Liquid- Liquid Heater (Condensate or Duplex juice Heater) Calculation

Condensate or Duplex Heater (Liquid- Liquid Heater)  Design Calculation formulas with online calculation sheet

• According to the  in the energy conservation point of view Sugar process industry used liquid liquid heaters for raw juice  heating . It is also called condensate heater or duplex heater( for specific design).
• In liquid- liquid heater raw juice heated with process condensate water and It having two types of designs.

    1. One is normal multi passes arranged in single tube plate design and it located horizontally or vertically. Generally for condensate heaters have located in horizontal position because in the horizontal position heat transfer coefficient having high and also in this design will get proper baffle plate arrangement to the passing of hot fluid(Condensate).
    2.   Another design is called Duplex heater. In this type design will get maximum heat transfer coefficient upto 1200±50 Kcal/m2/hr/oC.  When compare to another liquid liquid heater design its having higher heat transfer value , because the passing of hot and cooled fluid is perfectly in counter current direction from entry to leave the heater.  Another advantage is high flexibility to proved spare heater or expansion the capacity of heater. In Duplex heater also flexible to collect the condensate (heating media) in different stages as per our process requirement.(i. e as per our required temperature  we will get condense  in middle stage of heater).
  • In sugar process industry while using vapour or steam as a heating media than formulas used for heat transfer coefficient  {6 \ Tv \ \times\frac{U}{1.8} ^{0.8}and for evaluate heating surface used \frac{M \times Cp \times Ln [(Tv-ti)/(Tv-to)] }{K} . But in condensate heater calculation both are not applicable.
  • In this article explain about condensate heater heating surface calculation and for heat transfer coefficient calculation will published in another article.

Liquid- Liquid Heater (Condensate or Duplex juice Heater) Calculation - sugarprocesstech

Required data for calculation heating surface of Liquid Liquid heater:

  • Crushing rate = M in T/hr
  • Juice % cane = P
  • Velocity of Juice = Vj in m/sec
  • Juice inlet temperature = ti in oC.
  • Condensate Inlet temperature = Ti in oC.
  • Condensate Outlet temperature requirement =To in oC.
  • Specific heat of juice = Cp in Kal/Kg
  • Legment = Lg in mm (Generally Legment taken for Juice heater 12mm, and for evaporators will take 10mm)
  • Tube OD = OD in mm
  • Tube Thickness = Tk in mm
  • Tube length = L in mm
  • Tube plate thickness = Tp in mm
  • Total Quantity of Condensate water percent on Mixed Juice = W
  • Heat transfer coefficient = K in Kcal/m2/hr/oC. (Note : For Dulex Heater this value lies 1200±50 and for Normal condensate heater with proper baffle plate arrangement lies 1000±50  Kcal/m2/hr/oC)
  • Proportional factor = β in mm

Steps in Calculation of heating surface for Liquid Liquid heater:

Quantity of juice to be heating = Q =M x P/100 in T/hr
Quantity of heating media (Condensate) = Q xW/100 in T/hr

Fundamental formula :

  • Heat received by one  = Heat rejected by another.
  • M x Cp x (to – ti) = Q x Cw x (To- Ti)  Note : Here Cw = specific heat of heating media,  for condensate it will take value 1)
  • Juice outlet temperature = to  ( From the above formula it can be find out the final juice outlet temperature)

Heating Surface :

  • For heating surface calculation  M x Cp x ΔT = S x K x ∆Tm
  • Heating Surface =S = [Q x Cp x ∆T]/ [ K x ∆Tm]
  • Here ∆Tm called as logarithmic mean temperaturelogarithmic mean temperature of liquid liquid heater -sugarprocesstech
  • ∆T = to-ti
  •  \bigtriangleup Tm =\frac{\bigtriangleup Ti - \bigtriangleup Te}{ Ln ( \frac{\bigtriangleup Ti}{\bigtriangleup Te})
  • ∆Ti = Ti-to
  • ∆Te = To-ti

Number of tubes per pass & Number of passes:

  • Number \ of \ tubes \ per pass = \frac{Volume \ of \ juice \ in M^3/sec }{Area \ of \ one \ tube \ in M^2 \times Velocity \ of \ juice \ in \ m/sec}
  • (Note :while calculating the area of tube take mean dia of tube i.e Tube OD – Tube Thickness)
  • No. of tubes Requirement = N = S/ [π x Mean dia of tube x Tube effective length]
  • Number of passes = n = N / number of tubes per pass
    In design point of view number of passes always should be even. According to this principle we consider the passes in even number. After the above consideration again calculates the actual heating surface and velocity of juice, it may be differ from required heating surface.

Pressure Drop and Tube Plate area calculation:

Pressure drop across the juice heater

  •  Pressure \ drop \ across \ the \ juice \ heater = 0.0025 \ \times n \times U^2 \times [ \frac{L}{D} \ + 3 ]

Here pressure drop in MWC , n = number passes , U = actual velocity of juice (after considering the even passes), L = Length of the tube, D = ID of the tube (Note : L & D to be take same units)

Tube Plate Area

  • Tube \ Plate \ Area \ in \ M^2 = \frac { (0.866 \times P^2 \times no. \ of \ tubes)} {\beta }


  • Tube Pitch (P ) = OD of the tube +Legment of the tube + tube clearance+hole clearance
  • Proportional factor(β) = Generally β value taken for multiple pass(i.e Juice heaters) 0.6 to 0.8 and for single pass(l.e evaporators or single pass duplex heater) 8 to 1.0.
  • Number of tubes will take as per the type of the heater. Suppose

For multi pass heater no. of tubes = Total number of tubes and

For Duplex having two pass in each section  than no. of tubes = No. of tubes per pass x 2

For Duplex having single pass in each section  than no. of tubes = No. of tubes per pass

(Note :Generally take extra dia in percentage on area occupied for tubes in tube plate  for partition plates arrangement, free withdrawal of condensate and noxious gases removal purpose. Its value lies in the range 10 to 20% on area occupied for tubes.)

