The Mechatronics Design for Measuring Fluid Friction Losses in Pipe Flows Rıza Gurbuz

Transcription

1 Solid State Phenomena Vol. 113 (2006) pp Online available since 2006/Jun/15 at (2006) Trans Tech Publications, Switzerland doi: / The Mechatronics Design for Measuring Fluid Friction Losses in Pipe Flows Rıza Gurbuz Ankara University Cankiri Technical College Cankiri-Türkiye Keywords: Mechatronic system design, the measurement of fluid friction, flow rate and pressure differential measurement Abstract. The purpose of this article is to design a mechatronics system to measure fluid friction losses in a specially designed fluid friction apparatus. It measured fluid flow rates by using venturi tube and orifice plate, and velocity of fluid is calculated in terms of flow rate and pipe diameter. Friction factor (K factor) of some valves and fittings such as tee, elbow, Y Junction, gate and globe valves and friction losses in pipe was measured in this system. It is one of the best methods to measure losses in pipes and fittings experimentally. It used a computer, data acquisition cards, pressure differential transmitters, venturi tube and orifice meter to measure the flow rate, pressure drops on flow rate measurement devices and pressure drops of some valves and fittings to be measured K factors. It also measured the temperature of fluid by using J type Thermocouple. A computer program is written to calculate the Reynold number of fluid, friction factor of pipe, velocity of fluid, frictional losses of fluid, flow rate and K factor of valves and fittings. Required data was received from measured quantities. The conclusion of experiments is shown in article. Volumetric flow rate range was determined 0-1 (L/s), while the pressure drop was kpa in experiments. Introduction The term mechatronics is used for the integration of microprocessor control systems, electrical systems and mechanical systems. A mechatronics system is not just a marriage of electrical and mechanical systems and is more than just a control system; it is a complete integration of all of them. Microprocessors as controllers of electrical sensors extracting information from the mechanical inputs and outputs via electrical actuators and data acquisition cards generally used in mechatronics systems [1, 4] In this experiment all the components of the mechatronics system are used. Mechatronics elements of this system are fluid friction apparatus; venture tube, orifice-plate, pressure differential transmitters, data acquisition cards and a computer. When fluid flows throughout a pipe or conduit, it counters resistance to flow. In straight piping, this resistance is caused by surface roughness. In addition to friction losses, there are losses due to the turning gate valve, globe valve, flow control valve, sudden enlargement, and 45 or 90 junctions etc. Finally, pressure drop in this section of fluid systems local losses took place. It must be taken care of in the system design. All losses can be determined for each of the various elements in the system and added together to get the total system loss. K factor of some elements can be determined by using empirical formulas that have been developed by experimentation [2]. This permits the calculation of energy losses for any system components. Bernoulli s equation and the continuity equation can be used to perform a complete analysis of a fluid power system. This includes calculating the pressure drops, and flow rates and horsepower losses for all components of fluid power system. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, (ID: , Pennsylvania State University, University Park, United States of America-03/06/14,21:35:32)

2 604 Mechatronic Systems and Materials There are two basic types of flow in pipes, depending on the nature of different factors mentioned above that affect the flow. The first type is laminar flow, which is characterized by the fluid flowing in smooth layers of laminar. This type of fluid motion is called streamline flow because all particles of fluid are moving in parallel paths. If the velocity of flow reaches a high enough value, the flow ceases to be laminar and becomes turbulent. Movement on a particular becomes random and fluctuates up and down in a direction perpendicular as well as parallel to the mean flow direction in turbulent flow. Reynolds numbers (Re) are very important because they help one to know whether the flow pattern inside a pipe is laminar or turbulent [3]. If Re is less than 2000 the flow is laminar, if Re is greater than 4000, the flow is turbulent. Reynolds numbers between 2000 and 4000 cover a critical zone between laminar and turbulent flow [5]. There are well-established methods for determining friction losses that can be found in numerous textbooks and engineering handbooks [6,7,9]. Additionally, manufacturer s produced data sheets and engineering handbooks frequently contain the design information to determine line losses. Friction losses are a function of velocity (flow rate); there is unique pressure value for each flow rate value. Therefore friction losses should be defined experimentally for the minimum and maximum flow rates [2,9] System Design of Loss Measurement in Pipes by Using Data Acquisition Cards Method The calculations of frictional loss in pipes was by computer needs pressure transmitters, Analog- Digital cards, fluid flow rate or velocity of flow device such as venture or orifice plate, computer and a program to evaluate the data. For calculating some data such as Reynolds numbers, friction factor, velocity, specific values should be given for parameters such as pipe diameters, pipe lengths, fluid specific gravity, and dimension of flow rate measurement devices: Analog-digital cards should be suitable for measured physical quantity and maximum-minimum values in a system [1,4]. In order to perform the enormous number of calculations required optimizing complete fluid friction measurement systems in a reasonable period of time, it becomes necessary to utilize computers. The value of any number s parameters can be changed and the effect on the overall system s performance. Thus, the use of computers permits one to analyze the some parameters very quickly and sensitively and all data can be stored and utilized for measurement; requested data can be got as a table or graphic. Block diagram of the developed mechatronics system to measure some quantities is shown in Fig. 1. Fluid Friction Apparatus Measurement Devices Venturi Orifice meter Transmitters Pressure Differentials Temperature Printer Hard-Disk CD Computer Program Analog-Digital Cards RS Fig. 1. Block Diagram of Computerized Fluid Friction Apparatus

