Refrigeration and Air Conditioning important question and answer

Question 1 : 
Heat removing capacity of a one-ton refrigerator is 
Option A: 25 Kcal / sec
Option B: 50 Kcal / min
Option C: 50 Kcal / hour
Option D: 100 Kcal / hour 
Explaination: 50 Kcal/min

Question 2 : 
In SI units, one tonne of refrigeration is equivalent to  
Option A: 1.5 kW
Option B: 2.5 kW
Option C: 3.5 kW
Option D: 5 kW
Explanation: In SI units, one tonne of refrigeration is equivalent to 3.5 kW and 210 kJ/min. 

Question 3 : 
In a refrigeration system, the moisture is removed by 
Option A: Driers
Option B: Desiccants
Option C: Filter driers
Option D: All of the above
Explanation: Moisture is removed by driers, filter driers and desiccants too. 

Question 4 :
Subcooling occurs when the vapour
Option A: Has high latent heat
Option B: Has low latent heat
Option C: Removes sensible heat from the refrigerant
Option D: Has high thermal conductivity
Explanation: Subcooling occurs when the vapour removes sensible heat from the refrigerant.

Question 5: 
In the sensible cooling process, specific humidity
Option A: Increases
Option B: Decreases
Option C: Remain constant
Option D: NONE
Explanation: In a sensible cooling process, specific humidity remains constant and relative humidity increases.  

Question 6: 
The dew point temperature as compared to wet bulb temperature for unsaturated air is
Option A: Equal
Option B: Less
Option C: More 
Option D: Unpredictable
Explanation: DPT is less than WBT for unsaturated air.

Question 7:
Air conditioning means?
Option A: Cooling and Heating
Option B: Removal of air impurities
Option C: Dehumidifying
Option D: All of the above
Explanation: A system for controlling the humidity, ventilation, and temperature in a building or vehicle, typically to maintain a cool atmosphere in warm conditions. 

Question 8: 
The main parts of a vapour compression refrigeration system in a sequence are
Option A: Compressor, Condensor, Evaporator and Throttle valve
Option B: Compressor, Throttle valve, Condensor, and Evaporator
Option C: Compressor, Evaporator, Condensor, and Throttle valve
Option D: Compressor, Condensor, Throttle valve, and Evaporator
Explanation: First compressor then condenser, throttle valve and last evaporator. 

Question 9: 
If a refrigerant is having low specific heat, then co-efficient of performance will be
Option A: Lower
Option B: Higher
Option C: Same
Option D: NONE
Explanation: Higher

Question 10: 
The ratio for sensible heat factor is 
Option A: Latent heat to Sensible heat
Option B: Sensible heat to Latent heat
Option C: Latent heat to Total heat
Option D: Sensible heat to Total heat
Explanation: SHF = Sensible heat / Total Heat 
Sensible heat is the heat which increases or decreases the temperature of the body.

Question 11: 
The subcooling in the refrigeration cycle, 
Option A: Increases COP
Option B: Reduce cooling
Option C: Increases work of compression
Option D: Reduce condenser size
Explanation: The subcooling process increases the COP of the refrigeration cycle. 
The coefficient of performance or COP of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work required. Higher COPs equate to lower operating costs. 

Question 12: 
The phenomenon of emf developed between two dissimilar metals in contact is which of the following effect
Option A: Seeback effect
Option B: Thomson effect
Option C: Peltier effect
Option D: Thermocouple effect

Explanation: A temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference is called as seeback effect. 

Question 13: 
In a refrigeration cycle, the heat is absorbed by a refrigerant in a and heat is rejected by a refrigerant in a
Option A: Evaporator, Condensor 
Option B: Evaporator, Compressor
Option C: Condensor, Evaporator
Option D: Evaporator, Expansion valve 
Explanation: The heat is absorbed by an evaporator and rejected by the condenser. 

Question 14: 
Mass of the water vapour present in 1 kg of dry air is called, 
Option A: Relative humidity
Option B: Absolute humidity
Option C: Humidity ratio
Option D: Percentage humidity
Explanation: Humidity ratio, it is also known as specific humidity. 

Question 15: 
Mass of the water vapour present in 1 m³ of dry air is called, 
Option A: Relative humidity
Option B: Absolute humidity
Option C: Percentage of humidity
Option D: Humidity ratio
Explanation: Absolute humidity

Question 16: 
Dew point is the temperature at which, 
Option A: Ice starts melting in the presence of air without external aid
Option B: Condensation of water vapour in air starts
Option C: Vapourisation of water vapour in air starts
Option D: NONE
Explanation: The dew point is the temperature to which air must be cooled to become saturated with water vapour. Dew point temperature indicates dryness of the air, moisture content of air, condition of air. 

