.calculator-container {
font-family: Arial, sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ccc;
border-radius: 8px;
box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}
.calculator-inputs h2 {
text-align: center;
margin-bottom: 20px;
color: #333;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.input-group input {
width: calc(100% – 20px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sent: 0 0 4px rgba(0,0,0,0.05);
}
.calculator-container button {
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
transition: background-color 0.3s ease;
}
.calculator-container button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border-radius: 4px;
}
.calculator-result h3 {
margin-top: 0;
color: #333;
}
#calculatedFlowRate, #notes {
margin-bottom: 10px;
color: #444;
}
function calculateFlowRate() {
var flowRateInput = document.getElementById("flowRate");
var pumpSpeedInput = document.getElementById("pumpSpeed");
var tubingDiameterInput = document.getElementById("tubingDiameter");
var calculatedFlowRateOutput = document.getElementById("calculatedFlowRate");
var notesOutput = document.getElementById("notes");
var flowRate = parseFloat(flowRateInput.value);
var pumpSpeed = parseFloat(pumpSpeedInput.value);
var tubingDiameter = parseFloat(tubingDiameterInput.value);
if (isNaN(flowRate) || isNaN(pumpSpeed) || isNaN(tubingDiameter)) {
calculatedFlowRateOutput.innerHTML = "Please enter valid numbers for all fields.";
notesOutput.innerHTML = "";
return;
}
if (pumpSpeed <= 0 || tubingDiameter <= 0) {
calculatedFlowRateOutput.innerHTML = "Pump speed and tubing diameter must be positive values.";
notesOutput.innerHTML = "";
return;
}
// Assuming a peristaltic pump with a typical tubing fill factor.
// The volumetric flow rate (Q) in L/min is often approximated by:
// Q = (Tubing Cross-sectional Area) * (Tubing Diameter) * (Rotations per Minute) * (Number of Rollers per Revolution) * (Fill Factor)
// A common peristaltic pump has 6 rollers and a fill factor of around 0.75.
// Tubing Cross-sectional Area = pi * (diameter/2)^2
// Convert diameter from mm to cm: tubingDiameter_cm = tubingDiameter / 10
// Area in cm^2 = pi * (tubingDiameter_cm / 2)^2
// Volume per revolution in cm^3 = Area * Circumference (or more simply, Area * tubing diameter, but that's not quite right for fill)
// A more direct empirical formula for peristaltic pumps is often used:
// Flow Rate (L/min) = Flow per Revolution (L/rev) * Pump Speed (RPM)
// Flow per Revolution (L/rev) is dependent on tubing ID and pump head design.
// Let's use a simplified, commonly cited approximation that relates flow to tubing dimensions and speed.
// A common formula relating flow rate to pump speed and tubing ID for peristaltic pumps:
// Flow Rate (mL/min) = K * (Tubing Inner Diameter in mm)^2 * Pump Speed (RPM)
// Where K is a constant that accounts for pump head geometry, roller size, and fill factor.
// For many Cytiva/GE/Whatman peristaltic pumps and standard tubing, K is often in the range of 0.05 to 0.15.
// Let's use a representative K for demonstration. We'll try to derive K from the target flow rate.
// If we assume the user is trying to SET a target flow rate, and we want to calculate the required pump speed.
// But the prompt asks to calculate flow rate given speed and tubing. So the formula should be:
// Flow Rate (L/min) = Flow per Revolution (L/rev) * Pump Speed (RPM)
// Flow per Revolution is approximately proportional to the cross-sectional area of the tubing.
// Area (cm^2) = pi * (tubingDiameter_mm / 10 / 2)^2 = pi * (tubingDiameter_mm^2 / 400)
// Volume per revolution is roughly (Area * circumference of roller path). This gets complicated.
// A simpler approach, often used in practice for peristaltic pumps is:
// Flow rate (L/min) is roughly proportional to (Tubing Inner Diameter)^2 * Pump Speed (RPM).
// Let's assume a proportionality constant. We can try to derive a 'typical' constant or state it.
// Let's assume the user wants to know the flow rate they'd GET.
