thermal lab

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Gbyyb7

Engineering

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formal lab , i put all files and you must see them to get full mark on the lab, there is pdf file which is worksheet , we did the lab and there are calculations you must do it

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Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner Scanned with CamScanner RUBRIC FOR ASSESSING LAB REPORTS 0 Missing 1 Beginning or incomplete 2 Developing 3 Accomplished Objective/ Background Very little background information provided or information is incorrect Some introductory information, but still missing some major points Introduction is nearly complete, missing some minor points Experimental procedure Missing several important experimental details or not written in paragraph format Written in paragraph format, still missing some important experimental details Data, figures, graphs, tables, etc. Calculations are missing or mostly incorrect. Figures, graphs, tables contain errors or are poorly constructed, have missing titles, captions or numbers, units missing or incorrect, etc. Uncertainty is not included. Very incomplete or incorrect interpretation of trends and comparison of data indicating a lack of understanding of results There are multiple mistakes with the calculations. Most figures, graphs, tables are OK, some still missing some important or required features. Uncertainty calculations have many mistakes or omissions. Some of the results have been correctly interpreted and discussed; partial but incomplete understanding of results is still evident Conclusions regarding major points are drawn, but many are misstated, indicating a lack of understanding Sections in order, contains the minimum allowable amount of handwritten copy, formatting is rough but readable More than 2 calculations, questions, or data are missing. But reasonable effort is apparent. Written in paragraph format, important experimental details are covered, some minor details missing Most calculation are correct. All figures, graphs, tables are correctly drawn, but some have minor problems or could still be improved. Uncertainty is included but may have one or two errors or omissions. Almost all of the results have been correctly interpreted and discussed, only minor improvements are needed Discussion of Results Conclusions Conclusions missing or missing the important points Appearance and formatting Sections out of order, too much handwritten copy, sloppy formatting Appednix Only a few calculations or questions re answered, missing raw data, etc. Clearly not complete work. All important conclusions have been drawn, could be better stated 4 Exemplary Total Score x Weight Introduction complete and wellwritten; provides all necessary background principles for the experiment Well-written in paragraph format, all experimental details are covered ___ x 2.5 ___ x 2.5 All calculations and results are correct. All figures, graphs, tables are correctly drawn, are numbered and contain ___ x 7.5 titles/captions. Uncertainty calculations are correct and indicated in figures/tables. All important trends and data comparisons have been interpreted correctly and ___ x 2.5 discussed, good understanding of results is conveyed All important conclusions have been clearly made, student shows ___ x 2.5 good understanding All sections in order, formatting generally good but could still be improved All sections in order, wellformatted, very readable Only 1 or 2 calculations, questions, or data are missing, but otherwise is complete. Entire worksheet is complete; including calculations, tables, figures, and discussion ___ x 2.5 ___ x 5 Total: ______ Technical Report Writing Note: This document has been modified from the ME 360 technical writing handout. Major differences between ME 360 and ME 460 presented in italics. This article provides some general guidelines and "tips" for writing technical reports. Throughout the Mechanical Engineering curriculum you will be required to write formal reportslab reports in ME 360 and ME 460; design project reports in ME 372 and ME 415; a capstone design project report in ME 490; and similar reports in other courses. Each of these reports has particular requirements established by the course instructor. However, the following rules for references, figures, tables, tense and voice, equations, etc., apply to all mechanical engineering writing. Specific instructions for ME 460 are spelled out at the end of this section. How to Write a Report All engineers must report their work, usually in writing. Skilled writers impress their readers favorably. Clear writing helps in preparing oral presentations. Follow the three rules given below for all reports, oral and written. 1. Imagine your audience. In ME 460, imagine you are on your first job and your boss has assigned you to do this experiment. Your boss has an engineering background similar to yours, but does not know the details of the experiment (has not read the ME 460 handout). Your reader (your boss) relies on you for clear explanations. 2. Be thorough and brief. Include all the required sections (discussed below) and informative tables, equations, etc. Write a first draft, then edit it carefully for redundancy, wordiness, clutter, etc. 3. Organize for readability. The question "Is the reader ready for this material?" guides the structure of the report. Overly detailed material, such as calculations, belong in the appendix. Sections of the Lab Report 1. Title Page. Include the title of the lab, the author’s name, the names of all lab partners, and the date. 2. Objective. Describe in one or two sentences the purpose of the laboratory exercise: the “why.” Be specific. Possible objectives are “to evaluate,” “to verify,” “to measure,” “to compare,” etc. Avoid non-engineering objectives, such as “to teach us” or “to show the student.” In general, you will write a technical report where experimental results are compared to theory. The Objective section is written in the present tense. 