AbstractAn investigation was carried out to determine the effects of pipe materials and fittings on piping system, particularly pressure drops (energy losses). This was accomplished by a setup that included 3 pipe material types (glass, plastic, and steel) some with same diameter and some with bends fitted flow pathway. A comparison was done on pipes with same diameter but different material (roughness test), pipes with same material but different diameters (size effect), pipes with same diameter but different bends fittings (bend effect).It was found that pipes with rougher materials, smaller sized diameters, and bigger degree of bend generally give rise to larger pressure drops in pipe systems. Assumptions that had to be made in carrying out the experiment included constant density, viscosity and average temperature of the working fluid (water) and elevation changes can be neglected in applying appropriate equations. Limitations encountered included the control of water temperature since it was rising due to increase in internal energy and therefore had to be replaced often to maintain same temperature to make our comparisons meaningful. Some pipes could not register pressure drops at low and high rotameter height which means a bigger rotameter was necessary to ensure pressure measurements that had statistical averages that were representative.

Table of Contents1. Introduction 12. Literature Review and Theory 2 2.1 Fundamentals of pressure drop in pipes2 2.2 Pipe material selection 4 2.3. Pipe size selection 53. Experiment setup 64. Results 74.1 Rotameter calibration curve 7 4.2 Theoretical and Experimental comparison ..7 4.3 Effect of pipe diameter on Pressure drop with PVC pipes .8 4.4 Effect of pipe material on pressure drop 84.5 Effect of bends on pressure drop.9 4.6 Effect of diameter on Pressure Drop with galvanic pipes ..9 5. Discussion of results 106. Conclusions 117. Recommendations128. References139. Appendices14 Appendix A (Calibration data)14 Appendix B (Experimental data)16 Appendix C (Moody Chart)19 10. Nomenclature (Symbols and constants)20

1

14

1. Introduction

Pressure drop Material transportation can be achieved in many ways, for example conveyor belts and pipes. The sole objective of a pipe designer is to transport fluids in the safest and most economical way while ensuring high quality of material. In the process industries (on plants such as water treatment, petroleum) pipes have found more use than their counter-parts due to their ability to accommodate all kinds of fluids for continuous transportation of products and raw materials( feed fluids) over long distances from storage tanks to operating units such as reactors, distillation columns, mixer and others (Coulson & Richardson, 1977). Pipes can be made from a variety of materials such as steel, poly vinyl chloride (plastic), glass, iron, wood, concrete and others for different purposes depending on operating conditions (temperatures and pressures-susceptibility to corrosion and wear), strength requirement, type of fluid, ease of maintenance if required, and costs. Usually energy is supplied to the fluid by the use of a pump. According to Coulson and Richardson (1977) when a fluid is flowing through a pipe, the configuration of flow will vary with the type of materials used to manufacture the pipe, flow rate, and the shapes present on the pipe (bends, corners). Sudden changes in the cross-sectional area and the shape of flow path affect the pattern of fluid flow and result in pressure losses within the pipes. Since magnitude of flow is depended on pressure on the fluid, pressure losses present a problem for the pipe designers because more pressure losses mean more energy supply is needed from the pump to over-come the losses (to reach a final destination) which implies more costs (electrical energy in running the pump).A fluid flows from a region of high pressure to a region of low pressure. An input of energy is required to make the fluid flow through the pipe. When a fluid flows, there is a loss of energy due to multiple factors; resistance to flow (viscosity), roughness of the pipe (the friction between the pipe wall and the fluid) , pipe diameter, pipe fittings (bends, valves etc.) on the pipe system. For inviscid fluids, the loss of energy is usually quantified by considering minor losses (due to fittings) and major losses (due to friction in straight pipes) and measuring the pressure drop between two points of interest on a pipe indicates the effect of bends and pipe material on fluid flow. This information can then be analysed and used to make appropriate changes to the pipe system to reduce costs of transporting process fluids.Pressure is one of the most important parameters that are measured to provide information on the operating conditions and safety of the plant (Coulson & Richardson, 1977). Knowing pressure losses is important in terms of; knowing how much energy is required and finding ways to reduce energy usage, it helps in plant design and control, it also helps companies to price their products appropriately and set standards.

