Thermodynamics Calculator
Solve heat transfer, calorimetry, thermal resistance and ideal gas problems for engineering and physics.
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Thermodynamics calculations show up everywhere from sizing a home furnace to designing an industrial heat exchanger. HVAC technicians need to estimate heating loads, mechanical engineers calculate thermal resistance through wall assemblies and physics students work through calorimetry problems regularly. These tools handle the standard formulas for conduction, energy balance and gas behavior so you can focus on the design decisions rather than the arithmetic.
Frequently asked questions
For steady-state conduction, use Q = k times A times delta-T divided by thickness. A concrete wall 0.2 m thick with thermal conductivity 1.7 W/(m K) and 20 degrees C temperature difference loses about 170 W per square meter. Adding 5 cm of foam insulation (k = 0.04) drops the heat loss to roughly 15 W per square meter.
Use Q = m times c times delta-T. Water has a specific heat of 4.186 J/(g K), so heating 1 liter (1000 g) by 50 degrees C requires 209,300 J or about 209 kJ. That is roughly 0.058 kWh of energy - at typical electricity rates around $0.15/kWh, it costs less than a penny to heat a liter of water for tea.
Thermal resistance (R-value) measures how well a material resists heat flow. It equals thickness divided by thermal conductivity (R = L/k) in SI units of m squared K/W. Fiberglass insulation has an R-value of about 0.66 per centimeter, while still air has roughly 0.40 per centimeter. For composite walls, add the R-values of each layer in series.
PV = nRT connects pressure (Pa), volume (m cubed), moles, temperature (K) and the gas constant (8.314 J/(mol K)). One mole of gas at 25 degrees C in a 1-liter container exerts about 2.48 MPa or 24.5 atm. Doubling the temperature in kelvin (to 596 K) doubles the pressure to roughly 49 atm if the volume stays fixed.
Log mean temperature difference (LMTD) is the effective average driving force for heat exchange between two fluid streams. For a counterflow exchanger with hot inlet/outlet of 90/50 degrees C and cold inlet/outlet of 20/60 degrees C, delta-T1 = 30 and delta-T2 = 30, so LMTD = 30 degrees C. When the two delta-T values differ, the LMTD is always between them - for delta-T values of 70 and 30, LMTD is about 47.2 degrees C.
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