Question 17:
Dry bulb, wet bulb and dew point temperature are the same for, 
Option A: Dry air
Option B: Saturated air
Option C: Wet air
Option D: NONE
Explanation: Saturated air 

Question 18: 
The difference between the dry bulb and wet bulb temperature is called
Option A: Dry bulb temperature
Option B: Wet-bulb temperature
Option C: Dew point temperature
Option D: NONE
Explanation: WBT = DBT - WBT 

Question 19: 
The moisture content of air is indicated by, 
Option A: Dry bulb temperature
Option B: Wet-bulb temperature
Option C: Dew point temperature
Option D: Both A and B
Explanation: Moisture content of air is indicated by the dry bulb and wet bulb temperature. 

Question 20: 
If wet-bulb depression is zero, it indicates
Option A: Relative humidity is zero
Option B: Relative humidity is 100%
Option C: Rain is likely to occur
Option D: NONE
Explanation: If the wet-bulb depression is zero relative humidity is 100% as wet-bulb depression indicates relative humidity. 

Lenoir cycle | Working process | Thermal efficiency

The Lenoir cycle is a thermodynamic cycle that can be invented by Jean Joseph Etienne Lenoir in 1860 is often used to model a pulse jet engine. 

Process of Lenoir cycle :

All type of process individually done in a heat engine in Lenior cycle. 

The Lenoir cycle consists of four processes which are following below. 

• A constant-volume gas expansion process. From the diagram shown below the ideal gas in the system absorbs some amount of heat from the heat source at a high temperature and then expands thus the work was done on surroundings. 
• A reversible adiabatic gas expansion process. In this process, the system is thermally insulated. The gas expands continuously and does work on surrounding, which causes the system to cool to a lower temperature. 
• A reversible isothermal gas compression process. In this process, work has done surrounding gas and cause a loss of heat.
• A reversible adiabatic gas compression process. In this process, surrounding continue to do work to a gas, which causes the temperature to rise back to high temperature attain in the first process. 

Lenoir cycle PV and TS Diagram

The thermal efficiency of Lenoir cycle : 

Thermodynamically, the efficiency of Lenoir cycle is given by

ŋ_Lenoir = Work done by the system / Heat supplied to the system

CAM full form

What is the full form of CAM?

Answer: 

• Computer-Aided Manufacturing

What does CAM mean?

CAM is computer-controlled machinery to automate the manufacturing process. 

CAM uses CAD software created models and assemblies to generate tool paths that drive machine tools to turn a design into the physical parts.


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VMC full form

What is the full form of VMC?

Answer : 

• Vertical Milling Center

What does VMC mean?

VMC is a specific type of milling machine which is controlled by CNC. The cutting head of this type of machine is vertical where a spindle runs in a vertical axis known as the z-axis. 


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Concept of production

Production is the transformation of inputs into output where inputs are used in many ways such as land, labour, capital, raw material etc. 

Production concept emphasis on low production costs, and high production efficiency and mass production simply said a large amount of the cheapest goods. 

The function of production :

The function of production is the technological relationship between inputs and output in physical terms. An algebraic expression for production is Q = f (K, L)

Where Q = The quantity of output produced per unit time
K = Capital 
L = Labour 

Characteristics of the production system : 

• The production system has its own objective.
• The system transforms the various inputs to the useful output.
• Does not operate in isolation from the other organization system. 
• There exists a procedure which controls and improve system performance. 

Types of production : 

• Continuous production 
• Batch production 
• Mass production 
• Job-shop production 

Definition of production

Production is the method of turning raw materials or inputs into finished goods or products means the creation of something from basic inputs. Production is the process of transformation because it is done to satisfy human wants. The process of transformation is done in the following ways. 

1. Disintegration: One input is used to produce many types of output. 
2. Integration or Assembly: Many inputs are used to produce only one output. 
3. Service: Value of the product is increased by providing services. 

CNC full form

What is the full form of CNC?

Answer

• Computerized Numerical Control

What does CNC mean?

CNC uses Computer-Aided Design Software (CAD) to produced design converts the design into numbers. The numbers can be considered to be the coordinate of the graph and it controls the movement of the cutter. 


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Difference between CNC and VMC

CNC full form is Computer Numerical Control while VMC full form is Vertical Machining Center. CNC is a machine and VMC is just part of the machine. Now, let us have a deep insight into the comparison and difference between CNC and VMC. 

Difference between CNC and VMC :

• CNC having two axis x and z whereas VMC having three-axis x,y, and z. 
• We have to change the tool for different operations in CNC while an automatic change of tool is done in VMC. The tool changing process is done by a turret index in CNC whereas by ATC arm in the case of VMC. 
• CNC most often used for cutting metal whereas VMC is very expensive and at the same time are very precise. 
• CNC mainly used for turning inner and outer diameter whereas VMC mainly used for milling end and milling face. 
• Geometry offset in CNC is z and x-axis and only z-axis is for VMC. 
• The tool is rotated in VMC whereas not in the case of CNC. 
• In CNC, a turret is worked as a tool holding and supporting device while Magzine is used for tool holding and a Spindle is used as a tool supporting device in VMC.

