Temp Dewpoint RH Calculator

Dewpoint Formula:

\[ T_d = \frac{b \times \alpha}{a - \alpha} \]

where

\[ \alpha = \frac{a \times T}{b + T} + \ln\left(\frac{RH}{100}\right) \]

Temperature (T):

°C

Relative Humidity (RH):

Constant (a):

Constant (b):

Dewpoint Temperature (T_d):

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1. What is a Dewpoint Calculator?

Definition: This calculator estimates the dewpoint temperature based on air temperature and relative humidity using the Magnus formula.

Purpose: It helps meteorologists, HVAC professionals, and others determine when condensation will occur at a given temperature and humidity.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ T_d = \frac{b \times \alpha}{a - \alpha} \]

where

\[ \alpha = \frac{a \times T}{b + T} + \ln\left(\frac{RH}{100}\right) \]

Where:

\( T_d \) — Dewpoint temperature (°C)
\( T \) — Air temperature (°C)
\( RH \) — Relative humidity (%)
\( a \) — Constant (typically 17.27)
\( b \) — Constant (typically 237.7)

Explanation: The formula approximates the relationship between temperature, humidity, and the condensation point.

3. Importance of Dewpoint Calculation

Details: Knowing the dewpoint helps predict fog, frost, and condensation problems in buildings and industrial processes.

4. Using the Calculator

Tips: Enter the air temperature in °C, relative humidity (0-100%), and constants a (default 17.27) and b (default 237.7).

5. Frequently Asked Questions (FAQ)

Q1: What is dewpoint temperature?
A: The temperature at which air becomes saturated with water vapor and dew forms.

Q2: Why are there constants a and b?
A: These are empirical coefficients in the Magnus formula that vary slightly for different temperature ranges.

Q3: When would I change constants a and b?
A: For temperatures below 0°C, different constants might be more accurate (e.g., a=21.87, b=265.5).

Q4: How accurate is this calculation?
A: It's accurate to within about ±0.4°C for temperatures between -40°C and 50°C.

Q5: What if the RH is 100%?
A: When RH=100%, the dewpoint equals the air temperature (saturated air).