Heat Flow Rate Formula

Heat Flow Rate Formula:

\[ Q_{btu} = W \times c \times \Delta T \]

Mass Flow Rate (W):

lb/hr

Specific Heat Capacity (c):

BTU/lb·°F

Temperature Difference (ΔT):

°F

Heat Flow Rate (Q_btu):

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1. What is Heat Flow Rate?

Definition: Heat flow rate measures the amount of thermal energy transferred per unit time, typically expressed in BTU per hour (BTU/h).

Purpose: This calculation is essential for HVAC system design, thermal management, and energy efficiency analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q_{btu} = W \times c \times \Delta T \]

Where:

\( Q_{btu} \) — Heat flow rate (BTU/h)
\( W \) — Mass flow rate (lb/hr)
\( c \) — Specific heat capacity (BTU/lb·°F)
\( \Delta T \) — Temperature difference (°F)

Explanation: The formula calculates thermal energy transfer by multiplying mass flow rate by specific heat capacity and temperature difference.

3. Importance of Heat Flow Calculation

Details: Accurate heat flow calculations ensure proper equipment sizing, energy efficiency, and system performance in heating/cooling applications.

4. Using the Calculator

Tips: Enter mass flow rate in lb/hr, specific heat capacity (default 1.0 for water), and temperature difference in °F. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical specific heat value for water?
A: Water has a specific heat of 1.0 BTU/lb·°F, which is the default value in the calculator.

Q2: How do I convert this to other units?
A: 1 BTU/h = 0.293071 watts. For kW, divide BTU/h by 3412.14.

Q3: When would I need to adjust the specific heat value?
A: When working with fluids other than water (e.g., oils: ~0.5, air: ~0.24 BTU/lb·°F).

Q4: Does this account for phase changes?
A: No, this formula is for sensible heat only. Latent heat requires additional calculations.

Q5: How do I find mass flow rate?
A: Measure volumetric flow (gal/min) and multiply by fluid density (water: 8.34 lb/gal × 60 min/hr).