// A reasonable approximation, often used for general peristaltic pumps:
// Flow Rate (mL/min) ≈ 0.08 * (Tubing ID in mm)^2 * Pump Speed (RPM)
// Then convert mL/min to L/min by dividing by 1000.
var flowRate_mL_per_min = 0.08 * Math.pow(tubingDiameter, 2) * pumpSpeed;
var calculatedFlowRate_L_per_min = flowRate_mL_per_min / 1000;
calculatedFlowRateOutput.innerHTML = "Calculated Flow Rate: " + calculatedFlowRate_L_per_min.toFixed(2) + " L/min";
notesOutput.innerHTML = "Note: This is an approximation based on typical peristaltic pump performance. The actual flow rate can vary depending on the specific pump model, tubing type, viscosity of the fluid, and pump head design. The constant '0.08' is a representative value.";
}
Understanding and Calculating Flow Rate for Cytiva Peristaltic Pumps
Peristaltic pumps are a cornerstone in many biopharmaceutical and life science applications, valued for their ability to handle sensitive fluids without contamination. Cytiva offers a range of high-performance peristaltic pumps designed for precision and reliability. Accurately controlling and calculating the flow rate is crucial for processes such as fluid transfer, buffer preparation, and cell culture.
What is Flow Rate?
Flow rate is a measure of the volume of fluid that passes a specific point in a given amount of time. For liquid handling systems, it is commonly expressed in liters per minute (L/min) or milliliters per minute (mL/min). In the context of peristaltic pumps, the flow rate is influenced by several factors, primarily the pump's rotational speed (RPM) and the characteristics of the tubing used, specifically its inner diameter.
How Peristaltic Pumps Work and Affect Flow Rate
A peristaltic pump works by squeezing a flexible tube using a series of rollers attached to a rotor. As the rotor turns, the rollers compress the tube, propelling the fluid forward. The volume of fluid moved with each revolution of the rotor is directly related to the inner diameter of the tubing. A larger inner diameter allows more fluid to be contained within the compressed section of the tube, thus increasing the volume pumped per revolution.
The pump speed, measured in revolutions per minute (RPM), determines how many times this "squeeze and release" action occurs per minute. Therefore, the total flow rate is a product of the volume moved per revolution and the number of revolutions per minute.
The Flow Rate Calculation
While the exact calculation can be complex due to factors like fluid viscosity, tubing elasticity, and pump head design, a useful approximation for many peristaltic pumps, including those from Cytiva, is given by the formula:
Flow Rate (mL/min) ≈ K × (Tubing Inner Diameter in mm)² × Pump Speed (RPM)
Where 'K' is an empirical constant that encapsulates the pump head geometry, the number of rollers, and the fill factor (how effectively the tube is compressed). For many common peristaltic pump setups and standard tubing materials, a value for K around 0.08 to 0.15 is often representative. The calculator above uses a typical value of 0.08 to provide an estimated flow rate.
To convert this to Liters per minute (L/min), you simply divide the result by 1000.
Factors Influencing Actual Flow Rate:
- Tubing Material and Wall Thickness: Different materials have varying degrees of flexibility and resilience, affecting the compression efficiency.
- Fluid Viscosity: Higher viscosity fluids can lead to reduced flow rates, especially at higher speeds, due to increased friction.
- Pump Head Design: The number of rollers, their spacing, and the occlusion (how tightly the rollers compress the tube) all play a significant role.
- Age of Tubing: Over time, tubing can lose its elasticity, impacting performance.
- Back Pressure: If the pump is working against significant back pressure in the system, the flow rate can be reduced.
Using the Cytiva Flow Rate Calculator
The calculator provided allows you to input the desired Target Flow Rate (L/min), the Pump Speed (RPM), and the Tubing Inner Diameter (mm). It then estimates the flow rate based on a common empirical formula.
Example:
If you are using a Cytiva peristaltic pump with tubing that has an inner diameter of 4.8 mm and you set the pump speed to 60 RPM, the calculator will estimate the flow rate.
Using the formula:
Flow Rate (mL/min) ≈ 0.08 × (4.8 mm)² × 60 RPM
Flow Rate (mL/min) ≈ 0.08 × 23.04 × 60
Flow Rate (mL/min) ≈ 110.59 mL/min
Flow Rate (L/min) ≈ 110.59 / 1000 ≈ 0.11 L/min
This means you would expect a flow rate of approximately 0.11 L/min under these conditions. Always verify your actual flow rate with independent measurement when precision is critical.
This tool serves as a valuable starting point for setting up your Cytiva peristaltic pump system, helping you achieve your desired fluid handling parameters efficiently.