Flow Measuring Apparatus Essay

The flow measuring apparatus is designed to study which the most preferable flow meter from different typical methods of measuring the discharge of an incompressible fluid. This can be identify by measuring the flow rate and the head loss with later to be compared to the different flow meter which is venture meter, orifice meter and rotameter. INTRODUCTION The objectives of this experiment are to demonstrate the characteristics of some various commonly used methods of measuring fluid flow rates and to identify the head losses associated with each flow measuring apparatus.

The devices to measure the flow rate are determined by using a venturi meter, an orifice plate meter and a rotameter. Head losses associated with each meter are determined and calculated. This experiment is related to the applications of the Steady Flow Energy Equation (Bernoulli’s Equation). It can be written in the form; p1? g + 122g + z1 = p2? g + 2 2g + z2 + ? H12 (1) Where p? g is termed the hydrostatic head. 22g is termed the kinetic head (is the mean ratio of velocity i. e. he ratio of volumetric discharge to cross-sectional area of tube) z is termed potential head p/? g + 2/2g + z represents the total head. EXPERIMENT DESIGN Apparatus 1. Flow measuring apparatus (model H1D) 2. Volumetric hydraulic bench/water 3. Digital stopwatch I rotameter wide angle diffuser manometer tappings D E F G Venturi meter

Hflow A C B 20mm 26mm 26mm 16mm 51mm Orifice meter| Figure 1: Explanatory diagram of flow measuring apparatus Methods The maximum value of rotameter reading is determined so that all the manometers readings from A to I can be recorded. As the water been discharged, the stopwatch is started in the same time. The readings in the manometers been taken during the water discharging in the tank. Procedures 1. Firstly the pump in the hydraulic bench is turn on and the valve on the bench is slowly opened until the water is started to flow. 2. The opening of the valve is continued until the rotameter reach its maximum reading. 3. During this period, the reading of the manometers from A to I are recorded. 4. As the discharge of water is weighed in the weighing tank, the stopwatch is started when the water level showed zero reading. 5.

The stopwatch is stopped when the water level reached a certain reading in order to get the mass flow rate. 6. Steps 3 to 5 are repeated for seven set of readings with equidistant values of rotameter readings which taken twice for every reading. 7. Mass flow rate and head loss is determined from the value taken. 8. The data obtained is recorded in a table. 9. The rotameter calibration curve is plotted to identify the head loss for rotameter RESULTS Manometer levels (mm)| Rotameter (cm)| Water mass, m (kg)| Time, t (s)| Test no| A| B| C| D| E| F| G| H| I| | | | 1| 310. 5| 186. 5| 286. 0| 291. 0| 299. 5| 164. | 188. 0| 158. 5| 43. 0| 15. 0| 9. 957| 104| 2| 301. 0| 205. 0| 281. 5| 284. 5| 292. 0| 185. 5| 207. 5| 186. 0| 75. 0| 13. 5| 9. 957| 133| 3| 296. 5| 213. 0| 279. 5| 282. 0| 288. 5| 206. 0| 215. 5| 197. 0| 87. 5| 12. 0| 9. 957| 144| 4| 291. 5| 223. 5| 277. 5| 281. 0| 285. 5| 213. 0| 226. 0| 211. 0| 105. 0| 10. 5| 9. 957| 176| 5| 287. 5| 236. 0| 276. 0| 278. 5| 283. 0| 228. 5| 238. 0| 227. 0| 122. 0| 9. 0| 9. 957| 224| 6| 286. 5| 241. 5| 276. 0| 278. 5| 283. 0| 233. 5| 244. 5| 233. 5| 132. 0| 7. 5| 9. 957| 233| 7| 284. 0| 254. 5| 276. 0| 278. 0| 282. 0| 250. 0| 257. 5| 249. 5| 148. 5| 6. 0| 9. 957| 285| k/s)| H/inlet kinetic head| Venturi (4)| Orifice (8)| Rotameter calibration curve| Weigh tank m/t| Venturi*(10)/(11)| Orifice* (12)/(13)| Rotameter*(15)/(16)| Diffuser *(18)/(19)| Elbow* (21)/(22)| 0. 325| 0. 310| 0. 009| 0. 096| 1. 272| 93. 44| 5. 997| -4. 15| 0. 096| 0. 297| 0. 275| 0. 081| 0. 075| 1. 213| 87. 96| 6. 903| -2. 99| 0. 084| 0. 277| 0. 242| 0. 072| 0. 069| 1. 215| 78. 34| 7. 827| -2. 86| 0. 083| 0. 250| 0. 227| 0. 063| 0. 054| 1. 229| 84. 56| 9. 306| -4. 92| 0. 082| 0. 217| 0. 197| 0. 054| 0. 044| 1. 332| 83. 80| 12. 167| -4. 63| 0. 080| 0. 203| 0. 188| 0. 045| 0. 043| 1. 393| 87. 1| 13. 462| -5. 31| 0. 091| 0. 164| 0. 151| 0. 036| 0. 026| 1. 619| 86. 15| 20. 445| -6. 48| 0. 101| Figure 2: Table of results measurement *Numbers between brackets refer to the equation numbers ANALYSIS Calculation Taking the density of water as 995. 7 kg/m3when the temperature is 28? , the mass flow rate will be; a) Venturi meter m = 995. 7 ? AB2g1-ABAA2PA? g-PB? g12 (4) b) Orifice meter m = 995. 7? KAF2g1-AFAE2PE? g-PF? g12 (8)

