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					          ME495




Lab 5: Plate Heat Exchanger




        Group D:
       David Elting

    Christopher Goulet

    Gerardo Espinoza

     Rodolfo Gonzalez




 Professor Sam Kassegne




          10-3-07




             1
                                               Table of Contents



1. Title Page ...............................................................................................................1

2. Table of Contents ...................................................................................................2

3. Objective of the Experiment (David Elting) ..........................................................3

4. Equipment (Rodolfo Gonzalez) .............................................................................4

5. Experimental Procedure (Gerardo Espinoza) ...................................................... 5-6

6. Experimental Results (Christopher Goulet) ....................................................... 7-10

7. Discussion of Results (David Elting) ....................................................................11

8. Lab Guide Questions (Christopher Goulet) .........................................................12

9. Conclusion (Rodolfo Gonzalez) ...........................................................................13

10. References (David Elting).....................................................................................14




                                                            2
                                 Objective of the experiment

        To demonstrate indirect heating or cooling by transfer of heat from one fluid
stream to another when separated by a solid wall (fluid to fluid heat transfer). In this
exercise an HT30X Heat Exchanger Unit and HT32 unit (Plate Heat Exchanger) are used
for this laboratory. The HT30X and HT32 are test devices created for use in physics and
engineering laboratories by Armfield Limited, Ringwald, Hampshire England.1

Where:
Q      is change in heat between the inlet and the exit
T      is temperature
m      is mass
      is efficiency
Cp     is specific heat in a constant pressure process
ρ      is density
V      is volume

*any capital letter represents the same meaning as the lower case, except it represents
meaning for the system and not the process.
*a dot over a mass or volume symbol represents flow.




1
 Kassegne, Sam. "Plate Heat Exchanger." Blackboard. SDSU Engineering. 21 Sep 2007
<https://blackboard.sdsu.edu>.


                                                3
                                     Equipment list




Fig.1 HT32 Heat Exchanger              Fig.2 HT30X Heat Exchanger service unit

     HT32 Heat Exchanger
    - Volume: 0.03m3
    - Gross weight: 6 kg
    - Plate overall dimensions: 75mm x 115mm
    - Projected heat transmission area: 0.008m2 per plate
    - Maximum water temperature to 85°C
                1. Hot fluid inlet
                2. Hot fluid outlet
                3. Cold fluid inlet
                4. Cold fluid outlet
                5. Hot fluid inlet
                6. 5 effective plates
                7. Thermocouples resolution 0.1°C.
                8. Conditioning circuits
http://www.armfield.co.uk/ht3237_datasheet.html

     HT30X Heat Exchanger service unit
    - Volume: 0.33m³
    - Gross weight: 33kg
               1. Cold water supply stream
               2. Hot water supply stream
               3. Hot water vessel with an electrical heater
               4. Gear pump
               5. Variable flow valves
               6. Pressure regulator
               7. Flowmeters calibrated from 0.2 to 5 L/min
               8. Digital displays
               9. Conditioning circuit outlets for the Heat Exchanger
               10. Drain
http://www.armfield.co.uk/ht30xc_datasheet.html

      Lab table


                                            4
                                        Procedure

       Using the lab manual as a guide to do the experiment, the lab was started by

mounting the heat exchanger to the HT30X heat exchanger service unit. Then all the

sensors were connected to the main console in order to record the temperature and set the

hot and cold water flow rates. Also the hoses were connected to flow water through the

heat exchanger and the heater. Before the experiment was started, the hot and cold water

circuits had to be primed in order to remove any air bubbles that could give false

readings.

       The priming was done by connecting the heat exchanger hot water inlet to the

heat exchanger cold water outlet. Next, the heat exchanger hot water outlet was

connected to the HT30X hot water inlet. The hot water bypass valve had to be closed, and

the cold water pressure regulator was set to a minimum setting by pulling the control

knob out (to the right) and turning full counter clockwise. Then the cold water flow

control valve was fully opened and gradually adjusted the cold water pressure regulator

control knob clockwise until water was seen flowing through the hot water circuit

flexible tubing and into the clear plastic priming vessel. When the priming vessel was full

and there were no more air bubbles in the lines, the cold water flow control valve was

closed. Afterwards the tube from the heat exchanger cold water outlet was disconnected

and reconnected to the HT30X hot water outlet. The lid from the priming vessel was

removed and filled the vessel the rest of the way with water, and then the lid was

replaced. The hot water circulating pump and heaters were switched on. Finally the hot

water bypass valve was opened and closed several times until all of the air bubbles were

expelled from the tubing and the priming vessel was refilled when the water level

dropped.

