of Refrigeration and Air Conditioning.A sling psychrometer gives reading of 25 0 c dry bulb temperature 1 5 0 c wet bulb temperature. The barome ter indicates mm of hg assuming partial pressure of the vapour as 10 mm of Hg.
Determine 1. Specific humidity 2.
Solution Refrigeration & Air Conditioning Stoecker & Jones
Saturation ratio. Given Data:.
To Find:. Specific humidit y.
Specific humidity:. We know that Specific humidity. A two stages, single acting air compressor compresses air to 20bar. The air enters the L. P cylinder at 1bar a nd 27 o c and leaves it at 4. P cylinder is mm diameter and 5 00mm stroke. The compressor runs at rpm, taking index of compression and expansi on in the two cylinders as 1. The indicated power required to run the co mpressor; and 2. The heat rejected in the intercooler per minute.
Given data:. Indicated power required to run the compressor. Solution :. Total indicated work done by the compressor. In an oil gas turbine installationair is taken as 1 bar and 30 o C.
The air is compressed. Find the overall efficiency of the plant. Overall efficiency of the plant. BS Developed by Therithal info, Chennai. Toggle navigation BrainKart. The air is compressed to 4bar and then heated by b urning the oil to a temperature of o C.
Refrigeration and Air Conditioning. Classification of Refrigeration System. Types of Air Conditioning. Solved Problems: Refrigeration and Air Conditioning. Technical Terms of Refrigeration and Air Conditioning. Fundamentals of Computer Graphics.
Refrigeration system: problems, causes and solutions
Engineering Design Process. Morphology of Design. Sequential and Concurrent Engineering. Computer Graphics or Interactive Computer Graphics. Coordinate system.To ensure refrigerant charged correctly, weigh the refrigerant before charging. Evaporator starving of refrigerant and rapid rise in condenser pressure causes a compressor to short cycle.
In case of a hermetic compressor, moisture can cause corrosion and damage to the motor windings. It means the liquid is reaching suction of the compressor and is absorbing heat from the surroundings resulting in ice formation.
An overcharge of liquid refrigerant can cause high-pressure failure, may lead to damage in moving parts of the compressor. Refrigeration System Problems and Solutions: 1. Room temperature warm Lack of refrigerant present in the system. Blocked filter at the drier or expansion valve. Evaporator inlet solenoid closed. Condenser fan motor issue, less heat transfer available for a given mass of refrigerant. Defrosting element still operational. Compressor capacity control faulty leading to less coolant effect across the thermostatic expansion valve.
Compressor suction pressure high Fractured compressor valvescausing the compressor capacity to fall. Evaporator load too highcaused by room items recently changed entry door left open. Excess refrigerant charge. This fault is combined with a low compressor superheat and indicates liquid in the suction line.
The solenoid valve should be closed quickly to prevent liquid damage to the compressor. Expansion valve stuck in a fully open positioncaused by dirt in the expansion valve. Compressor suction pressure low Blocked filter or closed valve in the system.
In this mode, the compressor is extracting more from the evaporator than the expansion valve is supplying leading to low suction pressure and possibly compressor to short cycle. Refrigerant charge too low. There is not enough refrigerant within the system to allow the compressor to operate at the present capacity setting. Increased compressor run time.
The liquid refrigerant flow may be disturbed : Fully open the valves in the liquid refrigerant line if not fully open. Confirm line filters not chocked. Thermostatic expansion valve clogged with ice or oil dust mixture: Dissemble expansion valve TEV and clean the ice with dry compressed air. Activate the desiccant of drier filter by the heater. Take off oil mixture dirt. Less opening for the expansion valve or superheat very low: Adjust the expansion valve opening and ensure temperature sensor attached properly to the evaporator outlet.
Evaporator cooling capacity lowered by dust and frost: Check fan operation working normal. Remove dust by soft brush and carry out defrosting.Before you know it, those living in the residential building you manage will be cranking up their air conditioning systems. A preemptive air conditioning troubleshooting mission and appropriate residential air conditioning maintenance can aid you in your goal of smoothly operating air conditioning systems and happy residents.
When warm weather hits and the heat is on, the last thing you want is for your air conditioning to be off. Here are some of the most prevalent problems that you can avoid by following common sense operational procedures and with routine residential air conditioning maintenance.
It also could be the result of broken or loose wiring or thermostat problems. Thermostat glitches If your thermostat is not working or if it is incorrectly calibrated, it may not tell the air conditioner to turn on. The older, dial-type thermostats are more often subject to calibration problems, but sometimes the newer programmable thermostats are not easy to program.
When doing air conditioning troubleshooting, you should consult your thermostat manual to make sure you have programmed your thermostat properly. Air conditioner problems are not cool — low refrigerant equals low efficiency While air conditioning troubleshooting uncovers an under-performing unit, that can be the result of low refrigerant. If the refrigerant level is low, it usually means it was either undercharged at installation or it has a leak.
If you notice your building is not cooling properly or the air is somewhat sticky, a low refrigerant level could be the culprit. Without the right refrigerant level, heat and humidity cannot efficiently be removed from the air. The refrigerant is the lifeblood of your air conditioning unit and is akin to the motor oil in your vehicle.
Likewise, with an air conditioner system, low refrigerant is often the sign of a leak and you will need a qualified HVAC experts to fix it. The condenser has an important job to do. It is responsible for discharging the heat removed from the air by releasing it outside of the building.
Example Problem with Complete Solution
If the coils are dirty, it will interfere with the transfer of heat and make your unit worker harder and add to the wear and tear on your system. This coil contains refrigerant that absorbs heat. When airflow is diminished, a layer of ice can form on the evaporator coil. If this occurs, you could end up with warm air or no air from your air conditioner supply registers.