Jawaharlal Nehru Engineering College Laboratory Manual For MOMENTUM TRANSFER Second Year Students Chemical Engineering Author JNEC, Aurangabad
FORWARD It is my great pleasure to present this laboratory manual for Second year engineering students for the subject of Momentum transfer in view the vast coverage required for visualization of concepts of the subject. As a student, many of you may be wondering with some of the questions in your mind regarding the subject and exactly what has been tried is to answer through this manual. As you may be aware that MGM has already been awarded with ISO 9000 certification and it is our endure to technically equip our students taking the advantage of the procedural aspects of ISO 9000 Certification. Faculty members are also advised that covering these aspects in initial stage itself, will greatly relived them in future as much of the load will be taken care by the enthusiasm energies of the students once they are conceptually clear. Principal
LABORATORY MANNUAL CONTENTS This manual is intended for the Second Year Students Chemical Engineering branch in the subject of Momentum and heat transfer. This manual typically contains practical/lab Sessions related to the subject covering various aspects related to enhanced understanding. We have made the efforts to cover various aspects of the subject covering Various concepts of used in Momentum and heat transfer in industry will be complete in itself to make it meaningful, elaborative understandable concepts and conceptual visualization. Students are advised to thoroughly go though this manual rather than only topics mentioned in the syllabus as practical aspects are the key to understanding and conceptual visualization of theoretical aspects covered in the books. Good Luck for your Enjoyable Laboratory Sessions
SUBJECT INDEX 1. Experiment to verify Bernoulli s Equation. 2. Experiment to calculate the friction factor in helical coil. 3. Experiment to calculate the friction factor in spiral coil. 4. Experiment to determine Stefan Boltzmann Constant. 5. Experiment to calculate thermal conductivity of insulating powder. 6. Experiment to determine the effective thermal conductivity and effective thermal resistance of composite slab. 7. Experiment to determine the heat transfer coefficient of natural convective system.
DOs and DON T DOs in Laboratory: 1. Do not enter the laboratory without wearing apron, preferably use shoes. 2. Safety should be given topmost priority. 3. Follow the instructions given by the teacher. 4. Do not touch any Equipment/Chemicals without prior permission. 5. Check the glassware before getting issued. 6. Handle the chemicals carefully as per instructions. 7. Do not pipette any solution/chemical with mouth. 8. During performance of the practical if any glassware is broken inform immediately. 9. Return the borrowed apparatus after the experiment is over. 10. Observe safety precautions while performing the experiments. Instruction for Laboratory Teachers:: 1. Submission related to whatever laboratory work has been completed should be done during the next laboratory session. 2. The promptness of submission should be encouraged by way of marking and evaluation patterns that will benefit the sincere students.
EXPERIMENT NO: I - To Verify Bernoulli s Theorem AIM-: To verify the Bernoulli s theorem. Apparatus-: Bernoulli s Set Up, Stop Watch, & Meter Scale. Theory-: Bernoulli s Theorem states that, in steady, ideal flow of an in compressible fluid, the total energy at any point of the fluid is constant. The total energy consists of Pressure Energy, Kinetic Energy, & Potential Energy (Datum Energy). The energy per unit weight of the fluid is Pressure Energy. Therefore, Pressure Energy = P / ρg Kinetic Energy = V 2 / 2g & Datum Energy = Z The applications of Bernoulli s theorem are-: 1) Venturi Meter 2) Orifice Meter 3) Pilot Tube
Description-: The equipment is designed as a self sufficient unit; it has a sump tank, measuring tank, & 0.5 HP monoblock pump for water circulation. The apparatus consists of Supply Tank & Delivery Tank, which are connected to a Perspex flow channel. The channel tapers for a length of 25 cm & then piezo-meter tubes are fixed at a distance of 5 cm, centre to centre for measurement of pressure head. Procedure-: 1. Keep the bypass valve open & start the pump & slowly start closing the valve. 2. The water shall start flowing through the flow channel. The level in the piezometer tubes shall start rising. 3. Open the valve at the delivery tank side, & adjust the head in piezometer tubes to a steady position. 4. Measure the heads at all the points and also discharge with the help of Diversion Pan in the measuring tank. 5. Change the discharge & repeat the procedure. 6. Do the necessary calculations using the readings noted down before. 7. Specifications-:
Tube No. C/S Area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 3.6 3.2 2.8 2.4 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 Observation Table-: Result-: 1) At discharge..liters / second, Total head is..centimeters. 2) At discharge..liters / second, Total head is..centimeters.
