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  • Friday, 6 May 2016

    Tonne of Refrigeration, How to Calculate required TR



    Hello viewers.....!!!

    Hope you all having a Good Day and a Good Weekend too....!!!

    Today i gonna clear you some of the questions that you think when you remember the topic               " TONNE OF REFRIGERATION ", shortly TR.

    This is most common term used in Pharma industry when ever projects or chiller plants were concerned. Now, the basic questions that arise when you start on this topic were.,


    What is the value of  1 TR ??What does Actually TR means ??How the value for 1 TR derived and how it got to be 3024 KCal, ??

    So, before clearing all these doubts and demonstrating the way to calculate required TR, i wish to present you the basics required to understand this topic fluently.

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    This term TR or Tonne Of Refrigeration has been started from US, and apart from US the cooling terminology is basically in the format of MW or KW.
    And whenever we start to discuss over the units of any figure then the most disgusting thing that leads us to confusion is having two types, one is British units and the other one is English units.
    All the British countries will keep on using the British units and the English countries will be using English or SI units, in between there will be some countries conducting debate over the units, what to choose without keeping to something consistently, because we want to know everything in this world, and in turn this will lead to confusion.


    And while going deep into this you will be stopped at some point, distinguishing between the terms Short Ton and Long Ton. So, now its better to learn about these,

    What is a Short Ton and Long Ton ?? 
    The British ton is the long ton, which is 2240 pounds, and the U.S. ton is the short ton which is 2000 pounds.
    Both tons are actually defined in the same way. 1 ton is equal to 20 hundredweight. It is just the definition of the hundredweight that differs between countries. In the U.S. there are 100 pounds in the hundredweight, and in Britain there are 112 pounds in the hundredweight. This causes the actual weight of the ton to differ between countries.
    To distinguish between the two tons, the smaller U.S. ton is called short, while the larger British ton is called long.
    There is also an third type of ton called the metric ton, equal to 1000 kilograms, or approximately 2204 pounds. The metric ton is officially called tonne. The SI standard calls it tonne, but the U.S. Government recommends calling it metric ton.

    So its Clear about Short Ton and Long Ton.

    Now, i'll explain you the above mentioned questions,
    Actually 1 TR holds the value 3024 KCal. It means that Energy required or to be removed to freeze one ton of water to Ice in one day i.e., 24 hrs, So mathematically 1 TR means 288,000 Btu are required to make one ton of ice, divide this by 24 hours to get 12,000 Btu/h required to make one ton of ice in one day, In Simple words one 1 TR means energy required for change of phase from water at 0°C to Ice at 0°C.
    In British terminology, 1 TR is 3.517 KW,
    In English terminology, 1 TR is 3024 KCal.

    Learn How the value of 3024 KCal or 3.517 KW derived.....!!



    The latent heat of ice (also the heat of fusion) = 333.55 kJ/kg = 144 Btu/lb
    One short ton = 2000 lb, Heat extracted = 2000 x 144/24 hr = 288000 Btu/24 hr = 12000 Btu/hr = 200 Btu/min, 
    1 ton refrigeration = 200 Btu/min = 3.517 kJ/s = 3.517 kW = 4.713 HP .


    Another unit of measure is the calorie which is the amount of heat removal required to raise or lower the temperature of one gram of water by one °C. A kilo-calorie is the amount of heat required to raise or lower 1 kg of water by 1°C. One ton of refrigeration is equal to 3024 kilo-calories per hour. This is 12,000 BTU/ h divided by 2.204 (pounds per kilogram) divided by 1.8 (°C to °F). 

    So, i think you got answers for the hidden questions, So now i'll show you how to calculate the TR required for an operation. Let it, i need to cool 350 L toluene vapour which is produced at 35°C under 710 mm Hg vacuum, so how much TR required ??

    Soln. Volume to be cooled 350 L toluene. Mass to be cooled  350 L x 0.868 Kg/L = 303.8 Kg.

    Specific heat for Toluene vapour at 35°C is 1.72 KJ / Kg. °K,

    and the Sensible heat change is not in my hand, so i'll consider the temperature change of condensate as 5°C, so the Total Sensible heat load of the vapor can be calculated as 

    Qs = 303.8 x 1.72 x 5 = 2612.68 KJ = 625.04 KCal.

    And now i need to calculate the major thing the Latent heat, QL  

    QL = 303.8 x 351 = 106633.8 KJ = 25510.48 KCal.

    So the Total energy is Q = Qs + QL = 625.04 +25510.48 = 26135.52 KCal.

    So Now the required TR is 26135.52 / 3024 = 8.64 TR.

    So for the above operation of cooling a 350 L toluene vapour at 35°C which is produced at 710 mm Hg, i need 8.64 TR.

    So, simply TR required = Total Heat Load / 3024.

    That's it...... Cheers!!

    Hope you all understand the above topic clearly without any doubts .  Still any doubts We are Happy to Help, Contact Us through the Contact us Button available on page top,

    Comments are most appreciated.........!!




