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energy equivalency

Laboratory Work Result Wednesday,28th April 2010

Thermodynamics and Heat Transfer

DETERMINATION OF ENERGY EQUIVALENCY FOR VARIOUS BIOMASS MATERIALS

By :

Ahmad Eriska Dwi Hutama Putra

F14080122

ipb_logo

DEPARTMENT OF AGRICULTURAL ENGINEERING

FACULTY OF AGRICULTURAL TECHNOLOGY

BOGOR AGRICULTURAL UNIVERSITY

2010
  1. INTRODUCTION

The energy equivalency of a material, also known calorific value, is the energy that can be released by the material per weight unit if it experiences a complete combustion. The released energy can be transferred to the surroundings measured by various apparatus such as the calorimeter and the Denwar vessel.

The calorimeter generally comprises of a smaller vessel inside a large one, so that there is an empty spaces between the two that functions as an isolation for the heat transfer. A type of the calorimeter is the Bomb Calorimeter commonly used for the determination of the energy equivalency of the solid and liquid materials. The measurement is done by a constant volume in a close vesselsalled the Bomb.

The Bomb Calorimeter can be run by both the isothermic and the adiabatic conditions. In isothermic condition, the differences between the calorimeter and the surrounding temperatures are kept constant at the initial and final states. When this condition achieved then the amount of heat transfer from and to the surroundings will be equaled and canceled each other.

In the adiabatic condition, the heat transfer between the system to the surroundings is assumed zero, by adjusting the increase of the surrounding temperature equal to increase of the water temperature caused by combustion inside the Bomb. This can be achieved by controlling the temperature using the Beckman thermometer.

To obtain the energy equivalency of materials, the heat capacity of the calorimeter (water equivalent) has to be first determined by combusting a material whose energy equivalent of material, the water amount inside the inner vessel and the other vessel has to be equal to the water amount used for measuring the water equivalent.

The water equivalent and the energy equivalent of any materials i.e. expressed in :

…..( 1 ) …….( 2 )

Where,

Ew : water equivalent value (0.5925 kg)

EEr : energy equivalency of pressure sample, benzoid acid (26.48 2 kJ)

EEm : energy equivalency of measured material (kJ/kg)

Wr : mass of reference sample, benzoid acid (kg)

Wm : mass of measured material (kg)

Way : mass of water inside the inner vessel (kg)

∆T : temperature increased inside the inner vessel (kg)

However, a correction is necessary to be done for

i. the presectation of nickel cord and the wrapper of measured material, and

ii. the energy equivalency of the combustion fuel when the energy equivalency of the measured material is small.

  1. OBJECTIVES

1. To asses the principles of energy equivalency measurement using the adiabatic Bomb Calorimeter.

2. The energy equivalency of various materials

  1. MATERIALS AND EQUIPMENTS

The measured materials are charcoal husk and wood. The references sample is benzoic acid crystal. The equipments are the Improved Nenken Type Adiabatic Bomb Calorimeter OSK 100, and Beckman Thermometers.

  1. METHODS

1. Weigh 0.001 kg biomass as the measured material, wrap by a tissue paper and bind with an ignition nickel-wire. Put the wrapped material in the combustion crucible, connect both the end of the nickel wire to electrodes (B6 and B7), insert into the bomb and close tightly.

2. Connect the oxygen lead-pipe with the bomb at B4. feed in the oxygen, into the bomb until the pressure reaches kPa (20 – 30 kg/cm2)

3. Fill up the hot water tank with water to the maximum level (about 2 l) and heat to 85°C.

4. Weigh 2.1 kg water and pour into the inner vessel, and set the inner vessel on tripod bakelite vase on the bottom of the intermediate vessel

5. Connect the 2 lead-wires on the back of the cover of intermediate vessel with the screw B5 into the end of electrode- terminal B14

6. Pour the water into the jacket until it covers immediately

7. Fix the vessel stirrer (9), connect motor-pulley, jacket-stirrer pulley and inner vessel stirrer with a ring belt, and the Beckman thermometer. Connect the ignition cord

8. Start the motor, and strovoskop will indicated 800-850 rpm. Read the initial temperature of water three times in 3 minutes, take the average.

