This calculator helps estimate the evaporation rate of a cooling tower, a crucial factor in water management and makeup water requirements. Understanding evaporation is key to optimizing cooling tower performance and minimizing water loss.
function calculateEvaporationRate() {
var flowRate = parseFloat(document.getElementById("flowRate").value);
var range = parseFloat(document.getElementById("range").value);
var heatLoad = parseFloat(document.getElementById("heatLoad").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(flowRate) || isNaN(range) || isNaN(heatLoad)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (flowRate <= 0 || range <= 0 || heatLoad <= 0) {
resultDiv.innerHTML = "Please enter positive values for all inputs.";
return;
}
// Method 1: Using Heat Load (BTU/hr)
// Evaporation (GPH) = Heat Load (BTU/hr) / 1000 (BTU/lb water) / 8.34 (lb/gal water)
var evaporationRateFromHeat = heatLoad / 1000 / 8.34;
// Method 2: Using Flow Rate and Range (for approximation if heat load is unknown)
// This method assumes typical conditions and may be less precise.
// The latent heat of vaporization is approximately 1000 BTU/lb.
// 1 GPM = 60 GPH
// 1 gallon of water weighs approx 8.34 lbs.
// Evaporation (GPM) = Flow Rate (GPM) * Range (°F) / 1000 (BTU/lb) * (8.34 lb/gal) / (60 min/hr) – This is not the standard formula.
// A common simplified formula for evaporation rate based on heat load and flow rate is:
// Evaporation (GPH) = Heat Load (BTU/hr) / 1000 (BTU/lb water) / 8.34 (lb/gal water)
// If only flow rate and range are known, it's usually calculated as:
// Evaporation Rate (GPM) ≈ Range (°F) * Flow Rate (GPM) / 2400 (empirical constant)
// Let's prioritize the heat load method as it's more direct. If heat load is provided, we use it.
// If not, we might infer it or use the simplified range/flow method.
// For this calculator, we'll show both if possible, or emphasize the heat load method.
// Let's re-evaluate. The most common formula uses the heat load.
// The formula relates heat transfer to evaporation.
// Heat Transfer Rate (BTU/hr) = Mass Flow Rate (lb/hr) * Specific Heat Capacity (BTU/lb°F) * Temperature Change (°F)
// Mass Flow Rate (lb/hr) = Flow Rate (GPM) * 8.34 (lb/gal) * 60 (min/hr)
// So, Heat Load (BTU/hr) = (Flow Rate (GPM) * 8.34 * 60) * 1 * Range (°F)
// This implies Heat Load = Flow Rate * Range * 499.4 (approx 500)
// And Evaporation (lb/hr) = Heat Load (BTU/hr) / Latent Heat of Vaporization (BTU/lb)
// Latent Heat of Vaporization of water is approx 1000 BTU/lb at typical cooling tower temperatures.
// Evaporation (lb/hr) = Heat Load (BTU/hr) / 1000
// Evaporation (GPH) = Evaporation (lb/hr) / 8.34 (lb/gal)
// Evaporation (GPH) = (Heat Load (BTU/hr) / 1000) / 8.34
// Evaporation (GPH) = Heat Load (BTU/hr) / 8340
// Let's refine the calculation based on the provided inputs and standard formulas.
// It's common to calculate evaporation based on heat load.
// The amount of water evaporated is proportional to the heat removed from the water.
// The latent heat of vaporization of water is approximately 1000 BTU per pound.
// Density of water is approximately 8.34 pounds per gallon.
// Therefore, to evaporate 1 gallon of water, approximately 1000 BTU/lb * 8.34 lb/gal = 8340 BTU must be removed.
var evaporationRateGPH = heatLoad / 8340; // Evaporation in Gallons Per Hour
// If flow rate and range are also provided, we can cross-check or estimate.
// The heat removed from the water is also given by:
// Heat Removed (BTU/hr) = Flow Rate (GPM) * 8.34 (lb/gal) * 60 (min/hr) * 1 (BTU/lb°F) * Range (°F)
// Heat Removed (BTU/hr) = Flow Rate * Range * 499.4 (approx 500)
// If the provided heat load is consistent with flow rate and range, it's good.
// Let's assume the user provides the most accurate heat load.
// Additional calculation: Evaporation as a percentage of circulating water
var evaporationPercentage = (evaporationRateGPH / (flowRate * 60)) * 100; // (GPH / GPM_total) * 100
resultDiv.innerHTML = `
Estimated Evaporation Rate:
${evaporationRateGPH.toFixed(2)} GPH (Gallons Per Hour)
This is based on the heat load removed from the water.
Note: This is an estimate. Actual rates can be affected by ambient humidity, air flow, and tower design.Water Loss Relative to Flow:
${evaporationPercentage.toFixed(2)}% of circulating water is evaporated.
`;
}
.cooling-tower-calculator {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
background-color: #f9f9f9;
}
.cooling-tower-calculator h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.cooling-tower-calculator p {
line-height: 1.6;
color: #555;
}
.inputs {
margin-bottom: 20px;
}
.form-group {
margin-bottom: 15px;
}
.form-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #333;
}
.form-group input[type="number"] {
width: calc(100% – 12px);
padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box; /* Include padding and border in the element's total width and height */
}
.cooling-tower-calculator button {
display: block;
width: 100%;
padding: 10px 15px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 16px;
cursor: pointer;
transition: background-color 0.3s ease;
margin-top: 10px;
}
.cooling-tower-calculator button:hover {
background-color: #0056b3;
}
.results {
margin-top: 25px;
padding-top: 15px;
border-top: 1px solid #eee;
background-color: #fff;
padding: 15px;
border-radius: 4px;
box-shadow: inset 0 0 5px rgba(0,0,0,0.05);
}
.results p {
margin-bottom: 10px;
}
.results strong {
color: #333;
}
.results em {
font-size: 0.9em;
color: #777;
}