Project Readiness Package ME Demo Hardware: Rev. 5/12/12 Natural vs. Forced Convection

Transcription

1 Roadmap Overview The Rochester Institute of Technology Mechanical Engineering Department is in need of developing new demonstration software and hardware to assist in the enhancement of student education in the fields of thermodynamics and heat transfer. These demonstrations will be integrated into the Thermodynamics, Heat Transfer, and other related courses. The ME Demo Thermodynamic and Heat Transfer Hardware family of projects will be responsible for the design, development, and production of this demo hardware. This project will have a lasting impact of the future generations of mechanical engineering students at RIT. The core thermodynamic principles in need of enhancement are: 1. Entropy 2. Real versus Isentropic Systems 3. Specific Internal Energy The core heat transfer principles in need of enhancement are: 1. Natural versus Forced Convection 2. Lumped Capacitance, 1 st Term, and Semi-Infinite Heat Transfer Methods 3. Internal versus External Convection 4. Thermal Conductivity 5. Modes of Heat Transfer 6. Extended Surfaces Administrative Information Project Name: Natural versus Forced Convection Project Number: Unknown Project Family: ME Demo Thermodynamic and Heat Transfer Hardware Parent Roadmap: Planning Term: (Spring) Preferred Start Term: (Fall) Preferred End Term: (Winter) Faculty: TBA Project Customer: RIT KGCOE Project Sponsors: Dr. Edward Hensel Jr. MSD Program Project Budget: $500 (Estimate) Project Overview The Mechanical Engineering Department at RIT has adopted the goal of establishing itself as one of the top 25 ME programs in the world. As part of this goal, RIT s ME Department wishes to demonstrate revolutionary advances in engineering education. In order to accomplish this goal, students need to have a strong understanding and foundation of engineering skills and knowledge that they can appropriately apply to problems to help advance society. To assist in developing a better ME program and create a stronger foundation of engineering theory, RIT s ME Department wishes to develop demonstrations to enhance comprehension in the fields of thermodynamics and heat transfer. Page 1 of 11

2 This project is to be designed to demonstrate convective heat transfer concepts. The Natural versus Forced Convection project objective is to develop an apparatus with appropriate instructions that demonstrates the differences between natural and forced convection reinforcing Newton s Law of Cooling. The apparatus should consider each case separately, isolated from one another. MSD teams will create a demo hardware that incorporates the measuring of temperature of the ambient air, temperature of the object (by location(s) where the convective coefficient is to be calculated), and fluid flow rate (for the forced convection). These measurements will be used to define the properties of the working fluid and calculate the Reynolds number and Nusselt number. This is explained in greater detail in the "basic convective heat transfer background section". The calculation of the Nusselt number will lead to the calculation of the convective coefficient (h). The objective of the lab is to examine how the convective coefficient varies between natural and forced convection. The hardware may include DAQ software to collect data measurements for temperature and air flow and then analyze the results to find the convective coefficient. MSD teams can be creative in the design of the apparatus by measuring how the convective coefficient changes by location on the object and/or with object geometries. This demonstration is intended to assist the instructor in demonstrating the concept in a time efficient manner so that it takes minimal time from lecture. The hardware needs to be easily transportable between rooms, easily stored, and require minimal maintenance for instructor ease and convenience. The results of the demonstration should be distinct and repeatable. The overall goal is to enhance student s comprehension related to convective heat transfer by comparing convective coefficients resulting from natural and forced convection. During , a team (P12361) undertook a similar roadmap project in developing new ME Lab Hardware to demonstrate concepts of kinematics, Newton s laws, and the Work Energy Theorem. This team s work is available to you on EDGE and may contain information that can be used to help develop the foundation of this project. Basic Convective Heat Transfer Background Information Newton s Law of Cooling: Newton s Law of Cooling defines a relationship in which the rate of change in temperature of an object is proportional to the difference between its own temperature and the ambient temperature. This relationship is defined as ( ). Natural Convection: Natural convection is the transfer of heat due to a temperature gradient in a system that is independent of fluid motion from external sources (hence natural convection). Due a temperature gradient, a difference in densities is relevant which in turn creates the fluid motion (the driving force is buoyancy). In a system where natural convection occurs, the fluid around the heat source heats up becoming less dense and thus rises. As this fluid rises cooler fluid is replaced because its density is now relatively larger. The cycle is repeated generating a convective flow of heat through natural fluid motion. An example of natural convection would be letting a hot plate cool to room temperature naturally. Page 2 of 11

