M.E LAB 3 Experiment 4 Heat Losses From Pipes (3)

Experiment No. 4

HEAT LOSSES FROM BARE AND LAGGED PIPES

Course Code: MEP510L2Program: BSME

Course Title: ME LABORATORY 3Date Performed:

Section:ME51FA1Date Submitted:

Leader: Instructor: Engr. Nelson Dela Pea Jr.

Members:

1. Objective:

The activity aims to provide knowledge on the calculation of heat losses from bare and lagged pipes.

2. Intended Learning Outcomes (ILOs):

The students shall be able to:2.1 Explain the principles of heat loss and heat gain from bare and lagged pipes considering the materials used in the system.2.2 Apply the appropriate standards and tables in the calculation of heat losses to improve the system efficiency.2.3 Develop professional work ethics, including precision, neatness, safety and ability to follow instruction.

3. Discussion:

A good pipe covering, in addition to being a good insulator, should be fireproof, waterproof, vermin proof, odorless, and light in weight. It should also be mechanically strong and should suffer no loss of insulating value due to time.

The only logical method for testing commercial pipe coverings is to mount these coverings on pipe of the size for which they were intended. Extensive tests of commercial coverings have been made by various investigators, and two general methods for heat measurement have been used. For steam-pipe coverings, the most natural method is to fill the covered pipe with steam, to measure the heat content of the steam entering and leaving the test section, and to condense and weigh the steam. A dead-end pipe is ordinarily used, the test pipe itself acting as the steam condenser.

Movement of cooling water, brine, compressed air and steam is essential in any industrial complex. Fluid movement takes place in piping due pressure difference. For carrying out study in these systems, knowledge of pressure at various points is essential. For a given length of pipe, pressure drop can be measured or calculated. Measurement of pressure drop is recommended if instruments of good accuracy are available and measurement is practically possible. In systems where measurement is not possible, estimation of pressure drop is recommended.

The measurements and estimations enables to take a decision whether the energy cost due to pressure drop in existing piping system is more than the total cost of installing a new pipeline of same size or higher size in order to reduce pressure drop. Recommended pipe size for steam systems is given to help in proper selection and to verify whether existing piping is properly sized. As a general rule, the pressure drop should not normally exceed 0.1 bar/50 m.

Piping if left bare can lose heat due to temperature difference between pipe surface temperature and ambient temperature. The methods of measurements and calculations for estimation of heat losses and heat gain in piping systems and insulation thickness are described. Measurements of fluid temperature and pipe surface temperatures are necessary for above calculations.

Heat Loss Calculations:

Heat Loss from Pipes:

Simplified formula for calculating the heat transfer coefficient h (mW/cm2-K) are given below. This is useful if the temperature difference between surface and the ambient is less than 150C.

For horizontal pipes, h = C1 + 0.005 (Th - Ta)

For vertical pipes, h = C2 + 0.009 (Th - Ta)

where: h = heat transfer coefficient, (mW/cm2-C)Th = hot surface temperature, C Ta = ambient temperature, C

Using the coefficients C1 and C2 as given below:

SurfaceC1C2

Aluminum, bright rolled0.050.250.27

Aluminum, oxidized0.130.310.33

Steel0.150.320.34

Galvanized sheet metal, dusty0.440.530.55

Non metallic surfaces0.950.850.87

Area of pipe surface, A = x D x Leff, cm2

where: D = pipe surface outside diameter, cmLeff = effective length of pipeline, cm

Types of pipe insulation

Bare and Lagged Pipes

4. Materials and Equipment:

Bare and lagged pipe assembly Personal protective equipment Automation unit Laser Thermometers Steel tape Outside calipers Sling psychrometer Psychrometric Chart Log sheets

5. Procedure:

The ASME Test Code specifies that each run should be at least 1 hour long. If the time available for this experiment necessitates shorter runs, all readings should be taken every 5 minutes.

