Template COBEM 2007
Contents
1. 1 2 PVC courbe Pc 1 12 mm 1 2 cooper Tee Pc 1 12 mm 1 2 PVC reinforced tubing m 6 5 mm double wire m 4 1 mm double wire m 1 Sindal type electric connector Pc 1 NPT male pipe adapter Pc 4 Rubber for fixation cm 200 3 OPERATIONAL TESTS They had been carried through a series of operational tests in order to verify the test ring capability the presence of leakage and to determine the exchanger operational parameters It was verified that the electric heater only worked at high flows being necessary to modify the heater mechanism so that it functioned at low flows in order to get bigger temperatures From these tests a guide was written for the heat exchangers practical class annex 1 with the operational methodology and results to be obtained 4 SOFTWARE A heat exchanger simulation software for HP48 calculators was developed in order to compare the obtained experimental data against the theoretical predictions The reason to develop software for HP48 calculator is that a large majority of the students has assess to this type of calculator Therefore the students can use this software during the laboratory class and make in class the heat exchanger computational simulation This simulation aid the laboratory class first it allows the student to predict their results that will be obtained with the experiment correcting the assembly and operation errors Moreover the use of the calculator allows to the manipulat2. Software User s Manual This HP 48 calculator software compute the heat exchanger output temperatures by the effectiveness NUT method 1 Install the software in the calculator 2 Find the folder EXCH 3 Press the RUN key to start the software Ist Window Heat Exchanger Input Data Input hot water temperature C Input cold water temperature C Hot water flow kg s Cold water flow kg s To change the data move the cursor to the data that want change Type the new value and to pressure OK 2nd Pop Up Window Heat Exchanger Flow Type countercurrent or concurrent Select the heat exchanger flow type Press OK Press OK to start the software 3rd Window Calculation Results Output hot water temperature C Output cold water temperature C Press any key to finish the software 4 Press the RUN key to restart the software How to install the software in the Calculator 1 Connect the calculator to the computer serial port 1 or 2 2 Install the Kermit software in the computer http www columbia edu kermit 3 Set the connection port SET PORT 1 4 Set the speed connection to 9600 Baud SET BAUD 9600 5 Send the file to the calculator SEND EXCH TXT 6 Open the Calculator Kermit protocol left shift I O gt Transfer 7 Receive the file RECV 8 Close the Calculator Kermit Protocol OK
3. Proceedings of COBEM 2007 19th International Congress of Mechanical Engineering Copyright 2007 by ABCM November 5 9 2007 Brasilia DF HEAT EXCHANGER LAB CLASS TEST RING AND OPERATIONAL PROCEDURE Paulo Cesar da Costa Pinheiro PauloCPinheiro ufmg br pinheiro netuno cc ufmg br Departamento de Engenharia Mec nica da UFMG Av Antonio Carlos 6627 31270 901 Belo Horizonte MG Abstract The aim of the lab class is to identify and to apply the theoretical concepts acquired in classroom into the industrial practice The most common thermal equipment used in the industry is the heat exchanger This paper describes the construction of a heat exchanger test ring and presents an operational procedure and some academic results A double pipe type heat exchanger was constructed with copper pipes and installed in the metallic rack with all the others devices heater thermocouples control valves and digital thermometer A software for HP48 programmable calculator was also developed to simulate the heat exchanger test ring Keywords Heat Exchanger Lab Class Teaching Aid Engineering Education 1 INTRODUCTION The classes of Mechanical Engineering course are normally carried through of the traditional form expositive classes and problems resolution At the end of the course the student doesn t have engineering project feeling and work experience The main objective of the laboratory class is identify theoretical concepts learned in classroom and ap
4. ba CEFET PR Dept Eng Industrial 62p PINHEIRO Paulo C sar da Costa e KOURY Ricardo Nicolau Nassar A Estrutura de um Artigo Cientifico em Engenharia In XXII Congresso Brasileiro de Ensino de Engenharia COBENGE 94 24 27 Outubro 1994 Porto Alegre Anais Porto Alegre ABENGE Associa o Brasileira de Ensino de Engenharia 1994 p 464 469 PINHEIRO Paulo C sar da Costa Calculadoras Programaveis uma Ferramenta Computacional Para o Ensino de Engenharia IN XXXV Congresso Brasileiro de Educa o em Engenharia COBENGE 2007 10 13 de Setembro de 2007 Curitiba Pr Anais Curitiba Centro Universitario Positivo UnicenP 2007 cod 463 sess o 1G08 8p CD ROM PINHEIRO P C C RAAD T J Use of Programmable Calculator for Engineering Teaching In ICECE International Conference on Engineering and Computer Education 1999 Rio de Janeiro Anais of Rio de Janeiro IEEE The Institute of Electrical and Electronics Engineers Section RJ 1999 v 1 5 RESPONSIBILITY NOTICE The author is the only responsible for the printed material included in this paper Proceedings of COBEM 2007 19th International Congress of Mechanical Engineering Copyright 2007 by ABCM November 5 9 2007 Brasilia DF Annex 1 Heat Exchanger Laboratory Class Operational Procedure HEAT EXCHANGER LABORATORY CLASS OPERATIONAL PROCEDURE Mechanical Engineering Course Heat Exchanger Laboratory Class EMA103 Responsible Prof Paulo Cesar
