Thermal & HVAC

33 tools list this domain in the app. A tool can appear in more than one domain. The page lives under the first domain on that tool.

0–10 V to Engineering Units

Linear voltage signal to temperature. Over-range is not clamped.

ACH from Airflow

Air changes per hour from measured airflow and room volume. Inverse of THERM-09.

Air Temperature Differential

ΔT = T1 − T2 with sign preserved. Subtracts absolute temperatures so mixed °C/°F is valid.

Airflow from Velocity and Area

Q = v A for a grille, opening, or duct. Enter area, or width × height, or diameter — not both area and geometry.

Condensation Risk

Whether a surface is at or below the air dew point. A surface-condition check, not a prediction of standing water.

COP / EER

COP = useful thermal power / electrical input. EER = (Btu/h of cooling) / (W electrical) = COP × 3.412.

Dew Point

Magnus dew point from dry-bulb temperature and relative humidity (a = 17.62, b = 243.12 °C).

Diameter from Flow

Required inside diameter for a target mean velocity. Does not pick a commercial size.

Duct Airflow from Geometry

Airflow from measured velocity and rectangular or round duct size. Circular pipe continuity is also FLUID-01.

Fan Heat

Heat to the airstream = electrical input × heat-to-air fraction. The fraction is required — motors do not dump 100% into the duct by default.

Flow from Velocity

Volumetric flow from mean velocity in a full circular pipe.

Heat Exchanger Area

A = Q / (U F ΔTlm). Leave F blank for 1.

Heat Exchanger Duty

Q = ṁ cp (T_out − T_in) for a single fluid stream (water, glycol, air, process).

Heat Transfer Through Assembly

Q = U A ΔT through a wall, panel, or other boundary.

Humidity Ratio

W = 0.621945 Pv / (P − Pv) with Pv = RH × Psat(T) from Magnus saturation pressure.

HVAC Sensible Capacity from Airflow

Sensible coil capacity from airflow and ΔT (or return − supply). Same physics as THERM-04, labeled in Btu/h and tons.

Latent Heat Transfer

Q = ṁ h_fg for evaporation, condensation, or moisture removal. Enter h_fg for the actual temperature.

Log Mean Temperature Difference

ΔTlm = (ΔT1 − ΔT2) / ln(ΔT1/ΔT2). Equal ends return ΔT1 instead of dividing by zero.

Moist-Air Density

ρ = Pd/(Rd T) + Pv/(Rv T) with Rd = 287.05 J/kg·K and Rv = 461.495 J/kg·K.

Moist-Air Enthalpy

h = 1.006 T + W (2501 + 1.86 T) kJ/kg with T in °C, per kg dry air. Approximate, not a certified property.

Overall R-Value / U-Value

Series area-normalized resistance R″ = Σ(L/k) + surface resistances. U = 1/R″. Not parallel paths.

Psychrometric State

Dew point, humidity ratio, enthalpy, and density from dry bulb, RH, and pressure. Composes THERM-11–14.

Refrigeration Subcooling

Saturation temperature minus liquid-line temperature. No refrigerant table.

Refrigeration Superheat

Suction-line temperature minus saturation temperature. No refrigerant table — enter Tsat yourself.

Reynolds Number

Dimensionless Reynolds number from velocity, diameter, and dynamic or kinematic viscosity.

RTD Lead-Wire Error

How much extra series lead resistance shifts the indicated IEC 60751 temperature.

RTD Resistance to Temperature

IEC 60751 Callendar–Van Dusen platinum RTD. Default R0 = 100 Ω (Pt100).

RTD Temperature to Resistance

Inverse of INST-22. IEC 60751 platinum characteristic.

Sensible Air Heating / Cooling

Q = ρ V̇ cp ΔT. Defaults are standard air 1.204 kg/m³ and 1006 J/(kg·K), shown as optional fields.

Thermal Resistance

Component resistance R = L / (k A) in K/W.

Thermocouple Temperature

NIST ITS-90 inverse polynomials with cold-junction compensation. Types K, J, T, E, N, R, S.

Velocity from Flow

Mean velocity from volumetric flow in a full circular pipe.

Ventilation Airflow from ACH

V̇ = ACH × volume. ACH is a frequency (1/h); SI flow is m³/s.