Where AA = ? r2 which the area of section respective to A pA = the value taken from the manometer respective to A g = taking gravity as 9. 81 K = 0. 601 depend on the apparatus provided c) Rotameter Calculation of head loss using the Equation 1; a) Venturi meter hA-hC = HAC (10) VA22g. = ABAA2 11-ABAA2PA? g-PB? g (11) b) Orifice meter HEF = 0. 3(hE – hF ) (mm) (12) VE22g = 116VA22g. (13) c) Rotameter hH-hI = HHI (15) VH22g = VA22g. (16) d) Diffuser hc – hD = ? HCD (18) VC22g = 116VA22g (19) e) Elbow G- hH = ? HGH (21) VG22g = 16VA22g. (22) DISCUSSION From the table, it is obvious that the venture meter is the most accurate flow meter because it has low head loss compared to the orifice and the rotameter. Venturi meter consist of two conical parts with a short portion of uniform cross-section in between. These feature ensure a rapid converging and gradual diverging passage in the direction of flow to avoid the loss of energy due to separation. 1) The velocity of fluid flow in the venture meter increases according to the principle of continuity thus the pressure decreases as referred to the Bernoulli’s equation. (1) For the orifice, it has the highest head loss compared to the others. This is because it has the simplest design and occupies minimal spaces as it consists of a plate with a hole in the middle. The sudden change in the flow area in it causes considerable swirl and thus significant head loss and permanent pressure loss. (2) The rotameter is less accurate than venturi meter.

It is a simple, reliable and easy to install with low pressure drop. A variable area of the meter consists of float inside which is free to move. As fluid flow through the transparent tube, the float rises within the tube to a location where all the forces acting on the load is balanced each other. (2) The inlet to the diffuser may be considered to be at C and the outlet at D (referred to the Figure 1). The kinetic head is one-sixteenth of the venture’s inlet kinetic head. Its function is to reduce the velocity of the fluid flow that will increase the pressure at exit of the system. 5) Thus, it will eliminate as far as possible eddies which cause the dissipation of energy. The loss of head that occur in a diffuser depends on the angle of divergence and the ratio of the upstream and downstream areas. (3) The inlet to the bend is at G and outlet is at H (referred to the Figure 1) which has kinetic head is approximately sixteen times the venturi’s inlet kinetic head. When a fluid flows in a curved path, the velocity of the fluid along any streamline will undergo a change due to its irrespective of alteration. (4) CONCLUSION AND RECOMMENDATION

In conclusion, it is proved that the most accurate flow meter is venturi meter because it has the lowest head loss as compared to the orifice and rotameter. Its gradual contraction and expansion prevent flow separation and swirling which suffers only frictional losses on the inner wall surfaces. It should be preferred for applications that cannot allow large pressure drop. The parallax error occurred when taking the reading of the manometer as the water inside the tappings keeping moving upwards and downwards. This apparatus should be improved so that the reading of the manometer can be record accurately.

REFERENCES (1) S K Som; G Biswas (1998). Introduction to Fluid Mechanics and Fluid Machines. 2nd Ed, Tata McGraw-Hill. (2) Yunus A. Cengel. ; and John M Cimbala (2006). Fluid Mechanics Fundamentals and Applications. 1st Ed, McGraw-Hill. (3) Bernard Massey (1998). Mechanics of Fluids. 7th Ed, Stanley Thornes Ltd. (4) John F. Douglas; Janusz M. Gasiorek; John A. Swaffield (2001). Fluids Mechanics 4th Ed, Prentice Hall. (5) White F. M. (2003). Fluid Mechanics. 5th Ed, McGraw-Hill. PREFIX The picture taken in the laboratory.