5. da Costa Pinheiro 110V Electricity point F a PROCEDURE 01 Connect the test ring to water point 02 Connect the test ring to drainage 03 Connect PVC tubing hoses in order to establish a countercurrent regimen hot water in inner pipe 04 Open the cold water tap and adjust the flow 05 Verify and repair the leaks 06 Turn off the electric heater 07 Connect the test ring to 110V MAKE ATTENTION 08 Verify the temperatures meter and thermocouples operation Press the keys to read the thermocouples to 4 1 hot water input temperature 2 cold water input temperature 3 hot water output temperature 4 cold water output temperature 09 Read the input cold water temperature 10 Set the hot water valve to obtain a flow of near 0 05 kg s Verify and repair the leaks 11 Turn on the electric heat medium power and verify its correct operation 12 Change the cold water flow minimum maximum and media Wait the steady flow Measure the flow and input and output temperature of hot and cold water The low flow is near 0 01 kg s and high 0 13 kg s Due the ater flow fluctuation it s necessary take more than 3 flow measurements and calculate the average flow 13 Repeat all the procedure for the concurrent flow hot water is always in inner pipe 14 After the experiment turn off the instrumentation the electricity and water flow 15 Empty heat exchanger water 16 Turn off the lamps before leaving laboratory r
6. his configuration one fluid flows inside the 12 mm 1 2 pipe and the other fluid inside the annular space Table 1 Heat Exchanger Material List Material Unit Quantity 25 mm 1 copper tube m 3 12 mm 1 2 copper tube m 3 Reductions Pc 6 12 mm 1 2 cooper courbe Pc 2 25 mm 1 cooper tee Pc 2 It was constructed a metallic rack figure 1 with 12 mm 1 steel angle L welded with coated electrode The exchanger was installed inside the rack fixed for U type cramps with support rubber In the interior of rack had been installed all the auxiliary devices digital thermometer thermocouples electric heater valves connections These devices are located in such a way that no part of the set is outside of rack The rack supports all devices and assures its physical integrity By security the hydraulically connections had been located in the rack at opposing side of electronic equipment 2 Figure 1 The Rack with the Heat Exchanger and Accessories One Euro Control TC 904 digital thermometer was installed inside a metallic box and this box inside of rack in order to protect it of leakage This digital thermometer has a selector key that allows the reading of 4 thermocouples The 4 thermocouples had been installed in the fluid inputs and outputs Two globe valves control the fluid flows A direct electric heater 4250 W heats the cold water in order to simulate the hot fluid figure 2 F
7. igure 2 Rack Details and thermometer installation The water feeding is carried through by PVC reinforced tubing connected by NPT male tube adapter in the control valves The PVC tubing that drain the water for the sewer are connected in NPT male tube adapter installed in the exchanger outputs This fast connection permits easily change of countercurrent to concurrent parallel exchanger flow as showed in figure 3 CA MEDIDOR DE TROCADOR DE CALOR TEMPERATURA TI 4 b 4 S lt VALVULAS 1 e 2 AQUECEDOR O y ENTRADA DE SAIDA DE aes AGUA Figure 3 Test Ring Diagram Hydraulically tests had allowed in order to verify the valves and heater good operation and verify welds and unions and checking then for leaks Operational tests had allowed in order verifying the correct operation of the test ring and determination of operational parameters Proceedings of COBEM 2007 19th International Congress of Mechanical Engineering Copyright 2007 by ABCM November 5 9 2007 Brasilia DF Table 2 Materials for the Rack and Accessories Materials Unit Quantity 25 mm 1 Steel L angle m 4 1 4 x 5 16 U Clamp Pc 5 Thermopar Pc 4 Euro Control TC904 Electronic Thermometer Pc 1 110V 4300W Electric Heater Pc 1 1 2 globe Valve Pc 2 12 mm 1 2 PVC adapter Pc 1 12 mm
8. ion of a huge data amount and allows the use of more sophisticated statistical tools During the laboratory class the student follows the sequence of steps of the experiment guide and chooses and it adjusts the controlled variables of the experiment The software requires 9 kb of memory RAM for storage and more 2 8 kb for its execution The size of the table of water properties in the software is 2 1 kb The execution time is of approximately 35 seconds This software is being developed by change the water property table for property equations in order to become the software small and its faster execution The input and output water temperatures obtained by the software reproduce with good agreement the values obtained in the test ring Software with its manual and the laboratory class guide had been put in the homepage of the Thermal Laboratory class EMA 103 for download http www demec ufmg br disciplinas ema103 praticas pratTC htm 5 LAB DATA SHEET AND REPORT The students are requested to write a report of the activities developed in the laboratory class In order to teach the students who the report presentation is so important when the information contained them the evaluation is based on form and in the content technician Clarity and logic are as well as important how grammatical and vocabulary The criteria used in the report evaluation are presented in table 3 A rubber stamp with the data of table 3 is stamped on the report where is p