3. Background. This section gives the reader information necessary to understand or appreciate the balance of the report. It puts things in focus by providing background and perspective. It should answer such questions as: Why was this done? How does this effort fit into the overall scope of things? The Background section is also used to relate your efforts to previous work done by yourself or others. For example, if your report covers electrical filters, then you should discuss a few (three to four) applications of filters. Applications that ME 460 Technical Report Writing 1 relate to mechanical engineering are preferred over generic engineering, technical, or consumer applications. In a lab report, the Background section should also briefly describe the engineering theory used in the experiment and the analysis of its results. Any theoretically predicted results of your experiment would also be included. Commonly used engineering equations (such as Newton's 2nd law, F = ma) can be presented without attributing a source. However, equations taken directly from a textbook must be given proper reference. The Background section is written in the present tense. You may use the ME 460 Lab Manual (handouts) to find equations provided that you provide a proper reference. You will be given the MS Word file of the lab handout so that you can cut and paste equations and figures. 4. Experiment. Write what was done in the lab and how it was accomplished in chronological order. Imagine your group performing the experiment and describe what you did and what happened. Describe the experimental apparatus (including manufacturer and capacity or range of equipment used) and include a diagram, sketch, or scanned photograph with any relevant dimensions. This section should be complete enough for someone to duplicate the results of your efforts. Write the Experiment section in the past tense, since the experiment has already been done. Note that “raw” data does not belong in the Experiment section – it belongs in the Appendix. 5. Results. Present the results in words, tables, and figures. Be sure that tables and figures are mentioned in the text before the actual table or figure is presented. Include a comparison of actual results to theory, if appropriate, and an analysis of sources of error in your experimental technique. All formal reports require an uncertainty analysis. Discuss the results from the uncertainty analysis and use it to guide your discussion. Think carefully: Do the sources of error you have defined adequately explain your experimental results? Cite "human error" only if you discuss exactly what is meant. Remember that you never really know the exact source of error. Always address any specific questions asked in your lab handout. Write the Results section in the present tense. 6. Conclusions. Restate and interpret the major results using numerical values when possible. Were the objectives of the lab or design project met? What can you conclude from the lab? Write the Conclusions section in the present tense. 7. References. Any material taken directly from another author other than you, including the ME 460 Lab Manual, must be referenced. See the section on References in the Writing Style and Format Requirements section. No minimum number of references is required for ME 460 formal lab reports. 8. Appendix. All portions of the appendix should be specifically mentioned somewhere in the main part of the lab report. The appendix should include ♦ an outline of your appendix (continue page numbering from the main report), ♦ a clear listing of your assumptions about uncertainty values, ♦ an example / sample of each calculation required to generate your results - all necessary unit conversions required, ME 460 Technical Report Writing 2 ♦ an uncertainty analysis for all results computed from a formula (including both experimental values and theoretical values that use measured values in a formula), ♦ raw data sheets. Writing Style and Format Requirements Reports written for ME 460 will generally follow the style requirements of the APA (American Psychological Association) unless specifically contradicted in this handout. See the ME 360 website for a list of references to the APA style. Appearance 1. Word process the body of the report, from the title page through the conclusions. The appendix material may be neatly handwritten in either ink or pencil. 2. Figures should be embedded in the report, typically scanned or cut from another source, and then inserted. 3. Use the 12 point Times or Times New Roman fonts for your text, figure captions, and table headings. Use a 12 point Arial or Calibri font for text in figures. 4. Use a one-inch margin on all four sides. Do not right justify the text. 5. Double-space all of the text. 6. Put page numbers on all pages, starting with 1 on the title page. Page numbers are placed one-half inch from the top edge and one inch from the right edge. Use the Header feature of Word to automatically place your page numbers. 7. A header identifying the lab report immediately precedes the page number on all pages: ME 460 Lab Report 0. Leave five spaces between this header and the page number. Tense and Voice 1. Write in the passive voice: "Strain gages were used with a Wheatstone bridge to determine the bending stress in the cantilever beam." 2. Avoid -ing verbs with the passive voice (especially avoid the words “using” and “utilizing”): RIGHT: With a Wheatstone bridge, . . . or A Wheatstone bridge was used to . . WRONG: Using a Wheatstone bridge, . . . 3. Use present tense for the Objective, Background, Results and Conclusions section and any time you state general rules or truths: "The relationship between uniaxial stress and strain is σ =E." 4. Use past tense for the Experiment section. Tell what was done and what happened in your particular case. Spelling, Punctuation, and Word Selection 1. Use a colon only where a period would fit. 2. Put a comma before the conjunction (and, or, but) in lists of three or more. ME 460 Technical Report Writing 3 Set off the words “therefore,” “however,” with (a) comma(s). Spell out contractions (cannot, is not, could not, etc.). Use a plural verb for the word “data”: the data are (were); the datum is (was). Do not write in first person [I, me, my]. The report should be objective. In the group reports it will be acceptable to use third person [we]. 7. Second person pronouns are unacceptable--do not use the word “you” as in “You will see . . .” 8. Avoid non-technical language. Avoid the words “thing” and “stuff” as they relate no information. 9. Avoid the word “there” everywhere in the report. It does not carry any information. Choose more specific words. 10. Avoid referring to measurements by their units (“The psi in the cylinder was 34.”). Instead, use the dimension to refer to the measurement (“The pressure in the cylinder was 34 psi.”). 3. 4. 5. 6. Labeling, Referencing, and Placement of Tables and Figures Tables present numerical or textual material or information in a regular array. Figures present sketches, pictures, charts, graphs, etc. Put the independent values in the first column of a table and on the horizontal axis of plots when possible. 