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    Showing posts with label Practicals. Show all posts
    Showing posts with label Practicals. Show all posts

    Wednesday, March 18, 2020

    Essential software to learn in Mechanical Engineering

    The knowledge of different software in mechanical engineering is of great quality and can be helpful to get the required things done easily. Because software is a tool that can be used by an engineer to express the technical stuff via calculations.

    Below is the important and essential software which should be learned during a bachelor course in mechanical engineering. It might possible that some well-known software might not be on the list but can be learned very easily if you know the following software which is basics.

    1. AutoCAD ( A basic CAD software for design and drafting purpose)
    2. Pro/Engineer ( A complete parametric 3D CAD/CAM/CAE software)
    3. C Language (A programming language)
    4. ANSYS ( An analysis or simulation software)

    Thursday, January 23, 2020

    Importance of 'flash-point' and 'fire-point'

    In many engineering applications, fuels are used for getting thermal energy by combustion of fuel. For example, an oil-fired furnace, oil is ignited and heat is used for heating the metals to alter their properties.

    Fuel selection is also one of the most important parts. One needs to use and select fuel based on its properties like calorific value, density, viscosity, specific heat, and flash/fire point. Now, what is the meaning of a flashpoint and fire point?

     'Flash Point is temperature and the property of a volatile lubricant/fuel which suggests when volatile lubricant/fuel gives off sufficient vapor when heated, it will start to ignite for a moment but not lasts more than few seconds.

     'Flash Point' requires ignition source whereas 'auto-ignition temperature' does not require a source of heat. While 'Flash Point' depends on the vapor pressure of that lubricant/fuel and it increases as the temperature of fuel/lubricant increases. Flashpoint and fire point can be determined experimentally by use of Cleveland's open apparatus and Abel's closed cup apparatus. 

    Thursday, December 5, 2019

    'Bomb Calorimeter' for determination of Calorific Value of solid and liquid fuel

    Calorific value (CV) of a fuel is a characteristic of fuel which is defined as the energy liberated per kg of fuel burnt. Fuels are found in three phase viz. solid, liquid and gaseous. Junker's calorimeter is used to measure the CV of gaseous fuels.

    Bomb Calorimeter experiment to measure calorific value of fuel:
    • It is used to measure the calorific value (CV) of solid as well as liquid fuel. But to determine the CV of gas, one need to choose Junker's calorimeter.
    • A calorimeter contains thick walled cylindrical vessel and it consists of the lid which supports two electrodes which are in contact with fuse and fuel sample of known weight. 
    • The lid also contains oxygen inlet valve through which high-pressure oxygen gas (at about 25 to 30 atm) is supplied.
    • Entire lid with fuel sample is now held in a copper calorimeter containing known weight of water. A mechanical stirrer is provided to stirred well for uniform heating of water. 
    • A thermometer is also provided to measure the change in temperature of water due to combustion of fuel in Lid. 

    Tuesday, July 30, 2019

    Determination of viscosity of oil by 'Redwood Viscometer' - Thermodynamic Practical

    What is Viscosity? : It is a measure of the resistance offered by one layer of fluid to the other layer of the same fluid during motion. It is expressed in Pa.s unit

    Redwood Viscometer is normally used for the determination of the viscosity of petroleum products.

    'Redwood Viscometer' determines the viscosity in terms of seconds (which are terms as Redwood seconds), a time taken by oil to pass through a standard orifice and collection of the same oil in 50 cc flask.

    Originally Redwood Viscometer was developed for the measurement of viscosity of petroleum products.

    'Redwood Viscometer' are of two types:

    1. Redwood Viscometer No.1 (For fluid having viscosity corresponds to Redwood seconds less than 2000)
    2. Redwood Viscometer No. 2 ( For fluid having viscosity corresponds to Redwood seconds greater than 2000)

    or Redwood Viscometer No. 1 & 2 is used depending on the time of oil flow through an orifice at the desired temperature is greater or less than 2000 seconds. Normally viscosity of highly viscous fluids is determined by the use of Redwood Viscometer 2.

     Buy and Know more about Viscometer

    The difference between Redwood Viscometer 1 & 2 is the difference of orifice diameter.

    Formula to convert Redwood seconds to kinematic viscosity unit i.e. centistokes.

    = At-B/t  (Where A = 0.26 and B = 171).

