- Email: [email protected]
Developing an educational software for heat exchangers and heat exchanger networks projects
ELSEVIER
Computers &Chemical Engineering Computers and Chemical Engineering 24 (2000) 1247-1251 www.elsevier.com/locate/compchemeng
Developing an educational software for heat exchangers and heat exchanger networks projects L.M.F. Lona *, F.A.N. Fernandes, M.C. Roque, S. Rodrigues Laborat6rio de Andlise, Simula¢ao e Sintese de Processos Qulmicos, LASSPQ, Faculdade de Engenharia Quimica, DPQ-UNICAMP, Cidade Universitdria Zeferino Vaz-C.P. 6066, Distrito de Barao Geraldo, CEP 13081-970 Campinas, SP, Brazil
Abstract
The shell and tube heat exchanger is an equipment largely used at chemical industries. The most known methods used for its design are the methods of Kern, Bell-Delaware and Tinker, for what a lot of equations are necessary. In this way, the calculation without using any computer aid takes a lot of time. This paper present a didactical software developed for the design of shell and tube heat exchanger and heat exchangers networks, this last one using Pinch analysis. The software called heat exchanger simulator (HES), was developed to be used in the undergraduate classes of Chemical Engineering. Since the use of a software can decrease the necessary time for evaluations, a fairly more time can be saved, which can be used in the analysis of the results, study of parametric sensitivity, research of backing subjects, amongst other essential tasks in the modern context of engineering. The use of the software facilitates the development of individual or group projects, in which the student can develop its creativity through the scanning of a real problem. The benefits of such practice are several, being the starting point for the process of stand alone and continued education, unique capable to allow the future professional to remain itself brought up to date with the increasing development of new technologies. © 2000 Elsevier Science Ltd. All rights reserved. Keywords: Educational software; Heat exchangers; Education; Simulation
1. Introduction
Teaching Chemical Engineering has changed throughout the past years. Computer aids are being used more and process simulation has gained an important role in this field. However, softwares guided for a specific subject and developed to make students get in touch with real situations are not so common. Based on the previous experience with teaching unit operations (heat exchangers project) from Ph.D. Lona Batista, the group started to develop heat exchanger simulator (HES). The first problem in teaching heat exchangers is the difficulty felt by the students in having an idea of the equipment. The understanding of the equipment devices and their operation are not so clear for the students because most of them have never seen a heat exchanger
* Corresponding author. E-mail addresses: [email protected] (L.M.F. Lona), [email protected] (F.A.N. Fernandes), [email protected]. br (M.C. Roque), [email protected] (S. Rodrigues)
before. Other problem is the large number of equations involved in the methods that turns the evaluation of m a n y exercises at classroom almost impossible and can make the class less productive and sometimes boring. HES was developed in order to improve the classes as well as making them more interesting and solving the difficulties mentioned before. The software can help the teacher to do his lectures and brings the student to analyze the effects of his decisions over heat exchanger parameters and operational conditions. The student can have an overview of these aspects by checking out the simulation results. Some of the exercises even ask the student to write a report, so that HES can also be used as an evaluation tool. The software uses, Kern (1980) and Bell-Delaware methods (Bell, 1963). Previously, a simple program using this method was made by Rodrigues and Lona Batista (1997). This program was used with undergraduate students and improved a lot in the classes. Based on this experience the program was improved and become an educational software (HES), which was
0098-1354/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII: S0098-13 54(00)00324-0
1248
L.M.F.
Lona et al. /Computers
and Chemical Engineering 24 (2000) 1247-1251
Fig. 1. HES main menu.
structured in modules, the electronic text book where the student will find all the theory involved in Kern and Bell-Delaware methods and illustrations of the equipment and parts of it such as the tubes settings and baffles. Some of the illustrations are animated. One of them allows the view of the flux inside the equipment. In this way, the software also be teaching and not only displaying spare results. The exercise module brings real situations usually found at chemical industries, bringing the student to analyze his decisions over these specific situations. And finally there is the simulator module that can be used either associated with the exercise mode or to create new processes conditions. Besides the heat exchanger evaluation and project the software also brings the module in which the Pinch analysis is inserted. Since its usefulness on the present
energy saving scenery, students are put in contact with its theory and how it works, by using graphs such as the composite curve and their meanings. In this module, the student has to set-up the complete network. The software provides a list of all possible matches and the student has to develop his network explaining and analyzing his decisions. The aim of this software is to provide the student with a quick answer from his decisions during the project of heat exchanger units and networks since the project itself held without any computer aid is hard and takes long hours to be concluded. In this way, the student can also concentrate on acquiring technical feeling and not only learning how to proceed with calculations.
