Mechanical Engineering Principles and Practives III Expt.8 – Bare and Lagged Pipes Apparatus De La Salle University College of Engineering Mechanical Engineering Department Experiment 8 Bare & Lagged Pipe Apparatus Date Performed: Date Submitted: Instructor: Subject/Section: Group Number: Submitted by: LBYME16 / 2 Amparo, Carlos Manuel Cuyco, Kevin Delos Santos, Dann June 6, 2011 June 27, 2011 Presentations Data and Results Analysis and Conclusion Answers to Questions Total :________________ :________________ :________________ :________________ :________________ Remarks _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ Instructor’s Signature: ________________ To determine the combined radiation and convection coefficient (hr +hc) at various temperatures from different surfaces: 1. The only logical method for testing commercial pipe covering is. This method eliminates the “end correction”. Bare pipe 5. Pipe painted with aluminum paint 3. 85% Magnesia insulation 2. odorless and light in weight. To compare the experimentally determined (hc + hr) with those calculated from empirical equations. should be fire proof. It should also be mechanically strong and should suffer no loss of insulating value with age. of course.8 – Bare and Lagged Pipes Apparatus OBJECTIVES: A. and to condense and weigh the steam. Two general methods for heat measurement have been used. Asbestos and carbonate magnesia are the most commonly used pipe-covering materials. The second and more accurate method is to supply and measure the heat electrically. A dead-end pipe is ordinarily used. THEORY AND ANALYSIS: A good pipe covering. to mount those coverings on pipes of the size for which they were intended. to measure the heat content of the steam entering and leaving the test section. the heat from the main test section cannot travel along the pipe and must escape radially through the covering under test. Heat escapes from a pipe. to the room in two ways: (1) by conduction trough an air film. To determine the efficiency of these insulating materials. For steam-pipe coverings. the pipe itself acting as the steam condenser. and then by convection in the bulk of the air. Foam insulation B. When covering pipe ends with heavily insulated caps and maintaining separately heated end sections adjacent to the caps at the same temperature as the test section. . the most natural method is to fill the covered pipe with steam. water proof. in addition to being a good insulator. C. Pipe painted with black paint 4. vermin proof. and (2) by direct radiation to the cooler walls of the room.Mechanical Engineering Principles and Practives III Expt. or other surface. Btu/(hr sq ft ftoF) hr = coefficient of heat transfer by radiation. Btu/hr qr = heat transferred from surface to room by radiation Btu/hr hc = coefficient of heat transfer by conduction and convection.Mechanical Engineering Principles and Practives III Expt. sq ft .25 and: hr = 0.8 – Bare and Lagged Pipes Apparatus That proportion of the heat which is lost by conduction and convection can be calculated by the equation: qc = hc A(ts – tg) and that proportion which is lost by radiation may be expressed by simplified equation: qc = hr A(ts – tw) where: qc = heat transferred from surface to room by conduction and convection.42 (Δ t/d)0. Btu/hr (hc + hr) = combined coefficient of heat transfer A = surface area. Btu/(hr-sq ftoF) A = surface area ts = temperature of the surface oF tg = temperature of the air oF tw = temperature of the walls of the room oF the convection coefficient hc can be evaluated from equation: hc =0.173 p (_ts_)4 – (_tw_)4 100 100 Δt Substituting can result in: q = qc + qr = (hr + hc)(A)(ts – tw) and q = (hc + hr)(A)(Δt) where: q = total heat transfer from the surface by conduction and convection. and by radiation. 5 pcs. The test pipes are connected to a common header into which steam is introduced either directly from the main or from a line containing a reducing valve. and foam insulation. aluminum paint. 1 pc.63 inches per foot in a framework of welded two-inch steel angles. Graduated cylinder 1000ml capacity 4. Beaker 1000 ml capacity 2. = WB – WL x100 WB Where WB and WL are the quantities of condensate from the bare and logged pipes. respectively. = qB – qL x 100 qB where: qB = heat loss from bare pipe qL = heat loss from logged pipe Since the heat loss is proportional to the quantitiy of condensate collected. One of the lengths is bare and the other are covered with asbestos insulation. then L. The test section consists of four 10 feet lengths of one-inch standard steel pipe mounted with a slope of 0. Thermometer 0-360ᵒC SET-UP OF THE EXPERIEMENT: .8 – Bare and Lagged Pipes Apparatus Δt = temperature difference. 1. surface to room oF The lagging efficienct of a pipeline with insulation can be calculated from the equation: L.Mechanical Engineering Principles and Practives III Expt. and surface temperatures are measured by means of a portable thermocouple potentiometer. heat is supplied by the dead condensation of steam. Stopwatch 3. 