2. Literature review and theory

2.1 Fundamentals of pressure drop in pipes Movement of fluids within pipes is one of the most important studies of a process because it is also an essential tool for the control of the entire process. From theories of fluid mechanics, fluid flow in process units such as pipe can be caused many different driving forces e.g. pressure gradient (pressure drop), gravity, shear stresses, etc. (Fox & McDonald, 1985). The phenomenon where the movement of the fluid is solely governed by the pressure drop throughout the length of a pipe will be studied in greater detail within this experiment, with the fluid being represented by water.According to Sinnot and Towler (2009, p. 239), the pressure drop caused by friction is a function of the fluid flowrate, fluid density, and viscosity,, pipe diameter, pipe surface roughness and the length of the pipe. This can be illustrated mathematically by the following expression: (2.1) Where: -2 -3 -1The friction factor of a particular pipe (f, dimensionless quantity) is obtained from theoretical data such as plots and tables (see Figure C1). A friction factor is a function of the pipes material (different materials have different absolute roughness, associated with them) and the Reynolds number (Skogestad, 2009) The mathematical expression to calculate the Reynolds number is given as: . (2.2)Where: -3 -1 -1.s -1The Reynolds number of the fluid will determine the nature of the fluid flow i.e. if the flow is laminar or turbulent. According to Skogestad, (2009, p. 243), the fluid flow pattern changes from laminar to turbulent flow when the Reynolds number exceeds approximately 2300.The pressure drop equation (2.1) represents the pressure gradient in horizontal, straight pipes. As process designer always investigates ways of reducing operation costs, some might think of using bent or curved pipes which occupy less surface area than straight pipes thus reducing space costs. The process of manufacturing pipes which are curved (pipes in which direction of flow is at an angle neither 00 nor 1800) is called pipe fittings. The pressure drop calculations (also called miscellaneous losses) for pipe fittings are performed differently compared to those for straight pipes.According to Sinnott (2005, p.204), approximation of miscellaneous losses can be made through two ways:(a) Finding the total number of velocity heads (K, in units of length) lost due to all the fittings (bends, joints and tees) and valves. K can be calculated using the following expression: ..... (2.3)Where: -1 -2NB. If there are n number of bends on the same pipe the total velocity head loss is given by n multiplied by velocity head loss at each bend (nK )The total velocity head loss is then converted to pressure loss by the expression: .. (2.4) Where: -2 -3 -2The total pressure drop for the pipe of this nature (with bends) is obtained by adding the pressure drop obtained from equations (2.1) {this is the part of the pipe where there are no bends} and the one obtained from equation (2.4) {the section of the pipe with bends}(b) The equivalent pipe diameter method. With this approach, there are values readily tabulated in literature for various pipe fittings e.g. for a 900 standard long elbow the number of equivalent pipe diameters is 23(NB: This is for just one bend). To calculate the pressure drop along the pipe with bends using this method, the total value for the equivalent pipe diameters (dimensionless) is obtained and multiplied by the pipes internal diameter, the resulting value is then added to the length of the pipe; this will give the new length to be used on the pressure drop equation (2.1) to get the pressure drop.

The other mathematical expression which is used to calculate the friction factor within a pipe (pipe with an undefined pressure drop length) is called the Colebrooks equation, which is as follows: . (2.5)Where:

In almost all industrial processes which involve the transportation of fluids in pipes, the process designer has to conduct a pipe-selection procedure. Selection of pipes involves making informed decisions on what type of pipes (material selection), sizes of their internal area (pipe size selection), what types of connections are needed between the pipes and also other process units (pipe fittings), etc. in order to achieve an effective fluid transportation (Sinnott, 2005) . The procedure is mainly dependant on the type and/or properties of the fluid concerned; and also the external factors such as the average ambient temperature, the economic constraints (costs during pipe purchase and maintenance).2.2 Pipe material selection The material of which the pipe is made up of will have a very significant effect on the transportation of the fluid. This is a result because different materials have different roughness values associated with them.Since it was established that pipes can be made out of many materials (plastics, glass, pure metals, metal alloys, etc.), a process designer should make all the necessary comparisons and determine the pipe material (pipe type) which will be suitable for their process. A few types of pipes made up of different materials are discussed below.2.2.1 Polyvinyl chloride (PVC) pipes: These are the pipes which are made up of a combination of plastic and vinyl polymer called polyvinyl chloride (Holtshousen & Last, 1998).

