Calculating the Required HP for a Submersible Pump to Meet Daily Water Demand

To determine the horsepower (HP) required for a submersible pump to deliver 20,000 liters of water per day, we can follow a step-by-step approach. This guide will outline the process, providing a detailed breakdown of the necessary calculations.

Daily Water Requirement

The first step is to identify the daily water requirement. Given that we need 20,000 liters of water per day, we can convert this to cubic meters for further calculations:

Convert to Cubic Meters

20,000 liters 20 cubic meters (m3)

Flow Rate Calculation

The next step is to determine the flow rate in liters per second (L/s). We convert the daily requirement to seconds:

Flow Rate

Flow Rate (frac{20,000 , text{liters}}{24 , text{hours} times 3600 , text{seconds}} approx 0.231 , text{L/s})

Pump Power Calculation

The total dynamic head (TDH) needs to be estimated. For a 500 ft deep borewell, we assume a TDH of about 150 feet. This includes the depth and additional head loss. We then convert this to meters:

Convert TDH to Meters

TDH 150 ft (times) 0.3048 ≈ 45.72 m

The pump efficiency is assumed to be around 70%, or 0.7 for the calculations. The power in watts can be calculated using the formula:

Power in Watts

Power (W) (frac{text{Flow Rate (m}^3/text{s) (times) TDH (m) (times) Density (kg/m}^3text{) (times) g}}{text{Efficiency}})

Where:

Configuration: Density of water 1000 kg/m3g 9.81 m/s2 acceleration due to gravityFlow Rate 0.000231 m3/sTDH 45.72 mDensity 1000 kg/m3g 9.81 m/s2Efficiency 0.7

Let's calculate the power:

Convert Flow Rate to m3/s

0.231 L/s 0.000231 m3/s

Calculate Power

Power (W) (frac{0.000231 , text{m}^3/text{s} times 45.72 , text{m} times 1000 , text{kg/m}^3 times 9.81 , text{m/s}^2}{0.7} approx 16.57 , text{W})

Convert to Horsepower

Horsepower (HP) (frac{16.57 , text{W}}{746} approx 0.022 , text{HP})

For reliability, you would typically select a pump with a bit more capacity, so a 1/4 HP or 1/2 HP submersible pump would be suitable for this application.

Borewell Diameter

The diameter of the borewell depends on the pump size and the installation requirements. For a submersible pump:

Common Borewell Diameter

Typically, a 4-inch (100 mm) diameter borewell is used for small to medium submersible pumps.

For Larger Pumps

A 6-inch (150 mm) borewell may be necessary.

Summary

Required HP:

Approximately 0.022 HP. Use a 1/4 HP or 1/2 HP pump for reliability.

Borewell Diameter:

Typically 4 inches for small pumps, 6 inches for larger pumps.