9. laced the points The following topics will have to be mandatory in the reports a Bibliographic revision b Equipment and materials c Methodology and procedures d Results and conclusions e Bibliography Table 3 Criteria Used in the Evaluation of the Reports Technical Criteria Points Form Criteria Points Precision 10 Form 10 Effort 10 Procedure 10 Completeness 10 Coherence 10 Order cleanness 10 Originality 10 Timeless 10 Grammar and Orthography 10 TOTAL 100 6 CONCLUSIONS The Heat Exchanger test ring for laboratory class has functioned perfectly throughout the last 6 years and throughout this period it showed to be an equipment that contributes sufficiently in the process of learning of the students The interaction theoretical class practical class mathematical simulation creates foundations for a setting of the knowledge and stimulates the curiosity of the students As this laboratory class are doe only one time each semester before the construction of this test ring it was necessary to find the equipment in the store room to install and to test the equipment and after the class disassembling and returns them it the store room Many times the necessary equipment for the laboratory class were installed in a research project having been necessary a procedure for the request of the equipment removed of the initial place assembly and tests dismount and re assembly in the re
10. oom MATERIAL UTILIZATION 01 Take cares with equipment and instrumentation because this has fragile components 02 Proceed the assembly in order to make the measurements easy 03 Verify the correct electricity point 110V 04 Put the PVC tubing in correct direction to avoid splash water in digital thermometer RESULTS 01 Write all tests results temperature and flow 02 Plot graphs Temperature x flow 03 Calculate the exchanger output temperature by NUT method Consider 1 and 1 2 fine wall pipes 04 Compare the experimental results with the calculated results Analyze the differences and make the ncertainties analysis 05 Calculate the thermal losses and the exchanger thermal efficiency 06 Write all the difficulties found in this test Suggestions for the development of this class will be welcome 07 Conclusions What are you learned in that laboratory class that it wasn t in the book or wasn t learn in lassroom that you need discover create imagine guess etc to obtain the final result Executor Supervisor Bibliography 1 HOLMAN J P Experimental Methods for Engineers McGraw Hill New York 1994 616p 2 INCROPERA F P DE WITT D P Fundamentals of Heat and Mass Transfer John Willey amp Sons New York 3 ed 1990 970p 3 KERN Donald Q Process Heat Transfert McGraw Hill Kogakusha T quio 1950 871p This home page was reviewed at 26 Mars 2007 Annex 2 Heat Exchanger
11. plies then to real practices The application of laboratory classes allows the construction of professional skills develops the scientific and professional spirit and sediments theoretical concepts Aiming at these objectives this paper describes the construction of a heat exchangers test ring shows a laboratory class guide and its didactic results The heat exchanger is maybe the main thermal equipment utilized in the industry This laboratory class is part of the Thermal Laboratory course EMA 103 of the Engineering Mechanics course of Universidade Federal de Minas Gerais UFMG 2 THE TEST RING For the test ring was chosen a double pipe type heat exchanger This type has easy construction easy mathematical modeling and easy visualization Two double pipes heat exchangers has been joined by a curved tube forming a hairpin configuration The hairpin double pipe exchanger is extremely useful because it can be assembled in any pipe fitting shop form standard parts and provides inexpensive heat transfer surface The industrial hairpin exchangers are normally assembled with iron pipes and iron hydraulic connections Kern To make the assemble construction more ease the test ring exchanger was constructed with copper pipes with 1m length and diameter 25 mm and 12 mm 1 and 1 2 The 12 mm 1 2 internal pipes had been placed inside of the 25 mm 1 external pipes and placed and fixed by tees and return reads brazed with oxyacetylene weld In t
12. search With the construction of this test ring now all the equipment belongs to the test ring and the test ring is always ready to use The rack protects the physical integrity of the equipment and makes it difficult its withdrawal for other places To start up the test ring operation is now more easy and fast The software developed simulates with sufficient precision the heat exchanger performance and the values obtained in the laboratory class It is recommended to the students during the writing of the report who make use of others heat exchangers design softwares in order to compare the obtained results The pedagogical results had been excellent verifying an students enthusiasm development of critical thinking feeling practical skills work of group questioning the lesson learn and knowledge fixation In face of the results obtained with this test ring we are being developed other test rings solar energy evaporative cooling fins and combustion based in the same philosophy 7 REFERENCES BEJAN Adrian Transfer ncia de Calor Editora Edgard Bliicher Ltda Rio de Janeiro RJ 1994 540p COFFIN Chris An Easy Course in Using and Programming the HP 48G GX Corvallis USA Grapevine Publications Inc 1993 300p ISBN 0 931011 41 8 KERN Donald Q Processos de Transmiss o de Calor Editora Guanabara Dois Rio de Janeiro RJ 1982 455p MOREIRA Anderson Juarez RIBAS Luciano da Silva Curso de Programa o HP48G GX Curiti
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