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

Experiment No. 4 HEAT LOSSES FROM BARE AND LAGGED PIPES Course Code: MEP510L2 Course Title: ME LABORATORY 3 Section:ME51FA1 Leader: Members:

Program: BSME Date Performed: Date Submitted: Instructor: Engr. Nelson Dela Peña Jr.

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 150°C. For horizontal pipes, h = C1 + 0.005 (Th - Ta) For vertical pipes, h = C2 + 0.009 (Th - Ta) where: h = heat transfer coefficient, (mW/cm 2-°C) Th = hot surface temperature, °C Ta = ambient temperature, °C Using the coefficients C1 and C2 as given below: Surface Aluminum, bright rolled Aluminum, oxidized Steel Galvanized sheet metal, dusty Non metallic surfaces Area of pipe surface, A = π x D x Leff, cm2 where: D = pipe surface outside diameter, cm Leff = effective length of pipeline, cm

ε 0.05 0.13 0.15 0.44 0.95

C1 0.25 0.31 0.32 0.53 0.85

C2 0.27 0.33 0.34 0.55 0.87

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 = UA∆T conductivity of the insulating material k in conduction equation; qL = kA∆T outside-surface coefficient h in convection equation; q = hA∆T

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 +

h1

1 +

k

h2

where: q A T1 T2 MTD L k h U

= heat flow rate = area of surface on which heat transfer coefficient is based = higher temperature = lower temperature = mean temperature difference (arithmetic or logarithmic) = length of heat path = thermal conductivity = surface conductance = 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 Pipe

Material

1

Galvanized iron

2 3

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

4

Stainless Steel

5

Copper tube

6

Copper 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 inlet Inside Temperatures: (Reading based on temperature gauges) Surface Temperatures: (Using infrared gun thermometer)

trials

Pipe 1

Pipe 2

Pipe 3

Pipe 4

Pipe 5

Pipe 6

5mins 49psi 10mins 45psi 15mins 41psi 20mins 40psi 25mins 36psi 30mins 35psi 35mins 34psi 40mins 33psi 45mins 31psi 50mins 30psi 55mins 29psi 60mins 28psi

112.5 ºC 68.5 ºC 110 ºC 62.5 ºC 111 ºC 65.3 ºC 116 ºC 72.2 ºC 110 ºC 66.4 ºC 110 ºC 64.4 ºC 110 ºC 63.5 ºC 111 ºC 66.2 ºC 111 ºC 66.5 ºC 110 ºC 64.6 ºC 110 ºC 69.4 ºC 110 ºC 65.5 ºC

110 ºC 77.4 ºC 111 ºC 64.3 ºC 111 ºC 60.6 ºC 111 ºC 73.5 ºC 110 ºC 65 ºC 111 ºC 75.4 ºC 111 ºC 60.3 ºC 111 ºC 62.7 ºC 110 ºC 67 ºC 111 ºC 61.2 ºC 111 ºC 63.2 ºC 111 ºC 62.2 ºC

118 ºC 34.7 ºC 116 ºC 35 ºC 116 ºC 41.4 ºC 116 ºC 35.5 ºC 112 ºC 34.3 ºC 111 ºC 35.7 ºC 111 ºC 34.5 ºC 111 ºC 35.1 ºC 111 ºC 35.2 ºC 111 ºC 33.9 ºC 111 ºC 34.6 ºC 111 ºC 35.2 ºC

115 ºC 61.5 ºC 115 ºC 48.9 ºC 115 ºC 48.6 ºC 111 ºC 53.1 ºC 119 ºC 59.4 ºC 111 ºC 64.3 ºC 111 ºC 68.8 ºC 115 ºC 59.6 ºC 111 ºC 67 ºC 110 ºC 66.9 ºC 110 ºC 60.4 ºC 110 ºC 63.6 ºC

116 ºC 60.1 ºC 116 ºC 41.2 ºC 116 ºC 60.3 ºC 115 ºC 66.3 ºC 120 ºC 65 ºC 116 ºC 50.2 ºC 116 ºC 67.6 ºC 115 ºC 67.4 ºC 116 ºC 63.2 ºC 115 ºC 66.5 ºC 114 ºC 67.1 ºC 114 ºC 69.5 ºC