3 Solid State Phenomena Vol Fluid Friction Apparatus and Specifications Fluid friction apparatus is designed to allow the detailed study of fluid friction head losses that occur when an incompressible fluid flows through pipes bends, valves and pipe flow metering devices. Pressure differential transmitters (2) Thermocouple (J Model) transmitter and Analog-Digital Cards (6) were added to the system to measure some quantities (flow rate, velocity of fluid, Reynolds number, friction factor, losses etc.) and converting analogue quantities to digital quantities by using transmitters, DAC cards and computer [2,8]. Fig. 2. Front Picture of Fluid Friction Apparatus Table 1. Data of apparatus Input Data Fluid Type : Water Density (ρ) : 999 kg/m 3 Specific gravity (g) : 9.81 m/s 2 Viscosity (µ) : 0,001 Pa.s Pipe Diameter (d) : 7,5,16,18 mm Temperature (θ) : (25ºC) K factor of Venturimeter : 0,0007 K factor of Orifice Plate : 0,00112 Calculated Data Velocity (U) : m/s Flow Rate ( V ) : m 3 /s, L/s Reynold Number (Re) : Friction Factor (f) : Local Losses (H) : m K Factor (K L ) : Data to be Measured Pressure Drop ( p), Pa (Venture tube) used the flow rate and Reynolds number. Pressure Drop ( p), Pa (input-output of component) used K factor and losses. Schematic diagrams are shown in Figs. 3, 4. Some equations for measurement and calculation of fluid friction V =K h ; Re = DU ρ ; p = ρg h; (1), (2), (3) µ

4 606 Mechatronic Systems and Materials f= 0,079 Re 0,25 ; U = V ΠD 2 / 4 ; HL = K L 2 U. (4), (5), (6) 2g Fig. 3. Schematic Diagram of Flow Rate Measurement Fig. 4. Schematic diagram of local losses and K factor Experimental Analysis of Fluid Friction and Discussion Flow rate of fluid is calculated using equation 1 and 2 as shown below: V =K h ; U = V ΠD 2 / 4 ; V =K p / ρg. p signal is received from pressure differential transmitter between 4-20 ma and changed as pressure ( Figs. 3, 4) Flow rate is calculated with a computer program as m 3 /s and converted L/s by multiplying 1/1000. It is shown as graphics of experiments (Fig. 5). In these experiments Reynolds number is above the 4000, therefore fluid type is turbulence flow. Local losses can be found by using Darcy s equation (6). Local losses are generally between 0,5 2 (m) in these experiments (90 bend, 90 elbow, 45 elbow, 45 Y, 90 T, sudden enlargement, sudden contraction, ball valve, in line strainer, orifice meter, gate valve and globe vale). Flow rate is controlled by control valves to measure K factor at different flow rates. (See Fig. 2) Results of Experiments Developed computer program (Advantech Geniue) helps for calculating quickly and correctly he Fluid velocity, Reynold Number, friction factor of pipe Losses factor and other values that are shown in Fig. 5.

5 Solid State Phenomena Vol Fig. 5. Screen view of developed measurement program Responded data is stored in the exel file then Pressure drop and flow rate graphics were formed. Experimental test results have shown that local losses and frictional losses in pipe are proportional to the square of the velocity of the fluid and inside diameter of pipe and viscosity of fluid (Fig. 6). Determining the friction losses and K factor of some valves and fittings are used in experimental techniques. 0,6 0, 8 Local Losses, (m). 0,5 0,4 0,3 0,2 0, ,5 1 1,5 Flow Rate, V, (L/s) Friction Losses (m). 0, 7 0, 6 0, 5 0, 4 0, 3 0, 2 0, , 5 1 F lo w R a t e, V, ( L /s ) a Fig. 6. Flow rate losses graphics: a - elbow 90 0 pipe d=18 mm; b - L=1 m, pipe d=18 mm Summary and Conclusion Flow Rate ( L/s Flow Rate ( L/s ) Computerized fluid measurement system has a universal structure and it can be applied to all kinds of fluid measurement such as flow rate, velocity, pressure drop in pipe, local losses in fittings, valves, elbow, sudden enlargement, sudden contraction and Flow-rate-pipe friction losses and Local losses graphics that are shown in graphics Fig. 6a, b. b

6 608 Mechatronic Systems and Materials Pressure difference and other transmitters in according to range of the pressure, temperature, flow rate etc. must be changed Proportional valves or frequency converter of the motor can be used to control flow rate instead of a manual valve control. Mechatronics system provides us many advantages like in this fluid friction measurement system using some mechatronics equipments such as A/D cards, transmitters and computer, and program. References [1] W. Bolton: Mechatronics Electronic Control systems in Mechanical and Electrical Engineering (Addison Wesley Longman Publishing, USA, 1999). [2] R. Gurbuz: UICEE, World Transactions on Engineering and Technology Education, Vol. 2, No 3, (2003), p. 461 [3] J. E. Hardy, J. O. Hylton: Flow Measurement Methods and Applications (John Willey and Sons Publication, USA 1999). [4] D. Shetty: Mechatronics System Design (PWS Publishing Company USA 1997). [5] D. Spitzer: Industrial Flow Measurement (Resources for Measurement and Control Series, USA, 1990). [6] R. Daugherty, B. R. Franzini: Fluid Mechanics with Engineering Applications (McGraw-Hill Book Company, USA, 1985). [7] P. J. Carlo: Fundamental of Flow Measurement (Instrument Society of America, USA, 1984). [8] R. Gürbüz: UMTĐK Conference-2000 CD Turkey (2000), p. 433 [9] Armfield: Fluid Friction Apparatus (Issue 7a, England 1987),

7 Mechatronic Systems and Materials / The Mechatronics Design for Measuring Fluid Friction Losses in Pipe Flows /