Heat and mass transfer lab manual

heat and mass transfer lab viva questions heat and mass transfer lab viva questions and answers
KomalMittal Profile Pic
KomalMittal,India,Teacher
Published Date:13-07-2017
Your Website URL(Optional)
Comment
QMP 7.1 D/F Channabasaveshwara Institute of Technology (An ISO 9001:2008 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka. Department of Mechanical Engineering Heat & Mass Transfer Laboratory 10MEL67 B.E - VI Semester Lab Manual 2015-16 Name : ____________________________________ USN : ____________________________________ Batch : ________________ Section : ____________ Channabasaveshwara Institute of Technology (An ISO 9001:2008 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka. Department of Mechanical Engineering Heat & Mass Transfer Lab Manual Version 1.0 February 2016 Prepared by: Reviewed by: Ms. Sushma S Mr. Faheem Akthar Assistant Professor Assistant Professor Approved by: Mr. Giridhar S Kulkarni Associate Professor & Dean (Academics), Dept. of Mechanical Engineering. HEAT & MASS TRANSFER LAB 2015-16 Channabasaveshwara Institute of Technology (An ISO 9001:2008 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka. DEPARTMENT OF MECHANICAL ENGG. HEAT & MASS TRANSFER LABORATORY- SYLLABUS Subject Code : 10MEL67 IA Marks : 25 Hours/Week : 03 Exam Hours : 03 Total Hours : 42 Exam Marks : 50 PART-A: 1. Determination of Thermal Conductivity of a Metal Rod. 2. Determination of Overall Heat Transfer Coefficient of a Composite wall. 3. Determination of Effectiveness on a Metallic fin. 4. Determination of Heat Transfer Coefficient in a free Convection on a vertical tube. 5. Determination of Heat Transfer Coefficient in a Forced Convention Flow through a Pipe. 6. Determination of Emissivity of a Surface. 21 Hours PART-B: 1. Determination of Steffan Boltzman Constant. 2. Determination of LMDT and Effectiveness in a Parallel Flow and Counter Flow Heat Exchangers 3. Experiments on Boiling of Liquid and Condensation of Vapour 4. Performance Test on a Vapour Compression Refrigeration. 5. Performance Test on a Vapour Compression Air - Conditioner 6. Experiment on Transient Conduction Heat Transfer 21 Hours Scheme of Examination: One Question from Part A - 20 Marks (05 Write up +15) One Question from Part B - 20 Marks (05 Write up +15) Viva-Voce - 10 Marks - Total 50 Marks Dept. of ME, CIT, Gubbi Page 1 HEAT & MASS TRANSFER LAB 2015-16 INDEX PAGE Sl Date . Name of the Experiment N Submissio o Conduction Repetition n of Record Average Note: If the student fails to attend the regular lab, the experiment has to be completed in the same week. Then the manual/observation and record will be evaluated for 50% of maximum marks. Dept. of ME, CIT, Gubbi Page 2 Manual Marks (Max . 25) Record Marks (Max. 10) Signature (Student) Signature (Faculty) HEAT & MASS TRANSFER LAB 2015-16 Channabasaveshwara Institute of Technology (An ISO 9001:2008 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka. DEPARTMENT OF MECHANICAL ENGG. Course Objectives & Outcomes. The objectives of Heat & Mass Transfer laboratory is  to demonstrate the concepts discussed in the Heat & Mass Transfer course.  to experimentally determine thermal conductivity and heat transfer coefficient through various materials.  to experimentally measure effectiveness of heat exchangers.  to conduct performance tests on refrigeration & air conditioning systems. The expected outcome of Heat & Mass Transfer lab is that the students will be able  to practically relate to concepts discussed in the Heat & Mass Transfer course.  to conduct various experiments to determine thermal conductivity and heat transfer coefficient in various materials.  to select appropriate materials & designs for improving effectiveness of heat transfer.  to conduct performance tests and thereby improve effectiveness of heat exchangers.  