experiment of double pipe heat exchanger

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Double Pipe Heat Exchanger Performance.




OBJECTIVE:


To demonstrate the differences between co-current and counter –current heat

transfer by exploring the effect on the amount of heat transferred temperature

efficiencies and temperature profiles for both regimes.




PROCEDURE


The thermocouple is checked to be connected in co-current mode. Cold water is set

to flow to 1 l/min and the cold water is determined. Then, the hot water temperature

controller is set to 600C and flow to a 2 l/min above the cold water temperature.

When all temperature reading is stabilized, a full set of thermocouple readings are

recorded and it is repeated 7 more times at 2 min intervals. Then, the heater and hot

water flow is switched off then the apparatus is cooled down. The valves near the hot

water connections are closed. The all steps for co-current mode is repeated using

counter-current mode.




APPARATUS:


U-shaped double pipe, hot water and cold water
SUMMARY


Heat is thermal energy. It can be transferred from one place to another by

conduction, convection and radiation. This experiment is to demonstrate differences

between co-current and counter –current heat transfer. The cocurrent flow is

connected in the same direction and counter current flow is connected in the

opposite direction.this experiment is conducted using U-shaped double pipe.the

efficiency of the heat transfer is depend on the LMTD and flow rate.the counter

current flow is more efficiency compare to co current flow.the different flow rate of

hot water in counter current flow influence the efficiency of heat transfer.
         RESULTS:

         CO-CURRENT FLOW

         Hot water= 2 l/min             Cold water= 1 l/min

                                                                                                           Hot
                      Tem     Tem          Tem    Tem     Tem                                                        Cold
           Tem                                                   Temp       Temp    Temp       Temp      Water
Sample                 p       p            p      p       p                                                        Water
                                                                                                         Flowra
Number                                                                                                             Flowrate
              T1                                                  T7         T8       T9       T10          te
                       T2         T3        T4      T5     T6                                                        Fcold
             [°C]                                                [°C]       [°C]     [°C]      [°C]       Fhot
                      [°C]       [°C]      [°C]    [°C]   [°C]                                                      [l/min]
                                                                                                         [l/min]
  1        73.0       68.7       63.2      42.3   30.6    16.4   133.0      133.0    133.0     133.0        2.2      1.32
  2        69.7       64.1       59.7      40.6   31.6    16.6   133.0      133.0    133.0     133.0        2.1      1.22
  3        77.1       71.3       65.2      44.7   34.3    16.6   133.0      133.0    133.0     133.0        2.2      1.21
  4        72.6       65.9       61.8      42.2   32.4    16.7   133.0      133.0    133.0     133.0        2.0      1.37
  5        69.4       63.5       58.6      39.9   29.5    16.6   133.0      133.0    133.0     133.0        1.9      1.29
  6        74.3       68.0       62.6      42.5   32.9    16.6   133.0      133.0    133.0     133.0        2.0      1.26
  7        72.4       65.9       61.3      41.9   31.3    16.6   133.0      133.0    133.0     133.0        1.9      1.20




  Specific           Specific                                                                                        Overall
                                      Hot fluid        Cold Fluid
   Heat               Heat                                               LMTD         Heat                            Heat
                                      Average           Average                                     Heat
 Hot Fluid          Cold Fluid                                                      Transfer                        Transfer
                                    Temperature       Temperature                               Transferred,Q
   Cph                 Cpc                                                           Area,A                        Coefficient
                                        [°C]              [°C]
 [kJ/kg K]          [kJ/kg K]                                                                                          U
  4.188               4.178                68.3           29.8           17.457       0.0344           17951.65      29876.78
  4.186               4.178                64.5           29.6           21.233       0.0344           23516.30      32178.64
  4.190               4.178                71.2           31.9           21.866       0.0344           24081.40      31998.44
  4.187               4.178                66.8           30.4           24.923       0.0344           28009.83      32652.49
  4.186               4.178                63.8           28.7           22.034       0.0344           24601.69      32440.32
  4.188               4.178                68.3           30.7           23.615       0.0344           26383.41      32460.41
  4.187               4.178                66.6           29.9           24.223       0.0344           27193.30      32617.64
           COUNTER CURRENT