1. Mention each table and figure in the text before it appears in the report. Tables and figures should appear on the same page or on the next available page after they are mentioned. Do not leave large gaps at the bottom of a page if a figure or table will not fit. Continue the text and put the figure or table at the top of the next page. 2. Number and label each table and figure in order, e.g. Table 1, Table 2, etc., not Table 1.1, Table 1-2, etc. Tables are numbered independently of figures and not consecutively as one group. 3. Tables and figures are centered on the page within the one inch margins. 4. A modified version of the APA style for table headings and figure captions will be used in ME 360 & ME 460 as shown below. Note that the table title and the figure number are italicized as shown below. Table 1 Force Sensor Specifications Figure 1. Experimental setup for filter test. 5. Title each figure and table. Note that table titles are placed above the table, while figure titles (these are called captions) are placed below the figure. 6. Acknowledge all figures taken directly from any source. Failure to do so is PLAGIARISM! Follow the example below. Figure 6. Opposed piston engine (Bell & Parker, 1997). ME 460 Technical Report Writing 4 APA Style Tables (from http://web.indstate.edu/mary/tables.htm) • The first part of a table is the table number. Tables are numbered with Arabic numerals in the order of appearance. • The next part is the table title. The table title should be upper and lowercased, centered, and double spaced below the table number. The title should be italicized as well. Double space again after the table title before the actual table begins. • Next is the first horizontal line of the table, which separates the table title from the column headings. • Use upper and lowercase letters in the column headings. The column heading is the label which is centered over each column. Column headings are not boldface, italicized, or underlined. • A second horizontal line separates the column headings from the table data. Table data must be in the same style and size font used for the report’s text. It should also fit within the boundaries of the page’s margins. • The table is ended with a final horizontal line. Any table notes should follow this last line, being designated by Note. and followed by a period. • These three horizontal lines are the only lines which are required for an APA style table. In some cases additional horizontal lines may be used for clarification (American Psychological Association, 2001). • Strict APA style does not allow the use of vertical lines. Check with your instructor if you want to use vertical lines in a table. • In ME 460 we will single-space the table data. In strict APA style the entire table is double spaced, just like the rest of the paper. • Numbers used in tables should have approximately the correct number of significant digits. Do not let Excel determine how many significant digits you use! Correct APA style table (modified slightly for ME 360 and 460): Table 1 Desired and Actual Frequencies for Low Pass Filter Experiment Desired Actual Desired Actual Frequency Frequency Frequency Frequency (Hz) (Hz) (Hz) (Hz) 10 8 800 800 15 16 1500 1600 ME 460 Technical Report Writing 5 Incorrect APA style table (too many horizontal lines, vertical lines, Arial font): Table 1. Desired and actual frequencies for low pass filter experiment Desired Actual Desired Actual Frequency Frequency Frequency Frequency (Hz) (Hz) (Hz) (Hz) 10 8 800 800 15 16 1500 1600 Formatting Figures and Graphs 1. You may use scanned or copied figures taken directly from lab handout or course notes in your ME 460 lab report, but you must reference the ME 460 Lab Manual. 2. All figures should be neatly drawn, either by hand or by computer. All plots of data must be computer generated with Excel, Matlab, or an equivalent program. 3. Plot the independent variable along the abscissa ("X axis") and the dependent variable(s) along the ordinate ("Y axis"). 4. Use appropriate scales for each axis: Divisions of 1, 2, 5, 10, or multiples are preferred. Avoid awkward fractions along labeled divisions (computer programs are particularly bad about this). Show 0 on the scale unless this would compress the data unnecessarily. Do not use numbers like “0.0, 1.0, 2.0, …” for labeling axes, but “0.0. 0.5, 1.0, 1.5, …” is OK. 5. Label the horizontal axis across the bottom of the plot, and the vertical axis along the left hand edge. A “secondary” vertical axis is sometimes provided along the right hand edge. 6. Label each axis with units as well as variable names. If you are plotting two or more variables along the ordinate, use multiple scales (or log scale) if a single scale would compress one set of data excessively. 7. Use similar scales for plots of similar data (perhaps the same experiment run with two different settings). 8. Align each figure so that it reads normally or from the right-hand edge of the page, (i.e., the page should be bound along the left or top side). 9. Plot theoretical relationships along a smooth line or curve, without individual data points (since any point along the curve is equally valid). 10. Plot empirical relationships with individual data points and smooth curves of the appropriate mathematical type. For example, a plot of measured resistance vs. displacement for a potentiometer would use a "best-fit" straight line, since this is the expected relationship. 11. Draw measured data not supported by theory or empirical formula as distinct data points without any lines. Make data points large enough to be easily read. ME 460 Technical Report Writing 6 Some specific comments about graphs in Microsoft Excel 12. Use the X-Y (Scatter) plot option for most of your plots--not Line plot (which equally spaces X axis data). The only exception to this rule is when no independent variable exists. An example of this case would be plotting the experimentally measured resistance of several resistors. 13. The default placement of the X and Y axis can be changed on the Format Axis – Scale option under “Value (X or Y) axis Crosses at ___”. 14. See the ME 360 website (www.me.ua.edu/me360) for additional comments on using Excel in your lab reports. This site is old, but still has some good information about report writing. Equations 1. Provide the reference for all equations taken from another source, including a textbook or a handout. Embed the reference in the text, do not put the reference on the same line as the equation: “Bernoulli's equation for incompressible flow is given by Equation 15.2 of Beckwith, Buck, & Marangoni (1982) as P1 − P2  = V22 − V12 ( Z 2 − Z1 ) g + 2 gc gc (1) 2. Define all symbols immediately after they are first used: Mechanical output power is calculated from the formula P =  (1) where P is the power (typically horsepower or watts),  is the torque (typically ft-lbf or N-m), and  is the angular velocity in RPM (revolutions per minute). 