Inter American University of Puerto Rico
Bayamon Campus
Mechanical Engineering Department
MECN 4201 THERMODYNAMICS
Fall - 2011
Professor: Dr. Rafael Salgado
Thermodynamics
Design Project
Rolando Santiago, Erik Rosado
12/13/2011
Inter American University of Puerto Rico
Bayamon Campus
Mechanical Engineering Department
Course Number and Name:
MECN 4201 THERMODYNAMICS
Semester and Year:
AUG-DEC 2011
Title of Design:
Design a scalding unit for chicken to loosen their feathers.
Names of Group Members:
Erik T. Rosado Gonzales Y00-22-4943
Rolando Santiago Y00-23-2734
Date of Report Submitted:
December 13, 2011
Instructor Comments:
Grade:
2
Table of Contents
Chapter 1 Objective and Introduction ............................................................................................. 6
Chapter 2 Theory ............................................................................................................................ 7
Conservation of mass .................................................................................................................. 7
Mass Balance .............................................................................................................................. 8
First Law of Thermodynamics .................................................................................................... 9
Heat exchanger.......................................................................................................................... 10
Heat Capacity “Cp”................................................................................................................... 11
Chapter 3 Results and Discussion ................................................................................................. 13
Chapter 4 Conclusions .................................................................................................................. 17
Chapter 5 Appendix ...................................................................................................................... 18
Appendix A-1 (scalding unit design) ........................................................................................ 18
Appendix A-2 (other calculus).................................................................................................. 19
Heating volume sizes: ........................................................................................................... 19
Specific volume @53°C ........................................................................................................ 19
Mass of water in heating size:............................................................................................... 20
Outlet temperature of the heat exchanger ............................................................................. 20
Outlet temperature of the mixing chamber ........................................................................... 21
Appendix A-3 (specific heat chicken) ...................................................................................... 22
Appendix A-4 (specific heat water) .......................................................................................... 25
Appendix A-5 (saturate water temperature table) ..................................................................... 29
Appendix A-6 (design problem 5-218) ..................................................................................... 31
Chapter 6 Works Cited ....................................................................Error! Bookmark not defined.
3
Table of Figure
Figure 2-1 Conservation of mass .................................................................................................... 8
Figure 2-2 Mass Balance ................................................................................................................ 9
Figure 2-3 First law of Thermodynamics ..................................................................................... 10
Figure 2-4 A water heater in steady operation .............................................................................. 10
Figure 2-5 Specific heat ................................................................................................................ 11
Figure 2-6 Heat Transfer ............................................................................................................... 12
Figure 5-1 Scalding unit design .................................................................................................... 18
Table of Symbols
4
ABSTRACT
In this project a design problem is presented in which a chicken preparation industry needed a
scalding unit to prepare chickens to be de-feathered. You’ll see all the analysis involved on the
process to build a successful scalding unit. Several equations were used to calculate the exact volume
needed of water to have the exact temperature exchange between the system, the chickens and the
gas furnace. Also, we have calculated the speed that the conveyor needs to have in order to have
each chicken 1.5 min underwater. At the end we proved why the chosen volume is the correct one
to make all that process a reality, and calculate the cost of that scalding unit.
5
Chapter 1 Objective and Introduction
We were presented with a situation that a chicken preparation industry had a situation, and it was
that they needed a scalding unit for slaughtered chickens to loosen their feathers before they
were routed to the feather-picking machine. That machine had a capacity of 1200 chicken per
hour and these conditions were given: The unit will be of an immersion type filled with hot water
at an average temperature of 53°C at all times. Chicken with an average mass of 2.2 kg and an
average temperature of 36°C will be dipped into the tank, held in the water for 1.5 min, and
taken out by a slow-moving conveyor. The chicken is expected to leave the tank 15 percent
heavier as a result of the water that sticks to its surface. The center to center distance between
chickens in any direction will be at least 30 cm. The tank can be as wide as 3 m and as high as 60
cm. The water is to be circulated through and heated by a natural gas furnace, but the
temperature rise of water will not exceed 5°C as it passes through the furnace. The water loss is
to be made up by the city water at an average temperature of 16°C. The walls and the floor of the
tank are well-insulated. The unit operates 24 h a day and 6 days a week.