    The absolute viscosity is found by measuring the density of the fluid whose viscosity is being measured. Thus, Absolute Viscosity = Kinematic Viscosity x Density


    1. Fill the oil cup with oil to the required oil level indicated by marker point
    2. Heat the water at a uniform temperature.
    3. When the required temperature of the oil is attained, lift the ball above the orifice hole.
    4. Allow the oil to pass through it (start the stopwatch) and collect 50 CC of oil in the volumetric flask.
    5. The measured seconds are in terms of viscosity of oil measured.

    To know more about the Redwood viscometer, refer to the following best book on
    thermodynamics by PK Nag

    Thursday, May 9, 2019

    How do we determine the refrigeration or cooling capacity experimentally ?

    Any refrigeration device's performance is measured in terms of its cooling capacity or refrigeration capacity in kW or Ton. There are many terms available to call the capacity of refrigeration systems such as cooling capacity, refrigeration capacity, refrigeration power or cooling power or refrigeration effect.

    What is the cooling capacity or refrigeration capacity or refrigeration power? 

    Any refrigeration device removes the heat from low-temperature body or space to high-temperature body or space by using external power or work (or compressor electric input) as per the Clausius statement of the second law of thermodynamics. The amount of heat (J/s) absorbed or removed from the low-temperature body or space or object to be cooled (for example, freezer, inside part of domestic refrigerator) is called the refrigeration capacity or refrigeration power or refrigeration effect.

    The cooling capacity is termed in J/s or W or in Ton capacity. 1 Ton = 3.5 kW that means a device of 1 Ton removes the 3.5 kW of energy or heat from the space to be cooled. 

    If the refrigerator works on the vapor compression refrigeration cycle, the heat Qa is absorbed at evaporator (low-temperature space) by taking work input (Win) and rejects the heat of Qa + Win amount to the condenser via heat exchange with the air. 

    How to obtain a refrigeration effect experimentally? 

    COP of a refrigeration device is the ratio of the Refrigeration effect to work input. Thus in order to determine the COP experimentally, one needs to obtain refrigeration power experimentally. 
    When a domestic refrigerator is turned ON, initially all the parts of the refrigerator are at room temperature i.e. 30 ℃. As the cycle continues or compressor runs, the heat is getting removed at the evaporator till the low temperature around -5 ℃ is reached. This temperature can be anything around 0 ℃ depending on the design and capacity of the refrigerator. It takes around 5 minutes to reach a low temperature. Once the low temperature is reached, no further temperature reduction is possible because the system reaches a steady-state condition. 

    Further heat load in the evaporator of the refrigerator starts pumping the heat and the temperature of the evaporator rises depending on the load. Again the system reaches at steady-state temperature if the load is steady. This steady load is called the refrigeration capacity at a given steady-state temperature. 

    For example, a domestic refrigerator is started from room temperature at 09:00 am and the temperature reduction starts. At 09:05 am, the low temperature of -5 ℃ is reached. This condition is called steady-state condition because, even if the compressor/refrigerator keeps on running, the temperature will not drop. If a heating coil of 5 W capacity is started in the evaporator, it will add 5 J of heating load every second. This extra heat load needs to be removed and thus, the compressor again starts pumping heat. Because of 5 W load, the new steady-state temperature is somewhat higher than -5 ℃. Suppose it is 3 ℃. This 3 ℃ will not change if the load remains 5 W. If the load changes, the steady-state temperature changes. Thus, 5 W of refrigeration capacity is obtained at 3℃. This is how cooling capacity or refrigeration power is obtained. 

    Tuesday, February 17, 2015

    Refrigeration system-Construction and working of 'Ice plant'

    We all are aware of the domestic refrigerator and its usage. We get ice cubes from the freezer compartment to meet daily requirements but to get ice in huge quantity we normally approach the ice plant or factory. Here, I am going to share an overview of the construction and working of ice making process and its layout. 

    Normally, any refrigeration system consists of four main types of elements:

    1. Compressor
    2. Condenser
    3. Throttle valve/flow control valve
    4. Evaporator

    Construction of Ice plant
    But in Ice plant or factory, two additional circuits help us to create ice in huge quantities. Refer to the figure and Video.

    Tuesday, February 14, 2012

    Thermodynamics Experiment: 'Grease Penetrometer'

    Aim: To find out the consistency of a given sample of grease.

    What is the Consistency of Grease?
    - The measure of relative hardness of grease is referred to a consistency number as per N.L.G.I (National Lubricating Grease Institute) which is a trade association that governs lubrication and related industry research.

     What is Grease?