3. Number each equation sequentially in parentheses as shown. The equation can then be referenced by number: "Equation (2) was used to compute motor power output." 4. Center equations (using tab that looks like a perpendicular symbol), and number them along the right margin (using a right align tab), e.g., see Equation 2 above. 5. Refer to a numbered equation with a capital E: Equation 1. If you use the abbreviations "Eqn" or "Eq." and "Eqns." or "Eqs.," do so consistently. 6. Place each equation on a separate line. Unless the equation is universally well known or very short, division should be shown on two separate lines. Note the ambiguity in the first two examples below and the clarity of the third. Not acceptable: ME 460 Technical Report Writing Ymax=3*Pa^4/16*E*t^3*(1-v^2) (4) 7 Not acceptable: ( Ymax = 3Pa4 /16 Et 3 1 − 2 Acceptable: Ymax = 3Pa4 ( 16 Et 3 1 − 2 ) ) (5) (6) 7. Equations should be generated using the Equation Editor that is included with Microsoft Word of (preferred) the MathType 6.0 upgrade. References All references must be specifically mentioned in the text of your report. References are cited in two different places: in text as part of the information within a sentence; OR in text parenthetically not as part of the sentence’s direct information [in which case they are put into parentheses]; AND in the references section. If a reference is cited by authors’ names in the text, the date should immediately follow in parentheses. The date only has to be stated the first time it is mentioned within a paragraph. When it is mentioned again in the next paragraph, the date must be restated. The names are separated by “and.” If a reference is cited parenthetically, the names and date are put in parentheses together. The names are separated by an ampersand (&). In the references section, the names are also separated by an ampersand. Here are the two ways reference citations can appear in text: 1) “… Wheeler and Ganji (1996) give the equation for gain as …” or 2) “Gain is the ratio of output amplitude to input amplitude (Wheeler & Ganji, 1996).” Note that both authors and dates are given in each style. Spell out the names for one or two authors. For three or more authors, name all of the authors the first time ( “Cuttino, Woodbury, and Parker (1996) described a process for group writing of reports.”), but use “et al.” for all subsequent references (“Cuttino et al. (1996) also described …”). Several examples of references using the APA style are listed below. References number 5 (Degelman & Harris, 2000) and number 6 (A guide for writing research papers, APA style, n.d.) listed below can be consulted for additional examples. The APA style for reference listings requires that references be listed alphabetically with a hanging indent format as shown below and in the ME 360 “Good Lab Report.” Note that strict APA style requires the reference list to be double-spaced, but single-spacing the entries with a double-space between entries is used in ME 360/460. 1. Book Franklin, G. F., Powell, J. D., & Emani-Naeini, A. (2002). Feedback control of dynamic systems (4th ed.). Upper Saddle River, NJ: Prentice Hall. 2. Article or chapter in an edited book Norton, H. N. (1997). Transducers and sensors. In D. Christiansen (Ed.), Electronic engineers’ handbook (pp. 13.1-13.50). New York: McGraw-Hill. ME 460 Technical Report Writing 8 3. Magazine article Viterna, L. A. (1998, July). Hybrid electric bus. Power Conversion and Intelligent Motion, 24, 38-47. 4. Journal article Parker, J. K., Bell, S. R. & Davis, D.M. (1992). An opposed piston engine. Journal of Engineering for Gas Turbines and Power, 115, 734-741. 5. Web document on university program or department Web site (with copyright) Degelman, D., & Harris, M. L. (2000). APA style essentials. Retrieved May 18, 2000, from Vanguard University, Department of Psychology Website: http://www.vanguard.edu/ psychology/index.cfm?doc_id=796  6. Stand-alone Web document (no author, no date) A guide for writing research papers, APA style. (n.d.). Retrieved October 13, 2008, from http://webster.commnet.edu/apa/ Note that web addresses can be and should be divided so that the type continues to the right margin. They can be forcefully split after a period or a slash only. The “shift-Enter” option in Word (instead of the “hard” Enter) often works well to force a split in a desired spot without causing other formatting problems. ME 460 Technical Report Writing 9 Specific Requirements for ME 460 Formal and Informal Lab Reports All of the laboratory work conducted in ME 460 will be done in teams. During the course of the semester, there will be two formal lab reports. These reports will be composed, edited, and graded on an individual basis both for technical content and writing. Reports for the remaining labs require less writing and are called “informal reports.” Unless stated otherwise in class, all lab reports are due in class on the last day of class of the week following the lab. Formal Lab Requirements Generally, each formal lab will have emphasized portions that will be the subject of the formal report. The formal report is written as if only the emphasized portions of the lab were performed. An uncertainty analysis is required for all results in the emphasized portion(s) of formal labs reports. The calculations, figures and data sheets for the remaining portion(s) of the lab are attached as separate appendices to the formal report following the rules for an informal report, described below. You will be told before the lab meeting which sections of each lab are to be emphasized in the formal report. Two copies of a formal report should be submitted. One complete physical (“hard-copy”) report (with appendices) for technical grading will be handed in to your lab instructor. One electronic copy must be submitted through Turnitin on Blackboard (appendices may be omitted) for English grading. Formal reports are to be written in accordance with the rules described in the previous technical writing section. You may work with your lab partners in data reduction calculations, answering questions, performing the uncertainty analyses, and preparing tables and figures. Each lab team may share/use the same figures and tables. However, the writing presented in formal lab reports is to be only that of the student turning in the report. Do not “share” in writing the reports. MEMO Report Requirements Essential elements are 1. A brief statement of the purpose of the experiment. It can be assumed that the person to whom the report is written is familiar with the problem or purpose, but s/he should be reminded in the opening paragraph. 