We were asked for the following unknowns:
a)
b)
c)
d)
The mass flow of the rate of the makeup water that must be supplied to the tank.
The rate of heat transfer from the water to the chicken.
The size of the heating system.
The operating cost of the scalding unit per month for a unit cost of $1.12/therm of natural
gas.
6
Chapter 2 Theory
Conservation of mass
The law of conservation of mass, also known as the principle of mass/matter conservation, states
that the mass of an isolated system (closed to all matter and energy) will remain constant over time.
This principle is equivalent to the conservation of energy, in the sense when energy or mass is
enclosed in a system and none is allowed in or out, its quantity cannot otherwise change (hence, its
quantity is "conserved"). The mass of an isolated system cannot be changed as a result of processes
acting inside the system. The law implies that mass cannot be created or destroyed, although it may
be rearranged in space and changed into different types of particles; and that for any chemical
process in a closed system, the mass of the reactants must equal the mass of the products.
The concepts of both matter and mass conservation are widely used in many fields such as
chemistry, mechanics, and fluid dynamics. Historically, the principle of mass conservation,
discovered by Antoine Lavoisier in the late 18th century, was of crucial importance in changing
alchemy into the modern natural science of chemistry.
In special relativity, the mass-energy equivalence theorem states that mass conservation is equivalent
to energy conservation, which is the first law of thermodynamics. In special relativity, mass cannot
be converted to energy, since energy always retains its equivalent amount of mass within any isolated
system. However, certain types of matter may be converted to energy, so long as the mass of the
system is unchanged in the process. When this energy is removed from systems (they are opened),
they lose mass.
In general relativity, mass (and energy) conservation in expanding volumes of space becomes a
complicated concept, subject to different definitions, and neither mass nor energy is as strictly and
simply conserved as is the case in special relativity and in Minkowski space. (1)
Equation 2-1
7
(2)
Figure 2-1 Conservation of mass
Mass Balance
A mass balance (also called a material balance) is an application of conservation of mass to the
analysis of physical systems. By accounting for material entering and leaving a system, mass flows
can be identified which might have been unknown, or difficult to measure without this technique.
The exact conservation law used in the analysis of the system depends on the context of the
problem but all revolve around mass conservation, i.e. that matter cannot disappear or be created
spontaneously.
Therefore, mass balances are used widely in engineering and environmental analyses. For example
mass balance theory is used to design chemical reactors, analyse alternative processes to produce
chemicals as well as in pollution dispersion models and other models of physical systems. Closely
related and complementary analysis techniques include the population balance, energy balance and
the somewhat more complex entropy balance. These techniques are required for thorough design
and analysis of systems such as the refrigeration cycle.
In environmental monitoring the term budget calculations is used to describe mass balance
equations where they are used to evaluate the monitoring data (comparing input and output, etc.) In
biology the dynamic energy budget theory for metabolic organisation makes explicit use of time,
mass and energy balances. (3)
8
(4)
Figure 2-2 Mass Balance
Steady Flow:
Equation 2-2
First Law of Thermodynamics
The first law of thermodynamics is an expression of the principle of conservation of work.
The law states that energy can be transformed, i.e. changed from one form to another, but cannot be
created nor destroyed. It is usually formulated by stating that the change in the internal energy of a
system is equal to the amount of heat supplied to the system, minus the amount of work performed
by the system on its surroundings. (5)
Equation 2-3
Equation 2-4
9
(2)
Figure 2-3 First law of Thermodynamics
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to
another. The media may be separated by a solid wall, so that they never mix, or they may be in direct
contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical
plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment. The
classic example of a heat exchanger is found in an internal combustion engine in which a circulating
fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools
the coolant and heats the incoming air. (6)
(4)
Figure 2-4 A water heater in steady operation
10
Heat Capacity “Cp”
Heat capacity (usually denoted by a capital C, often with subscripts), or thermal capacity, is the
measurable physical quantity that characterizes the amount of heat required to change a substance's
temperature by a given amount. In the International System of Units (SI), heat capacity is expressed
in units of joule(s) (J) per Kelvin (K).