           Hot water=2 l/min      Cold water=1 l/min



Samp     Tem     Tem               Tem                   Tem    Tem                                      Hot         Cold
                           Temp               Temp                        Temp    Temp      Temp
  le      p       p                 p                     p      p                                     Water        Water
Numb                                                                                                  Flowrate     Flowrate
                            T3                  T5                          T8     T9       T10
 er        T1     T2                 T4                   T6     T7                                     Fhot         Fcold
                           [°C]                [°C]                        [°C]   [°C]      [°C]
          [°C]   [°C]               [°C]                 [°C]   [°C]                                   [l/min]      [l/min]
 1       58.1    73.8      80.3     54.3       39.7      18.3   133.0     133.0   133.0     133.0        2.0         0.84
 2       66.1    84.1      92.1     64.5       45.2      18.5   133.0     133.0   133.0     133.0        2.0         0.87
 3       67.8    86.7      95.0     67.7       46.8      18.7   133.0     133.0   133.0     133.0        1.9         0.94
 4       66.6    83.8      91.8     66.0       44.7      18.9   133.0     133.0   133.0     133.0        1.6         0.74
 5       65.9    84.3      94.0     66.1       43.8      19.0   133.0     133.0   133.0     133.0        1.7         0.76
 6       64.7    81.5      91.8     65.0       44.4      19.0   133.0     133.0   133.0     133.0        1.5         0.84
 7       65.8    83.0      94.1     65.3       43.8      19.1   133.0     133.0   133.0     133.0        1.4         0.82




      Specific                                                                                                   Overall
                 Specific Heat       Density       Density
       Heat                                                                        LMTD              Heat         Heat
                  Cold Fluid        Hot Fluid     Cold Fluid        Heat
     Hot Fluid                                                                                     Transfer     Transfer
                      Cpc                                       Transferred,Q
       Cph                                                                                          Area,A     Coefficient
                   [kJ/kg K]         [kg/m³]          [kg/m³]
     [kJ/kg K]                                                                                                     U
      4.190             4.178         977.3           993.2            2568.7      51.788             0.0127     3905.4
      4.197             4.179         971.2           991.1            2922.5      62.574             0.0127     3677.5
      4.199             4.179         969.7           990.4            2928.5      65.193             0.0127     3537.1
      4.197             4.179         971.3           990.9            3049.5      61.840             0.0127     3882.9
      4.197             4.179         970.8           991.1            3099.9      63.645             0.0127     3835.1
      4.196             4.179         972.1           991.1            2840.0      62.417             0.0127     3582.7
      4.197             4.179         971.1           991.1            3067.8      64.031             0.0127     3772.5
         COUNTER CURRENT

         Hot water=3 l/min              Cold water= 1 l/min



                                                                                                             Hot
Sampl
          Temp        Temp       Temp      Temp    Temp       Temp     Temp     Temp      Temp     Temp    Water       Cold Water
  e
                                                                                                           Flowra       Flowrate
Numbe
               T1       T2        T3         T4      T5        T6        T7      T8         T9      T10       te          Fcold
  r
              [°C]     [°C]      [°C]       [°C]    [°C]      [°C]      [°C]    [°C]       [°C]     [°C]    Fhot         [l/min]
                                                                                                           [l/min]
  1           76.9     88.9      92.5      74.5     54.9      19.4      133.0   133.0     133.0    133.0      3.2         0.78
  2           77.6     89.8      94.1      75.9     55.4      19.4      133.0   133.0     133.0    133.0      3.5         0.81
  3           69.1     77.0      80.1      64.4     47.6      19.5      133.0   133.0     133.0    133.0      3.3         0.77
  4           68.9     80.2      85.1      63.7     46.8      19.5      133.0   133.0     133.0    133.0      3.1         0.90
  5           76.8     90.0      94.2      74.5     55.7      19.4      133.0   133.0     133.0    133.0      3.1         0.72
  6           70.2     77.9      80.5      65.8     49.0      19.4      133.0   133.0     133.0    133.0      3.3         0.78
  7           67.5     78.2      83.0      62.6     46.3      19.4      133.0   133.0     133.0    133.0      3.2         0.89