121 ºC 82.2 ºC 117 ºC 94.2 ºC 116 ºC 98 ºC 116 ºC 98.2 ºC 117 ºC 91.3 ºC 116 ºC 94.1 ºC 116 ºC 77.1 ºC 116 ºC 92.8 ºC 116 ºC 97.7 ºC 116 ºC 94.7 ºC 115 ºC 97.5 ºC 115 ºC 95.4 ºC

Ambient temperature 31 ºC 31 ºC 31 ºC 31 ºC 31 ºC 32 ºC 32 ºC 31.5 ºC 31 ºC 31.5 ºC 32 ºC 31.5 ºC

Table 3:Pipe inlet Corresponding Inside Pressure (Using Steam Table) Corresponding Surface Pressure (Using Steam Table) trials 5mins 49psi 10mins 45psi 15mins 41psi 20mins 40psi 25mins 36psi 30mins 35psi 35mins 34psi 40mins 33psi 45mins 31psi 50mins 30psi 55mins 29psi 60mins 28psi

Pipe 1 KPa 153.277 29.2312 143.376 22.3704 148.259 25.379 174.768 34.2914 143.376 26.6515 143.376 34.3767 143.376 23.4081 148.259 26.4162 148.259 26.7698 143.376 34.5965 143.376 30.3998 143.376 25.6065

Pipe 2 KPa 143.376 42.6385 148.259 23.4081 148.259 20.7915 148.259 36.2363 143.376 25.0411 148.259 39.2458 148.259 30.2244 148.259 22.5748 143.376 27.368 148.259 21.0801 148.259 23.0926 148.259 22.0668

Pipe 3 KPa 186.404 5.5359 174.768 5.62862 174.768 7.95369 174.768 5.78614 153.277 5.41433 148.259 5.85022 148.259 5.4782 148.259 5.65982 148.259 5.69118 148.259 5.29509 148.259 5.50529 148.259 5.69118

Pipe 4 KPa 169.177 21.3721 169.177 11.6926 169.177 11.5183 148.259 14.3812 192.455 19.3984 148.259 24.2674 148.259 29.6164 169.177 19.5794 148.259 27.368 143.376 27.2475 143.376 20.318 143.376 23.5141

Pipe 5 KPa 174.768 20.0383 174.768 7.87012 174.768 20.2244 169.177 26.5336 192.455 25.0411 174.768 12.4127 174.768 28.1009 169.177 27.8548 174.768 23.0926 169.177 26.7698 163.734 27.489 163.734 30.5321

Pipe 6 KPa 205.039 51.7996 180 .509 82.1479 174.768 94.3902 174.768 95.0743 180.509 73.7196 174.768 81.8445 174.768 42.1144 174.768 77.9842 174.768 93.3718 174.768 83.679 169.177 92.6979 169.177 85.8623

Ambient temperature 31 ºC 31 ºC 31 ºC 31 ºC 31 ºC 32 ºC 32 ºC 31.5 ºC 31 ºC 31.5 ºC 32 ºC 31.5 ºC

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

trials 5mins 49psi 10mins 45psi 15mins 41psi 20mins 40psi 25mins 36psi 30mins 35psi 35mins 34psi 40mins 33psi 45mins 31psi 50mins 30psi 55mins 29psi 60mins 28psi

Pipe 1

Pipe 2

Pipe 3

Pipe 4

Pipe 5

Pipe 6

113 ºC 76.4 ºC 116 ºC 72.4 ºC 112 ºC 79.7 ºC 117 ºC 72.6 ºC 117 ºC 76.3 ºC 115 ºC 60 ºC 110 ºC 77.8 ºC 117 ºC 71.3 ºC 110 ºC 77.8 ºC 115 ºC 75.6 ºC 112 ºC 70.6 ºC 111 ºC 72.5 ºC

