Please fill in all fields correctly. Thickness must be greater than 0.
Heat Transfer Rate (Power):– W
Kilowatts:– kW
BTU per Hour:– BTU/hr
Temperature Difference (ΔT):– °C
Understanding Heat Transfer Rate Calculation
The rate of heat transfer measures how quickly thermal energy moves from a hotter region to a cooler region. This calculator specifically solves for heat transfer via Conduction, which is the process of heat flowing through a solid material due to a temperature difference.
Fourier's Law Formula:
Q/t = (k · A · ΔT) / d
Input Parameters Explained
Thermal Conductivity (k): A measure of a material's ability to conduct heat. Metals like copper have high values (good conductors), while insulation materials like foam have low values (good insulators).
Surface Area (A): The total area of the face of the material through which heat is flowing (in square meters).
Thickness (d): The distance the heat must travel through the material (in meters). Thicker materials slow down heat transfer.
Temperature Difference (ΔT): The difference between the hot side (Th) and the cold side (Tc). Heat always flows from hot to cold.
Example Calculation
Imagine a glass window (Thermal Conductivity = 0.8 W/m·K) that is 1 meter wide and 1 meter tall (Area = 1 m²). The glass is 5mm thick (0.005 m). The temperature inside is 20°C and outside is 0°C.
Using the formula:
k = 0.8
A = 1.0
ΔT = 20 – 0 = 20
d = 0.005
Calculation: (0.8 × 1.0 × 20) / 0.005 = 3,200 Watts. This represents the rate of heat energy escaping through the window.
Why is this important?
Calculating the heat transfer rate is critical in engineering, construction, and environmental science. It helps determines the efficiency of thermal insulation in buildings, the cooling requirements for electronics, and the design of heat exchangers in industrial processes.
function updateConductivity() {
var select = document.getElementById('materialSelect');
var kInput = document.getElementById('conductivity');
var val = select.value;
if (val !== 'custom') {
kInput.value = val;
} else {
kInput.value = ";
}
}
function calculateHeatTransfer() {
// Get Input Values
var k = parseFloat(document.getElementById('conductivity').value);
var area = parseFloat(document.getElementById('area').value);
var thickness = parseFloat(document.getElementById('thickness').value);
var tHot = parseFloat(document.getElementById('tempHot').value);
var tCold = parseFloat(document.getElementById('tempCold').value);
var errorMsg = document.getElementById('errorMsg');
var resultsDiv = document.getElementById('results');
// Validation
if (isNaN(k) || isNaN(area) || isNaN(thickness) || isNaN(tHot) || isNaN(tCold)) {
errorMsg.style.display = 'block';
resultsDiv.style.display = 'none';
errorMsg.innerText = "Please ensure all fields contain valid numbers.";
return;
}
if (thickness <= 0) {
errorMsg.style.display = 'block';
resultsDiv.style.display = 'none';
errorMsg.innerText = "Thickness must be greater than zero.";
return;
}
// Hide error if previously shown
errorMsg.style.display = 'none';
// Calculation: Fourier's Law: Q_dot = (k * A * deltaT) / d
// We use Math.abs for Delta T to get the magnitude of transfer regardless of which side is hotter
var deltaT = tHot – tCold;
var absDeltaT = Math.abs(deltaT);
var watts = (k * area * absDeltaT) / thickness;
// Conversions
var kilowatts = watts / 1000;
// 1 Watt = 3.412142 BTU/hr
var btu = watts * 3.412142;
// Display Results
document.getElementById('resWatts').innerText = watts.toFixed(2) + " W";
document.getElementById('resKW').innerText = kilowatts.toFixed(4) + " kW";
document.getElementById('resBTU').innerText = btu.toFixed(2) + " BTU/hr";
document.getElementById('resDeltaT').innerText = absDeltaT.toFixed(2) + " °C";
// Show result container
resultsDiv.style.display = 'block';
}