to conduct performance tests and thereby improve effectiveness of refrigeration and air conditioning systems. Dept. of ME, CIT, Gubbi Page 3 HEAT & MASS TRANSFER LAB 2015-16 Channabasaveshwara Institute of Technology (An ISO 9001:2008 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka. DEPARTMENT OF MECHANICAL ENGG. General Instructions to the Students.  Laboratory uniform, shoes & safety glasses are compulsory in the lab.  Do not touch anything with which you are not completely familiar. Carelessness may not only break the valuable equipment in the lab but may also cause serious injury to you and others in the lab.  Please follow instructions precisely as instructed by your supervisor. Do not start the experiment unless your setup is verified & approved by your supervisor.  Do not leave the experiments unattended while in progress.  Do not crowd around the equipment’s & run inside the laboratory.  During experiments material may fail and disperse, please wear safety glasses and maintain a safe distance from the experiment.  If any part of the equipment fails while being used, report it immediately to your supervisor. Never try to fix the problem yourself because you could further damage the equipment and harm yourself and others in the lab.  Keep the work area clear of all materials except those needed for your work and cleanup after your work. Dept. of ME, CIT, Gubbi Page 4 HEAT & MASS TRANSFER LAB 2015-16 Channabasaveshwara Institute of Technology (An ISO 9001:2008 Certified Institution) NH 206 (B.H. Road), Gubbi, Tumkur – 572 216. Karnataka. DEPARTMENT OF MECHANICAL ENGG. CONTENTS Sl. Page Particulars No No 1 Thermal conductivity of metal rod apparatus 01 2 Composite wall apparatus 07 3 Heat transfer through pin - fin 11 4 Natural convection 19 5 Heat transfer through forced convection 23 6 Emissivity measurement 29 7 Stefan Boltzmann apparatus 33 8 Parallel flow & Counter flow heat exchanger 37 9 Filmwise and Dropwise condensation 49 10 Performance test on vapor compression refrigeration test rig 57 11 Air conditioning test rig 63 12 Transient heat conduction 71 13 Critical heat flux apparatus 79 14 Viva questions 81 15 References 85 Dept. of ME, CIT, Gubbi Page 5 HEAT & MASS TRANSFER LAB 2015-16 Experiment -1 SPECIFICATION: THERMAL CONDUCTIVITY OF METAL ROD: Metal rod: Copper Total length of the metal bar : 400 mm Effective length : 320 mm Diameter of the Metal rod : 35 mm Insulation: Chalk powder Distance between two consecutive thermocouple : 60 mm(T to T ) 1 5 Radial distance of the thermocouple in the insulating Shell: Inner radians r = 42.5 mm + (35/2) i Outer radians r = 55 mm+ (35/2) o TABULAR COLUMN: Sl Flow Rate Water Temp. Temp. of Metal Rod Temp. in Insulating No. of water shall C C/min Kg/sec T T T1 T2 T3 T4 T5 T6 T7 T8 T9 10 11 RESULTS (STANDARD): 0 Metal Thermal Conductivity W/m k State 0 Pure Copper 330 – 385 at 20 C 0 Brass 95 – 107 at 20 C 0 Steel 20 – 45 at 20 C 0 Stainless Steel 55 – 65 at 20 C Dept. Of Mechanical Engg, CIT, Gubbi 1 HEAT & MASS TRANSFER LAB 2015-16 THERMAL CONDUCTIVITY OF METAL ROD APPARATUS AIM: To determine the thermal conductivity of the given metal rod INTRODUCTION: Thermal conductivity is the physical property of the material. Based on the value of thermal conductivity of material Thermal conductivity of a material depend on the chemical composition of the substance, the phase(solid, liquid or gas) in which it exists, its crystalline structure if a solid, the temperature and pressure to which it is subjected, and whether or not it is homogeneous material. DESCRIPTION: The experimental setup consists of a metal bar, one end of which is heated by an electrical heater while the other end projects inside a cooling water jacket. The middle portion is surrounded by a cylindrical shell filled with insulating powder and five thermocouple are placed on the bar for temperature measurement. For radial measurement of temperature 4 thermocouples are placed at a