3 Forced Convection: Unlike natural convection, forced convection is relevant when heat is transferred due to forced fluid motion by external sources. For example, a fan blowing cold air over a hot plate would be forced convection. Reynolds Number: Reynold s number is the ratio of inertial forces to viscous forces. For this project, Reynold s number will be used to determine whether flow is characterized as laminar or turbulent and will be used to find the Nusselt number (discussed below). Reynold s number as a function of length is Nusselt Number: The Nusselt number is defined as the convective to conductive heat transfer across a boundary. The Nusselt number is how the convective coefficient is solved for directly. The relationship between the convective coefficient and the Nusselt number is Methodologies for computing the Nusselt number (independent of the convective coefficient) for different geometries for both free and forced convection can be found in most heat transfer books and online resources. As part of the objective of the project, the MSD team should create an apparatus that shows the differences between natural and forced convective coefficients. Note that the convective coefficient will vary depending on location on the object. The MSD should strive to demonstrate this. Use of DAQ software could be used in the apparatus to collect data from the demo hardware (such as temperature and/or rate of flow for forced convection) and in turn be used to calculate the convective coefficient by programming in the necessary equations to solve for the heat transfer coefficient. Prandtl Number: The Prandtl number is the ratio of momentum diffusivity to thermal diffusivity. The Prandtl number is used to help determine the Nusselt number. The Prandtl number is defined by the relationship. This number for fluids of a given temperature can generally be found in a table via a heat transfer book or online resource. When determining the Prandtl number, the average temperature between the object and ambient air of the fluid is often used. Natural vs Forced Convection: The heat transfer and convective coefficient associated with forced convection is larger than that of natural convection as large amounts of heat can be transported very efficiently. In systems where natural and forced convection are evident, the dominate convection must be established. In order to do so, Archimedes number is used. Archimedes number is the represents the ratio of buoyant forces to inertial forces and is defined as dominates and if Ar<<1, then forced convection is dominate.. If Ar>>1, natural convection Page 3 of 11

4 Detailed Project Description Customer Needs/Objectives and Assessment: The following table summarizes the customer s objectives. The objective s are rated on a scale where 1=least important, 3=important, and 9=very important. Customer Need # Importance Description CN1 9 Reinforce topics from lecture CN2 9 Requires minimal maintenance CN3 9 Easily transported from one location to another CN4 9 Safe for both students and instructors CN5 9 Can be performed in a time efficient manner CN6 9 Compare and contrast natural versus forced convection CN7 9 Relate to students with various learning styles CN8 3 Large enough to be view by entire class CN9 3 Simple to set up and break down CN10 3 Produce distinct, quantifiable results CN11 3 Demonstrate that solutions vary with assumptions CN12 3 Robust system CN13 3 Relatable to students CN14 3 Easily adaptable to any classroom environment CN15 3 Applies lecture theory to physical applications CN16 1 Easily stored when not in use CN17 1 Create open source materials for potential nationwide adoption CN18 1 Use commercially available Off-The-Shelf (COTS) parts Page 4 of 11

5 Functional Decomposition: Reinforce convective heat transfer Demonstrate natural convection Demonstrate forced convection Perform within class period Integrate into classroom Display results so that all students can see Enhance student comprehension in the convective heat transfer concept of internal versus external convection Create a positive learning experience Transport easily between rooms Relate to students Increase student success Teach how to apply principles to "real life" applications Cater to diverse learning styles Simple and easy to use Easily stored Constraints Assemble and disassemble quickly Minimize maintenance Meets budget Prevents injury Page 5 of 11

