1. What is a Radiator BTU Calculator from Size?

Definition: This calculator estimates the heat output of a radiator based on temperature difference, material properties, and surface area.

Purpose: It helps HVAC professionals and homeowners determine the heating capacity of radiators for proper system design.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q \) — Heat output (BTU/hour)
• \( \Delta T \) — Temperature difference between radiator and room (°F)
• \( K \) — Material constant (BTU/hour·ft²·°F)
• \( A \) — Radiator surface area (ft²)

Explanation: The heat output increases with greater temperature difference, better heat transfer materials, and larger radiator surfaces.

3. Importance of Radiator Heat Calculation

Details: Proper heat output estimation ensures adequate room heating, energy efficiency, and correct radiator sizing.

4. Using the Calculator

Tips: Enter the temperature difference, material constant (default 5.0 for cast iron), and surface area. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical ΔT for residential radiators?
A: Typically 50-70°F difference between radiator surface and room temperature.

Q2: What are common K values for different materials?
A: Cast iron ≈5.0, Steel ≈5.5, Aluminum ≈6.0 BTU/h·ft²·°F.

Q3: How do I measure radiator surface area?
A: Calculate total exposed surface area including fins or convolutions.

Q4: Does this account for radiator color/finish?
A: No, darker colors may radiate slightly more heat (add 5-10%).

Q5: How does this relate to room size?
A: Typically need 20-30 BTU/h per sq ft of room area in cold climates.