1. A team leader should be elected or appointed from the group. The team leader must develop specific log sheets to be used by each member assigned to take data. Accomplished log sheets should be submitted together with this experiment.

2. Make sure to wear/use the personal protective equipment in the entire duration of the experiment.

3. With the assistance of the laboratory technician, set the main pressure of steam to 40 psig and difference of 10psig. Set-up and install the automation unit by attaching it to the terminal for bare and covered pipe assembly. Set the data collection default at 5 minute interval. Encode the instructor and technician names in the automation system.

4. Fire the boiler.

5. When desired steam pressure is achieved, direct the steam to the Bare and Lagged pipe assembly by opening and closing the corresponding valves in the steam line header.

6. With the drain valve open wide, turn the steam valve to allow steam to flow through the steam line long enough to purge apparatus of all air. Close the drain valve. Measure the air properties inside the boiler room. Plot the results on a psychrometric chart.

7. For the bare pipes, get the steam temperature and that of the outer surface of the pipe (both steam inlet and outlet). Record the data on the log sheet. Determine the heat losses for each pipe.

8. For the lagged pipe, get the steam temperature, outer surface temperature of the pipe, and that of outer surface of the covering (both steam inlet and outlet). Record the data on the log sheet. Identify the insulation used. Determine the heat loss on the lagged pipe. With the bare pipe of same material, compute the efficiency of the insulation.

9. For the finned pipe, get the temperature of the outer surface of the pipe and that of the outermost fin surface (both steam inlet and outlet). Record the data on the log sheet. Considering the total surface area of the finned pipe, compute the heat removed. With the bare pipe of same material, compute the efficiency of the fin.

10. Repeat the procedure for each bare and lagged pipes over a 2-hour period with readings every 5 minutes. Due to the large number of readings, much care is necessary in arranging and recording the data.

11. Upon completion of data gathering, stop the automation unit, making sure that data collected is stored in the hard drive. Print a hard copy. Data from automation unit when used in computation and diagram must be marked and cited accordingly.

12. For all pipes tested, draw a temperature-length diagram, pipe cross section showing dimensions, respective heat flow directions. Label each diagram properly.

The efficiency of the insulation is defined as follows:

(Heat lost from bare pipe) - (Heat lost from covered pipe) E = x 100% (Heat lost from bare pipe)

(Heat saved by insulation) = x 100% (Heat lost without insulation)

The heat-transfer coefficients to be calculated for each test pipe are:

over-all coefficient, U in over-all transmission equation; q = UAT conductivity of the insulating material k in conduction equation; qL = kAT outside-surface coefficient h in convection equation; q = hAT

The steam-side-surface coefficient and the contact resistance between covering and pipe may be neglected.

The value of U for a simple wall:

1 U = 1 L 1 + + h1 k h2

where:q = heat flow rateA = area of surface on which heat transfer coefficient is basedT1 = higher temperatureT2 = lower temperatureMTD = mean temperature difference (arithmetic or logarithmic)L = length of heat pathk = thermal conductivityh = surface conductanceU = transmittance or over-all coefficient

Notes and Precautions:

1. The same amount of condensate should be accumulated each successive 20 minutes by a given test pipe. If these amounts do not check after a reasonable warming-up period, look for trouble.

2. Most likely the source of error is due to insufficient venting of air before starting. Make sure that each test pipe is blown down thoroughly.

3. Use several thermometers for air temperature, place them on a level with the test section, but protect them from radiation. A piece of aluminum foil makes a good shield for the thermometer bulb.

4. Do not open doors or windows near the test unit during the conduct of the test.

6. Data and Results:

Table 1: Piping materials

PipeMaterial

1Galvanized iron

2Black iron

3

Black iron pipe with insulation (Perlite asbestos, outside aluminum)

4Stainless Steel

5Copper tube

6Copper tube fins (nonmetallic)

This experiment used 5 minutes interval for gathering data. For measuring surface temperature in every pipe we used laser thermometers and psychrometer for air temperature porperties.