EXPERIMENT NO: II TO CALCULATE FRICTION FACTOR OF HELICAL COIL A] Aim: To calculate friction factor in Helical coil Procedure: 1) Open the by pass valve and close the main valve. 2) Connect tapping to manometer and switch on the pump and allow the fluid to flow for 2 Min. 3) Make sure that there are no air bubbles in the manometer. 4) Open main valve gradually and note manometer reading. Measure the volumetric flow rate by catch and weigh method. 5) Repeat the step (4) by increasing the flow rate. Equations: IP= (em-ef)*g* h Nre = D1*V*ρ/µ Friction Factor = P * D / 2* FI V Observation: 1 Density of manometric fluid 2 Density of Fluid in tube 3 Viscosity of water 4 Length of coil 4 Diameter of tube 5 C/S Area of Tube Observation Table: Sr.N o 1 2 3 4 Manometric Reading Flow Measurement h1 h2 h Volume Tim e Velocity Pressure Drop Friction Factor Reynolds No. Result: Conclusion: Nature of Graph: P Vs Q, FF Vs Nre
EXPERIMENT NO: III TO CALCULATE FRICTION FACTOR OF SPIRAL COIL A] Aim: To calculate friction factor in Spiral coil Procedure: 1) Open the by pass valve and close the main valve. 2) Connect tapping to manometer and switch on the pump and allow the fluid to flow for 2 Min. 3) Make sure that there are no air bubbles in the manometer. 4) Open main valve gradually and note manometer reading. Measure the volumetric flow rate by catch and weigh method. 5) Repeat the step (4) by increasing the flow rate. Equations: IP= (em-ef)*g* h Nre = D1*V*ρ/µ Friction Factor = P * D / 2* FI V Observation: 1 Density of manometric fluid 2 Density of Fluid in tube 3 Viscosity of water 4 Length of coil 4 Diameter of tube 5 C/S Area of Tube Observation Table: Sr.N o Manometric Reading Flow Measurement Flow Rate Velocit y Pressure Drop Friction Factor Reynolds No. 1 2 3 4 h1 h2 h Volume Tim e Result: Conclusion: Nature of Graph: P Vs Q, FF Vs Nre
EXPERIMENT NO: IV HEAT TRANSFER THROUGH COMPOSITE WALL A] Aim: To determine the total thermal resistance and thermal conductivity of a composite wall. Apparatus: Composite wall consisting of three disks of different materials viz. Cast Iron, Pressed wood and Bakelite. A heating element is sandwiched between two identical sets of composite wall. The disks are kept pressed between two pressure plates with the help of a screw press. Thermocouples are fixed at the center of all the interfaces. The control panel consists of a dimmerstat (for varying the voltage supplied to the heater), a voltmeter, an ammeter and a digital temperature indicator with a selector switch. Procedure: 1) Keep the dimmerstat at lowest position. Switch ON the electric supply. 2) Adjust the dimmerstat to supply a particular voltage to the heating element. 3) Wait for steady state to be attained. 4) Note the temperature indicated by the thermocouples at the outer surfaces and interfaces of the composite wall. 5) Also note the voltage and current supplied to the heating element. Observations: 1. Diameter of disks, d=300 mm. 2. Thickness of CI disk=25 mm. 3. Thickness of Bakelite disk=12 mm. 4. Thickness of Wooden disk=12 mm. Observation Table: Sr. No. Voltage (V) Current (A) T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 Calculations: Area of wall, A=( /4) d2 Rate of Heat flow through the slab, Q=VI/2 Average temperature of outer surface of CI disk, T a =(T 1 +T 2 )/2 Avg. temp. at the interface between CI and Bakelite disks, T b =(T 3 +T 4 )/2 Avg. temp. at the interface between Bakelite disks and Wooden disks, T c =(T 5 +T 6 )/2 Average temperature of outer surface of Wooden disk, T d =(T 7 +T 8 )/2