       After the hot and cold water circuits were primed, the cold water flow had to be

set. First the cold water pressure regulator was set by connecting the heat exchanger cold

water inlet to the HT30X cold water inlet. Then the heat exchanger cold water outlet tube


                                             5
was routed to the center drain area of the HT30X. Next the flow indicator switch on the

main console was set to Fcold and the cold water flow control valve was fully opened. The

cold water pressure regulator control knob was adjusted until the flow display on the

main console indicated 3 liters/min. Finally, the cold water pressure regulator control

knob was locked into position by pressing to the left on the tip of the knob and then the

cold water flow control valve was closed. Now the experiment was ready to begin.

       The experiment began by connecting the fluid supply tubing so the flow was

countercurrent. All the thermocouple plugs were connected to their respective sockets in

the console display. Then 60C was added to the reading and the temperature controller

was set to this value by momentarily pressing the setpoint key. Next the increase key or

decrease key was pressed until the desired setting was indicated. the flow indicator switch

on the main console was set to Fcold and then the cold water control valve Vcold was

adjusted to read 1 liter/min. the flow indicator switch was set to Fhot and then the hot

water control valve Vhot was adjusted to read 2.5 liter/min. The heat exchanger was

allowed to stabilize by monitoring the temperatures using the console display. When the

temperatures were stable, the thermocouple selector knob was rotated to different

temperatures in order to record the values for T1, T2, T3, T4, Fcold, and Fhot. Finally the

flow indicator switch was set to Fcold and the cold water control valve Vcold was adjusted

to read 2 liter/min. After the heat exchanger was stabilized, the new values from the

sensor outputs were recorded.

       Once all the values were recorded, it was time to clean up the area. The heat

exchanger was removed from the HT30X heat exchanger service unit and put away in its

rightful location. The HT30X was shut down and disconnected and returned to its

location. Finally, all the water that was spilled on the units and on the floor was picked up

in order to keep the area safe and clean.




                                              6
                                         Experimental Results

                                             Data Reduction

Table 1 Temperature and flow data for 1 liter/min cold water flow
                                 Experiment 1
Fhot = 2.48 liters/min                     Fcold = 1.02 liters/min
Hot water inlet T1 = 54.8 deg C            Cold water inlet T3 =   25.6 deg C
Hot water outlet T2 = 47.4 deg C           Cold water outlet T4 =  47.6 deg C

Table 2 Temperature and flow data for 2 liter/min flow data
                                 Experiment 2
Fhot = 2.48 liters/min                     Fcold = 2.05 liters/min
Hot water inlet T1 = 47.2 deg C            Cold water inlet T3 =                         24.7 deg C
Hot water outlet T2 = 39.3 deg C           Cold water outlet T4 =                        37.0 deg C

2. Calculate the following for each set of data:

Experiment 1

Average hot water temperature and density
       T  T2 54 .8  47 .4                                            kJ                   kg
Thot  1                            51 .1 C  c p ,hot  4.18            ,  hot  987 3
            2              2                                       kg  C
                                                                        
                                                                                            m
Average cold water temperature and density
        T  T3 47 .6  25 .6                                             kJ                   kg
Tcold  4                            36 .6  C  c p ,cold  4.18            ,  cold  993 3
             2              2                                         kg  C
                                                                          
                                                                                              m
a. The heat emitted from the hot fluid
                                        kg           kJ 
 
Qhot  mhot c p ,hot Thot   0.0408  4.18
        
                              
                                                                    
                                                               7.4  C  1.26kW
                                        s         kg  C 
                                                         
                                                              
b. The heat absorbed from the cold fluid
                                            kg            kJ 
 
Qcold  mcold c p ,cold Tcold   0.0169  4.18
          
                                 
                                                                         
                                                                  22.0  C  1.55kW
                                            s        kg  C 
c. Mass flow rate for the hot fluid
                                 m 3        kg              kg
mhot  Vhot  hot   4.13e  5
                                      987 3   0.0408
                                       
                                   s         m                s
d. Mass flow rate for the cold fluid
                                   m 3        kg              kg
mcold  Vcold  cold  1.70e  5
                                         993 3   0.0169
                                          
                                     s         m                 s
e. The heat lost from the system
                
Qlost  Qhot  Qcold  1.26 kW  1.55 kW  0.290 kW
f. The temperature efficiency of the hot fluid



                                                      7
         T1  T2             54.8 C  47.4  C
 hot              100%                         100%  25.3%
         T1  T3             54.8 C  25.6  C
g. The temperature efficiency of the cold fluid
          T T                47.6  C  25.6  C
 cold  4 3  100%                                100%  75.3%
          T1  T3             54.8 C  25.6  C
h. The mean temperature efficiency
           cold 25.3%  75.3%
 m  hot                                 50.3%
             2                 2
i. The overall efficiency for the system
      Q         1.55kW
  cold                 123%
       