Table 2: Pipe inletInside Temperatures: (Reading based on temperature gauges)Surface Temperatures: (Using infrared gun thermometer)

trialsPipe 1Pipe 2Pipe 3Pipe 4Pipe 5Pipe 6Ambienttemperature

5mins49psi112.5 C68.5 C110 C77.4 C118 C34.7 C115 C61.5 C116 C60.1 C121 C82.2 C31 C

10mins45psi110 C62.5 C111 C64.3 C116 C35 C115 C48.9 C116 C41.2 C117 C94.2 C31 C

15mins41psi111 C65.3 C111 C60.6 C116 C41.4 C115 C48.6 C116 C60.3 C116 C98 C31 C

20mins40psi116 C72.2 C111 C73.5 C116 C35.5 C111 C53.1 C115 C66.3 C116 C98.2 C31 C

25mins36psi110 C66.4 C110 C65 C112 C34.3 C119 C59.4 C120 C65 C117 C91.3 C31 C



40mins33psi111 C66.2 C111 C62.7 C111 C35.1 C115 C59.6 C115 C67.4 C116 C92.8 C31.5 C

45mins31psi111 C66.5 C110 C67 C111 C35.2 C111 C67 C116 C63.2 C116 C97.7 C31 C




Table 3:Pipe inletCorresponding Inside Pressure (Using Steam Table)Corresponding Surface Pressure (Using Steam Table)

trialsPipe 1KPaPipe 2KPaPipe 3KPaPipe 4KPaPipe 5KPaPipe 6KPaAmbienttemperature

5mins49psi153.27729.2312143.37642.6385186.4045.5359169.17721.3721174.76820.0383205.03951.799631 C

10mins45psi143.37622.3704148.25923.4081174.7685.62862169.17711.6926174.7687.87012180 .50982.147931 C

15mins41psi148.25925.379148.25920.7915174.7687.95369169.17711.5183174.76820.2244174.76894.390231 C

20mins40psi174.76834.2914148.25936.2363174.7685.78614148.25914.3812169.17726.5336174.76895.074331 C

25mins36psi143.37626.6515143.37625.0411153.2775.41433192.45519.3984192.45525.0411180.50973.719631 C

30mins35psi143.37634.3767148.25939.2458148.2595.85022148.25924.2674174.76812.4127174.76881.844532 C

35mins34psi143.37623.4081148.25930.2244148.2595.4782148.25929.6164174.76828.1009174.76842.114432 C

40mins33psi148.25926.4162148.25922.5748148.2595.65982169.17719.5794169.17727.8548174.76877.984231.5 C

45mins31psi148.25926.7698143.37627.368148.2595.69118148.25927.368174.76823.0926174.76893.371831 C

50mins30psi143.37634.5965148.25921.0801148.2595.29509143.37627.2475169.17726.7698174.76883.67931.5 C

55mins29psi143.37630.3998148.25923.0926148.2595.50529143.37620.318163.73427.489169.17792.697932 C

60mins28psi143.37625.6065148.25922.0668148.2595.69118143.37623.5141163.73430.5321169.17785.862331.5 C

Table 4: Pipe outlet Inside Temperatures: (Reading based on temperature gauges) Surface Temperatures: (Using laser thermometers)

trialsPipe 1Pipe 2Pipe 3Pipe 4Pipe 5Pipe 6Ambienttemperature

5mins49psi113 C76.4 C116 C76 C116 C37 C111 C44 C110 C37.5 C110 C54.5 C31 C

10mins45psi116 C72.4 C123 C74 C120 C36.4 C112 C68 C110 C36.6 C116 C89.6 C31 C



25mins36psi117 C76.3 C115 C22.5 C119 C35.5 C110 C56.6 C108 C51.4 C111 C 80 C31 C

30mins35psi115 C60 C118 C46.5 C117 C38.4 C110 C63.8 C108 C70 C110 C100.7 C32 C


40mins33psi117 C71.3 C120 C74.1 C117 C39.8 C110 C64.8 C107 C75 C109 C95.1 C31.5 C