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    About The Author


    Hi! I am Ajay Kumar Kalva, Currently serving as the CEO of this site, a tech geek by passion, and a chemical process engineer by profession, i'm interested in writing articles regarding technology, hacking and pharma technology.
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    21 comments:

    1. Good one.. But my mind was tickling at one point,
      What is the correct definition of TR ??
      IS it energy req to freeze one ton of water to ice at 0°c
      Or
      Energy req to melt one ton of ice to water..
      So my doubt is both freezing and melting emphasis same meaning ???
      Freezing employs liq to solid phase and melting employs solid to liq..phase.. so what's the relation of both terms in TR
      Pls clear my query.

      ReplyDelete
    2. thats what we called energy balance, latent heat of freezing=latent heat of melting, but those operations should be at 0 degrees only

      ReplyDelete
    3. Now it makes me sense ☺ keep goin

      ReplyDelete
    4. I think the way TR is described is not correct . The Term TR is applicable for cooling or Heating irrespective of ICE formation . In room airconditioner capacity is defined in TR where the formation of ICE is not happening . TR means removal of 12000 BTU / Hr .

      A. K. BAKSI

      ReplyDelete
    5. Usually TR is used to define cooling rates, and being frank until now i haven't heard that TR is applicable for Heating also.

      ReplyDelete
    6. Can I used TR to calculate for the cooling tube capacity with information of dT of product temperature hot (in) to cold (out), weight of product pass through and time needed for all the product to pass through?

      ReplyDelete
    7. Sir plz provide PUMP CALCULATION ALSO ,IN A VERY SIMPME AND SYSTEMATIC MANNER

      ReplyDelete
      Replies
      1. Go through this, if you need any help mail me or comment here.

        https://pharmacalc.blogspot.in/2016/04/how-to-select-pump-and-motor-line.html

        Delete
    8. Could you calculate tr in SI unit

      Brine solution METHANOL 33% and minus chiller (-20C)

      Temperature delta T-5°C
      Flow - 100 M3/hr
      Specific heat - 3.744 kj/kgk

      Just tell about the unit conversion also

      ReplyDelete
      Replies
      1. Dear Prabakaran,

        TR = ((100 x 1000 x (3.744/4.187) x 5) + (100 x 1000 x 540)) / 3024.12 = 18004.72 TR,

        Since you haven't given any solvent, i've considered water latent heat which is 540 KCal,

        & TR itself is a unit,

        Unit conversions for TR :

        1 TR = 12000 BTU / Hr = 3024.12 KCal / Hr = 3517.2 Watts.

        Still if any queries please reply back.

        Regards,
        AJAY K

        Delete
    9. Dear sir,

      Thank for your quick response,
      But I am not able to get your calculation

      Actual formula is Q=M*Cp*delta T*specific gravity

      But how you are calculate I don't know could you expalin little deeper.
      I am a beginner so kindly guide me,

      TR = ((100 x 1000 x (3.744/4.187) x 5) + (100 x 1000 x 540)) / 3024.12 = 18004.72 TR,

      Note: using solvent is METHANOL by 33%
      Specific heat of methanol=3.744 kj/kgk

      Regarding units you are used for each terms
      Q= kW or kcal
      Cp= kj/kg k
      Delta T= °C
      M= M3/ hr

      Just correct me if my units used is worng

      Thanks & Regards
      PRABAKARAN


      ReplyDelete
      Replies
      1. Dear Prabhakaran,

        You have given input as for utility side, so there latent heat can be eliminated, so
        Q = M x Cp x dT = 100 x 920 x ( 3.744 / 4.187 ) x 5 = 411330 KCal.

        M = Mass flowrate = Volumetric flow rate x density = 100 x 920.

        Specific heat, Cp = 3.744 KJ/Kg.K = ( 3.744 / 4.187 ) KCal/Kg.K.

        dT = 5 degK.

        So, Q will be in KCal, since i've converted specific heat from Joules to Calories,

        So, now Q = 411330 KCal.

        TR = 411330 / 3024.12 = 136.016 TR.

        Note: Earlier your query is not that much clear, so i've considered calculating Total energy including Latent heat. Now its clear for me.

        Still any queries feel free to comment / message.

        Regards,
        AJAY K

        Delete
      2. Density i've considered as 920 Kg/Cu.m, since -20 degC brine will have a specific gravity of around 0.92.

        Regards,
        AJAY K

        Delete
    10. Super sir
      Now I understand

      One more doubt
      I need COP calculation for compressor(refrigeration compressor)

      Same parameters units and all others in details.
      Give the formula along with any excercise, it will be good.

      ReplyDelete
      Replies
      1. Dear Prabhakaran,

        May be you already know refrigeration means driving away the heat from low temperature medium to high temperature medium with some external work done on the system.

        COP = Cold reservoir heat energy / Work done = Tc / ( Th - Tc )

        Lets suppose, our system is at 50 degC(323 degK), and i wanna move it to 5 degC(278 degK), then the COP shall be,

        COP = 278 / ( 323 - 278 ) = 6.17.

        COP is unit less.

        Regards,
        AJAY K

        Delete
    11. In your above writings in cooling of 350L toluene vapour problem you have written "QL = 303.8 x 351 = 106633.8 KJ = 25510.48 KCal."..How it is so sir?

      ReplyDelete
      Replies
      1. It is latent heat, toluene having around 86.1 KCal/Kg, convert it into K Joules/Kg

        Regards,
        AJAY K

        Delete
    12. Oh sorry it is the latent heat of vaporization of toluene..

      ReplyDelete

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