Hvacpumpheadcalculationpdfdownload
Click Here >>> https://bytlly.com/2tuDlu
How to Calculate HVAC Pump Head for Chilled Water Systems
One of the most important aspects of designing a chilled water system is to determine the pump head required to circulate the chilled water through the system. The pump head is the pressure difference between the inlet and outlet of the pump, measured in meters of water column (mwc) or feet of water column (fwt). The pump head depends on several factors, such as the flow rate, pipe diameter, pipe length, pipe fittings, valves, and elevation changes.
In this article, we will explain how to calculate the pump head for a chilled water system using a simple formula and a spreadsheet tool. We will also provide some tips and watchpoints to avoid common errors and optimize the pump selection.
The Pump Head Formula
The pump head formula is based on the Bernoulli equation, which states that the total energy of a fluid remains constant along a streamline. The total energy consists of three components: pressure energy, kinetic energy, and potential energy. The formula can be written as:
where is the pump head, is the static head, and is the friction head.
The static head is the difference in elevation between the highest and lowest points of the system, plus any pressure losses or gains due to valves or other devices. The static head can be positive or negative depending on whether the system is uphill or downhill from the pump. The static head can be calculated as:
where is the elevation difference in meters or feet, and is the pressure difference due to valves or other devices in meters or feet of water column.
The friction head is the pressure loss due to the friction of the fluid against the pipe walls and fittings. The friction head can be calculated using the Darcy-Weisbach equation, which relates the friction factor, pipe diameter, pipe length, flow rate, and fluid density. The friction head can be calculated as:
where is the friction factor (dimensionless), is the pipe length in meters or feet, is the pipe diameter in meters or feet, is the fluid velocity in meters per second or feet per second, and is the gravitational acceleration in meters per second squared or feet per second squared.
The friction factor can be obtained from empirical correlations such as the Colebrook-White equation or from charts such as the Moody diagram. The friction factor depends on the Reynolds number, which is a dimensionless number that measures the ratio of inertial forces to viscous forces in a fluid flow. The Reynolds number can be calculated as: ec8f644aee