9. Push the HOT WATER VALVE button 1-2 seconds to let the hot water run into the jacket

10. Push the IGNITION button to start the combustion

11. If the water temperature in the inner vessel increases, push again the HOT WATER VALVE button to increase the water temperature inside the jacket to follow up the temperature inside the inner vessel. To reach high accuracy, maintain the temperature increase in the inner vessel equals to one in the jacket.

12. Read the water temperature inside the inner vessel 5 minutes before and 10 minutes after ignition. Record the temperature during the process until the rise is constant.

13. Repeat the procedures 5 times, and take the average

14. Repeat the procedures for all measure

  1. RESULT AND DISCUSSION

1. Result

Charcoal

Group 2A

Wm = 1.04 g = 0.00104 kg

Wa = 2.1 kg = 2100 ml

Ew = 0.5925

Data before action of burning

Time(s)

Tin1 (ºC)

Tout (ºC)

0

32

31.42

1

32

31.44

2

31.99

31.45

3

31.99

31.46

Average

31.995


Data after action of burning

Time(s)

Tin2 (ºC)

Tout (ºC)

0

33

32.1

1

33.2

32.7

2

33.25

32.8

3

33.27

32.84

4

33.28

32.97

5

33.28

33.09

6

33.29

33.1

Average

33.224


EEm =

=

=

= 13321.15 kj/kg

ΔT = ΔTin2 – ΔTin1

= 33.224 - 31.995

= 1.229 ºC

EEm literature = 13800 kJ/kg

Correction value = 1-|(13800-13321.602)/13800| x 100% = 96.53%

Group 2B

Data before burning

Times (minutes)

Temperature inside Tin (oC)

Temperature outside Tout (oC)

0

32.49

32.39

1

32.49

32.4

2

32.49

32.41

3

32.49

32.41

Average

32.49

32.4025

Data after burning

Times (minutes)

Temperature inside Tin’ (oC)

Temperature outside Tout’ (oC)

0

32.7

32.44

1

32.95

32.44

2

32.40

32.45

3

32.65

32.45

4

32.86

32.46

5

32.00

32.47

6

34.09

32.49

7

34.14

32.49

8

34.16

32.51

9

34.17

32.52

10

34.18

32.52

11

34.18

32.53

Average

33.79

32.48

Example of calculation:

Mass of cold water (Wa) = 2100 g = 2.1 kg

Mass of briquette (Wm) = 1.040 g = 0.001 kg

Water equivalent value (Ew) = 0.5925 kg

Mass of rest burning from briquette = 0.47 gram = 0.00047 kg

ΔT = 1.3oC

EEm = 4.1868 (Ew + Wa) (Tin’ - Tin)

Wm

= 4.1868 (0.5925 + 2.1) (33.79-32.49)

0.001

EEm = 14654.85 kJ/kg

EEm literature = 13800 kJ/kg

Correction value = 1-|(13800-14654.85)/13800| x 100% = 94%

2. Discussion

In this experiment the first group or group 2B used charcoal as the object to know the energy equivalency of that object. The same object also used for the second group or group 2A.

From the experiment of first group, EEm is got arround 13321.15 kj/kg. Then from the literature we get the value arround 13800 kJ/kg. If we compare the result and the literature our group get the correction value arround 96.53%. From the second group wich is the EEm is got arround 14654.85 kJ/kg, and then if we compare from the literature the correction is arround 94%.

After we get EEm from the two groups we get the average data arround 13987.5 kj/kg. After that we get the correction arround 98.6%.

If we see from the data, we know the energy equivalency for the charcoal is almost like the literature and the correction almost get 100%. So The two groups of this experiment have done well for this laboratory work.

  1. CONCLUSION

After the experiment, and get the data, we can conclude that the student have known how to find out the energy equivalency of the charcoal. In the other words the student did for this experiment.

REFERENCE

Anonymous. Instruction Manual. Ogawa Seiki Co. Ltd., Tokyo, Japan.

Purwanto, Y.Aris, U.Ahmad, and H.K.Purwadaria.2003.Laboratory Manual : Thermodynamics and Heat Transfer.IPB/DUE-LIKE PROJECT,Bogor.IPB.

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