Sobika S

EXPERIMENT NO: 1 DATE:- Fluid flow measurement using Venturi meter, Orifice meter and Rotameter OBJECTIVES: 1. To determine the fluid flow rate in pipes using flow measuring devices like venturi meter, Orifice meter and rotameter. 2. To determine the coefficient of discharge for flow measuring devices. PRINCIPLE: Flow measuring devices work on the principle of Bernoulli’s equation, which states that the total mechanical energy of the moving fluid comprising the gravitational potential energy of elevation, the energy associated with the fluid pressure and the kinetic energy of the fluid motion, remains constant. 1 p + ρ v2 + ρgh =constant 2 PROCEDURE: ➢ All the three devices are inserted in three different pipes which is connected to the pump, measuring tank and storage tank through a bypass pipe which regulates the flow rate of fluid in all three pipes. ➢ Pressure measuring taps are kept at two different places (one before the device and another on the orifice or inlet, or next to it). These are connected to the manometer, where the pressure difference between those two points is calculated. ➢ Initially, let the fluid flow in all three pipes simultaneously to clear the impurities and blockage in the pipe. This step prevents in determination of wrong value. ➢ Adjust the regulator of bypass pipe accordingly and close any two pipes containing flow measuring devices, Letting the fluid flow in one pipe (Venturi meter), which is collected at the storage tank. ➢ Note the readings in manometer (h1 and h2). Note the initial reading of measuring tank (R1). Now fix a time for 10 sec and redirect the fluid into the measuring tank. Note the reading in the measuring tank after 10 sec(R2), to calculate the rise in level of fluid. ➢ Repeat the same for Orifice meter and Rotameter. FORMULA: 𝐶𝑑 = 𝑄𝑎 𝑄𝑡 𝑄𝑎 = 𝑄𝑡 = 𝑎1= 𝜋𝑑2 4 1 𝐴.𝛥𝑅 𝑡 𝑎2= 𝜋 𝑑22 4 𝑎1 𝑎2 √2𝑔𝛥𝐻 √𝑎12 −𝑎22 Where, 𝐶𝑑 = Coefficient of discharge 𝑄𝑎 = Actual discharge 𝑄𝑡 = Theoretical discharge H1 and H2 – Readings in manometer R1 and R2 – Readings in measuring tank t- Time taken for the rise in water from R1 to R2 COLLECTED DATA: VENTURIMETER: 𝐻1 (𝑐𝑚) S.NO 1 2 3 60 58 57 𝐻2 (𝑐𝑚) 27 31 38 𝑅1 (𝑐𝑚) 4 10 14 𝑅2 (𝑐𝑚) T(sec) 6 12 16 - ORIFICEMETER: 𝐻1 (𝑐𝑚) S.NO 1 2 3 64 67 63 𝐻2 (𝑐𝑚) 26 24 38 𝑅1 (𝑐𝑚) 9 11 13 𝑅2 (𝑐𝑚) T(sec) 11 13 15 - ROTAMETER: S.NO FLOW RATE(LPH) 1 2 3 - 𝑅1 (𝑐𝑚) 10 14 16 𝑅2 (𝑐𝑚) 12 16 18 T(sec- CALCULATION: FOR 𝝙H: 𝝙H = 𝐻1 − 𝐻2 VENTURI METER: ORIFICE METER: 1. 60 – 27 = 33 1.64 – 26 = 38 2. 58 – 31 = 27 2. 67 – 24 = 43 3. 57 – 38 = 19 3. 63 – 38 = 25 FOR 𝑄𝑡 : 𝑄𝑡 = 𝑎1 = 3.14 𝑎2 = 3.14 4 4 𝑎1 𝑎2 √2𝑔𝛥𝐻 𝑎12−𝑎22 2.82 =- = 1.54 VENTURI METER: ORIFICE METER: 6.15∗1.54√2.980.33 1. 𝑄𝑡 = √6.152 −1.542 = 404.373 √6.152 −1.542 𝑄𝑡 = = 365.77 √6.152 −1.542 𝑄𝑡 = = 306.83 FOR 𝑄𝑎 : 𝑄𝑎 = 770∗2 3.36 5.56 770∗2 3. 