Advantages of using the PVC pipes Plastic pipes are more corrosion resistant than metallic ones. PVC pipes are durable i.e. they last longer when correctly manufactured and installed Like all other plastic pipes, PVC pipes are light in weight and are very tough The costs of transportation and handling are reduced greatly due to their lightweight property Friction within the plastic pipe (e.g. PVC pipes ) is less than that of a metal pipe thus plastic pipes are more efficient than metallic ones Plastic pipes have superior elastic properties over the glass and metallic onesDisadvantages of using the PVC pipes Plastic pipes are not suitable for transportation of fluid at very high temperatures. Their strength reduce greatly at high temperatures Plastic pipes can crack and crumble easily under stress2.2.2 Metallic pipes: These are the one made up of metals such as stainless steel, cast iron, galvanised steel and other alloysAdvantages of using metallic pipes for fluid transport Their stress tolerance is much higher than plastic and glass pipes They can be used for fluid transportation even at high temperaturesDisadvantages of using metallic pipes for fluid transport Metallic pipes are more susceptible to corrosion those made up of plastic and glass They are very heavy in weight thus their will result in high handling and transportation costs Metallic pipes have a very high rate of energy consumption during fluid transportation than any other pipe type (Holtshousen & Last, 1998)2.2.3 Glass pipes: the main advantage of using glass pipes is that they are very smooth and thus they produce the least friction compared to both the plastic and metallic pipes. Limitations associated with the glass pipes are that they are expensive to purchase; they are brittle and can easily get broken.2.3. Pipe size selection Pipe size selection is governed by the driving force which transports the fluid through the pipe e.g. if the fluid is primarily driven by gravity (free driving force), the smallest pipe diameter that gives the required flow-rate is suitable. When the driving force is not free i.e. if energy is required for the transportation of the fluid through the pipe (e.g. when the fluid is being pumped through the pipe), a size of the pipe should be selected in such a way to keep the operating costs as low as possible (Sinnott, 2005)3. Experimental SetupCentrifugal PumpPressure GaugePipe inlet valve

RotameterPipe 5(PVC)

Pipe outlet valve

Pipe 7(Glass)

Pipe 6(PVC)

Pipe 4(Galvanic Iron)

Pipe 3(galvanic Iron)

Pipe 2(PVC)Pipe 1(PVC)Pressure tappings

Figure 3.1 Experimental setupExperimental Procedure1. CalibrationAll valves except the inlet and outlet valves of pipe 1 were closed; the rotameter was set at different heights using the gate valve. The rotameter was calibrated using a graduated cylinder and stopwatch, the volume of water collected in the cylinder was measured after 10 seconds for low flow rates and 5 seconds for high flow rates. The volumetric flow rate was plotted against the float height in a calibration curve.2. Main ExperimentThe temperature of water was measured after each run using a thermometer and was limited to between 18-20 degrees by replacing water over 20 degrees with cooler tap water.Air was cleared in all pipes by filling each pipe with water while closing all other pipes, after this the experiment was begun.The following was done for each pipe: The inlet and outlet valves of the pipe were fully opened, all other pipe valves were fully closed, the float was set to a certain height using the main gate valve the pressure drop across the pipe was measured using the pressure gauge and recorded.4. Results

Figure 4.1: Rotameter Calibration curve

Figure 4.2: Theoretical vs Experimental Pressure Drops for PVC pipe (D=0.02)

Figure 4.3: Effect of pipe diameter on Pressure drop with PVC pipes

Figure 4.4: Effect of pipe material on pressure drop by comparing PVC with Stainless steel of the same diameter over a range of equal velocities (Reynolds number)

Figure 4.5: Effect of bends on pressure drop-[Minor losses encountered for different bends (90 vs. 45 degree)]

Figure 4.6: Effect of diameter on Pressure Drop with same material of construction-galvanic steel

5. Discussion of ResultsData for Graphs can be retrieved in the appendix section from Table B 2 through. Comparison of pipe diameters of the same pipe material From (Figure 4.3 and Figure 4.6), it apparent that pipes with smaller diameters ,regardless of type of material tend to give high pressure losses and the difference gets bigger as velocity (Reynolds number) gets large. It should be emphasized that it is difficult to measure pressure drop across a stainless steel pipe with a bigger diameter using a small rotameter because it only starts registering a pressure drop when the rotameter reaches its maximum height. This can be seen on figure 4; data had to be taken for a very short range of rotameter height close to the maximum and this makes results look rather absurd. Effect of pipe material due to roughness of each pipe material- by inspection of Figure 4.4, one can make 2 observations: PVC is almost frictionless compared to Stainless Steel since a plot of velocity vs. pressure drop produces approximately a flat graph. At very high velocities, stainless steel results in extremely abnormal pressure losses.With the information above stated, it looks like PVC pipes are a better option over stainless steel. But this could be misleading for cases of hot fluids, or where pipes have to be laid underground. In essence, though having small losses, the use of PVC is restricted and that of stainless steel is inevitable in most cases regardless of the losses encountered. These are just some of the thermodynamic limitations which are yet to be prevailed.3. Effect of pipe bends (elbows)-Just like a rolled hose pipe, a bend in a pipe system reduces the flow efficiency. That is simply to say there are energy losses (aside from frictional) that arise in certain pipe fittings (valves, sudden enlargement/contraction etc.) Demonstrated by Figure 4.5 are pressure losses resulting in two different setups- one with 4 (90o bends) and another with 4 (135o bends). The degree of turn around an elbow has a significantly & direct influence on pressure (energy losses).4. For Glass pipe, difficulties were encountered in obtaining any pressure drop readings.