Derived quantities that specify heat capacity as an intensive property, independent of the size of a
sample, are the molar heat capacity, which is the heat capacity per mole of a pure substance, and the
specific heat capacity, often simply called specific heat, which is the heat capacity per unit mass of a
material.
Temperature reflects the average kinetic energy of particles in matter. Heat is the transfer of thermal
energy; it flows from regions of high temperature to regions of low temperature. Thermal energy is
stored as kinetic energy in the random modes of translation in monatomic substances, and
translations and rotations of polyatomic molecules in gases. Additionally, some thermal energy may
be stored as the potential energy associated with higher-energy modes of vibration, whenever they
occur in interatomic bonds in any substance. Translation, rotation, and a combination of the two
types of energy in vibration (kinetic and potential) represent the degrees of freedom of motion
which classically contribute to the heat capacity of a thermodynamic system. On a microscopic scale,
each particle in a system absorbs heat energy among the few degrees of freedom available to it, and
this absorption contributes to a specific heat capacity which classically approaches a maximum per
mole of particles that is set by the Dulong-Petit law. The limit is achieved by many kinds of solids at
room temperature.
For quantum mechanical reasons, at any given temperature, some of these degrees of freedom may
be unavailable, or only partially available, to store thermal energy. In such cases, the specific heat
capacity will be a fraction of the maximum. As the temperature approaches absolute zero, the
specific heat capacity of a system also approaches zero, due to loss of available degrees of freedom.
Quantum theory can be used to quantitatively predict specific heat capacities in simple systems. (7)
(4)
Figure 2-5 Specific heat
11
(2)
Figure 2-6 Heat Transfer
12
Chapter 3 Results and Discussion
A. The mass flow rate of the makeup water that must be supplied to the tank.
13
B. The rate of heat transfer from the water to the chicken, in kW.
Equation 3-1
14
C. The size of the heating system in kJ/h.
Equation 3-2
15
D. The operating cost of scalding unit per month for a unit cost of $1.12/therm of natural
gas.
16
Chapter 4 Conclusions
This project was useful to be exposed to a real life problem, something that can be used at the
industry. The scalding unit was easy saw as a heat interchanger to solve the equations. Once we
figured out the right volume of the scalding unit we could then assume the temperatures of the
water so it could maintain the desired 53°C and have a perfect balance between the energy leaving
with each chicken and the energy entering because of the furnace. That allowed us prevented the
scalding unit to overheat and evaporate the water or loose the temperature because of the 16°C