7.20 6.15∗1.54√2.980.25 √6.152 −1.542 𝐴.𝛥𝑅 𝑡 ORIFICEMETER: = 458.33 770∗2 2. √6.152 −1.542 = 351.96 VENTURI METER: 1. 6.15∗1.54√2.980.43 = 461.59 6.15∗1.54√2.980.19 3. 𝑄𝑡 = √6.152 −1.542 = 433.93 6.15∗1.5√2.980.27 2. 𝑄𝑡 = 6.15∗1.54√2.980.38 𝑄𝑡 = 1. = 276.98 2. = 213.89 770∗-∗2 5.60 3. = 188.5 = 275 770∗2 5.72 = 269.23 ROTAMETER: 10 FOR 𝑄𝑡 : flow rate * 36 1. 2. 770∗2 7.14 300∗10 3. 36 770∗2 6.31 = 215.69 FOR 𝑄𝑎 = 1. 1000∗10 36 770∗2 = 83.33 2. = 244.05 3. 6.33 𝑡 : = 277.78 = 243.29 700∗10 36 𝐴.𝛥𝑅 = 194.44 CALCULATED DATA: VENTURIMETER: S. N0 t(s) 𝝙H(cm) 𝝙R(cm) 𝑄𝑡 ( 𝑐𝑚3 𝑠 ) 𝑄𝑎 ( 𝑐𝑚3 𝑠 𝐶𝑑 ) 1 3.36 33 2 404.37 458.33 1.13 2 5.56 27 2 365.77 276.98 0.75 3 7.20 19 2 306.83 213.89 0.697 ORIFICEMETER: 𝑐𝑚3 𝑐𝑚3 S. N0 t(s) 𝝙H(cm) 𝝙R(cm) 𝑄𝑡 ( 1 8.17 38 2 433.93 188.5 0.43 2 5.60 43 2 461.59 275 0.59 3 5.72 25 2 351.96 269.23 0.76 𝑠 ) 𝑄𝑎 ( 𝑠 𝐶𝑑 ) ROTAMETER: Flow rate (LPH) T(s) 𝝙R(cm) 𝑄𝑡 ( 𝑐𝑚3 𝑠 ) 𝑄𝑎 ( 𝑐𝑚3 𝑠 ) Error = 𝑄𝑡 −𝑄𝑎 ( 𝑐𝑚3 𝑠 ) 1000 7.14 2 277.78 215.69 62.09 300 6.33 2 83.33 243.29 -159.96 700 6.31 2 194.44 244.05 -49.61 RESULT: • Cd value of venturi meter = 0.86 • Cd value of Orifice meter = 0.59 • Error in rotameter = -49.16 𝑐𝑚3 𝑠 DISCUSSION: Discharge coefficient (Cd) is the ratio of actual discharge to the theoretical discharge. It is a dimensionless quantity. With this value we can determine the efficiency of the fluid flow rate measuring devices. It is necessary to find Cd value as it shows, to what extent a particular device works to produce the correct flow rate. The cd value should not exceed 1, as the actual value will never be greater than theoretical value due to some energy losses and friction, which is not taken into account for theoretical value. Cd value of venturi meter is higher than that of orifice meter as losses are less in venturi meter. It is because, it has converging and diverging cone where some losses are compensated. Orifice meter does not contain this structure and as a result more losses occur. Here we have achieved the desired Cd values. In Rotameter, we obtain theorical value from the device itself during experiment. Here we did not obtain desired result as there is a great deviation between theoretical and actual value of discharge. This deviation may be caused due to the inaccuracy in reading the measurement from rotameter, also the material and float shape of rotameter plays a crucial role as it can change the viscosity value, which has high impact on flow accuracy. When the fluid is of high viscosity, there is a possibility for the device in deviating from the desired accuracy. CONCLUSION: Venturi meter can be preferred comparing to Orifice meter since losses are less and Cd value is high, as it has convergent and divergent cones.