       Qhot 1.26kW
j. Hot fluid volume flow rate
Vhot  Fhot 1.667 x10 5    2.48
                                        L                                3
                                            1.667 e  5  4.13e  5 m
                                      min                              s
k. Cold fluid volume flow rate
   F 1.667 x10 5   1.02 L 1.667 e  5  1.70 e  5 m
                                                                             3
Vcold       cold                             
                                       min                              s
l. Reduction in hot fluid temperature
 Thot  T1  T2  54 .8  C  47 .4  C  7.4  C
m. Reduction in cold fluid temperature
 Tcold  T4  T3  47 .6  C  25 .6  C  22 .0  C

Experiment 2

         T1  T2 47 .2  39 .3                                  kJ                   kg
Thot                          43 .25  C  c p ,hot  4.18         ,  hot  995 3
            2          2                                      kg  C
                                                                  
                                                                                     m
          T  T3 37 .0  24 .7                                    kJ                   kg
Tcold    4                     30 .85  C  c p ,cold  4.18         ,  cold  990 3
             2          2                                       kg  C
                                                                    
                                                                                       m
                                        kg       kJ 
   
a. Qhot  mhot c p ,hot Thot   0.0411  4.18
          
                                
                                                                     
                                                          7.9  C  1.36kW
                                        s     kg  C 
                                                         
                                            kg       kJ 
   
b. Qcold  mcold c p ,cold Tcold   0.0338  4.18
           
                                    
                                                                          
                                                             12.3 C  1.74kW
                                            s     kg  C 
                                                         
                                                            
                                  m 3       kg         kg
c. mhot  Vhot  hot   4.13e  5
                                       995 3   0.0411
                                        
                                    s        m           s

                                     m 3      kg          kg
    cold  Vcold  cold   3.42e  5
d. m                                       990 3   0.0338
                                           
                                       s       m            s
                   
e. Q  Q  Q  1.36 kW  1.74 kW  0.382 kW
        lost   hot    cold




                                                    8
                                T1  T2          47.2  C  39.3 C
f.  hot                                100%                       100%  35.1%
                                T1  T3          47.2  C  24.7  C
           T4  T3          37.0  C  24.7  C
g.  cold          100%                       100%  54.7%
           T1  T3          47.2  C  24.7  C
             cold 35.1%  54.7%
h.  m  hot                            44.9%
              2              2
       Q      1.74kW
i.   cold             128%
        
       Qhot 1.36kW

                                                 
       F  1.667 x10 5   2.48 L 1.667 e  5  4.13e  5 m
                                                                              3
j.. Vhot      hot                            
                                         min                               s
                                     
                                           L 
                                                        
                                                                                3
k.  Vcold  Fcold  1.667 x10 5   2.05
                                                1.667 e  5  3.42 e  5 m
                                          min                                s
l. Thot  T1  T2  47 .2 C  39 .3 C  7.9 C
                                               


m. Tcold  T4  T3  37 .0  C  24 .7  C  12 .3 C

3.
                                                            Hot water temperature   Cold water temperature

                           60




                           50




                           40
     Temperature (deg C)




                           30




                           20




                           10




                           0
                                                inlet                                                        outlet


Figure 1 Temperature data for 1 liter/min cold water flow rate




                                                                             9
                                     Hot water temperature   Cold water temperature

                        50




                        40
  Temperature (deg C)




                        30




                        20




                        10




                        0
                             inlet                                                    outlet