6 Specifications: Source Specification (metric) Unit of Marginal Ideal Measure Value Value Comments/Further Detail S1 CN1, CN8 Demo viewing radius Meters >=7 >=11 Students can see demo from moderate distance S2 CN1, CN8 Demo viewing angle Degrees Students can see demo from moderate distance S3 CN7 Auditory, visual, and written aspects Y/N Y S4 CN5, CN9 Demo time length away from lecture time Minutes <=30 <=15 S5 CN3, CN5, CN9 Demo running time length Minutes <=50 S6 CN3, CN8, CN16 Size envelope when assembled Length (m) <=1 Demo size specification based on size needed to fit Height (m) <=1.25 through door adequately and fit on standard ME cart. Width (m) <=0.75 S7 CN3, CN4, CN5 Force required to start and continue motion on a standard ME cart Newtons <=130 <=65 S8 CN3, CN4, CN5, Weight CN16 Newtons <=170 <=130 S9 CN1, CN7, CN13, CN15 Student familiarity Percentage >=70 S10 CN1, CN7, CN17 *Increase in historical average grade Percentage >=1 >=2 Survey percentage of student familiar with idea of device (min sample size of 20 students) S11 CN1, CN15 *Students recognize how demo applies to "real life" applications Percentage >=50 >=70 Done via survey (min sample size of 20 students) Length (m) >=0.5 S12 CN9, CN16 Size envelope when disassembled Height (m) >=0.75 Width (m) >=0.5 S13 CN5, CN9 Time to disassemble/assemble Minutes <=10 <=5 S14 CN5, CN9 Time to read and understand instructions for use Minutes <=30 <=20 S15 CN4 *Injuries per year # <=1 0 S16 CN9, CN14 Lab can be performed in classroom without additional resources Y/N Y The professor understands how to use the device in this time w/o need for further instruction than given Appropriate interfaces for power source if needed (220V to 240V). No outlet for liquid flow. Page 6 of 11

7 S17 CN14 Lab can be performed inside Y/N Y S18 CN12 Robust design- Survives drop test Meters Components do not need replacement when dropped at this height S19 CN2, CN12, CN18 Time to replace parts if parts should break Minutes <=20 <=10 S20 CN2, CN12, *Demonstrations performed w/o need for CN18 replacement of parts # >=100 S21 CN2 *Maintenance required #/year <=2 <=1 Cleaning, calibration, etc. S22 CN1, CN10, Percentage avg. deviation from analytical values Accurate results Percentage <=40 <=30 CN11 using a minimum sample size of 10 runs. S23 CN1, CN10, Results must fall within this range of one another Reproducible results Percentage <=15 <=10 CN11 when 10 runs are performed. S24 CN1, CN6 **Fluid flow velocity measurement accuracy Percentage <=10 <=5 Air flow measured within 5% accuracy. Needed for forced convection. S25 CN1, CN6 **Allowable deviation in "uniform" flow velocity for forced flow Percentage <=15 <=5 S26 CN1, CN6 Measureable surface area Y/N Y S27 CN1, CN6 Temperature gradient accuracy Percentage <=10 <=5 S28 CN1, CN6 Measure of ambient air temperature accuracy Percentage <=10 <=5 Up to 5% allowable variation Surface area needs to be measureable for calculation purposes to find convective coefficient S29 CN1, CN6 **Measures temperature of object accuracy Percentage <=10 <=5 S30 CN1, CN6 Convective coefficient range if working fluid is a liquid W/m^2-C Convective coefficient calculation is main objective of demo hardware Convective coefficient range if working fluid is Convective coefficient calculation is main objective S31 CN1, CN6 W/m^2-C a gas of demo hardware *Disclaimer: MSD team may not be able to measure this, however, this objective should be kept in mind when designing the demo. **Constraints for these parameters provided in "Constraints" section Page 7 of 11

8 House of Quality: Needs & Metrics S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15 S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 S27 S28 S29 S30 S31 CN CN CN CN CN CN CN CN CN CN CN CN CN13 9 CN CN CN CN17 9 CN * 1 = Weak Correlation, 3 = Moderate Correlation, 9 = Strong Correlation Page 8 of 11