2. A summary of the most important results, with references to supporting tables or plots. This section should be the bulk of the report. Trivial details and descriptions of the procedures are not necessary. Tell the recipient only what s/he needs to know. 3. A short statement of recommendations or conclusions. Conclusions must be firmly supported by the results of the experiment. Opinions or speculations should be clearly labeled as such. 4. Supporting documents to include original data, sample calculations, equipment list, plots, tables etc. It is important that the report be neat and orderly. Give all figures and tables numbers and titles. ME 460 Technical Report Writing 10 MEMORANDUM To: Ralph Smartguy, Chief Engineer From: Billy Students Date: August 31, 2011 Subject: Calibration of entropy meters The seven thermal-induction entropy meters (list attached) were calibrated August 28, 2011, in the Energy Affairs Laboratory as requested. Standard entropy values used for the calibration were provided by the Model V Van Wylen entropy generator. Six of the meters were found to have an average percent error of less than 0.5% based on 10 data points per meter, distributed in regular increments throughout the instrument range. The Calibration curves for these six meters are attached. As seen from the curves, none of these meters exhibits significant hysteresis. It should be noted that the only errors were at the lower and upper ends of the range. The seventh meter (ID No. 12345) showed an average percent error greater than 10%. The calibration curve for this meter shows significant hysteresis, particularly in the upper range. During the testing period it appeared that small globules of entropy were becoming jammed in the meter. This could explain the inaccuracies, but the results are inconclusive in this regard. Calibration of the six meters indicates they are in sound condition and can be used with confidence. There were no signs of entropy jamming in them. Meter number 12345 should not be put back into use. It is recommended that further testing be done to pinpoint the cause if its inaccuracies. If the cause is jamming, it can be corrected by careful adjustment of the Carnot valve. I hope these tests and this report meet your needs. If further information is needed, feel free to call or email me. ME 460 Technical Report Writing 11 Heat Exchangers Descriptions of Test Heat Exchangers A heat exchanger is a device that facilitates the transfer of heat from one fluid stream to another. Heat exchangers of many types are widely used in industrial, HVAC, commercial, residential and transportation applications. A tube-in-tube heat exchanger is studied in this lab. The tube-in-tube heat exchanger is perhaps the simplest heat exchanger design other than a bare pipe exposed to external convection. As its name implies, this heat exchanger is constructed by passing a smaller tube through a larger tube. One fluid flows through the inside of the small tube and the other fluid flows in the annular space (washer-shaped cross section) between the inner wall of the larger tube and outer wall of the smaller tube. If the two fluids both enter at one end and exit at the other end, the heat exchanger is said to be in parallel flow, as shown in Figure 1. annulus flow tube flow parallel flow Th,i Th,o ΔT1 ΔT2 Tc,o Tc,i Figure 1. Tube-in-tube heat exchanger in parallel flow. ME 460 1 Heat Exchangers If the two fluids enter at opposite ends and flow past each other in opposite directions, the heat exchanger is said to be in counterflow, as shown in Figure 2. annulus flow tube flow counterflow Th,i ΔT1 Tc,o Th,o ΔT2 Tc,i Figure 2. Tube-in-tube heat exchanger in counterflow. All else equal, counterflow allows a more complete exchange of heat (higher effectiveness Heat Exchanger Analysis Two methods commonly used to calculate heat exchanger performance are the LMTD method and the effectiveness-NTU method. Both can be used to calculate the capacity of the heat exchanger, q. The heat rate to the cold fluid, qc, and heat rate from the hot fluid, qh, can be measured as 𝑞𝑐 = 𝑚̇𝑐 𝑐𝑐 ∆𝑇𝑐 = 𝜌𝑐 𝑄𝑐 𝑐𝑐 ∆𝑇𝑐 𝑞ℎ = 𝑚̇ℎ 𝑐ℎ ∆𝑇ℎ = 𝜌ℎ 𝑄ℎ 𝑐ℎ ∆𝑇ℎ (1) Theoretically, q = qc = qh; however, the measured values will likely be different because of 𝑞 +𝑞 inaccuracies in the experiments. In that case the best estimate of q is the average, 𝑞 = ℎ 2 𝑐. The log mean temperature difference (LMTD) method also allows (UA)meas to be determined as: 𝑞 = (𝑈𝐴)𝑚𝑒𝑎𝑠 𝐿𝑀𝑇𝐷 (𝑈𝐴)𝑚𝑒𝑎𝑠 = (2) 𝑞 𝐿𝑀𝑇𝐷 Recall, the LMTD is defined as: ME 460 2 Heat Exchangers LMTD = T2 − T1 ln (T2 T1 ) (3) where T1 = Th,in – Tc,out and T2 = Th,out – Tc,in in for counterflow exchangers, and T1 = Th,in – Tc,in and T2 = Th,out – Tc,out for parallel flow exchangers. See Figures 1 and 2. The second method of analysis is the effectiveness, number of transfer units (NTU) method. The NTU method allows the heat exchanger effectiveness, , to be calculated. The effectiveness is ratio of the heat transfer actually accomplished to the maximum heat transfer that could be accomplished for the same two flows and same entering temperatures in a counterflow heat exchanger of infinite UA. The maximum possible heat transfer, qmax, depends on the total heat capacities, C, of the two flows. C is defined as: 𝐶𝑖 = 𝑚̇𝑖 𝑐𝑖 (7) Then Cc is the total heat capacity of the cold flow, Ch is the total heat capacity of the hot flow, Cmin is the minimum of Cc and Ch, and Cmax is the maximum of Cc and Ch. The maximum heat that could possibly be transferred is that required to heat or cool the flow having C = Cmin from its entering temperature to the entering temperature of the other flow. Thus, qmax = Cmin(Th,in – Tc,in) (8) The measured heat transfer rates are: qc = Cc(Tc,out – Tc,in) qh= Ch(Th,in – Th,out) (9) Therefore, the effectiveness is:  meas = q q max q + qh q= c 2 (10) The number of transfer units is defined as: NTU = UA meas C min (11) Equations and charts are available that present  in the functional form of  (NTU, Cmin/Cmax) for a variety of heat exchanger types. Charts and equations are presented in the Appendix for parallel flow and counter flow HXs. The predicted effectiveness can be calculated from the appropriate formula. 