entering to the unit.
17
Chapter 5 Appendix
Appendix A-1 (scalding unit design)
Figure 5-1 Scalding unit design
18
Appendix A-2 (other calculus)
Heating volume sizes:
Specific volume @53°C
53° ------------------
19
Mass of water in heating size:
Outlet temperature of the heat exchanger
Equation 5-1
20
Outlet temperature of the mixing chamber
Equation 5-2
216.2889 y
21
Appendix A-3 (specific heat chicken)
Specific Heat above Freezing
Specific Heat below Freezing
Food
(Btu/lboF)
(KJ/kgoC)
(Kcal/kgoC)
(Btu/lboF)
(KJ/kgoC)
(Kcal/kgoC)
Apples
0.87
3.64
0.87
0.42
1.76
0.42
Apricots. fresh
0.88
3.68
0.88
0.43
1.8
0.43
Artichokes
0.87
3.64
0.87
0.42
1.76
0.42
Asparagus
0.94
3.94
0.94
0.45
1.88
0.45
Asparagus beans
0.88
3.68
0.88
0.43
1.8
0.43
Avocados
0.72
3.01
0.72
0.37
1.55
0.37
Bananas
0.8
3.35
0.8
0.4
1.67
0.4
Barracuda
0.8
3.35
0.8
0.4
1.67
0.4
Bass
0.82
3.43
0.82
0.41
1.72
0.41
Beef, carcass
0.68
2.85
0.68
0.48
2.01
0.48
Beef, flank
0.56
2.34
0.56
0.32
1.34
0.32
Beef, loin
0.66
2.76
0.66
0.35
1.47
0.35
Beef, rib
0.67
2.81
0.67
0.36
1.51
0.36
Beef, round
0.74
3.1
0.74
0.38
1.59
0.38
Beef, rump
0.62
2.6
0.62
0.34
1.42
0.34
22
Specific Heat above Freezing
Specific Heat below Freezing
Food
(Btu/lboF)
(KJ/kgoC)
(Kcal/kgoC)
(Btu/lboF)
(KJ/kgoC)
(Kcal/kgoC)
Beef, shanks
0.76
3.18
0.76
0.39
1.63
0.39
Beef, corned
0.63
2.64
0.63
0.34
1.42
0.34
Beets
0.9
3.77
0.9
0.43
1.8
0.43
Blackberries
0.87
3.64
0.87
0.42
1.76
0.42
Blueberries
0.87
3.64
0.87
0.42
1.76
0.42
Brains
0.84
3.52
0.84
0.41
1.72
0.41
Broccoli
0.92
3.85
0.92
0.44
1.84
0.44
Brussels sprouts
0.88
3.68
0.88
0.43
1.8
0.43
Butter
0.3
1.26
0.3
0.24
1
0.24
Butterfish
0.77
3.22
0.77
0.39
1.63
0.39
Cabbage
0.94
3.94
0.94
0.45
1.88
0.45
Candy
0.93
3.89
0.93
0.93
3.89
0.93
Carp
0.82
3.43
0.82
0.41
1.72
0.41
Carrots
0.91
3.81
0.91
0.44
1.84
0.44
Cauliflower
0.93
3.89
0.93
0.44
1.84
0.44
Celery
0.94
3.94
0.94
0.45
1.88
0.45
23
Specific Heat above Freezing
Specific Heat below Freezing
Food
(Btu/lboF)
(KJ/kgoC)
(Kcal/kgoC)
(Btu/lboF)
(KJ/kgoC)
(Kcal/kgoC)
Chard
0.93
3.89
0.93
0.43
1.8
0.43
Cherries, sour
0.88
3.68
0.88
0.41
1.72
0.41
Cherries, sweet
0.84
3.52
0.84
0.4
1.67
0.4
Chicken, squab
0.8
3.35
0.8
0.39
1.63
0.39
Chicken, broilers
0.77
3.22
0.77
0.38
1.59
0.38
Chicken, fryers
0.74
3.1
0.74
0.35
1.47
0.35
Chicken, hens
0.65
2.72
0.65
0.44
1.84
0.44
Chicken, capons
0.88
3.68
0.88
0.41
1.72
0.41
Clams, meat only
0.84
3.52
0.84
0.36
1.51
0.36
(8)
24
Appendix A-4 (specific heat water)
-t-
Absolute
pressure
-p-
Density
-ρ-
Specific
volume
-v-
Specific Heat
- cp -
Specific
entropy
-e-
(oC)
(kN/m2)
(kg/m3)
10-3 (m3/kg)
(kJ/kgK)
(kJ/kgK)
1.00
4.210
0
0
(Ice)
916.8
0.01
0.6
999.8
4
(maximum density)
0.9
1000.0
5
0.9
1000.0
1.00
4.204
0.075
10
1.2
999.8
1.00
4.193
0.150
15
1.7
999.2
1.00
4.186
0.223
20
2.3
998.3
1.00
4.183
0.296
25
3.2
997.1
1.00
4.181
0.367
30
4.3
995.7
1.00
4.179
0.438
35
5.6
994.1
1.01
4.178
0.505
40
7.7
992.3
1.01
4.179
0.581
45
9.6
990.2