2. Modules 2. I. Exercise module This module proposes some exercises in which the students must use the simulator and make decisions such as, the best-feed flow rate; the choice of a thermal fluid; the best place for some fluid (shell or tube side); and other operational parameters. Each exercise presents a usual situation commonly found at chemical industries. The exercises are structured in order to
Fig. 2. HES input
screen.
L.M.F.
Lona et al. /Computers
and Chemical Engineering 24 (2000) 1247-1251
1249
Fig. 3. HES output screen.
On heat pIckawe
squfpment,
the amount of heat conceded
tha hot fluid murt b, equal by the COY fldd
tothe
Inot conrldorfw
by
wnount of haat absorbed posslblc tosses to the
stionmant). E~tfm
W.
1 must satisfy the equakty presented
mlrr flw
of the hot fluld
1,
InftM
T,
final or outbt
or Inlet tempentwe
W.
mar Row of the cold fluid
Cp, heat capacity
develop the feeling over chemical proceedings and processes. Solving the exercises the student can feel itself as an engineer and it makes the class more interesting than the once in which the student only solves exercises without having any idea about the process. In Fig. 1 the main menu of the software is presented. The student can choose between using the exercise module or the simulator module. When the exercise module is being used the simulator is accessed within the exercise and the necessary data is automatically transferred.
2.
of the hot fluid
Cp. heat capacity
tam~w,tura
of the hot ftuld of the hot fluid
of the cold fluid
tl
initial or Inlet trnporaturo
of the cold ftuld
1,
final or outlet temperature
of the cold fluld
Q
amount of heat oxchsnqed by the swtem
Fig. 4. Electronic text book -
on tqwtbn
theory.
2.2. Simulator module The simulator module can be used associated with the proposed exercises or not. When this module is used alone the user must provide all the necessary information such as, the construction parameters of the equipment as well the operational conditions. In Figs. 2 and 3 the input and output of the simulator are presented, respectively. With the data provided by the simulator the student can make decisions and design a heat exchanger. The
1250
L.M.F. Lona et al./ Computers and Chemical Engineering 24 (2000) 1247-1251
use of Pinch technology is similar. The results provided by the simulator using Pinch analysis are the Pinch temperature, which can be defined as being the restraining temperature of the process, which divides the process into two regions. About this topic, it is possible to mention five heuristics that are valid for Pinch analysis and used in this work, ,She//
Nozz/e
never transfer heat across the Pinch point; add heat only above the Pinch; • cool only below the Pinch; • always add heat to the lowest possible level of temperature relative of the Pinch point; • always cool the highest possible level of temperature relative to the Pinch point. Considering the heuristics presented before, the process is divided into two regions, below and above the pinch point. The heat balances are then made on these two regions, above and below Pinch point. The Pinch temperature is obtained by the problem table as presented by Linhoff and Ahamd (1990). The checking of all possible matches is the n made by considering two more heuristics. • Above Pinch, the match is possible only if, • •
F H o T C p H o T < FCoLDCpcOLD.
--Tubes
• Below Pinch,
Baffles d
the
match
is possible
only if,
FCoLDCpcOLD < FHoTCpHoT.
Fig. 5. Electronic text book -- internal scheme of a shell and tube heat exchanger. ~
HES use in the classroom Visual presentation
I
2.3. Electronic text book module
100, 80,
ntlJ
20,
0,
Excellent
Good
Not 8o good
1
Bad
Fig. 6. HES utilization in the classroom and visual presentation. Il
From this point on, the student has to choose the best configuration for the network based on the idea of maximum energy recovery. This data are given by the heat loads of the process before and after the network is set.