Figure 2 Temperature data for 2 liter/min cold water flow rate




                                                     10
                                  Discussion of Results

    The data obtained was consistent with the hypotheses with regards to temperature
variation at the heat exchanger outlets. In both experiments, the hot and cold water
streams approached an equilibrium temperature. When the cold water flow was
increased while keeping the hot water flow the same, both outlet temperatures decreased.
More heat was transferred from the hot stream to the cold stream at the higher cold water
flow rate, resulting in a greater hot stream temperature drop. The higher cold water flow
resulted in lower cold water outlet temperatures because the cold water was exposed to
the hot water in the heat exchanger for a shorter period of time.
    At T3 (cold water inlet) the temperature decreased 0.9° C between experiment one
and two. This is probably due to a larger cold water flow or a longer time allowed for the
system to stabilize.
    At T1 (hot water inlet) the temperature dropped 7.6° C between experiment one and
two. This is possibly due to the larger cold water flow, which may have cooled the plate
heat exchanger exterior. The hot water at the inlet may have been cooler as a result of a
larger temperature difference at contact with the heat plate, resulting in heat transfer
between the hot water stream and the exterior of the plate heat exchanger. Additionally,
the hot water flowing towards the inlet may have been in contact with the tubes carrying
the cold water, resulting in heat loss from the hot stream before it entered the heat
exchanger.
    There were a few noticeable sources of experimental error. The hot water
temperature at T1 (hot water inlet) was measured at 54.8° C in experiment one despite the
heater being set to 60° C. This is probably a consequence of not allowing the system to
warm up for long enough before beginning the experiment. Small air bubbles
(approximately 2mm diameter) trapped in the hot and cold water circuits may have
altered the volume flow measurements. Air pockets may have also caused temperature
variations and affected the speed of the water pump. Also, as the system warmed up, the
variables in the system probably became a little more consistent and efficient. Examples:
water density, temperature, flow rate, air bubbles, and pressure.
    Despite the fact that the temperatures changed in accordance with the hypotheses, the
calculated efficiency for the heat exchanger was greater than 100%, indicating that the
cold water was absorbing more heat than the hot water was emitting. As the cold water
flow rate increased, the efficiency of the heat exchanger increased from 123% to 128%.
One possible explanation is that the cold water experienced frictional heating as it entered
the heat exchanger, resulting in an increased outlet temperature. However, it seems
unlikely that frictional heating would result in such a large increase in cold water
temperature at the low flow rates of this experiment. Thus, it seems more likely that
these impossible efficiencies were the result of faulty flow sensors or thermocouples,
incorrect setup, or incorrectly primed flow. If the cold water flow was measured as being
higher than it actually was by a faulty flow sensor, the calculated heat absorption of the
cold water would also be higher than it actually was, resulting in a higher calculated
efficiency. Also, the ambient temperature was higher than the cold water inlet
temperature, which may have added additional heat to the heat exchanger, thus
transferring more heat than expected to the cold water outlet. The actual room
temperature was not measured but was noticeably higher than the cold water inlet.



                                            11
                                   Lab Guide Questions

1. Did the heat exchanger remove more or less heat from the hot stream as the flow rate
    of the cold water increased?
        More heat was removed from the hot stream at the 2 liter/min cold water flow rate
(1.36 kW) than at the 1 liter/min cold water flow rate (1.26 kW). The higher cold water
flow resulted in a larger average temperature difference in the heat exchanger, resulting
in increased heat transfer from the hot stream to the cold stream. Increased cold water
flow may have also generated increased turbulence, which may have enhanced heat
transfer.

2. Did the system efficiency increase or decrease as the cold water flow rate increased?
        The system efficiency increased slightly as the cold water flow increased. More
of the heat from the hot water stream appeared to be absorbed by the cold water stream at
the higher cold water flow rate. However, both efficiencies were over 100%, making it
difficult to make any definitive claims about the effect of flow on efficiency. The data
suggests that there is some other factor adding significant heat to the cold water flow
stream, thus increasing the apparent efficiency.




                                           12
                                    Conclusion

        This lab has demonstrated how the heat exchanger removed more heat from the
hot stream as the flow rate of the cold water increased and the effects of several factors
that affected the overall efficiency of the system. The objective of this lab was to
demonstrate the indirect heating or cooling by transfer of heat from one fluid stream to
another when separated by a solid wall (fluid to fluid heat transfer). The objective was
accomplished by using the HT30X Heat Exchanger Unit and HT32 unit (Plate Heat
Exchanger) to measure the inlet and outlet temperatures of fluids flowing through the
HT31 Heat Plate, as well as their flow rates. More heat was removed from the hot stream
when the flow rate of the cold water was increased since the higher cold water flow
resulted in a larger average temperature difference in the heat exchanger, thus increasing
heat transfer from the hot stream to the cold stream. The system efficiency increased as
the cold water flow rate increased slightly, possibly due to the increase in friction as the
flow rate was augmented. The overall efficiency of our system was so high that we had to
question the validity of some of these results. The possible reasons for such a high
efficiency could be faulty sensors. The cold water flow may have been measured as being
higher than it actually was by a faulty flow sensor. Another possibility is that the ambient
temperature in which the experiment was conducted was higher than the cold water
temperature, which would have added heat to the system from its surroundings.




                                            13
                                     Works Cited

Kassegne, Sam. "Plate Heat Exchanger." Blackboard. SDSU Engineering. 21 Sep 2007

   <https://blackboard.sdsu.edu>.

< http://www.armfield.co.uk/ht3237_datasheet.html> 21 Sep 2007

< http://www.armfield.co.uk/ht30xc_datasheet.html> 21 Sep 2007




                                        14

				
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