sections/radius of 42.5 mm&55mm in the insulating shell. The heater is provided with a dimmerstat for controlling the heat input, water under a constant head is circulated through the jacket and its flow rate and temperature rise are measured using measuring jar and temperature sensors. PROCEDURE: (1) Adjust the flow of water to 0.1-0.2 litres / min on Rotameter (2) Put on the Power supply and adjust the variac to obtain the required Heat input (3) Wait till the steady state is reached. (4) Take the readings of thermocouples T1 – T 11 (5) Repeat experiment for different heat input and water flow rate RESULT: The thermal conductivity of the given metal rod is Dept. Of Mechanical Engg, CIT, Gubbi 2 HEAT & MASS TRANSFER LAB 2015-16 CALCULATIONS: Heat carried away by water Qw = mw Cpw T mw = Mass of flow rate of water in kg/sec 0 Cpw = Specific heat of water = 4.178 KJ / Kg K T = Two – Twi (21 x k (T5-T1)) q = Qw + (ln(ro / ri)) k = Thermal conductivity of insulating powder q = Heat flux Plot the graph of temp. V/s distance dT V/s dx And find out the temp. Gradient dT / dx dT dt dx dX 2K. l(T5-T1) Q = Q + Q = Q + w conduction w ro / ri k = 0.12w/m k for insulating powder Also dT  Q = -KA dx - Q  K = dT A. dx 2 where A = c/s area of metal rod Πd /4 where K is the thermal conductivity of metal rod in (W/ mºk) Dept. Of Mechanical Engg, CIT, Gubbi 3 HEAT & MASS TRANSFER LAB 2015-16 Work Sheet Dept. Of Mechanical Engg, CIT, Gubbi 4 HEAT & MASS TRANSFER LAB 2015-16 Dept. Of Mechanical Engg, CIT, Gubbi 5 HEAT & MASS TRANSFER LAB 2015-16 Work Sheet Dept. Of Mechanical Engg, CIT, Gubbi 6 HEAT & MASS TRANSFER LAB 2015-16 Experiment -2 SPECIFICATION: 0 1.Mild Steel 25 mm thick of 300 mm dia. 1 No. K1 = 25 w/m K 0 2.Hylam 19mm thick of 300 mm dia 1 No K = 0.05 w/m K 2 0 3.Wooden 12mm thick of 300 mm dia 1 No K = 0.08 w /m K 3 4. Mica Heater 300 watts of 300 mm dia 1No 5. Digital temperature indicator 12 channel 1No 6. Digital volt meter 1 No 7. Digital Ammeter 1No 8. Temperature Sensors PT 100 12 Nos COMPOSITE WALL: MILD STEEL HYLAM WOOD L1 = 25 mm L2 = 19 mm L3 = 12 mm K K K 1 2 3 T T T T T T T T T T T T 1 2 3 4 3 4 5 6 5 6 7 8 TABULER COLUMN: Sl. T T T T T T T T8 T9 V I Remarks 1 2 3 4 5 6 7 No CALCULATIONS: (a) Heat flow through composite wall Q = V x I (Watts) Dept. Of Mechanical Engg, CIT, Gubbi 7 HEAT & MASS TRANSFER LAB 2015-16 COMPOSITE WALL APPARATUS AIM: To determine the overall heat transfer coefficient of a composite wall INTRODUCTION: Heat transfer through composite wall is the transport of energy between two or more bodies of different thermal conductivity arranged in series or parallel. For example a fastener joining two mediums also acts as one of the layer between these two mediums. Hence thermal conductivity of the fastener is also much necessary in determining the overall heat transfer through the medium. APPARATUS: The apparatus consists of three slabs of different materials of different thickness clamped in the center using screw rod, at the center of the composite wall a heater is fitted. End losses from the composite wall are minimized by providing thick insulation all round to ensure unidirectional heat flow. Temperature sensors are fitted at the interface of the plates at different points as to obtain average temperature for each surface. Heat conducted through the composite wall is taken away atm air. PROCEDURE: 1. Check for the symmetrical arrangement of plates and ensure the perfect contact between the plates. 2. Switch ON mains and the console. 3. The heat input to the heater is fixed for any desired temperature (assume T = T ) of the 1 i plates. 4. After a steady state condition is reached, average temperature of the slabs at the interface is noted. 