.ct-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
background: #f9f9f9;
padding: 20px;
border-radius: 8px;
box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
.ct-calculator-box {
background: #ffffff;
padding: 25px;
border-radius: 8px;
border: 1px solid #e0e0e0;
margin-bottom: 30px;
}
.ct-calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.ct-input-group {
margin-bottom: 15px;
display: flex;
flex-direction: column;
}
.ct-input-group label {
font-weight: 600;
margin-bottom: 5px;
color: #444;
font-size: 14px;
}
.ct-input-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
width: 100%;
box-sizing: border-box;
}
.ct-input-group .hint {
font-size: 12px;
color: #666;
margin-top: 3px;
}
.ct-row {
display: flex;
gap: 20px;
flex-wrap: wrap;
}
.ct-col {
flex: 1;
min-width: 200px;
}
.ct-btn {
background-color: #0073aa;
color: white;
border: none;
padding: 12px 20px;
font-size: 16px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
width: 100%;
margin-top: 10px;
transition: background-color 0.3s;
}
.ct-btn:hover {
background-color: #005177;
}
.ct-results {
margin-top: 25px;
background: #f0f7fb;
border: 1px solid #cce5ff;
border-radius: 6px;
padding: 20px;
display: none;
}
.ct-result-item {
display: flex;
justify-content: space-between;
margin-bottom: 10px;
padding-bottom: 10px;
border-bottom: 1px solid #dcebf7;
}
.ct-result-item:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.ct-result-label {
color: #555;
font-weight: 500;
}
.ct-result-value {
font-weight: 700;
color: #2c3e50;
}
.ct-highlight {
color: #d63638;
font-size: 1.1em;
}
.ct-content {
line-height: 1.6;
color: #333;
}
.ct-content h2 {
color: #2c3e50;
border-bottom: 2px solid #0073aa;
padding-bottom: 10px;
margin-top: 30px;
}
.ct-content h3 {
color: #444;
margin-top: 20px;
}
.ct-content ul {
padding-left: 20px;
}
.ct-content li {
margin-bottom: 8px;
}
@media (max-width: 600px) {
.ct-row {
flex-direction: column;
gap: 0;
}
}
function calculateAirFlow() {
// Get input values
var waterFlow = parseFloat(document.getElementById('waterFlow').value);
var tempIn = parseFloat(document.getElementById('tempIn').value);
var tempOut = parseFloat(document.getElementById('tempOut').value);
var enthalpyIn = parseFloat(document.getElementById('enthalpyIn').value);
var enthalpyOut = parseFloat(document.getElementById('enthalpyOut').value);
var specVol = parseFloat(document.getElementById('specVol').value);
// Validation
if (isNaN(waterFlow) || isNaN(tempIn) || isNaN(tempOut) || isNaN(enthalpyIn) || isNaN(enthalpyOut) || isNaN(specVol)) {
alert("Please fill in all fields with valid numbers.");
return;
}
if (tempIn <= tempOut) {
alert("Inlet Temperature must be higher than Outlet Temperature.");
return;
}
if (enthalpyOut <= enthalpyIn) {
alert("Outlet Enthalpy must be higher than Inlet Enthalpy.");
return;
}
// Constants
var cpWater = 4.186; // Specific heat of water in kJ/kg°C
var waterDensity = 1000; // kg/m^3 approximation
// 1. Calculate Water Mass Flow (kg/h)
// m^3/h * 1000 = kg/h
var waterMassFlow = waterFlow * waterDensity;
// 2. Calculate Cooling Range (Delta T)
var range = tempIn – tempOut;
// 3. Calculate Heat Load (Q) in kJ/h
// Q = m * Cp * dT
var heatLoadKJ = waterMassFlow * cpWater * range;
// Convert Heat Load to kW for display (kJ/h / 3600 = kW)
var heatLoadKW = heatLoadKJ / 3600;
// 4. Calculate Air Mass Flow Required (kg/h)
// G = Q / (h_out – h_in)
var enthalpyDiff = enthalpyOut – enthalpyIn;
var airMassFlow = heatLoadKJ / enthalpyDiff;
// 5. Calculate Volumetric Air Flow
// Volume = Mass * Specific Volume
var airVolPerHour = airMassFlow * specVol;
// Convert to CMM (Cubic Meters per Minute)
var airCMM = airVolPerHour / 60;
// Convert to CFM (Cubic Feet per Minute)
// 1 m^3 = 35.3147 ft^3
var airCFM = airCMM * 35.3147;
// Update UI
document.getElementById('resHeatLoad').innerText = heatLoadKW.toLocaleString(undefined, {maximumFractionDigits: 1}) + " kW";
document.getElementById('resRange').innerText = range.toFixed(1) + " °C";
document.getElementById('resMassFlow').innerText = Math.round(airMassFlow).toLocaleString() + " kg/h";
document.getElementById('resCMM').innerText = Math.round(airCMM).toLocaleString() + " m³/min";
document.getElementById('resCFM').innerText = Math.round(airCFM).toLocaleString() + " ft³/min";
// Show results
document.getElementById('resultBox').style.display = 'block';
}
Cooling Tower Air Flow Calculator
Circulation water volume
Standard is approx 0.88
Hot water entering tower
Cold water leaving tower
Approx 50-80 depending on Wet Bulb
Typically 110-140 at discharge
Heat Load Rejected:
0 kW
Cooling Range (ΔT):
0 °C
Mass Air Flow Required:
0 kg/h
Volumetric Air Flow (CMM):
0 m³/min
Volumetric Air Flow (CFM):
0 ft³/min
How to Calculate Cooling Tower Air Flow
Calculating the required air flow rate for a cooling tower is critical for ensuring that the tower can reject the necessary amount of heat from the process water to the atmosphere. The efficiency of a cooling tower relies heavily on the heat and mass balance between the hot water entering the tower and the cooler air flowing through it.
The Core Calculation Logic
The calculation is based on the principle of heat conservation: Heat Lost by Water = Heat Gained by Air.
The heat load ($Q$) removed from the water is calculated using the specific heat capacity of water, the flow rate, and the temperature difference (Range):
$$Q = L \times C_p \times (T_{in} – T_{out})$$
- L: Water Circulation Rate (kg/h)
- C_p: Specific Heat of Water (4.186 kJ/kg°C)
- T_in: Hot Water Inlet Temperature
- T_out: Cold Water Outlet Temperature
Once the Heat Load is known, the Air Mass Flow rate ($G$) required to absorb this heat depends on the change in enthalpy ($\Delta h$) of the air as it passes through the tower:
$$G = \frac{Q}{h_{out} – h_{in}}$$
- h_out: Enthalpy of outgoing air (saturated at discharge)
- h_in: Enthalpy of incoming ambient air (based on Wet Bulb temperature)
Understanding the Inputs
- Water Flow Rate: The volume of water being pumped through the system per hour.
- Range ($\Delta T$): The difference between the hot water temperature entering the tower and the cold water temperature leaving it. A higher range requires more air flow or a larger tower.
- Enthalpy: This represents the total heat content of the air. The cooling capability is driven by the difference between the inlet air enthalpy (determined by local weather/wet bulb) and the outlet air enthalpy.
Units and Conversions
The calculator provides results in both Metric (CMM – Cubic Meters per Minute) and Imperial (CFM – Cubic Feet per Minute) units.
1 CMM $\approx$ 35.31 CFM.
Proper fan sizing requires selecting a fan that can deliver this volumetric flow rate against the static pressure of the cooling tower fill and drift eliminators.