5. Conclusion The experiment was compared with the existing theory for validation; it is evident that our experiment collaborated with the theory. The comparison is shown in Figure 4.2. The pressure drop increases with increasing velocity forming a linear and quadratic relationship when the flow is laminar and turbulent respectively. Our experiment mostly covered turbulent flow and it revealed that in turbulent flow, the pressure drop is directly proportional to velocity. Pipes with bigger diameter have less pressure drop compared with the ones with smaller diameter regardless of the type materials used. However, the smaller diameter pipes have the capability of delivering a fluid at a very high velocity compared to the one with bigger diameter. The high velocity is often followed by an increased friction and resistant to flow that results in a high pressure drop. The conclusion is based on the observation on the stainless steel and Polyvinyl chloride pipes shown on Figure 4.3 and 4.6 respectively. The type of material used has an impact on pressure drop, according to Figure 4.4 galvanised steel has more pressure drop compared to PVC pipe. This is due to the fact that galvanised steel has a more relative roughness, hence it experience more friction. The bends with a higher angle have less pressure drop compared to the one with a less angle (comparing 135 with 90) as shown in Figure 4.5. It was observed that as the Reynolds number increases the relative error between the theoretical and the experimental pressure decreased.

6. RecommendationsTo minimise pressure loses along the pipes, pipes with smooth interior walls (less surface rough) must be used. Increased roughness increase the wall shear stress which is one the factors contributing to pressure drop within pipes. In the experiment pipes made from glass and Polyvinyl chloride are smoother compared to other pipes. Pipes that are relatively less rough (smooth) have less pressure difference; I recommend the use of a pressure gauge with a lesser scale as opposed to using the one measuring the pressure in kilo Pascal. The pressure difference that was recorded on the glass pipe is very small and few measurements were possible. More research is required on finding possible better materials to use to make pipes and improvement of current materials in order to minimise or reduce the loss of energy encountered in fluid flow in terms of pressure drop. Bends should be avoided in the piping system, as they significantly increase pressure drop.

7. References 1. Coulson, J.M., & Richardson, J.F. (1977).Chemical engineering (Vol 1), (3rd ed.). Oxford: Pergamon Press 2. Fox, R.W., & McDonald, A.T. (1985).Introduction to fluid mechanics (3rd ed.).New York: Wiley & Sons3. Holtshousen, P. & Last, J. (1998). Pipes & Pipelines: Principles & Practice (2nd ed.). Northcliff: K. Myles and Associates cc 4. Sinnott, R.K. (2005). Chemical Engineering Design (Vol.6), (4th ed.). London: Elsevier Ltd5. Sinnott, R., & Towler, G. (2009). Chemical Engineering Design (5th ed.). London: Elsevier Ltd6. Skogestad, S., (2009).Chemical and Energy Process Engineering. New York: CRC PRESS 7. Retrieved from http://www.mathworks.com/matlabcentral/fileexchange/screenshots/796/original.jpg

8. AppendicesAppendix ATable A1: Data for calibration of rotameterRotameter Height(cm)Volume (measuring Cylinder)(ml)Volume (measuring Cylinder)(ml)Volume (measuring Cylinder)(ml)average VolumeTimeVolumetric Flow rate(l/s)Flow rate(m^3/s)

10800825783802.67100.088.03E-05

141225113011501168.33100.121.17E-04

181600156015201560.00100.161.56E-04

221880187001875.00100.191.88E-04

262360228002320.00100.232.32E-04

302720260002660.00100.272.66E-04

343060298003020.00100.303.02E-04

383360347003415.00100.343.42E-04

423800377003785.00100.383.79E-04

544340434004340.00100.434.34E-04

663360350003430.0050.696.86E-04

744160426004210.0050.848.42E-04

Appendix BTable B1: Data for PVC pipes with (4X90) bends

Table B2: Data for PVC with no bends pipe D= 0.01628 m

Table B3 Data for PVC pipe D= 0.0183 m

Table B4 Data for PVC pipe D= 0.0201 m

Table B5 Data for GS pipe D= 0.029 m

Table B6 Data for GS pipe D= 0.016 m

Table B 7 Data for PVC pipes with (4X135) bends

Appendix C

Figure C3: Moody chart

9. NomenclatureSymbols and constantsA -Area (m2)D -Diameter (m)e Relative Roughness (dimensionless)f - Darcy-Weisbach friction factor (dimensionless)v Velocity (m.s-1) Viscosity (kg.m-1.s-1) -Density (kg.m-3)P Pressure (kPa)L Length (m)K- Velocity Head loss (m)Re Reynolds Number (dimensionless)g Gravitational acceleration (m.s-2) - Absolute Roughness (m)