45mins31psi110 C77.8 C120 C81 C118 C35.9 C109 C62.6 C107 C81.5 C108 C84 C31 C

50mins30psi115 C75.6 C119 C79 C118 C36 C109 C65.6 C106 C70.2 C107 C87.5 C31.5 C

55mins29psi112 C70.6 C120 C74.8 C119 C35.3 C110 C64.6 C108 C83 C110 C 78.5 C32 C

60mins28psi111 C72.5 C112 C68.2 C114 C35.1 C109 C68.9 C108 C77.7 C110 C 86.6 C31.5 C

Table 4: Pipe OutCorresponding Inside Pressure (Using Steam Table)Corresponding Surface Pressure (Using Steam Table)

trialsPipe 1KPaPipe 2KPaPipe 3KPaPipe 4KPaPipe 5KPaPipe 6KPaAmbienttemperature

5mins49psi158.43541.253174.76840.2389174.7686.28185148.2599.1118143.3766.45505143.37615.387731 C

10mins45psi174.76834.5847218.28737.0088198.6656.07933153.27728.5986143.3766.1462174.76869.122931 C

15mins41psi153.27746.8417198.66552.8422186.4045.9802143.37613.4317138.62621.6675153.27717.0131 C

20mins40psi180.50934.8802198.66552.6323198.6655.78614143.37624.2674138.62647.607143.37661.117631 C

25mins36psi180.50940.7433169.1772.72697192.4555.78614143.37617.01134.00713.2353148.25947.414731 C

30mins35psi169.17719.9458186.40410.3595180.5096.77724143.37623.7272134.00731.2006143.376103.97832 C

35mins34psi143.37643.3458198.66535.3274180.5097.07521143.37627.8548129.51417.9165138.62643.16832 C

40mins33psi180.50932.9971198.66537.1649180.5097.30605143.37624.8179129.51438.5954138.62684.920831.5 C

45mins31psi143.37643.3458198.66549.3676186.4045.9149138.62622.4724129.51450.369134.00755.635531 C

50mins30psi169.17739.5745192.45545.5271186.4045.94747138.62625.7208125.14731.4715129.51463.77731.5 C

55mins29psi153.27732.0192198.66538.2735192.4555.72268143.37624.5965134.00753.4762143.37644.607332 C

60mins28psi148.25934.7322153.27728.8502163.7345.65982138.62629.7456134.00743.168143.37661.594131.5 C

Computation:

Heat Loss Calculations:

Logarithmic Mean Temperature Difference (LMTD):

Note: use LMTD if > 2

Arithmetic Mean Temperature Difference (AMTD):

Note: use AMTD if 2 with 4% error

Table 35:

Mean Inside Temperature

Pipe 1Pipe 2Pipe 3Pipe 4Pipe 5Pipe 6

Inlet102.5102.4167100.833397.25101.5833101.1667

Outlet100.4167101.6667100.833398.91667108.039296.33333

Mean Surface Temperature

Pipe 1Pipe 2Pipe 3Pipe 4Pipe 5Pipe 6

Inlet55.8554.37534.2916747.97546.0333360.15

Outlet70.4583373.12536.1666759.6266764.9583374.675

For Pipe 1:

Such that;

Therefore we use AMTD:

Summary MTD outputs:

Table 36:

PipeTmaxTmintmax / tminMTD

146.6529.958371.55716138.30419

248.041728.54171.68321138.2917

366.5416364.666631.02899565.60413

449.27539.291.25413644.2825

555.5499743.080871.28943549.31542

641.016721.658331.89380731.33752

Inside and Outside Pipe Diameters

Table 37:

Pipe NumberPipe MaterialOutside Diamater, Do (m)Inside Diamater, Di (m)Thermal Conductivity, k