HES use I
The electronic text book module can be independently accessed and can be used without the simulator. This module present the theory involved in the studied methods as well the equations. This module was included in order to make the student know the method being used and not only use the software as a black box without knowing where the results come from (Figs. 4 and 5). The software also provides a thermal fluid data bank in which the student can find the operational range and the properties of the thermal fluids used in the software. If the user desires the use of another thermal fluid it is also possible. The illustrations of the heat exchanger components allow the understanding of how the equipment works and flow distributed inside it.
~1050-
3. Results o~ 4on"
UJ 30.
(/) 20.
z <
10.
~a~lenl
Good
I~t aogtmd
X Title Fig. 7. Easiness of using HES.
Bad
The software HES was used by the undergraduate students at state University of Campinas, Brazil (UNICAMP). The students showed a large interest using this kind of software and the class was more productive as well the course was given in an easier way. The use of the software allowed the exploration of the Bell-Delaware method which is more complex but more accurate than the Kern method. This method is hardly ever studied because of its complexity and the short time available for the course.
L.M.F. Lona et al./ Computers and Chemical Engineering 24 (2000) 1247-1251
In order to evaluate the software acceptance by the students a questionnaire was done for the students. The answers of this research are presented in the following plots. The result of acceptance showed in Figs. 6 and 7 were obtained with the questionnaire by 76% of the students who used the software HES. According to the results the software is a good tool for teaching the evaluation and project of heat exchangers and heat exchanger networks.
1251
References Bell, K. J. (1963). Delaware method for shell side design. Kern, D. P. (1980). Heat transfer processes. Linhoff, B., & Ahamd, S. (1990). Cost optimum heat exchanger networks - - minimum energy and capital using simple models for capital cost. Computers & Chemical Engineering, 14, 729750. Rodrigues, S., & Lona Batista, L. M. F. (1997). Shell and tube heat exchanger simulation. In II-COBEQ-IC-Uberlhndia-Brazil.
Computers &Chemical Engineering Computers and Chemical Engineering 24 (2000) 1247-1251 www.elsevier.com/locate/compchemeng
Developing an educational software for heat exchangers and heat exchanger networks projects L.M.F. Lona *, F.A.N. Fernandes, M.C. Roque, S. Rodrigues Laborat6rio de Andlise, Simula¢ao e Sintese de Processos Qulmicos, LASSPQ, Faculdade de Engenharia Quimica, DPQ-UNICAMP, Cidade Universitdria Zeferino Vaz-C.P. 6066, Distrito de Barao Geraldo, CEP 13081-970 Campinas, SP, Brazil
Abstract
The shell and tube heat exchanger is an equipment largely used at chemical industries. The most known methods used for its design are the methods of Kern, Bell-Delaware and Tinker, for what a lot of equations are necessary. In this way, the calculation without using any computer aid takes a lot of time. This paper present a didactical software developed for the design of shell and tube heat exchanger and heat exchangers networks, this last one using Pinch analysis. The software called heat exchanger simulator (HES), was developed to be used in the undergraduate classes of Chemical Engineering. Since the use of a software can decrease the necessary time for evaluations, a fairly more time can be saved, which can be used in the analysis of the results, study of parametric sensitivity, research of backing subjects, amongst other essential tasks in the modern context of engineering. The use of the software facilitates the development of individual or group projects, in which the student can develop its creativity through the scanning of a real problem. The benefits of such practice are several, being the starting point for the process of stand alone and continued education, unique capable to allow the future professional to remain itself brought up to date with the increasing development of new technologies. © 2000 Elsevier Science Ltd. All rights reserved. Keywords: Educational software; Heat exchangers; Education; Simulation
1. Introduction
Teaching Chemical Engineering has changed throughout the past years. Computer aids are being used more and process simulation has gained an important role in this field. However, softwares guided for a specific subject and developed to make students get in touch with real situations are not so common. Based on the previous experience with teaching unit operations (heat exchangers project) from Ph.D. Lona Batista, the group started to develop heat exchanger simulator (HES). The first problem in teaching heat exchangers is the difficulty felt by the students in having an idea of the equipment. The understanding of the equipment devices and their operation are not so clear for the students because most of them have never seen a heat exchanger