𝜀𝑝𝑟𝑒𝑑𝑖𝑐𝑡𝑒𝑑 = 𝑓(𝑁𝑇𝑈, 𝐶𝑚𝑖𝑛 , 𝐶𝑚𝑎𝑥 ) (12) ME 460 3 Heat Exchangers Other types of heat exchangers Tube-in-tube exchangers are very simple and are easily analyzed using heat exchanger theory and therefore are the main focus of this lab. However, these heat exchangers are bulky and impractical for routine use. Two common liquid/liquid heat exchanger geometries are the coiled (or helical) tube-in-tube, and the plate frame exchanger. Helical Exchanger By taking a tube-in-tube exchanger and bending it into a coiled or helical shape, a much more compact exchanger results. Additionally, the continuous curvature of the passage induces a secondary flow in the fluid, which enhances mixing and increases the heat transfer coefficient. Other types of heat transfer enhancement are possible, notably use of flow tubes with spiraled cross sections, which both enhance heat transfer and increase the area for heat transfer. Plate Heat Exchanger Another type of heat exchanger that makes use of the same basic principles as the tube-in-tube exchanger it the plate heat exchanger. This exchanger has a number of flow passages that allow hot and cold fluids to flow in alternating passages in either a parallel- or counter-flow arrangement. These heat exchangers are very compact and are widely used in industry. An added advantage is that the plates can be stacked into a frame and bolted together (rather than permanently brazed or bonded) so that the exchanger can be disassembled and cleaned periodically to remove scale or organic build-up. ME 460 4 Heat Exchangers Objective The objective of this experiment is to experimentally test the correlations for the Effectiveness-NTU relationships for parallel and counter flow heat exchangers, and to measure the effectiveness of other types of heat exchangers. Procedure Make sure to record measurements in worksheet. Testing Activities- Tube-in-Tube Exchanger 1. Connect hot and cold water supplies for full double length counterflow, in the tube-intube heat exchanger as detailed by lab instructor. Make sure that rotameters are placed at each of the appropriate two outlets. Make sure that rotameters are vertical at all times. Cold water should flow in the annulus and hot in the inner tube. 2. Set the flow rates as close as possible to those indicated in Table 2. For the first three cases, adjust the flows so that cold and hot are as close to equal as you can. For the last two, adjust the flows so that the hot is as close to twice the cold as possible. It is important that the heat transfer be steady state. Monitor the exit temperatures; after both have stabilized, wait and additional minute. To get good results, temperatures must be stable, not rising or falling! For each case, record the actual flow rates as indicated by the rotameters and the four temperatures in a table like Table 1. 3. Shut off water to both sides of the exchanger. Reverse the supply and discharge connections for the cold flow so that the heat exchanger is now in parallel flow. 4. Repeat the cases in Table 2 following the procedure outlined in Step 2. 5. Repeat “Case 1” using the plate heat exchanger. Test in both parallel and counterflow. 6. Clean up any water spilled during the testing activities, and assist the lab instructor in any other manner he/she requests. Documentation Activities Record model, manufacturer, range and accuracy of all rotameters used. Record model, manufacturer and accuracy of thermocouple reader. Estimate the accuracy of the type-K thermocouples Calculations and Data Presentation 1. Set up an Excel spreadsheet to take the measurements in Table 2 and calculate the values as shown in Table 3, one table each for parallel and counter flow. Values for ρ and Cp will be taken from property data for water at the appropriate average temperature. Add any additional rows, if needed, to complete your calculations. ME 460 5 Heat Exchangers 2. For the tube-in-tube exchanger, compare εmeas (data points) and εpredicted (curve) for both flow arrangements by plotting the ε’s versus NTU based on UAmeas. Include error bars for εmeas. Use Cmin/Cmax = 1 and 0.5 for the predicted curves. 3. For the plate exchanger and the coiled exchanger, create a table comparing the measured effectiveness and NTU to that of the tube-in-tube exchanger for the same flow rates. 4. Compare the effectiveness of parallel flow HX and counter flow HX and discuss the comparison of the experimental values with the predicted values. 5. Compare the effectiveness and NTU of the plate and coiled exchangers with those from the tube-in-tube exchanger. Uncertainty Analysis The dominant sources of uncertainty in εmeas are the inaccuracies in the measurement of flow rates using the rotameters and the inaccuracies in the temperature measurements using the thermocouples. Combining the equations from the discussion of analysis 𝜀𝑚𝑒𝑎𝑠 = 𝜌𝑐 𝑄𝑐 𝐶𝑝,𝑐 (𝑇𝑐,𝑜 −𝑇𝑐,𝑖 )+𝜌ℎ 𝑄ℎ 𝐶𝑝,ℎ (𝑇ℎ,𝑖 −𝑇ℎ,𝑜 ) (13) 2𝜌𝑚𝑖𝑛 𝑄𝑚𝑖𝑛 𝐶𝑝,𝑚𝑖𝑛 (𝑇ℎ,𝑖 −𝑇𝑐,𝑖 ) For each case, estimate uncertainties for the Q’s and T’s. Don’t just guess; accuracies should be given in the online catalogs by the manufacturers. Use these estimates to determine and estimated uncertainty in εmeas. Treat the ρ’s and Cp’s as constants. The math will be much easier if you treat the above equation as 𝜀𝑚𝑒𝑎𝑠 = 𝑞𝑎𝑣𝑔 𝑞𝑚𝑎𝑥 . You can solve for the uncertainty in qavg and qmax separately. References Hodge, B. K., and Taylor, R. P., 1999, Analysis and Design of Energy Systems, 3rd ed, Prentice-Hall, Upper Saddle River, N.J. ME 460 6 Heat Exchangers Appendix—Charts and formulae for effectiveness NTU Counter Flow A x i s T i t l e 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Parallel Flow A x i s Cmin/Cmax =1 Cmin/Cmax =0.5 0 1 2 3 4 5 T i t l e 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Cmin/Cmax =1 Cmin/Cmax =0.5 0 1 2 3 4 5 NTU NTU Figure A-1. Chart for determination of heat exchanger effectiveness,  Equations for parallel and counter flow HX’s can be found in Hodge and Taylor (1999). For parallel flow, 𝜀= 𝐶 1−exp[−𝑁𝑇𝑈(1+ 𝑚𝑖𝑛 )] 𝐶 1+ 𝑚𝑖𝑛 𝐶𝑚𝑎𝑥 𝐶𝑚𝑎𝑥 (A-1) For counter flow, 𝜀= 𝐶 1−exp[−𝑁𝑇𝑈∗(1− 𝑚𝑖𝑛 )] 𝐶𝑚𝑎𝑥 𝐶𝑚𝑖𝑛 𝐶 1− exp[−𝑁𝑇𝑈∗(1− 𝑚𝑖𝑛 )] 𝐶𝑚𝑎𝑥 𝐶𝑚𝑎𝑥 (A-2) When Cmin/Cmax = 1 Equation A-2 is indeterminate as 0/0. In that case, l’Hopital’s rule from calculus must be used to evaluate the limiting formula as Cmin/Cmax approaches 1. The result is 𝑁𝑇𝑈 𝜀 = 𝑁𝑇𝑈+1 ME 460 7 (A-3) Heat Exchangers ME 360/460 Formal Lab Grading Rubric (Writing Grade) In evaluating the writing quality for the formal labs submitted in ME 360/460, grades will be assigned based on the following criteria. Correct grammar, tense, spelling, etc., are all critical to good writing. Compiled from previous semesters of 360/460 lab reports, the following list represents the most common mistakes students typically make—and thus the types of mistakes that will be assessed. Critical common mistakes: 1. 