From Fourier s Law of heat conduction, Q=(T a -T b )/(b/ka) Where b= total thickness of composite wall, in m k= thermal conductivity of composite wall, in W/mK Total thermal resistance of composite wall, R th =b/(ka) Therefore R th =(T a -T b )/Q Thermal conductivity of composite wall, k= b/ (R th A) Result: Total thermal resistance of composite wall is...k/w Thermal conductivity of composite wall is...w/mk
EXPERIMENT NO: V- THERMAL CONDUCTIVITY OF INSULATING POWDER A] Aim: To determine the thermal conductivity of an insulating powder. Apparatus: The apparatus consists of two thin walled concentric copper spheres. The inner sphere houses the heating coil. The insulating powder is packed between the two shells. The power supply to the heating coil is adjustable. Fe-Constantan thermocouples are used to measures the temperatures. Thermocouples 1 to 4 are embedded on the inner surface of the inner sphere and thermocouples 5 to 8 are embedded on the outer shell. Procedure: 1. Keep the dimmerstat at minimum voltage position. Switch ON the electric supply. 2. Adjust the dimmerstat to supply maximum 40W to the heating coil. Maintain this constant throughout the experiment. 3. Wait for steady state to be attained. 4. Note down the reading in the observation table as given below. Observations: i. Radius of inner sphere, r i =50 mm. ii. Radius of inner sphere, r o =100 mm. Observation Table: Sr. No. Voltage (V) Current (A) T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 Calculations: Assume steady state one-dimensional heat conduction across the wall of a hollow sphere filled with insulating powder packed between the two spheres (in radial direction only). Applying Fourier s law of heat conduction, Q= -k (4 r 2 ) dt/dr Where Q=rate of heat conducted through the hollow sphere, W k= thermal conductivity of insulating powder, W/m K r= radius of spherical layer, m dt/dr= temperature gradient in the radial direction, K/m Integrating between the limits r i and r o and temperature T i and T o, Q= 4 k r i r o (T i -T o )/ (r i - r o )
Where r i = inner radius of inner sphere r o = outer radius of outer sphere T i = Avg. temperature of inner surface of inner sphere T o = Avg. temperature of outer surface of outer sphere Q=V I T i = (T 1 +T 2 +T 3 +T 4 )/4 T o = (T 5 +T 6 +T 7 +T 8 )/4 Therefore Thermal conductivity of insulating powder, k= Q (r i - r o )/ [4 r i r o (T i -T o )] Result: The thermal conductivity of insulating powder is...w/m
EXPERIMENT NO: VI - Heat Transfer In Natural Convection A] Aim: To determine the average surface heat transfer coefficient in natural convection and compare it with the value obtained by using appropriate correlations. Apparatus: The apparatus consists of a brass tube fitted in a rectangular duct in a vertical fashion. The duct is open at the top and bottom and forms an enclosure and serves the purpose of undisturbed surrounding. One side of the duct is made up of a transparent material for visualization. An electric heating element is kept in the vertical tube, which in turn heats the tube surface. The heat is lost from the tube to the surrounding air by natural convection. The temperature of the vertical tube is measured by seven thermocouples. The heat input to the heater is measured by an ammeter and a voltmeter and is varied by a dimmerstat. The vertical cylinder with the thermocouple, positions are shown in fig. The tube surface is polished to minimize the radiation losses. Procedure: 1. Switch ON the electric supply and adjust the dimmerstat to obtain the required heat input (say 40W, 60W, 70W). Note the voltage and current supplied to the heater. 2. Wait till steady state is reached. Which is confirmed from temperature readings (T 1 tot 7 ). 3. Note the surface temperature at the seven points viz. T 1 to T 7 4. Note the ambient temperature, T 8 5. Repeat experiment at different heat inputs. (Do not exceed 80 watts). Observations: i. O.D. Cylinder, d=38 mm. ii. Length of cylinder, l=500 mm. Observation Table: Sr. No. Voltage (V) Current (A) T 1 T 2 T 3 T 4 T 5 T 6 T 7 T 8 Calculations: a) Actual heat transfer coefficient: Rate of heat transfer, Q=V I watts