1.01
4.181
0.637
50
12.5
988
1.01
4.182
0.707
55
15.7
986
1.01
4.183
0.767
25
-t-
Absolute
pressure
-p-
Density
-ρ-
Specific
volume
-v-
Specific Heat
- cp -
Specific
entropy
-e-
(oC)
(kN/m2)
(kg/m3)
10-3 (m3/kg)
(kJ/kgK)
(kJ/kgK)
60
20.0
983
1.02
4.185
0.832
65
25.0
980
1.02
4.188
0.893
70
31.3
978
1.02
4.191
0.966
75
38.6
975
1.03
4.194
1.016
80
47.5
972
1.03
4.198
1.076
85
57.8
968
1.03
4.203
1.134
90
70.0
965
1.04
4.208
1.192
95
84.5
962
1.04
4.213
1.250
100
101.33
958
1.04
4.219
1.307
105
121
954
1.05
4.226
1.382
110
143
951
1.05
4.233
1.418
115
169
947
1.06
4.240
1.473
120
199
943
1.06
4.248
1.527
125
228
939
1.06
4.26
1.565
130
270
935
1.07
4.27
1.635
135
313
931
1.07
4.28
1.687
26
-t-
Absolute
pressure
-p-
Density
-ρ-
Specific
volume
-v-
Specific Heat
- cp -
Specific
entropy
-e-
(oC)
(kN/m2)
(kg/m3)
10-3 (m3/kg)
(kJ/kgK)
(kJ/kgK)
140
361
926
1.08
4.29
1.739
145
416
922
1.08
4.30
1.790
150
477
918
1.09
4.32
1.842
155
543
912
1.10
4.34
1.892
160
618
907
1.10
4.35
1.942
165
701
902
1.11
4.36
1.992
170
792
897
1.11
4.38
2.041
175
890
893
1.12
4.39
2.090
180
1000
887
1.13
4.42
2.138
185
1120
882
1.13
4.45
2.187
190
1260
876
1.14
4.46
2.236
195
1400
870
1.15
200
1550
864
1.16
220
225
240
840
2550
834
814
2.282
4.51
2.329
4.63
1.20
4.65
2.569
4.78
27
-t-
Absolute
pressure
-p-
Density
-ρ-
Specific
volume
-v-
Specific Heat
- cp -
Specific
entropy
-e-
(oC)
(kN/m2)
(kg/m3)
10-3 (m3/kg)
(kJ/kgK)
(kJ/kgK)
250
3990
799
125
4.87
2.797
260
784
4.98
275
5950
756
1.32
5.20
3.022
300
8600
714
1.40
5.65
3.256
325
12130
654
1.53
6.86
3.501
350
16540
575
1.74
10.1
3.781
360
18680
528
1.90
14.6
3.921
(9)
28
Appendix A-5 (saturate water temperature table)
29
(4)
30
Appendix A-6 (design problem 5-218)
31
Chapter 6 Bibliography
1. contributors, Wikipedia. Conservation of mass. Wikipedia . [Online] November 23, 2011.
[Cited: December 3, 2011.] http://en.wikipedia.org/wiki/Conservation_of_mass.
2. NASA. NASA. NASA. [Online] http://www.grc.nasa.gov/WWW/k12/airplane/Images/mass.gif.
3. contributors, Wikipedia. Mass balance. Wikipedia . [Online] November 30, 2011. [Cited:
December 3, 2011.] http://en.wikipedia.org/wiki/Mass_balance.
4. Yunus A. Cengel, Michael Boles. Thetmodynamics.
5. Wikipedia. First law of thermodynamics. Wikipedia . [Online] November 27, 2011. [Cited:
Dcenber 3, 2011.] http://en.wikipedia.org/wiki/First_law_of_thermodynamics.
6. —. Heat exchanger. Wikipedia . [Online] November 28, 2011. [Cited: December 3, 2011.]
http://en.wikipedia.org/wiki/Heat_exchanger.
7. Heat capacity. Wikipedia . [Online] Wikipedia , December 2, 2011. [Cited: December 3,
2011.] http://en.wikipedia.org/wiki/Heat_capacity.
8. Engineeringtoolbox. Food and Foodstuff - Specific Heats. Engineeringtoolbox. [Online]
http://www.engineeringtoolbox.com/specific-heat-capacity-food-d_295.html.
9. —. Water - Thermal Properties. Engineeringtoolbox. [Online] 2011.
http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html.
32