2. 3. 4. 5. 6. 7. 8. 9. Comma-splices and run-on sentences Sentence fragments Capitalization errors APA formatting issues Misuse of commas, semi-colons, and colons Spelling Subject-verb agreement Not following tense requirements for specific sections Formatting of units of measure Any single manifestation of mistakes 1-9 will result in a two-point deduction, with a maximum of four points within that particular category. After finding two occurrences of a mistake, the grader will stop looking for this specific variety. Thus, a maximum overall deduction of 36 points is possible within these nine common mistakes. Beyond these types of mistakes, which are easy to evaluate, the overall quality of writing will be evaluated subjectively. What your writing sounds like matters a great deal, and your ability to construct sentences and entire paragraphs that flow well and effectively convey the message is critical. The writing grader will deduct up to 15 points in assessing your overall writing quality. A deduction of 0 points indicates an overall high quality of writing, a 5-point deduction indicates general competency with only minor lapses, a 10-point deduction indicates overall deficiency, and a 15-point deduction indicates clear lack of effort or proofreading. Summary: Up to 36 points of deduction for common editing/proofreading/presentation mistakes. Up to 15 points deduction for overall writing quality. Please review the attached “What to Keep in Mind” document for further details and reference you can review regarding the common mistakes and subjective evaluation. What to Keep in Mind Lab Reports for ME 360/460 1. In formal writing, avoid ​comma-splices ​(use of a comma to join two independent clauses) and ​run-on sentences ​(two independent clauses joined without punctuation) at all costs. ○ comma-splice example: “Jillian left for Tennessee, she won’t be back until Friday.” ○ example of a run-on sentence: “We haven’t eaten yet we’re getting dinner later.” 2. Sentence fragments​ aren’t acceptable in lab reports. Use complete sentences. ○ This is a sentence fragment: “Leaving campus at 9 PM.” ○ Here’s another: “Which is why I can’t meet you there.” ○ And another: “Because my car broke down.” 3. Capitalization ​mistakes are very common in 360/460 lab reports. ​Consult the rules​. Don’t capitalize words to indicate emphasis or particularity. In the sentences forming the body of your report, for example, terms such as “operational amplifier” and the “second law of thermodynamics” call for lowercase letters. 4. Formatting: I’ll show no mercy here. Adhere strictly to the APA template provided for your lab reports (including citations). 5. Misuse of commas, semi-colons, and colons: Review the accepted conventions. ​Make an appointment at the UA Writing Center​ if you need help navigating the many rules. 6. Spelling mistakes: When you’re drafting a document on a computer, there’s no excuse for making spelling mistakes. Misspellings will make you appear slovenly and uneducated. 7. Subject-verb agreement: ​Singular subjects take singular verbs; plural subjects take plural verbs. 8. Follow the ​tense requirements​ for each section to a T. 9. Units of measure: ​Insert a space between numbers and any associated units of measure. Refer ​here​ for more information. 10. Rhythm: What your writing ​sounds ​like matters a great deal. Modulate the lengths and structures of your sentences. ○ Here’s an example of excellent writing by ​Nicola Twilley​: “Just over a billion years ago, many millions of galaxies from here, a pair of black holes collided. They had been circling each other for aeons in a sort of mating dance, gathering pace with each orbit, hurtling closer and closer. By the time they were a few hundred miles apart, they were whipping around at nearly the speed of light, releasing great shudders of gravitational energy. Space and time became distorted, like water at a rolling boil. In the fraction of a second that it took for the black holes to finally merge, they radiated a hundred times more energy than all the stars in the universe combined. They formed a new black hole, sixty-two times as heavy as our sun and almost as wide across as the state of Maine. As it smoothed itself out, assuming the shape of a slightly flattened sphere, a few last quivers of energy escaped. Then space and time became silent again.” ○ The following writing isn’t atrocious, but it’s far from good. Notice the monotony of its rhythm—the sentences are all long and of similar lengths. And be precise when choosing your words. Avoid the lack of specificity (“the theoretical formula,” “decrease significantly,” “very similar to the experimental ones”) exhibited here. “Sinusoidal input signals of different frequencies were applied to an electrical low-pass filter. At frequencies below the break frequency the input and output signals had the same amplitude. As the input frequency was increased above the break frequency, the output signal amplitude began to decrease significantly. The theoretical formula that predicts the magnitude response gave results very similar to the experimental ones. This experiment was successful in demonstrating the validity of the theoretical formula for a first-order, low-pass filter constructed from a single resistor and capacitor. Therefore, the objectives of the lab were met.” ○ This passage is plain awful: “Op amps are used to amplify a signal so that it can be more easily measured. Ideally electronic amplifiers have no offset voltage so they should be perfectly accurate when amplifying a signal. However real operational amplifiers have an offset voltage that can change the measured voltage in a circuit. This offset voltage must either be accounted for or preferably removed using the circuits described in the later sections of the lab. Using one operational amplifier to provide the gain necessary for the experiment and a potentiometer along with resistors can help to remove this offset voltage. Potentiometers are adjustable instruments that can be used to measure electromotive force by balancing it against the potential difference by passing it through a circuit of known resistance. Using these with a voltage follower and summing amplifier allows for the removal of the offset voltage using a complex circuit that will be constructed in this lab.”
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Heat Exchanger Experiment Outline paper
Objective of the experiment
Background
Experiment
Result
Conclusion
References
Appendix