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1. Difference between NC and CNC
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Advantages and disadvantages of continuous variable transmission

Continuous variable transmission differs from automated manual transmission, which can seamlessly change through an infinite number of effective gear ratios between maximum and minimum values. It is a clutchless gearbox but in some applications, a centrifugal clutch is added to ease neutral stance. It consists of a belt that rotates and slides between two tapered drums as you accelerate the vehicle, The belt begins to rotate on the drums and, at the same time, to slide on the drums from one side to the other. This decides the drive to a driven ratio of torque which further varies the speed of the vehicle. It delivers a constant acceleration from a complete stop to cruising speed with the ability provide to set the operating point, an engine can be run to provide the maximum fuel efficiency. Let us have a deep insight into the pros and cons of continuous variable transmission (CVT) in this article. 

Advantages of continuous variable transmission : 

• Vehicle weight is reduced. 
• To provide smooth operation. 
• The efficiency of the engine is increased since there is no repetitive engagement and disengagement of the power from the engine. 
• To provide quick acceleration. 

Disadvantages of continuous variable transmission : 

• This transmission may affect the performance and life of the belt since there is an initial slip in the transmission belt. 
• There will be a speed limit. 
• The cost of CVT is high as compared with AMT is the reason why car makers are not putting in entry-level hatchbacks and small cars. 
• The cost of the transmission belt is high. 

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1. Automatic transmission system - Advantages and Disadvantages
2. Automated manual transmission - Advantages and Disadvantages
3. Dual-clutch transmission - Advantages and Disadvantages

Advantages and disadvantages of automated manual transmission

The automated manual transmission is also known as a semi-automatic transmission is not fully automatic or clutch-less transmission. This type of transmission mechanism involves the use of two key parts such as a hydraulic actuator system and an electronic control unit that engages and disengages the clutch while executing gear shifts. It is just the same as a kit that can be added to any regular manual transmission thus car makers use it on some low-cost cars because this type of transmission is very cost-effective and is relatively cheaper than the other auto transmission. Let us have a deep insight into the pros and cons of an automated manual transmission. 

Advantages of automated manual transmission : 

• Low maintenance.
• Great mileage.
• Fuel efficiency is close to their similar cars.
• Cheaper than a conventional fully automatic gearbox.

Disadvantages of automated manual transmission : 

• It is not best while driving on hills or on a slope. 
• No smoothness like an automatic car. 
• Jerky shifts if you drive aggressively.
• Who wants a pure automatic car experience, not for enthusiasts. 

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1. Continuous variable transmission - Advantages and Disadvantages
2. Dual-clutch transmission - Advantages and Disadvantages
3. Automatic transmission system - Advantages and Disadvantages

Advantages and disadvantages of dual clutch transmission

A dual-clutch transmission works on a similar principle of an automated manual transmission but this transmission uses two clutches instead of one. They are used for odd and even gear sets that makes it more efficient gearbox contained into one single housing. Let us have a deep insight into the pros and cons provided by dual-clutch transmission.  

Advantages of dual-clutch transmission :

• Provide smooth acceleration by preventing changes in torque or gear shifts.
• The fuel economy improved by up to 10%.
• It can handle the high torque demands of high-performance cars. 
• Switch gears far faster than others. 
• Drivers can tell computers when to take action with the help of paddles or gearshift even with automatic engagement and disengagement of the clutch. 

 Disadvantages of dual-clutch transmission : 

• Fuel efficiency is lower. 
• Not as reliable as wear and tear are more in this type of transmission. 
• Complexity is more. 

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1. Automatic transmission system - Advantages and Disadvantages
2. Automated manual transmission - Advantages and Disadvantages
3. Continuous variable transmission - Advantages and Disadvantages

Advantages and disadvantages of fluid clutch

What is the fluid clutch?

The fluid clutch power transmission is happened by means of hydraulic pressure. 

Advantages of fluid clutch : 

• Extremely smooth start and stop.
• Ability to absorb shocks. 

Disadvantages of fluid clutch : 

• There is always chances of slip.
• The fluid used should be compatible with the clutch material.

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1. Electromagnetic clutch - Advantages and Disadvantages

Advantages and disadvantages of electromagnetic clutch

What is the electromagnetic clutch?

The electromagnetic clutch power transmission is achieved by means of an electromagnetic field. There are three types of clutch such as magnetic hysteresis clutch, eddy current clutch, and magnetic particle clutch. 

Advantages of electromagnetic clutch : 

• Easy to control. 
• Rapid response time.
• Start and stop are smooth.
• Less wear and tear at the contact point. 
• Mostly used to achieve automatic transmission.
• No linkage is required to operate the clutch. 

Disadvantages of electromagnetic clutch : 

• High initial cost.
• Not suitable for high temperature.
• During engagement risk of overheating.
• A periodic check should be done for coil brushes. 

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1. Fluid clutch - Advantages and Disadvantages