                      Specific
   Specific                                        Density
                       Heat        Density                                                                             Overall
    Heat                                            Cold                          Heat
                       Cold       Hot Fluid                      LMTD                                 Heat           Heat Transfer
  Hot Fluid                                         Fluid                       Transfer
                       Fluid                                                                      Transferred,Q       Coefficient
    Cph                                                                          Area,A
                        Cpc        [kg/m³]                                                                                 U
  [kJ/kg K]                                        [kg/m³]
                     [kJ/kg K]
      4.202            4.180        967.7           988.2            39.2        0.0127              3085.1             4627.7
      4.203            4.180        967.0           987.9            38.5        0.0127              3108.7             4755.5
      4.193            4.179        974.6           990.7            34.1        0.0127              3010.2             5191.5
      4.195            4.179        972.9           990.9            33.6        0.0127              3088.8             5401.1
      4.203            4.180        967.1           988.1            40.4        0.0127              2945.0             4283.4
      4.193            4.179        974.1           990.3            35.5        0.0127              2960.8             4901.0
      4.193            4.179        974.1           991.1            32.9        0.0127              2960.8             5299.5
           COUNTER CURRENT

           Hot water=1 l/min           Cold water=below 1 l/min



                                                                                                           Hot       Cold
           Temp     Temp     Temp         Temp      Temp     Temp    Temp      Temp    Temp     Temp
Sample                                                                                                   Water      Water
Number                                                                                                  Flowrate   Flowrate
             T1       T2         T3        T4        T5        T6     T7         T8     T9      T10
                                                                                                          Fhot       Fcold
            [°C]     [°C]       [°C]      [°C]      [°C]      [°C]   [°C]       [°C]   [°C]     [°C]
                                                                                                         [l/min]    [l/min]
  1         36.3     58.3       70.8      41.9      27.9      17.3   133.0     133.0   133.0    133.0       1.1       0.99
  2         37.7     57.6       67.5      41.7      28.8      17.3   133.0     133.0   133.0    133.0       0.0       0.96
  3         36.5     51.1       57.4      36.9      26.3      17.3   133.0     133.0   133.0    133.0       1.0       1.03
  4         33.5     44.4       51.0      32.4      24.5      17.2   133.0     133.0   133.0    133.0       1.0       0.98
  5         36.1     58.0       71.8      40.8      27.8      17.0   133.0     133.0   133.0    133.0       1.0       0.93
  6         42.1     71.0       88.6      50.8      33.6      17.0   133.0     133.0   133.0    133.0       0.9       0.94
  7         45.4     74.5       91.3      53.8      35.3      17.0   133.0     133.0   133.0    133.0       1.0       1.00




  Specific          Specific                           Density                                                       Overall
                                         Density
   Heat              Heat                               Cold           Heat                             LMTD          Heat
                                        Hot Fluid                                      Heat
 Hot Fluid         Cold Fluid                           Fluid        Transfer                                       Transfer
                                                                                   Transferred,Q
   Cph                Cpc                                             Area,A                                       Coefficient
                                         [kg/m³]
 [kJ/kg K]         [kJ/kg K]                           [kg/m³]                                                         U
   4.217             4.217                999.8            999.8      0.0127           4267.5           43.087       7798.7
   4.217             4.217                999.8            999.8      0.0127           4053.0           40.676       7845.7
   4.217             4.217                999.8            999.8      0.0127           3487.0           32.228       8519.5
   4.217             4.217                999.8            999.8      0.0127           2793.3           28.488       7720.5
   4.217             4.217                999.8            999.8      0.0127           4244.7           45.756       7304.6
   4.217             4.217                999.8            999.8      0.0127           5253.4           59.531       6948.5
   4.217             4.217                999.8            999.8      0.0127           5508.9           60.976       7113.9
DISCUSSION:


The aim of this experiment is to demonstrate the differences between co current and

counter-current heat transfer by exploring the effect on the amount of heat

transferred, temperature efficiencies and temperature profiles for both regimes.U-

shaped double pipe .there are three basic mechanisms of heat transfer. There are

conduction, convection and radiation. In heat exchanger equipment, the temperature

of the flowing fluid is continuously changing and hence ∆T is also changing. Heat

transfer can be determined using the equation Q=UA∆T. the heat transfer of hot

water is more efficiency compared to cold water.


The meant of co current in this experiment is the both cold water and hot water can

be connected to flow in the same direction as the hot water in u-shaped double pipe.

Besides, counter current is the both cold water and hot water is connected to flow in

the opposite direction.In counter cuurent mode the exchanger takes place between

two liquids which flowing in contrary sense.From the experiment data it can be said

that the counter current flow is more efficient for heat transfer compare to co current

flow. It is expected because the log mean temperature different, ∆T of co current flow

is lower compared to counter current flow. Thus it will influence the transfer in u-

shaped double pipe. That means co current flow is less efficient for heat transfer

than counter current flow. In co current flow, since the cold water and hot water flow

in the same direction it will reduce the temperature. The heat transfer in the counter

current flow also depends on the flow rate of both cold water and hot water. It means

the different of flow rate will influence the heat transfer. The efficiency of the heat

transfer process is the amount of energy absorbed by the cold stream divide by the

amount of energy loss from the hot stream, Qe . The measurement of heat transfer u-
shaped double pipe might be inaccurate because some human error when recording

the data. The actual flow rate is hard to set accurately.


The heat transfer also depends on the flow rate. When the hot flow rate alters thus

log mean temperature different increase and when the cold flow rate alters thus the

log mean temperature decrease. It is also observed that with increase in flow rate of

hot fluid, both heat transfer coefficient increases but the heat transfer coefficient

decrease when the cold flow rate appears.




CONCLUSION:

Heat transfer is the transition of the thermal energy from a higher temperature object

to lower temperature object.the heat transfer occur when the body and the

surrounding reach thermal equilibrium.when there is temperature different between

object in proximity the heat transfer can be stopped but it can be slow down.
NOTATION:



  1. Overall heat transfer coefficient, U (W/m2.K)

  2. Rate of heat transfer, Q (J/s=W)

  3. Area available for heat flow ,A (m2)

  4. Log mean temperature, LMTD,∆T (K or 0C)

  5. Inner tube, di (m)

  6. Inner tube, do (m)

  7. Heat transmission length, L (m)

  8. Specific heat hot fluid, Cph (kJ/kg k)

  9. Specific heat cold fluid, Cpc (kJ/kg k)

  10. Density hot fluid, dc (kg/m3 )

  11. Density cold fluid, dh (kg/m3 )
EXAMPLE CALCULATION:



Q=mcp∆T

 m = flow rate x density

 = (2 x 1000m3/60 s) x 967.8 kg/m3

 = 32260 kg/s

Q=32260 x 4.17 x (76.5 – 49.7)

 =356489 k W




LMTD= (∆Tin - ∆Tout)/ln (∆Tin/∆Tout)

     = (85.5-39.3)-(76.2-59.7)/ ln (85.5-39.3)-(76.2-49.7)

     =37.3 0C

A=2πrL

 =2π x 0.0083/2 x 0.66

 =0.0017 m2




Q=U A LMTD

U=Q/A LMTD

 = 356489 /(0.0017 x 37.3)

 = 5621968 W/m2.K

				
DOCUMENT INFO
Description: this is a experiment of double pipe heat exchanger