Running head: HEAT EXCHANGER EXPERIMENT

Heat Exchanger Experiment
Name
Lab Partners:
Date

1

Attached.

Running head: HEAT EXCHANGER EXPERIMENT

Heat Exchanger Experiment
Name
Lab Partners:
Date

1

HEAT EXCHANGER EXPERIMENT

2

Contents
Objective ............................................................................................................................. 3
Background ......................................................................................................................... 3
Log Mean Temperature Difference (LMTD) method ..................................................... 5
Number of Transfer Units (NTU) ................................................................................... 6
Procedure ............................................................................................................................ 7
Results Calculation and Data Presentation ......................................................................... 8
Discussion ......................................................................................................................... 12
References ......................................................................................................................... 13
Appendix........................................................................................................................................ 14

Table of Tables
Table 1: Nominal Flow rates for test cases ..................................................................... 8
Table 2: Measurement for parallel flow.............................................................................. 8
Table 3: Measurement for counter flow.............................................................................. 9
Table 4:Calculation for parallel flow .................................................................................. 9
Table 5: Calculation for counter flow ............................................................................... 10
Table 6: Comparison of tube-in-tube and plate heat exchangers. ..................................... 11
Table 7:Uncertainty Analysis and Calculation ................................................................. 11
Table of Figures
Figure 1:Tube-in-tube heat exchanger in parallel flow....................................................... 4
Figure 2:Tube-in-tube heat exchanger in counterflow........................................................ 4
Figure 3:Effectiveness versus NTU curve for the parallel flow ....................................... 10
Figure 4: Effectiveness versus NTU curve for the counter flow: ..................................... 11

HEAT EXCHANGER EXPERIMENT

3

Objective
The purpose of this experiment is to test the correlation for the effectiveness-NTU, the relationship
between parallel and counter flow heat exchangers and to measu...


Anonymous
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