Average temperature of surface, T s = (T 1 +T 2 +T 3 +T 4 + T 5 +T 6 +T 7 )/7 Ambient temperature in the duct, T a = T 8 Area of heat transfer, A s = d l Q= h actual A s (T s -T a ) Hence h actual = Q/ [A s (T s -T a )] a) Theoretical heat transfer coefficient: h theoretical is calculated using the appropriate correlation between Nu, Gr and Pr from the data book. (Nu =c (Gr Pr) n Result: The actual value of heat transfer coefficient value of is found to be...w/ m 2 K 4 and the theoretical value of heat transfer coefficient is found to be...w/ m 2 K 4
7. Quiz on the subject: Quiz should be conducted on tips in the laboratory, recent trends and subject knowledge of the subject. The quiz questions should be formulated such that questions are normally are from the scope outside of the books. However twisted questions and self formulated questions by the faculty can be asked but correctness of it is necessarily to be thoroughly checked before the conduction of the quiz. 8. Conduction of Viva-Voce Examinations: Teacher should oral exams of the students with full preparation. Normally, the objective questions with guess are to be avoided. To make it meaningful, the questions should be such that depth of the students in the subject is tested Oral examinations are to be conducted in co-cordial environment amongst the teachers taking the examination. Teachers taking such examinations should not have ill thoughts about each other and courtesies should be offered to each other in case of difference of opinion, which should be critically suppressed in front of the students. 9. Submission: Document Standard: A] Page Size A4 Size B] Running text Justified text C] Spacing 1 Line D] Page Layout and Margins (Dimensions in Cms) Normal Page Horizantal 2.0 2.5 2.0 2.5 2.0 2.0 0.7 2.0 0.7 2.0
Desription Font Size Boldnes Italics Underline Capitalize s College Name Arial 24 ----- ------ Yes ---------- Document Title Tahoma 22 ----- ------ --------- ---------- Document Subject Century Gothic 14 ----- ------ --------- Capital Class Bookman old 12 ----- ------ --------- ---------- Slyle Document No Bookman old 10 ----- ------ --------- ---------- Slyle Copy write inf Bookman old 9 ----- ------ --------- ---------- Slyle Forward heading Bookman old 12 ----- ------ Yes Capital Slyle Forward matter Bookman old 12 ----- ------ --------- ---------- Slyle Lab man Contents Bookman old 12 ----- ------ Yes Capital title Slyle Index title Bookman old 12 Yes ------ Yes Capital Slyle Index contents Bookman old 12 ----- ------ --------- ---------- Slyle Heading Tahoma 14 Yes Yes Yes ---------- Running Matter Comic Sans MS 10 ----- ------ --------- ---------- 9. Evaluation and marking system: Basic honesty in the evaluation and marking system is absolutely essential and in the process impartial nature of the evaluator is required in the examination system to become popular amongst the students. It is a wrong approach or concept to award the students by way of easy marking to get cheap popularity among the students to which they do not deserve. It is a primary responsibility of the teacher that right students who are really putting up lot of hard work with right kind of intelligence are correctly awarded. The marking patterns should be justifiable to the students without any ambiguity and teacher should see that students are faced with unjust circumstances.