18 pcs.E. 1pc. black paint. APPARATUS: For determining the heat loss from bare and lagged pipes. The steam condensate is drained from the opposite ends of the pipes through plug-type valves and is collected in beakers and measured.E. Mechanical Engineering Principles and Practives III Expt. Make at least two runs with steam at approximately 20 psig and 30 psig. at least three sets of readings should be taken during each run) 3. as determined by surface temperature measurements. Room Temperature iii. DATA SHEET: . After adjusting the system to the desired pressure. During this period record the following data: i. crack the drain cock under the header to remove water from the steam line and header. c. collect and measure the condensate from each pipe over a time interval of 15 to 30 minutes. From the experimental data for each run. 2. Steam pressure and Temperature iv. Barometric Pressure ii. calculate the combined film coefficient for convection and radiation and the lagging efficiencies and compare the experimental values of the coefficients with those calculated from empirical equations. Open the four plug-type valves to blow out any condensate from the pipes and then close them until only a small amount of steam escapes along with the condensate. b. For each run: a.8 – Bare and Lagged Pipes Apparatus PROCEDURE: 1. Surface Temperature (should be taken at three equally spaced points along each test pipe. When the system has reached equilibrium. 5 110 89 40 40 110 110 110 90 40 40 114 111 110 90 40 40 116 109 110 90 40 c 39 118 100 108 38 39.5 111 104 100 38 40 111 101 100 39 40 102 104 100 39 Steam Temp.5 120 110 120 90 40 39.5 92 47 40 111 109 91 45 40 114 110 90 44 b 38.5 111 109.8 – Bare and Lagged Pipes Apparatus Steam Pressure : 20 psi Time (mins. In (oC) 5 130 10 127 15 130 20 131 25 133 Steam Pressure: 30 psi Time (mins.5 109 101 100 39 39.5 111 109 90 45 40 111 109.Mechanical Engineering Principles and Practives III Expt.) Pipe 1 2 3 4 5 6 1 2 a 40 124 119 98 48 40 124 b 40 120 118 119 90 40 40 122 C 40 120 110 110 38 40 120 Steam Temp.) Pipe 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 a 39 120 110 90 45 39. In (oC) 5 135 10 138 . 14 Temp.49 35.424671366 0.5 232.Mechanical Engineering Principles and Practives III Expt.126 198.09 33.91 243.3232779396 0.33 16.2743770848 0.2377038833 89. Average Surface Temp.428909356 8 0.1970706054 hc+hr 0.67 100 .7 221.E.726 10. Pipe no. (surface) oF 103.250854716 0.3 12.434774488 7 L.39 59. 20 psi 30psi 1 1250 340 2 270 470 3 440 390 4 550 690 5 660 400 6 150 190 Pipe No.1549123688 0. in ML. 1 2 3 4 5 0.1822262704 0.525231800 8 0.00423799076 9 0.5 120 98 40 40 129 120 120 94 40 41 124 119 118 96 40 41 121 119 118 96 40 110 110 38 40 120 110 110 39 40 120 109 108 40 40 118 108 108 39 15 139 20 138 25 138 Volume of Condensate.477110032 6 0.2948837622 0.26 hc hr 0.8 – Bare and Lagged Pipes Apparatus 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 119 98 48 40 126 119 98 48 41 124 119 98 48 40 124 119 98 48 119.478190308 4 0.1 24. Difference (surface to room) oF 104. odorless.00411173282 9 0. 3.Mechanical Engineering Principles and Practives III Expt. 2. conduction through air film. convection from air bulk.186 101. water proof. How does black paint effect the heat emission of steam from a pipe? .27 SAMPLE COMPUTATIONS: Formulas used: CONCLUSION: Through the experiment we conducted. How is heat lost from a pipe? Heat is generated by the substance inside the pipe and heat travels from medium to medium: substance to pipe and pipe to surroundings wherein heat loss due to friction.8 – Bare and Lagged Pipes Apparatus 6 107. Therefore. and must have a long lifetime at operating temperature. besides providing insulation that a good insulation must have for a hot surface? A good insulation material must have a high dielectric strength. good mechanical properties .425380670 5 77.214 0. putting insulation in pipes lead to higher efficiency due to less heat loss. light in weight. we found that the pipes without insulation have higher surface temperature readings than those with insulation. What are the properties. vermin proof.fire proof. Insulation materials must withstand the operating temperatures that occur. and heat absorbed by insulation.4212689377 0. radiation. QUESTIONS: 1. Calculate the lagging efficiencies of the asbestos insulated pipe and the foam insulated pipe using the results of the first run.8 – Bare and Lagged Pipes Apparatus Black paint affects the emission of steam in pipe because of its thermal conductivity or simply called as “black body” which in turn absorbs more heat than other colors. ft-ᵒR.27 5. What is the heat rate q if ambient temperature is 77.5/12)2(10)(96. Solved from the previous table using the formula Asbestos: |660-1250|/660 X 100 = 89.0.Mechanical Engineering Principles and Practives III Expt.4ᵒF? q = (0. A 75% magnesia insulated 10-foot steel 0.1416)(3.3) q = 1.3ᵒF and surface temperature is 96.39 Foam: |660-150|/660 x 100 = 77.5 inch has a radiation and convection coefficient of 0. = 3.0099 Btu/hr-sq.4-77.0099)(2)(3. 4.01 Btu/hr .