116 ºC 76 ºC 123 ºC 74 ºC 120 ºC 82.6 ºC 120 ºC 82.6 ºC 115 ºC 22.5 ºC 118 ºC 46.5 ºC 120 ºC 72.9 ºC 120 ºC 74.1 ºC 120 ºC 81 ºC 119 ºC 79 ºC 120 ºC 74.8 ºC 112 ºC 68.2 ºC

116 ºC 37 ºC 120 ºC 36.4 ºC 118 ºC 36.1 ºC 120 ºC 35.5 ºC 119 ºC 35.5 ºC 117 ºC 38.4 ºC 117 ºC 39.2 ºC 117 ºC 39.8 ºC 118 ºC 35.9 ºC 118 ºC 36 ºC 119 ºC 35.3 ºC 114 ºC 35.1 ºC

111 ºC 44 ºC 112 ºC 68 ºC 110 ºC 51.7 ºC 110 ºC 64.3 ºC 110 ºC 56.6 ºC 110 ºC 63.8 ºC 110 ºC 67.4 ºC 110 ºC 64.8 ºC 109 ºC 62.6 ºC 109 ºC 65.6 ºC 110 ºC 64.6 ºC 109 ºC 68.9 ºC

110 ºC 37.5 ºC 110 ºC 36.6 ºC 109 ºC 61.8 ºC 109 ºC 80.1 ºC 108 ºC 51.4 ºC 108 ºC 70 ºC 107 ºC 57.7 ºC 107 ºC 75 ºC 107 ºC 81.5 ºC 106 ºC 70.2 ºC 108 ºC 83 ºC 108 ºC 77.7 ºC

110 ºC 54.5 ºC 116 ºC 89.6 ºC 112 ºC 56.6 ºC 110 ºC 86.4 ºC 111 ºC 80 ºC 110 ºC 100.7 ºC 109 ºC 77.7 ºC 109 ºC 95.1 ºC 108 ºC 84 ºC 107 ºC 87.5 ºC 110 ºC 78.5 ºC 110 ºC 86.6 ºC

Ambient temperature 31 ºC 31 ºC 31 ºC 31 ºC 31 ºC 32 ºC 32 ºC 31.5 ºC 31 ºC 31.5 ºC 32 ºC 31.5 ºC

9. Assessment Rubric: T I P - V PAA– 0 5 4 D Revision Status/Date:0/2009 September 09

CRITERIA

TECHNOLOGICAL INSTITUTE OF THE PHILIPPINES RUBRIC FOR LABORATORY PERFORMANCE BEGINNER ACCEPTABLE PROFICIENT 1 2 3

Laboratory Skills Manipulative Members do not Skills demonstrate needed skills. Experimental Members are unable to Set-up set-up the materials.

Members occasionally demonstrate needed skills. Members are able to set-up the materials with supervision. Members occasionally demonstrate targeted process skills.

Members always demonstrate needed skills. Members are able to set-up the material with minimum supervision. Members always demonstrate targeted process skills.

Process Skills

Members do not demonstrate targeted process skills.

Safety Precautions

Members do not follow safety precautions.

Members follow safety Members follow safety precautions most of the precautions at all time. times.

Members do not finish on time with incomplete data.

Members finish on time with incomplete data.

Work Habits Time Management/ Conduct of Experiment Cooperative and Teamwork

Members finish ahead of time with complete data and time to revise data. Members do not know Members have defined Members are on tasks their tasks and have no responsibilities most of and have defined responsibilities. the time. Group responsibilities at all Group conflicts have to conflicts are times. Group conflicts be settled by the cooperatively managed are cooperatively teacher. most of the time. managed at all times. Neatness and Messy workplace during Clean and orderly Clean and orderly Orderliness and after the workplace with workplace at all times experiment. occasional mess during during and after the and after the experiment. experiment. Ability to do Members require Members require Members do not need independent supervision by the occasional supervision to be supervised by the work teacher. by the teacher. teacher. Other Comments/Observations:

TOTAL SCORE

SCORE

RATING= x 100%