 Heating media (Condensate water) inlet and out line dia :

  • Both inlet and outlet will take same dia meter.
  • Area required for condensate water entry (m2) =Quantity of heating media ( Q ) in M3/sec / Velocity of Condensate water in m/sec. (Note : Velocity of condensate will take 1.8 to 2.0 m/sec while coming from the pump )
  • Dia of the condensate water in mtr = SQRT [ (Area required for condensate water in m2  x (4/π ) ]

Remaining all design parameter can be calculated as same as the normal juice heater calculation.

Related Articles:

Fundamental theory  of Overall Heat Transfer Coefficient (OHTC)

Overall heat transfer coefficient for shell and tube heat exchanger

How to find Condensate Juice Heater Heat Transfer Coefficient Calculation

Heat Transfer Coefficient calculation of Liquid -Liquid Tubular Heater

Design Calculation of Juice Defecator and Sulphitor with online calculator

Shell and Tube Multipass Heat Exchanger Design | Tubular juice heater design calculation with online calculator

Condensate Receiving Tank Design Calculation | Condensate Mound

Flash Vapour Calculation | Flash Vapour Recovery Vessel Design Calculation.


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Post Author: siva alluri

The aim of this Blog "sugarprocesstech" is Providing basic to advance knowledge in sugar process industry and providing maximum calculation regarding capacity and equipment design online calculators .

9 thoughts on “Liquid- Liquid Heater (Condensate or Duplex juice Heater) Calculation

    Mukesh gupta

    (June 18, 2017 - 5:32 am)

    Sir, I want to know, how to calculate HTC in case of DUPLEX heater. I think, rate of heat transfer in duplex in low in comparison of other heater. Another opnion, U prefer vertical type or horizontal type. Sir, please suggest me

      siva alluri

      (June 18, 2017 - 4:35 pm)

      For calculation of HTC :
      Estimate overall heat transfer coefficient
      1/U = 1/hi + 1/ho + Th/Km + 1/Uis

      U = Heat transfer coefficient
      hi= Tube inside juice film coefficient
      ho= Shell side vapour film coefficient
      Km = Thermal conductivity of material
      Th = Thickness of the tube
      Uis = Tube inside and outside scaling factor but generally consider inside scaling factor only while heating media is water vapour because tube outside not consider due to it is negligible for vapour side.

      For more information please refer
      CHEMICAL ENGINEERING by Coulson & Richardson’s (VOLUME 6) page no. 662 onwards
      When a saturated vapour such as steam, transmits its heat to a metal surface and is condensed, the condensation may takes place in either of two entirely distinct forms. One is film type condensation, in which the condensed liquid wets the surface on which it is condensing and forms a continuous film of condensate. If the condensations occurring on the outside surface of horizontal metal tube (a very common case) this film of condensate drops off the underside of the tube: it runs down the condensation is drop wise condensation. In this case the condensed liquid does not wet the surface, but collects in drops that may range from microscopic size up to drops easily seen with the naked eye. These drops grow for while and then fall off the surface, leaving an apparently bare area in which new drops from.
      For the case of vertical tube in true film type condensation on which there is considering a saturated vapour, free from any NCG and moving at low velocities,
      Nusselt has derived the following equation

      For vertical tubes
      ho =0.943 \ \left [  \frac{Kc^{3} \times \rho c^{2} \times g \times\lambda}{L \times \mu c \times  \Delta  T} \right ]^{0.25}

      For horizontal tubes

      ho =0.725 \ \left [  \frac{Kc^{3} \times \rho c^{2} \times g \times\lambda}{D \times \mu c \times  \Delta  T} \right ]^{0.25}

      ho = Shell side condensate film coefficient
      Kc = Thermal conductivity of condensed vapour
      Ρc = Density of condensate
      g = acceleration due to gravity
      λ = Latent heat of vapour
      D = Outside dia of tube
      μc = Viscosity of condensate film
      L = Length of the tube
      ΔT = Temperature difference between vapour and metal (tube surface) = LMTD

      If we can substitute values for same heater in the above equations than definitely we can get HTC more in horizontal type heater. So according to HTC horizontal type heater to be prefer but according to cleaning the heater, mechanical operation and space occupation point of view vertical type design is preferable. So according to our requirement we can go through the horizontal or vertical heater design.

    sri winarno

    (August 17, 2017 - 9:36 am)

    sir , I want to know drawing or skets liquid-liquid juice heater in cane sugar….(duplex heater). tanks sir

    sri winarno

    (August 17, 2017 - 9:37 am)

    sir I want to know drawing or skets liquid-liquid juice heater in cane sugar….(duplex heater). tanks sir

    Ashish Verma

    (November 1, 2017 - 4:49 pm)

    Dear Sir
    Plz give capacity factor for juice heater and rotary vacuum filter

    Ashish Verma NSI


    (November 9, 2017 - 7:09 pm)

    Sir I want use thermifluid boiler for my Jaggery plant so pls help mi what is the boiler capacity calculated for open pan system for 35 tcd jaggery plants


    (November 9, 2017 - 7:28 pm)

    Sir is it possible to use of thermal fluid boilers for 35 tcd jaggery plants by using open pan ss vessel,then how to calculate boilers capacity and vessel size and limpiting pipeing size for vessel or in market any company give such setup for jaggery plant as per TCD

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