Calculating Emission Uniformity for Drip Emitters
Emission Uniformity (EU) measures how uniformly emitters deliver water. It is calculated based on pressure variations and emitter discharge variations. The tree spacing, shading, and wetting geometry details provided are contextual and not directly used in the calculation of EU based on emitter characteristics.
Key Parameters Identified
The following parameters are essential for calculating Emission Uniformity:
- Average operating pressure: $P_{avg} = 120$ kPa
- Minimum operating pressure: $P_{min} = 100$ kPa
- Emitter discharge exponent: $x = 0.6$
- Coefficient of variation of emitter discharge: $CV_q = 0.06$
Pressure Uniformity ($U_p$) Calculation
The uniformity resulting from pressure variations across the system can be estimated using the ratio of minimum to average pressure, adjusted by the emitter exponent.
The formula used is:
$ U_p = \left(\frac{P_{min}}{P_{avg}}\right)^x $
Substituting the values:
$ U_p = \left(\frac{100 \text{ kPa}}{120 \text{ kPa}}\right)^{0.6} = \left(\frac{5}{6}\right)^{0.6} \approx 0.8333^{0.6} \approx 0.8941 $
Manufacturing Uniformity ($U_m$) Calculation
The uniformity related to variations in emitter manufacturing ($CV_q$) is estimated. A common approximation, assuming a specific statistical relationship (effectively $k=1$), is used here:
The formula used is:
$ U_m = (1 - k \times CV_q) $
Assuming $k=1$ for this calculation:
$ U_m = (1 - 1 \times 0.06) = 1 - 0.06 = 0.94 $
Final Emission Uniformity (EU) Calculation
The overall Emission Uniformity (EU) is determined by combining the pressure uniformity ($U_p$) and the manufacturing uniformity ($U_m$).
The formula is:
$ EU = U_p \times U_m \times 100\% $
Substituting the calculated values:
$ EU = 0.8941 \times 0.94 \times 100\% $
$ EU \approx 0.8394 \times 100\% = 83.94\% $
The calculated Emission Uniformity is approximately 83.94%, which falls within the range of 83% to 86%.
Important Questions from Micro Irrigation Methods
- From the performance evaluation of drippers, the discharge exponent value and the coefficient of variation were obtained as 0.5 and 0.04, respectively. The drippers are categorized as
- The average discharge, operating pressure and emitter constant of a drip emitter are 4 L h$^{-1}$, 110 kPa and 0.3, respectively. The type of emitter is
- In a field test of drip irrigation system having an application efficiency of 90%, the minimum, maximum and average flow rates are found to be $45 \ L\cdot h^{-1}$, $65 \ L\cdot h^{-1}$ and $50 \ L\cdot h^{-1}$, respectively. The manufacturer's coefficient of variation of the emitter is 0.07. If there is one emitter per plant, the drip irrigation efficiency in percent is ______ [round off to 2 decimal places]
- In a citrus orchard, planting is done at a spacing of 5 m × 5 m. The daily pan evaporation of the orchard is 6 mm. The pan coefficient, wetting factor (crop canopy factor) and crop coefficient are 0.8, 0.6 and 0.6, respectively. Four drippers each of 4 L $h^{-1}$ discharge are used to irrigate each plant. The time of operation of drip irrigation system in hours will be