5. By varying the heat input to the system through a variac different set of readings can be obtained. RESULT: The overall heat transfer coefficient of a composite wall is Dept. Of Mechanical Engg, CIT, Gubbi 8 HEAT & MASS TRANSFER LAB 2015-16 ’ ’ ‘ ’ ’ ’ K A1 (T T ) K A2 (T T ) K A3 (T T ) 1 1 – 2 2 2 – 3 3 3 – 4 Q = = = L L L 1 2 3 2 QL1 D K1 = -, where A = where D = 300 mm. ’ ’ A (T1 – T2 ) 4 1 QL2 K2 = - ’ ‟ A (T2 – T3 ) 2 QL3 K3 = - ‟ A (T3 – T4’) 3 Where A1 = A2 = A3 = A. ‟ Note: T = (T +T )/2. 1 1 2 ‟ T = (T +T )/2. 2 3 4 ‟ T = (T +T )/2. 3 5 6 ‟ T = (T +T )/2. 4 7 8 (b) Overall heat transfer coefficient (U0) 1 U0 = 1 L L L 1 2 3 - - + - + - A K K K 1 2 3 Dept. Of Mechanical Engg, CIT, Gubbi 9 HEAT & MASS TRANSFER LAB 2015-16 Work Sheet Dept. Of Mechanical Engg, CIT, Gubbi 10 HEAT & MASS TRANSFER LAB 2015-16 Experiment -3 NATURAL CONVECTION:- SPECIFICATIONS: Length of the pin – fin (L) = 120mm Diameter of the pin fin (D) = 13mm Diameter of the orifice (D ) = 30mm 0 Diameter of the pipe (Dp) = 50mm Coefficient of discharge C = 0.64 d Thermal conductivity of fin material (K) = 110 W/mK Duct size = 150 mm x 100mm Distance between each thermocouple on pin fin = 20 mm TABULAR COLUMN: SI.No. Voltage Current Position of the thermocouple from the pin base Amb. In in mm & Temp. along the pin – fin in Temp o o amps C In C 0 20 40 60 80 V I t t t t t t 1 2 3 4 5 6 1 2 3 4 Dept. Of Mechanical Engg, CIT, Gubbi 11 HEAT & MASS TRANSFER LAB 2015-16 HEAT TRANSFER THROUGH PIN - FIN AIM: To determine the following in natural convection and forced convection:  Theoretical and Experimental temperature along the length of the pin – fin  Effectiveness of the pin – fin  Efficiency of the pin – fin INTRODUCTION: Fins are deliberately provided protrusions on metallic surfaces to increase the heat transfer area . Fins could be of uniform cross sectional area or the area may be varying along the length of the fin. Under same conditions , a surface with a fin transfer heat faster than a surface without a fin. A common example is the fin provided in the cylinder of an air cooled internal combustion engine . Heat is transferred by the heated surface to the fin by conduction and in turn the pin transfer heat to then surrounding fluid either by natural or forced convection. „Effectiveness of a Fin‟ (E) is defined as the ratio of the heat transfer from a surface with a fin and without the fin. „Fin Efficiency‟ (η ) is defined as the ratio of actual heat transfer from a surface to the heat that would have been transferred had the entire fin area were to be at the base temperature APPARATUS: The apparatus, mainly, consists of a fin in the form of a horizontal metallic pin. The pin is heated at one end.( i.e., the base of the fin) by an electric heater. The pin is located in the middle of a long duct which can be supplied by air from a blower. When the blower is on and air is being forced against the fin, the fin is subjected to forced convection heat transfer. When the blower is off the pin is subjected to natural convection heat transfer. There are five Temp sensors (t1 to t5) fixed on the surface of the fin. Each is separated from the next one by 20 mm. The first sensors is at the fin. One more sensors (t6) measures the room air temperature. The air flow rate through the duct is measured using an orfice meter. The power supplied to heater is evaluated by measuring the voltage and the current. PROCEDURE: (a) Natural Convection:- 1. The electric heater is switched on. 2. The potential drop across the heater coil is adjusted to be around 60 V. 3. Wait until near steady state conditions are reached. Dept. Of Mechanical Engg, CIT, Gubbi 12 HEAT & MASS TRANSFER LAB 2015-16 CALCULATIONS : (i) (a) Draw the temperature profile along the length of the pin – fin using the experimentally measured temperatures along the length of the pin fin. Q =VI A=DL We have, T =T a 6 Q H= - A(T -T ) s a T +T +T +T +T 1 2 3 4 5 Where Ts= - 5 We have m= (HP/ KA) P= D (ii) Effectiveness, Effectiveness is evaluated from: Tanh (mL) E = HA/ KP Fin Effectiveness = Dept. Of Mechanical Engg, CIT, Gubbi 13