9 Constraints: Project Measureable Data Forced convective gas flow must not exceed 15 m/s. Convective liquid flow must not exceed 2 m/s. Temperature of object must not exceed 75 o C. Regulatory Constraints The design and project report shall comply with all applicable federal, state, and local laws and regulations as well as RIT Policies and Procedures. Appropriate citations need to be documented as necessary within the project report. Economic Constraints The team will be required to budget any allocated funds and not exceed the amount that is agreed upon between the team and customer. The expected budget for the project is $500. The team will be required to keep track of all expenses incurred during the duration of project. Purchases for this road map will be approved and channeled through the corresponding department for which they are needed. All purchases must follow any departmental guidelines that are currently set in place. Environmental Constraints Adverse environmental impacts of the project are to be minimized. Material Safety Data Sheets (MSDS) are required for all materials used. Ethical Constraints Every member of every team is expected to comply with RIT s Academic Honesty Policy. Health and Safety Constraints Equipment should be safe for both the students and the faculty. To ensure this, the project components should comply with industry codes and standards, (e.g. Restriction of Hazardous Substances (RoHS), FCC regulations, IEEE standards, and relevant safety standards as prescribed by IEC, including IEC60601). Intellectual Property Constraints All work done on this project, including any intellectual property associated with the project, is property of RIT and must be released to RIT. Students, Faculty, and Staff associated with the project are expected to respect the intellectual property of others, including copyright and patent rights. Page 9 of 11

10 Student Staffing Position Title Mechanical Engineer Design of Natural vs. Forced Convection Apparatus (3 Students) Position Description ME1 & ME2: These two students will be responsible for the design and manufacturing of the hardware that compares and contrasts the differences between natural and forced convection. They will be responsible for ensuring that constraints of the design such as its size envelope, weight, budget, assembly/disassembly time, simplicity, and ease of use are satisfied. They will provide CAD drawing of components that need to be machined. The apparatus must be robustly designed with the intention that the device will last through many generations at RIT. ME3: Student will be responsible for analysis of thermodynamic and heat transfer characteristics of the apparatus and thermo-mechanical structural analysis of the device and its components. This engineer should make sure that the experimental convective coefficient matches within reasonable accuracy of theoretical results. This student is also responsible for ensuring that the apparatus is mechanically functional and safe. Students should have experience from completion of the following courses offered at RIT or equivalent: Engineering Design Graphics, Numerical Methods, ACT, Thermodynamics, Heat Transfer, Transport Phenomena, Fluid Mechanics, Design of Machine Elements, Statics, Mechanics of Materials, Material Science, and Measurement Instrument Controls. Machine shop experience and additional coursework in thermodynamics/heat transfer and design would also be helpful in creating a well developed demo hardware for the ME department. Industrial Engineer Ergonomics, Test Plan, and Manufacturability (1 Student) This student will develop appropriate instructions for the apparatus. Student will be responsible for the development of a testing plan for the device and statistical verification of results expected with theory within reasonable accuracy. This student should make every effort to incorporate principles of 5S into the design, usability, functionality, assembly/disassembly, operation, and storage of the demonstration hardware. This IE will also be responsible for the review and approval of assembly drawing and components. Student should be in pursuit of a degree in Industrial Engineering and should have experience in coursework related to design, management, manufacturing, and statistical analysis. Preferred academic coursework at RIT or equivalent include Design of Experiments I, Engineering Management, Engineering of Systems, and Data Analysis. Page 10 of 11

11 Additional Required Resources Category Source Description Resource Available (Y/N) Faculty Environment Equipment Materials RIT ME/IE Departments RIT Senior Design Space RIT Senior Design Space Online and local suppliers Expertise from mechanical engineering faculty for consulting is available in: Mechanical Design, Heat Transfer, Thermodynamics, Fluid Mechanics, Materials Science, and Controls. In the industrial engineering department Design of Experiments may be needed for consultation. A facility designated to store material and work on mechanical design and structure will be necessary for the completion of the project. Senior design team should have access to the MIC lab ( ) and the Machine Shop for the duration of the project. Materials that may be needed for the completion of the project include: metal stock, fasteners, sheet metal, wires, various meters, thermocouples, pumps, etc. Y Y Y Prepared by: John Harrington Jr. Date: 5/12/12 Page 11 of 11