* Corresponding author. E-mail addresses: [email protected] (L.M.F. Lona), [email protected] (F.A.N. Fernandes), [email protected]. br (M.C. Roque), [email protected] (S. Rodrigues)
before. Other problem is the large number of equations involved in the methods that turns the evaluation of m a n y exercises at classroom almost impossible and can make the class less productive and sometimes boring. HES was developed in order to improve the classes as well as making them more interesting and solving the difficulties mentioned before. The software can help the teacher to do his lectures and brings the student to analyze the effects of his decisions over heat exchanger parameters and operational conditions. The student can have an overview of these aspects by checking out the simulation results. Some of the exercises even ask the student to write a report, so that HES can also be used as an evaluation tool. The software uses, Kern (1980) and Bell-Delaware methods (Bell, 1963). Previously, a simple program using this method was made by Rodrigues and Lona Batista (1997). This program was used with undergraduate students and improved a lot in the classes. Based on this experience the program was improved and become an educational software (HES), which was
0098-1354/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved. PII: S0098-13 54(00)00324-0
1248
L.M.F.
Lona et al. /Computers
and Chemical Engineering 24 (2000) 1247-1251
Fig. 1. HES main menu.
structured in modules, the electronic text book where the student will find all the theory involved in Kern and Bell-Delaware methods and illustrations of the equipment and parts of it such as the tubes settings and baffles. Some of the illustrations are animated. One of them allows the view of the flux inside the equipment. In this way, the software also be teaching and not only displaying spare results. The exercise module brings real situations usually found at chemical industries, bringing the student to analyze his decisions over these specific situations. And finally there is the simulator module that can be used either associated with the exercise mode or to create new processes conditions. Besides the heat exchanger evaluation and project the software also brings the module in which the Pinch analysis is inserted. Since its usefulness on the present
energy saving scenery, students are put in contact with its theory and how it works, by using graphs such as the composite curve and their meanings. In this module, the student has to set-up the complete network. The software provides a list of all possible matches and the student has to develop his network explaining and analyzing his decisions. The aim of this software is to provide the student with a quick answer from his decisions during the project of heat exchanger units and networks since the project itself held without any computer aid is hard and takes long hours to be concluded. In this way, the student can also concentrate on acquiring technical feeling and not only learning how to proceed with calculations.
2. Modules 2. I. Exercise module This module proposes some exercises in which the students must use the simulator and make decisions such as, the best-feed flow rate; the choice of a thermal fluid; the best place for some fluid (shell or tube side); and other operational parameters. Each exercise presents a usual situation commonly found at chemical industries. The exercises are structured in order to
Fig. 2. HES input
screen.
L.M.F.
Lona et al. /Computers
and Chemical Engineering 24 (2000) 1247-1251
1249
Fig. 3. HES output screen.
On heat pIckawe
squfpment,
the amount of heat conceded
tha hot fluid murt b, equal by the COY fldd
tothe
Inot conrldorfw
by
wnount of haat absorbed posslblc tosses to the
stionmant). E~tfm
W.
1 must satisfy the equakty presented
mlrr flw
of the hot fluld
1,
InftM
T,
final or outbt
or Inlet tempentwe
W.
mar Row of the cold fluid
Cp, heat capacity
develop the feeling over chemical proceedings and processes. Solving the exercises the student can feel itself as an engineer and it makes the class more interesting than the once in which the student only solves exercises without having any idea about the process. In Fig. 1 the main menu of the software is presented. The student can choose between using the exercise module or the simulator module. When the exercise module is being used the simulator is accessed within the exercise and the necessary data is automatically transferred.
2.
of the hot fluid
Cp. heat capacity
tam~w,tura
of the hot ftuld of the hot fluid
of the cold fluid
tl
initial or Inlet trnporaturo
of the cold ftuld
1,
final or outlet temperature
of the cold fluld
Q
amount of heat oxchsnqed by the swtem
Fig. 4. Electronic text book -
on tqwtbn
theory.