1Galvanized Iron0.03340.0265480.2

2Black Iron0.03340.0266480.2

3Black Iron0.03340.0266480.2

Perlite Asbestos0.126520.03340.02

Aluminum0.0126640.012652205

4Stainless Steel0.03340.0266415.1

5Copper Tube0.028580.025281401

6Copper Tube with Fins0.029580.02858401

Outside Surface Conductance (ho)

Since the pipes are in horizontal position then we use the equation:

Pipe 1: @ Entry

Pipe 1: @ Outlet

Summary:

Table 38: @ Pipe Inlet

PipeC1ThTa

10.5355.85306.5925

20.3254.375304.41875

30.3234.29167303.4146

40.3247.975304.09675

50.8546.03333309.3017

60.8560.153010.0075

Table 39: @ Pipe Outlet

PipeC1ThTa

10.5370.4583330.57.2979

20.3273.12530.57.43125

30.3236.1666730.55.5833

40.3259.6266730.54.09675

50.8564.9583330.510.2229

60.8574.6753010.7338

Surface Area

For Pipe 1 to 5

Summary:

Table 40:

Pipe

Surface Area

10.03342.340.245

20.03342.340.245

30.126642.340.931

40.03342.340.246

50.028582.340.210

For Pipe 6 (Copper Tube with fins)

Such that:

For the number of fins (

Where:

f in = tanh(mL) mL (2) where m = (hC/KA) h = film heat transfer coefficient from the fin surface [Kcal/hrm2C ] C = circumference of the fin [m] K = thermal conductivity of fin material [Kcal/hr mC ] A = cross-sectional area of fin [m2 ]

Where;

x 2.33m

mL = .273

(Finned tube must be 50 75%)

Heat Loss Calculation

Pipe Inlet:

Pipe 1

Pipe

1

2

3

4

5

8. Conclusion and Recommendation:

After gathering the data from the experiment, We were able to compute for the heat loss from the bare and covered pipes. We learn more in the principles of heat loss and heat gain from bare and covered pipe. We were able to get the heat loss by measuring the size, temperature and pressure of the pipe. We also learned how to compute efficiency of finned pipes.

Recommendation We recommend getting new laser thermometer so we can able to get more accurate measurement of the surface temperature of the pipes.

9. Assessment Rubric:

T I P - V P A A 0 5 4 D Revision Status/Date:0/2009 September 09TECHNOLOGICAL INSTITUTE OF THE PHILIPPINESRUBRIC FOR LABORATORY PERFORMANCECRITERIABEGINNER1ACCEPTABLE2PROFICIENT3SCORE

Laboratory Skills

Manipulative SkillsMembers do not demonstrate needed skills.Members occasionally demonstrate needed skills.Members always demonstrate needed skills.

Experimental Set-upMembers are unable to set-up the materials.Members are able to set-up the materials with supervision.Members are able to set-up the material with minimum supervision.

Process SkillsMembers do not demonstrate targeted process skills.Members occasionally demonstrate targeted process skills.Members always demonstrate targeted process skills.

Safety PrecautionsMembers do not follow safety precautions.Members follow safety precautions most of the time.Members follow safety precautions at all times.

Work Habits

Time Management/Conduct of ExperimentMembers do not finish on time with incomplete data. Members finish on time with incomplete data.Members finish ahead of time with complete data and time to revise data.

Cooperative and Teamwork Members do not know their tasks and have no defined responsibilities. Group conflicts have to be settled by the teacher.Members have defined responsibilities most of the time. Group conflicts are cooperatively managed most of the time.Members are on tasks and have responsibilities at all times. Group conflicts are cooperatively managed at all times.

Neatness and OrderlinessMessy workplace during and after the experiment.Clean and orderly workplace with occasional mess during and after the experiment.Clean and orderly workplace at all times during and after the experiment.

Ability to do independent workMembers require supervision by the teacher.Members require occasional supervision by the teacher.Members do not need to be supervised by the teacher.

Other Comments/Observations:TOTAL SCORE

RATING= x 100%

M.E LAB 3 Experiment 4 Heat Losses From Pipes (3)

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