2.2. Simulator module The simulator module can be used associated with the proposed exercises or not. When this module is used alone the user must provide all the necessary information such as, the construction parameters of the equipment as well the operational conditions. In Figs. 2 and 3 the input and output of the simulator are presented, respectively. With the data provided by the simulator the student can make decisions and design a heat exchanger. The
1250
L.M.F. Lona et al./ Computers and Chemical Engineering 24 (2000) 1247-1251
use of Pinch technology is similar. The results provided by the simulator using Pinch analysis are the Pinch temperature, which can be defined as being the restraining temperature of the process, which divides the process into two regions. About this topic, it is possible to mention five heuristics that are valid for Pinch analysis and used in this work, ,She//
Nozz/e
never transfer heat across the Pinch point; add heat only above the Pinch; • cool only below the Pinch; • always add heat to the lowest possible level of temperature relative of the Pinch point; • always cool the highest possible level of temperature relative to the Pinch point. Considering the heuristics presented before, the process is divided into two regions, below and above the pinch point. The heat balances are then made on these two regions, above and below Pinch point. The Pinch temperature is obtained by the problem table as presented by Linhoff and Ahamd (1990). The checking of all possible matches is the n made by considering two more heuristics. • Above Pinch, the match is possible only if, • •
F H o T C p H o T < FCoLDCpcOLD.
--Tubes
• Below Pinch,
Baffles d
the
match
is possible
only if,
FCoLDCpcOLD < FHoTCpHoT.
Fig. 5. Electronic text book -- internal scheme of a shell and tube heat exchanger. ~
HES use in the classroom Visual presentation
I
2.3. Electronic text book module
100, 80,
ntlJ
20,
0,
Excellent
Good
Not 8o good
1
Bad
Fig. 6. HES utilization in the classroom and visual presentation. Il
From this point on, the student has to choose the best configuration for the network based on the idea of maximum energy recovery. This data are given by the heat loads of the process before and after the network is set.
HES use I
The electronic text book module can be independently accessed and can be used without the simulator. This module present the theory involved in the studied methods as well the equations. This module was included in order to make the student know the method being used and not only use the software as a black box without knowing where the results come from (Figs. 4 and 5). The software also provides a thermal fluid data bank in which the student can find the operational range and the properties of the thermal fluids used in the software. If the user desires the use of another thermal fluid it is also possible. The illustrations of the heat exchanger components allow the understanding of how the equipment works and flow distributed inside it.
~1050-
3. Results o~ 4on"
UJ 30.
(/) 20.
z <
10.
~a~lenl
Good
I~t aogtmd
X Title Fig. 7. Easiness of using HES.
Bad
The software HES was used by the undergraduate students at state University of Campinas, Brazil (UNICAMP). The students showed a large interest using this kind of software and the class was more productive as well the course was given in an easier way. The use of the software allowed the exploration of the Bell-Delaware method which is more complex but more accurate than the Kern method. This method is hardly ever studied because of its complexity and the short time available for the course.
L.M.F. Lona et al./ Computers and Chemical Engineering 24 (2000) 1247-1251
In order to evaluate the software acceptance by the students a questionnaire was done for the students. The answers of this research are presented in the following plots. The result of acceptance showed in Figs. 6 and 7 were obtained with the questionnaire by 76% of the students who used the software HES. According to the results the software is a good tool for teaching the evaluation and project of heat exchangers and heat exchanger networks.
1251
References Bell, K. J. (1963). Delaware method for shell side design. Kern, D. P. (1980). Heat transfer processes. Linhoff, B., & Ahamd, S. (1990). Cost optimum heat exchanger networks - - minimum energy and capital using simple models for capital cost. Computers & Chemical Engineering, 14, 729750. Rodrigues, S., & Lona Batista, L. M. F. (1997). Shell and tube heat exchanger simulation. In II-COBEQ-IC-Uberlhndia-Brazil.